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  • 201. Ackermann, M.
    et al.
    Larsson, Stefan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik. Oskar Klein Centre for Cosmoparticle Physics, Sweden..
    Li, L.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik. Oskar Klein Centre for Cosmoparticle Physics, Sweden..
    Wood, M.
    et al.,
    CONTEMPORANEOUS BROADBAND OBSERVATIONS OF THREE HIGH-REDSHIFT BL LAC OBJECTS2016Ingår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 820, nr 1, artikel-id 72Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We have collected broadband spectral energy distributions (SEDs) of three BL Lac objects 3FGL J0022.1-1855 (z = 0.689), 3FGL J0630.9-2406 (z≳ 1.239), and 3FGL J0811.2-7529 (z = 0.774), detected by Fermi with relatively flat gigaelectronvolt spectra. By observing simultaneously in the near-infrared to hard X-ray band, we can well characterize the high end of the synchrotron component of the SED. Thus, fitting the SEDs to synchro-Compton models of the dominant emission from the relativistic jet, we can constrain the underlying particle properties and predict the shape of the gigaelectronvolt Compton component. Standard extragalactic background light (EBL) models explain the high-energy absorption well, with poorer fits for high-ultraviolet models. The fits show clear evidence for EBL absorption in the Fermi spectrum of our highest-redshift source 3FGL J0630.9-2406. While synchrotron self-Compton models adequately describe the SEDs, the situation may be complicated by possible external Compton components. For 3FGL J0811.2-7529, we also discover a nearby serendipitous source in the X-ray data, which is almost certainly another lower synchrotron peak frequency (vpk sy) BL Lac, that may contribute flux in the Fermi band. Since our sources are unusual high-luminosity, moderate vpk sy BL Lacs, we compare these quantities and the Compton dominance, the ratio of peak inverse Compton to peak synchrotron luminosities (Lpk IC/Lpk sy), with those of the full Fermi BL Lac population.

  • 202. Ackermann, M.
    et al.
    Larsson, Stefan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik. Oskar Klein Centre for Cosmoparticle Physics, Stockholm, Sweden .
    Li, L.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik. Oskar Klein Centre for Cosmoparticle Physics, Stockholm, Sweden .
    Zampieri, L.
    et al.,
    An extremely bright gamma-ray pulsar in the Large Magellanic Cloud: An extremely bright gamma-ray pulsar in the Large Magellanic Cloud2015Ingår i: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 350, nr 6262, s. 801-805Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Pulsars are rapidly spinning, highly magnetized neutron stars, created in the gravitational collapse of massive stars. We report the detection of pulsed giga-electron volt gamma rays from the young pulsar PSR J0540-6919 in the Large Magellanic Cloud, a satellite galaxy of the Milky Way. This is the first gamma-ray pulsar detected in another galaxy. It has the most luminous pulsed gamma-ray emission yet observed, exceeding the Crab pulsar's by a factor of 20. PSR J0540-6919 presents an extreme test case for understanding the structure and evolution of neutron star magnetospheres.

  • 203.
    Ackley, K.
    et al.
    Monash Univ, Sch Phys & Astron, Clayton, Vic 3800, Australia..
    Bulla, Mattia
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. Stockholm Univ, Roslagstullsbacken 23, S-10691 Stockholm, Sweden..
    Levan, A. J.
    Univ Warwick, Dept Phys, Coventry CV4 7AL, W Midlands, England.;Radboud Univ Nijmegen, Dept Astrophys, IMAPP, POB 9010, NL-6500 GL Nijmegen, Netherlands..
    Young, D. R.
    Queens Univ Belfast, Astrophys Res Ctr, Sch Math & Phys, Belfast BT7 1NN, Antrim, North Ireland..
    et al.,
    Observational constraints on the optical and near-infrared emission from the neutron star-black hole binary merger candidate S190814bv2020Ingår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 643, artikel-id A113Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Context. Gravitational wave (GW) astronomy has rapidly reached maturity, becoming a fundamental observing window for modern astrophysics. The coalescences of a few tens of black hole (BH) binaries have been detected, while the number of events possibly including a neutron star (NS) is still limited to a few. On 2019 August 14, the LIGO and Virgo interferometers detected a high-significance event labelled S190814bv. A preliminary analysis of the GW data suggests that the event was likely due to the merger of a compact binary system formed by a BH and a NS.Aims. In this paper, we present our extensive search campaign aimed at uncovering the potential optical and near infrared electromagnetic counterpart of S190814bv. We found no convincing electromagnetic counterpart in our data. We therefore use our non-detection to place limits on the properties of the putative outflows that could have been produced by the binary during and after the merger.Methods. Thanks to the three-detector observation of S190814bv, and given the characteristics of the signal, the LIGO and Virgo Collaborations delivered a relatively narrow localisation in low latency - a 50% (90%) credible area of 5 deg(2) (23 deg(2)) - despite the relatively large distance of 26752 Mpc. ElectromagNetic counterparts of GRAvitational wave sources at the VEry Large Telescope collaboration members carried out an intensive multi-epoch, multi-instrument observational campaign to identify the possible optical and near infrared counterpart of the event. In addition, the ATLAS, GOTO, GRAWITA-VST, Pan-STARRS, and VINROUGE projects also carried out a search on this event. In this paper, we describe the combined observational campaign of these groups.Results. Our observations allow us to place limits on the presence of any counterpart and discuss the implications for the kilonova (KN), which was possibly generated by this NS-BH merger, and for the strategy of future searches. The typical depth of our wide-field observations, which cover most of the projected sky localisation probability (up to 99.8%, depending on the night and filter considered), is r similar to 22 (resp. K similar to 21) in the optical (resp. near infrared). We reach deeper limits in a subset of our galaxy-targeted observations, which cover a total similar to 50% of the galaxy-mass-weighted localisation probability. Altogether, our observations allow us to exclude a KN with large ejecta mass M greater than or similar to 0.1 M-circle dot to a high (> 90%) confidence, and we can exclude much smaller masses in a sub-sample of our observations. This disfavours the tidal disruption of the neutron star during the merger.Conclusions. Despite the sensitive instruments involved in the campaign, given the distance of S190814bv, we could not reach sufficiently deep limits to constrain a KN comparable in luminosity to AT 2017gfo on a large fraction of the localisation probability. This suggests that future (likely common) events at a few hundred megaparsecs will be detected only by large facilities with both a high sensitivity and large field of view. Galaxy-targeted observations can reach the needed depth over a relevant portion of the localisation probability with a smaller investment of resources, but the number of galaxies to be targeted in order to get a fairly complete coverage is large, even in the case of a localisation as good as that of this event.

  • 204.
    Acuner, Zeynep
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Photosphere and Synchrotron Emission During the Prompt Phase in GRBs Observed with Fermi/GBM: \\%Comparison of Bayesian EvidencesManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    There is no complete description of the emission physics during the prompt phase in gamma-raybursts. Spectral analyses, however, indicate that many spectra are narrower than what is expectedfor non-thermal emission models. Here, we reanalyse the sample of 37 bursts in Yu et al. (2019), byfitting the narrowest time-resolved spectrum in each burst. We perform model comparison between aphotospheric and a synchrotron emission model based on Bayesian evidences. We choose to compare theshape of the narrowest expected spectra: emission from the photosphere in a non-dissipative flow andslow-cooled synchrotron emission from a narrow electron distribution. We find that the photosphericspectral shape is preferred by 54% of the spectra (20/37), while 38% of the spectra (14/37) prefer thesynchrotron spectral shape; three spectra are inconclusive. We hence conclude that GRB spectra areindeed very narrow and that more than half of the bursts have a photospheric emission episode. Wealso find that a third of all spectra, not only prefer, but are also compatible with a non-dissipativephotosphere, confirming previous similar findings. Furthermore, we notice that the spectra, that preferthe photospheric model, all have a low-energy power-law indicesα&−0.5. This means that theαisa good estimator of which model is preferred by the data. Finally, we argue that the spectra whichstatistically prefer the synchrotron model, could equally well be caused by subphotospheric dissipation.If that is the case, photospheric emission during the early, prompt phase would be even more dominant.

  • 205.
    Acuner, Zeynep
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Ryde, Felix
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Appearances of the jet photosphere in GRB spectra2018Ingår i: 14th Marcel Grossman Meeting On Recent Developments in Theoretical and Experimental General Relativity, Astrophysics and Relativistic Field Theories, Proceedings, World Scientific Publishing Co. Pte. Ltd. , 2018, s. 2921-2930Konferensbidrag (Refereegranskat)
    Abstract [en]

    There are several strong arguments for considering photospheric emission in GRBs. Here, we describe the two main appearances of the photospheric emission that are currently discussed. In the multi-component models the photosphere only contributes to a part of the spectrum, while the main part is due to optically-thin synchrotron emission. In the photospheric emission models the whole emission spectrum is from the photosphere: The emission spectrum has been altered due to subphotospheric dissipation and/or off-axis emission. In many cases, though, it is difficult to distinguish between these models on a purely statistical ground. Therefore, more detailed predictions from different physical scenarios should be tested on the observations.

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  • 206.
    Adams, J. H., Jr.
    et al.
    Univ Alabama Huntsville, Huntsville, AL USA..
    Bertaina, M.
    Ist Nazl Fis Nucl, Sez Torino, Turin, Italy.;Univ Torino, Dipartimento Fis, Turin, Italy..
    Capel, Francesca
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    von Ballmoos, P.
    Univ Toulouse, CNRS, IRAP, Toulouse, France..
    Zotov, M.
    Lomonosov Moscow State Univ, Skobeltsyn Inst Nucl Phys, Moscow, Russia..
    A Review of the EUSO-Balloon Pathfinder for the JEM-EUSO Program2022Ingår i: Space Science Reviews, ISSN 0038-6308, E-ISSN 1572-9672, Vol. 218, nr 1, artikel-id 3Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    EUSO-Balloon is a pathfinder for JEM-EUSO, the mission concept of a spaceborne observatory which is designed to observe Ultra-High Energy Cosmic Ray (UHECR)-induced Extensive Air Showers (EAS) by detecting their UltraViolet (UV) light tracks "from above." On August 25, 2014, EUSO-Balloon was launched from Timmins Stratospheric Balloon Base (Ontario, Canada) by the balloon division of the French Space Agency CNES. After reaching a floating altitude of 38 km, EUSO-Balloon imaged the UV light in the wavelength range similar to 290-500 nm for more than 5 hours using the key technologies of JEM-EUSO. The flight allowed a good understanding of the performance of the detector to be developed, giving insights into possible improvements to be applied to future missions. A detailed measurement of the photoelectron counts in different atmospheric and ground conditions was achieved. By means of the simulation of the instrument response and by assuming atmospheric models, the absolute intensity of diffuse light was estimated. The instrument detected hundreds of laser tracks with similar characteristics to EASs shot by a helicopter flying underneath. These are the first recorded laser tracks measured from a fluorescence detector looking down on the atmosphere. The reconstruction of the direction of the laser tracks was performed. In this work, a review of the main results obtained by EUSO-Balloon is presented as well as implications for future space-based observations of UHECRs.

  • 207.
    Addazi, A.
    et al.
    Sichuan Univ, Coll Phys, Ctr Theoret Phys, Chengdu 610065, Peoples R China.;Ist Nazl Fis Nucl, Lab Nazl Frascati, Via Enrico Fermi 54, I-00044 Rome, Italy..
    Carmona, J. M.
    Univ Zaragoza, Ctr Astroparticulas & Fis Altas Energias CAPA, Dept Fis Teor, C Pedro Cerbuna 12, E-50009 Zaragoza, Spain..
    Obers, Niels A.
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. Stockholm Univ, Hannes Alfvens Vag 12, SE-10691 Stockholm, Sweden.;Univ Copenhagen, Niels Bohr Inst, DK-2100 Copenhagen, Denmark..
    Zornoza, J. D.
    Univ Valencia, CSIC, Inst Fis Corpuscular, Parc Cient UV,C Catedrat Jose Beltran 2, E-46980 Paterna, Spain..
    Quantum gravity phenomenology at the dawn of the multi-messenger era-A review2022Ingår i: Progress in Particle and Nuclear Physics, ISSN 0146-6410, E-ISSN 1873-2224, Vol. 125, artikel-id 103948Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    The exploration of the universe has recently entered a new era thanks to the multi-messenger paradigm, characterized by a continuous increase in the quantity and quality of experimental data that is obtained by the detection of the various cosmic messengers (photons, neutrinos, cosmic rays and gravitational waves) from numerous origins. They give us information about their sources in the universe and the properties of the intergalactic medium. Moreover, multi-messenger astronomy opens up the possibility to search for phenomenological signatures of quantum gravity. On the one hand, the most energetic events allow us to test our physical theories at energy regimes which are not directly accessible in accelerators; on the other hand, tiny effects in the propagation of very high energy particles could be amplified by cosmological distances. After decades of merely theoretical investigations, the possibility of obtaining phenomenological indications of Planck-scale effects is a revolutionary step in the quest for a quantum theory of gravity, but it requires cooperation between different communities of physicists (both theoretical and experimental). This review, prepared within the COST Action CA18108 "Quantum gravity phenomenology in the multi-messenger approach", is aimed at promoting this cooperation by giving a state-of-the art account of the interdisciplinary expertise that is needed in the effective search of quantum gravity footprints in the production, propagation and detection of cosmic messengers.

  • 208.
    Adithya, H. N.
    et al.
    Young Innovators Educ Serv Pvt Ltd YIESPL, Bangalore 560040, Karnataka, India.;Nagoya Univ, Inst Space Earth Environm Res ISEE, Nagoya, Aichi, Japan..
    Kariyappa, Rangaiah
    Nagoya Univ, Inst Space Earth Environm Res ISEE, Nagoya, Aichi, Japan.;Indian Inst Astrophys, Bangalore 560034, Karnataka, India..
    Shinsuke, Imada
    Nagoya Univ, Inst Space Earth Environm Res ISEE, Nagoya, Aichi, Japan..
    Kanya, Kusano
    Nagoya Univ, Inst Space Earth Environm Res ISEE, Nagoya, Aichi, Japan..
    Zender, Joe
    European Space Res & Technol Ctr ESTEC, NL-2200 AG Noordwijk, Netherlands..
    Dame, Luc
    LATMOS Lab Atmospheres Milieux Observat Spatiales, 11 Blvd Alembert, F-78280 Guyancourt, France..
    Giono, Gabriel
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Rymd- och plasmafysik.
    DeLuca, Edward
    Harvard Smithsonian Ctr Astrophys, 60 Garden St, Cambridge, MA 02138 USA..
    Weber, Mark
    Harvard Smithsonian Ctr Astrophys, 60 Garden St, Cambridge, MA 02138 USA..
    Solar Soft X-ray Irradiance Variability, I: Segmentation of Hinode/XRT Full-Disk Images and Comparison with GOES (1-8 angstrom) X-Ray Flux2021Ingår i: Solar Physics, ISSN 0038-0938, E-ISSN 1573-093X, Vol. 296, nr 4, artikel-id 71Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    It is of great interest and importance to study the variabilities of solar EUV, UV and X-ray irradiance in heliophysics, in Earth's climate, and space weather applications. A careful study is required to identify, track, monitor and segment the different coronal features such as active regions (ARs), coronal holes (CHs), the background regions (BGs) and the X-ray bright points (XBPs) from spatially resolved full-disk images of the Sun. Variability of solar soft X-ray irradiance is studied for a period of 13 years (February 2007-March 2020, covers Solar Cycle 24), using the X-Ray Telescope on board the Hinode (Hinode/XRT) and GOES (1 - 8 angstrom). The full-disk X-ray images observed in Al_mesh filter from XRT are used, for the first time, to understand the solar X-ray irradiance variability measured, Sun as a star, by GOES instrument. An algorithm in Python has been developed and applied to identify and segment coronal X-ray features (ARs, CHs, BGs, and XBPs) from the full-disk soft X-ray observations of Hinode/XRT. The segmentation process has been carried out automatically based on the intensity level, morphology and sizes of the X-ray features. The total intensity, area, and contribution of ARs/CHs/BGs/XBPs features were estimated and compared with the full-disk integrated intensity (FDI) and GOES (1 - 8 angstrom) X-ray irradiance measurements. The XBPs have been identified and counted automatically over the full disk to investigate their relation to solar magnetic cycle. The total intensity of ARs/CHs/BGs/XBPs/FD regions are compared with the GOES (1 - 8 angstrom) X-ray irradiance variations. We present the results obtained from Hinode/XRT full-disk images (in Al_mesh filter) and compare the resulting integrated full-disk intensity (FDI) with GOES X-ray irradiance. The X-ray intensity measured over ARs/CHs/BGs/XBPs/FD is well correlated with GOES X-ray flux. The contributions of the segmented X-ray features to FDI and X-ray irradiance variations are determined. It is found that the background and active regions have a greater impact on the X-ray irradiance fluctuations. The mean contribution estimated for the whole observed period of the background regions (BGs) will be around 65 +/- 10.97%, whereas the ARs, XBPs and CHs are 30 +/- 11.82%, 4 +/- 1.18% and 1 +/- 0.52%, respectively, to total solar X-ray flux. We observed that the area and contribution of ARs and CHs varies with the phase of the solar cycle, whereas the BGs and XBPs show an anti-correlation. We find that the area of the coronal features is highly variable suggesting that their area has to be taken into account in irradiance models, in addition to their intensity variations. The time series results of XBPs suggest for an existence of anti-correlation between the number of XBPs and the sunspot numbers. It is also important to consider both the number variation and the contribution of XBPs in the reconstruction of total solar X-ray irradiance variability.

  • 209. Adriani, O.
    et al.
    Ambriola, M.
    Barbarino, G. C.
    Basili, A.
    Bazilevshja, G. A.
    Bellotti, R.
    Boezio, M.
    Bogomolov, E. A.
    Bonechi, L.
    Bongi, M.
    Bongiorno, L.
    Bonvicini, V.
    Bruno, A.
    Cafagna, F.
    Campana, D.
    Carlson, Per J.
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Casolino, M.
    Castellini, G.
    De Pascale, M. P.
    De Rosa, G.
    De Simone, N.
    Di Felice, V.
    Fedele, D.
    Galper, A. M.
    Hofverberg, Petter
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Koldashov, S. V.
    Krutkov, S. Y.
    Kvashnin, A. N.
    Lundquist, J.
    Maksumov, O.
    Malvezzi, V.
    Marcelli, L.
    Menn, W.
    Mikhailov, V. V.
    Minori, M.
    Misin, S.
    Mocchiutti, E.
    Morselli, A.
    Nikonov, N. N.
    Orsi, Silvio
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Osteria, G.
    Papini, P.
    Pearce, Mark J.
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Picozza, P.
    Ricci, M.
    Ricciarini, S. B.
    Runtso, M. F.
    Russo, S.
    Simon, M.
    Sparvoli, R.
    Spillantini, P.
    Stozhkov, Y. I.
    Taddei, E.
    Vacchi, A.
    Vannuccini, E.
    Vasilyev, G.
    Voronov, S. A.
    Yurkin, Y. T.
    Zampa, G.
    Zampa, N.
    Zverev, V. G.
    The PAMELA space mission2008Ingår i: Astroparticle, Part. Space Phys., Detect. Med. Phys. Appl. - Proc. Conf., 2008, s. 858-864Konferensbidrag (Refereegranskat)
    Abstract [en]

    The PAMELA (a Payload for Antimatter-Matter Exploration and Light-nuclei Astrophysics) experiment, is a satellite-borne particle spectrometer. It was launched on 15th June 2006 from the Baikonur cosmodrome in Kazakhstan, is installed into the Russian Resurs-DK1 satellite. PAMELA is composed of a time-of-flight system, a magnetic spectrometer, a silicon-tungsten electromagnetic calorimeter, an anticoincidence system, a shower tail catcher scintillator and a neutron detector. Among the PAMELA major objectives are the study of charged particles in the cosmic radiation, the investigation of the nature of dark matter, by mean of the measure of the cosmic-ray antiproton and positron spectra over the largest energy range ever achieved. PAMELA has been in a nearly continuous data taking mode since llth July 2006. The status of the apparatus and performances will be presented.

  • 210. Adriani, O.
    et al.
    Barbarino, G.
    Bazilevskaya, G. A.
    Bellotti, R.
    Boezio, M.
    Bogomolov, E. A.
    Bonechi, L.
    Bongi, M.
    Bonvicini, V.
    Borisov, S. V.
    Bottai, S.
    Bruno, A.
    Cafagna, F. S.
    Campana, D.
    Carbone, R.
    Carlson, Per
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Casolino, M.
    Castellini, G.
    Consiglio, L.
    De Pascale, M. P.
    De Santis, C.
    De Simone, N.
    Di Felice, V.
    Galper, A. M.
    Gillard, William
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Grishantseva, L. A.
    Jerse, G.
    Hofverberg, Petter
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Karelin, A. V.
    Koldashov, S. V.
    Krutkov, S. Y.
    Kvashnin, A. N.
    Leonov, A. A.
    Malakhov, V. V.
    Malvezzi, V.
    Marcelli, L.
    Mayorov, A. G.
    Menn, W.
    Mikhailov, V. V.
    Mocchiutti, E.
    Monaco, A.
    Mori, N.
    Nikonov, N. N.
    Osteria, G.
    Papini, P.
    Pearce, Mark
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Picozza, P.
    Pizzolotto, C.
    Ricci, M.
    Ricciarini, S. B.
    Rossetto, Laura
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Ritabrata, S.
    Runtso, M. F.
    Simon, M.
    Sparvoli, R.
    Spillantini, P.
    Stozhkov, Y. I.
    Vacchi, A.
    Vannuccini, E.
    Vasilyev, G. I.
    Voronov, S. A.
    Wu, Juan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Yurkin, Y. T.
    Zampa, G.
    Zampa, N.
    Zverev, V. G.
    Measurements of quasi-trapped electron and positron fluxes with PAMELA2009Ingår i: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 114, s. A12218-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents precise measurements of the differential energy spectra of quasi-trapped secondary electrons and positrons and their ratio between 80 MeV and 10 GeV in the near-equatorial region (altitudes between 350 km and 600 km). Latitudinal dependences of the spectra are analyzed in detail. The results were obtained from July until November 2006 onboard the Resurs-DK satellite by the PAMELA spectrometer, a general purpose cosmic ray detector system built around a permanent magnet spectrometer and a silicon-tungsten calorimeter.

  • 211. Adriani, O.
    et al.
    Barbarino, G. C.
    Bazilevskaja, G. A.
    Bellotti, R.
    Boezio, M.
    Bogomolov, E. A.
    Bonechi, L.
    Bongi, M.
    Bonvicini, V.
    Borisov, S.
    Bottai, S.
    Bruno, A.
    Cafagna, F.
    Campana, D.
    Carbone, R.
    Carlson, Per
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Casolino, M.
    Castellini, G.
    Consiglio, L.
    de Pascale, M. P.
    de Santis, C.
    de Simone, N.
    di Felice, V.
    Galper, A. M.
    Gillard, William
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Hofverberg, Petter
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Koldashov, S. V.
    Krutkov, S. Y.
    Kvashnin, A. N.
    Leonov, A.
    Malvezzi, V.
    Marcelli, L.
    Menn, W.
    Mikhailov, V. V.
    Mocchiutti, E.
    Mori, N.
    Nikonov, N. N.
    Osteria, G.
    Papini, P.
    Pearce, Mark
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Picozza, P.
    Ricci, M.
    Ricciarini, S. B.
    Simon, M.
    Sparvoli, R.
    Spillantini, P.
    Stozhkov, Y. I.
    Vacchi, A.
    Vannuccini, E.
    Vasilyev, G.
    Voronov, S. A.
    Yurkin, Y. T.
    Zampa, G.
    Zampa, N.
    Zverev, V. G.
    The PAMELA Space Mission for Antimatter and Dark Matter Searches in Cosmic Rays2010Ingår i: SCIENCE WITH THE NEW GENERATION OF HIGH-ENERGY GAMMA-RAY EXPERIMENTS / [ed] Cecchi, C; Ciprini, S; Lubrano, P; Tosti, G, 2010, Vol. 1223, s. 33-42Konferensbidrag (Refereegranskat)
    Abstract [en]

    On the 15(th) of June 2006, the PAMELA satellite-borne experiment was launched from the Baikonur cosmodrome and it has been collecting data since July 2006. The instrument allows precision studies of the charged cosmic radiation to be conducted over a wide energy range (100 MeV - 100's GeV) with high statistics. The primary scientific goal is the measurement of the antiproton and positron energy spectrum in order to search for exotic sources, such as dark matter particle annihilations. PAMELA is also searching for primordial antinuclei (anti-helium), and testing cosmic-ray propagation models through precise measurements of the antiparticle energy spectrum and precision studies of light nuclei and their isotopes. Moreover, PAMELA is investigating phenomena connected with solar and earth physics. Results of the antiproton and positron data will be presented.

  • 212. Adriani, O.
    et al.
    Barbarino, G. C.
    Bazilevskaya, G. A.
    Bellotti, R.
    Boezio, M.
    Bogomolov, E. A.
    Bonechi, L.
    Bongi, M.
    Bonvicini, V.
    Borisov, S.
    Bottai, S.
    Bruno, A.
    Cafagna, F.
    Campana, D.
    Carbone, R.
    Carlson, Per
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Casolino, M.
    Castellini, G.
    Consiglio, L.
    De Pascale, M. P.
    De Santis, C.
    De Simone, N.
    Di Felice, V.
    Formato, V.
    Galper, A. M.
    Grishantseva, L.
    Gillard, William
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Jerse, G.
    Karelin, A. V.
    Koldashov, S. V.
    Krutkov, S. Y.
    Kvashnin, A. N.
    Leonov, A.
    Malakhov, V.
    Marcelli, L.
    Mayorov, A. G.
    Menn, W.
    Mikiiailov, V. V.
    Mocciiiutti, E.
    Monaco, A.
    Mori, N.
    Nikonov, N.
    Osteria, G.
    Palma, F.
    Papini, P.
    Pearce, Mark
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Picozza, P.
    Pizzolotto, C.
    Ricci, M.
    Ricciarini, S. B.
    Sarkar, R.
    Rossetto, Laura
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Simon, M.
    Sparvoli, R.
    Spillantini, P.
    Stoziikov, Y. I.
    Vacciii, A.
    Vannuccini, E.
    Vasilyev, G.
    Voronov, S. A.
    Wu, Juan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Yurkin, Y. T.
    Zampa, G.
    Zampa, N.
    Zverev, V. G.
    OBSERVATIONS OF THE 2006 DECEMBER 13 AND 14 SOLAR PARTICLE EVENTS IN THE 80 MeV n(-1)-3 GeV n(-1) RANGE FROM SPACE WITH THE PAMELA DETECTOR2011Ingår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 742, nr 2, s. 102-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present the space spectrometer PAMELA observations of proton and helium fluxes during the 2006 December 13 and 14 solar particle events. This is the first direct measurement of the solar energetic particles in space with a single instrument in the energy range from similar to 80 MeV n(-1) up to similar to 3 GeV n(-1). For the December 13 event, measured energy spectra of solar protons and helium are compared with results obtained by neutron monitors and other detectors. Our measurements show a spectral behavior different from those derived from the neutron monitor network. No satisfactory analytical fitting was found for the energy spectra. During the first hours of the December 13 event, solar energetic particles spectra were close to the exponential form, demonstrating rather significant temporal evolution. Solar He with energy up to 1 GeV n(-1) was recorded on December 13. For the December 14 event, energy of solar protons reached 600 MeV, whereas the maximum energy of He was below 100 MeV n(-1). The spectra were slightly bent in the lower energy range and preserved their form during the second event. Differences in the particle flux appearance and temporal evolution of these two events may argue for special conditions leading to the acceleration of solar particles up to relativistic energies.

  • 213. Adriani, O.
    et al.
    Barbarino, G. C.
    Bazilevskaya, G. A.
    Bellotti, R.
    Boezio, M.
    Bogomolov, E. A.
    Bonechi, L.
    Bongi, M.
    Bonvicini, V.
    Borisov, S.
    Bottai, S.
    Bruno, A.
    Cafagna, F.
    Campana, D.
    Carbone, R.
    Carlson, Per
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Casolino, M.
    Castellini, G.
    Consiglio, L.
    De Pascale, M. P.
    De Santis, C.
    De Simone, N.
    Di Felice, V.
    Galper, A. M.
    Gillard, William
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Grishantseva, L.
    Jerse, G.
    Karelin, A. V.
    Koldashov, S. V.
    Krutkov, S. Y.
    Kvashnin, A. N.
    Leonov, A.
    Malakhov, V.
    Malvezzi, V.
    Marcelli, L.
    Mayorov, A. G.
    Menn, W.
    Mikhailov, V. V.
    Mocchiutti, E.
    Monaco, A.
    Mori, N.
    Nikonov, N.
    Osteria, G.
    Palma, F.
    Papini, P.
    Pearce, Mark
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Picozza, P.
    Pizzolotto, C.
    Ricci, M.
    Ricciarini, S. B.
    Rossetto, Laura
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Sarkar, R.
    Simon, M.
    Sparvoli, R.
    Spillantini, P.
    Stozhkov, Y. I.
    Vacchi, A.
    Vannuccini, E.
    Vasilyev, G.
    Voronov, S. A.
    Yurkin, Y. T.
    Wu, Juan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zampa, G.
    Zampa, N.
    Zverev, V. G.
    PAMELA Measurements of Cosmic-Ray Proton and Helium Spectra2011Ingår i: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 332, nr 6025, s. 69-72Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Protons and helium nuclei are the most abundant components of the cosmic radiation. Precise measurements of their fluxes are needed to understand the acceleration and subsequent propagation of cosmic rays in our Galaxy. We report precision measurements of the proton and helium spectra in the rigidity range 1 gigavolt to 1.2 teravolts performed by the satellite-borne experiment PAMELA (payload for antimatter matter exploration and light-nuclei astrophysics). We find that the spectral shapes of these two species are different and cannot be described well by a single power law. These data challenge the current paradigm of cosmic-ray acceleration in supernova remnants followed by diffusive propagation in the Galaxy. More complex processes of acceleration and propagation of cosmic rays are required to explain the spectral structures observed in our data.

  • 214. Adriani, O.
    et al.
    Barbarino, G. C.
    Bazilevskaya, G. A.
    Bellotti, R.
    Boezio, M.
    Bogomolov, E. A.
    Bonechi, L.
    Bongi, M.
    Bonvicini, V.
    Bottai, S.
    Bruno, A.
    Cafagna, F.
    Campana, D.
    Carlson, Per
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Casolino, M.
    Castellini, G.
    De Pascale, M. P.
    De Rosa, G.
    De Simone, N.
    Di Felice, V.
    Galper, A. M.
    Grishantseva, L.
    Hofverberg, Petter
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Koldashov, S. V.
    Krutkov, S. Y.
    Kvashnin, A. N.
    Leonov, A.
    Malvezzi, V.
    Marcelli, L.
    Menn, W.
    Mikhailov, V. V.
    Mocchiutti, E.
    Orsi, Silvio
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Osteria, G.
    Papini, P.
    Pearce, Mark
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Picozza, P.
    Ricci, M.
    Ricciarini, S. B.
    Simon, M.
    Sparvoli, R.
    Spillantini, P.
    Stozhkov, Y. I.
    Vacchi, A.
    Vannuccini, E.
    Vasilyev, G.
    Voronov, S. A.
    Yurkin, Y. T.
    Zampa, G.
    Zampa, N.
    Zverev, V. G.
    An anomalous positron abundance in cosmic rays with energies 1.5-100 GeV2009Ingår i: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 458, nr 7238, s. 607-609Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Antiparticles account for a small fraction of cosmic rays and are known to be produced in interactions between cosmic-ray nuclei and atoms in the interstellar medium(1), which is referred to as a 'secondary source'. Positrons might also originate in objects such as pulsars(2) and microquasars(3) or through dark matter annihilation(4), which would be 'primary sources'. Previous statistically limited measurements(5-7) of the ratio of positron and electron fluxes have been interpreted as evidence for a primary source for the positrons, as has an increase in the total electron+positron flux at energies between 300 and 600 GeV (ref. 8). Here we report a measurement of the positron fraction in the energy range 1.5-100 GeV. We find that the positron fraction increases sharply overmuch of that range, in a way that appears to be completely inconsistent with secondary sources. We therefore conclude that a primary source, be it an astrophysical object or dark matter annihilation, is necessary.

  • 215. Adriani, O.
    et al.
    Barbarino, G. C.
    Bazilevskaya, G. A.
    Bellotti, R.
    Boezio, M.
    Bogomolov, E. A.
    Bongi, M.
    Bonvicini, V.
    Borisov, S.
    Bottai, S.
    Bruno, A.
    Cafagna, F.
    Campana, D.
    Carbone, R.
    Carlson, Per
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Casolino, M.
    Castellini, G.
    Danilchenko, I. A.
    De Pascale, M. P.
    De Santis, C.
    De Simone, N.
    Di Felice, V.
    Formato, V.
    Galper, A. M.
    Karelin, A. V.
    Koldashov, S. V.
    Koldobskiy, S.
    Krutkov, S. Y.
    Kvashnin, A. N.
    Leonov, A.
    Malakhov, V.
    Marcelli, L.
    Mayorov, A. G.
    Menn, W.
    Mikhailov, V. V.
    Mocchiutti, E.
    Monaco, A.
    Mori, N.
    Nikonov, N.
    Osteria, G.
    Palma, F.
    Papini, P.
    Pearce, Mark
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Picozza, P.
    Pizzolotto, C.
    Ricci, M.
    Ricciarini, S. B.
    Rossetto, Laura
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Sarkar, R.
    Simon, M.
    Sparvoli, R.
    Spillantini, P.
    Stozhkov, Y. I.
    Vacchi, A.
    Vannuccini, E.
    Vasilyev, G.
    Voronov, S. A.
    Yurkin, Y. T.
    Wu, Juan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zampa, G.
    Zampa, N.
    Zverev, V. G.
    Measurement of the isotopic composition of hydrogen and helium nuclei in cosmic rays with the PAMELA experiment2013Ingår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 770, nr 1, s. 2-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The satellite-borne experiment PAMELA has been used to make new measurements of cosmic ray H and He isotopes. The isotopic composition was measured between 100 and 600 MeV /n for hydrogen and between 100 and 900 MeV /n for helium isotopes over the 23rd solar minimum from 2006 July to 2007 December. The energy spectrum of these components carries fundamental information regarding the propagation of cosmic rays in the galaxy which are competitive with those obtained from other secondary to primary measurements such as B/C.

  • 216. Adriani, O.
    et al.
    Barbarino, G. C.
    Bazilevskaya, G. A.
    Bellotti, R.
    Boezio, M.
    Bogomolov, E. A.
    Bongi, M.
    Bonvicini, V.
    Bottai, S.
    Bravar, U.
    Bruno, A.
    Cafagna, F.
    Campana, D.
    Carbone, R.
    Carlson, Per
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Casolino, M.
    Castellini, G.
    Christian, E. R.
    De Donato, C.
    de Nolfo, G. A.
    De Santis, C.
    De Simone, N.
    Di Felice, V.
    Formato, V.
    Galper, A. M.
    Karelin, A. V.
    Koldashov, S. V.
    Koldobskiy, S.
    Krutkov, S. Y.
    Kvashnin, A. N.
    Lee, M.
    Leonov, A.
    Malakhov, V.
    Marcelli, L.
    Martucci, M.
    Mayorov, A. G.
    Menn, W.
    Merge, M.
    Mikhailov, V. V.
    Mocchiutti, E.
    Monaco, A.
    Mori, N.
    Munini, R.
    Osteria, G.
    Palma, F.
    Panico, B.
    Papini, P.
    Pearce, Mark
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Picozza, P.
    Ricci, M.
    Ricciarini, S. B.
    Ryan, J. M.
    Sarkar, R.
    Scotti, V.
    Simon, M.
    Sparvoli, R.
    Spillantini, P.
    Stochaj, S.
    Stozhkov, Y. I.
    Thakur, N.
    Vacchi, A.
    Vannuccini, E.
    Vasilyev, G. I.
    Voronov, S. A.
    Yurkin, Y. T.
    Zampa, G.
    Zampa, N.
    Pamela's measurements of magnetospheric effects on high-energy solar particles2015Ingår i: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 801, nr 1, artikel-id L3Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The nature of particle acceleration at the Sun, whether through flare reconnection processes or through shocks driven by coronal mass ejections, is still under scrutiny despite decades of research. The measured properties of solar energetic particles (SEPs) have long been modeled in different particle-acceleration scenarios. The challenge has been to disentangle the effects of transport from those of acceleration. The Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA) instrument enables unique observations of SEPs including the composition and angular distribution of the particles about the magnetic field, i.e., pitch angle distribution, over a broad energy range (>80 MeV)-bridging a critical gap between space-based and ground-based measurements. We present high-energy SEP data from PAMELA acquired during the 2012 May 17 SEP event. These data exhibit differential anisotropies and thus transport features over the instrument rigidity range. SEP protons exhibit two distinct pitch angle distributions: a low-energy population that extends to 90 degrees and a population that is beamed at high energies (>1 GeV), consistent with neutron monitor measurements. To explain a low-energy SEP population that exhibits significant scattering or redistribution accompanied by a high-energy population that reaches the Earth relatively unaffected by dispersive transport effects, we postulate that the scattering or redistribution takes place locally. We believe that these are the first comprehensive measurements of the effects of solar energetic particle transport in the Earth's magnetosheath.

  • 217. Adriani, O.
    et al.
    Barbarino, G. C.
    Bazilevskaya, G. A.
    Bellotti, R.
    Boezio, M.
    Bogomolov, E. A.
    Bongi, M.
    Bonvicini, V.
    Bottai, S.
    Bruno, A.
    Cafagna, F.
    Campana, D.
    Carbone, R.
    Carlson, P.
    Casolino, M.
    Castellini, G.
    de Pascale, M. P.
    Santis, C. D. E.
    Simone, N. D. E.
    Felice, V. D. I.
    Formato, V.
    Galper, A. M.
    Giaccari, U.
    Karelin, A. V.
    Kheymits, M. D.
    Koldashov, S. V.
    Koldobskiy, S.
    Krutkov, S. Y.
    Kvashnin, A. N.
    Leonov, A.
    Malakhov, V.
    Marcelli, L.
    Martucci, M.
    Mayorov, A. G.
    Menn, W.
    Merge, M.
    Mikhailov, V. V.
    Mocchiutti, E.
    Monaco, A.
    Mori, N.
    Munini, R.
    Nikonov, N.
    Osteria, G.
    Palma, F.
    Papini, P.
    Pearce, Mark
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Picozza, P.
    Pizzolotto, C.
    Ricci, M.
    Ricciarini, S. B.
    Rossetto, L.
    Sarkar, R.
    Scotti, V.
    Simon, M.
    Sparvoli, R.
    Spillantini, P.
    Stozhkov, Y. I.
    Vacchi, A.
    Vannuccini, E.
    Vasilyev, G.
    Voronov, S. A.
    Yurkin, Y. T.
    Zampa, G.
    Zampa, N.
    Zverev, V. G.
    Antiprotons in primary cosmic radiation with PAMELA experiment2013Ingår i: Proceedings of the 33rd International Cosmic Rays Conference, ICRC 2013, Sociedade Brasileira de Fisica , 2013Konferensbidrag (Refereegranskat)
    Abstract [en]

    The latest measurements of antiprotons spectrum and antiproton-to-proton ratio in primary cosmic rays with PAMELA experiment are presented. They are in good agreement with model of secondary production of antiprotons in Galaxy, but they do not completely rule other sources at the high-energies. 

  • 218. Adriani, O.
    et al.
    Barbarino, G. C.
    Bazilevskaya, G. A.
    Bellotti, R.
    Boezio, M.
    Bogomolov, E. A.
    Bongi, M.
    Bonvicini, V.
    Bottai, S.
    Bruno, A.
    Cafagna, F.
    Campana, D.
    Carbone, R.
    Carlson, Per
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Casolino, M.
    Castellini, G.
    Danilchenko, I. A.
    De Donato, C.
    De Santis, C.
    De Simone, N.
    Di Felice, V.
    Formato, V.
    Galper, A. M.
    Karelin, A. V.
    Koldashov, S. V.
    Koldobskiy, S.
    Krutkov, S. Y.
    Kvashnin, A. N.
    Leonov, A.
    Malakhov, V.
    Marcelli, L.
    Martucci, M.
    Mayorov, A. G.
    Menn, W.
    Merge, M.
    Mikhailov, V. V.
    Mocchiutti, E.
    Monaco, A.
    Mori, N.
    Munini, R.
    Osteria, G.
    Palma, F.
    Panico, B.
    Papini, P.
    Pearce, Mark
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik. Oskar Klein Centre for Cosmoparticle Physics, AlbaNova University Centre, Sweden.
    Picozza, P.
    Pizzolotto, C.
    Ricci, M.
    Ricciarini, S. B.
    Rossetto, L.
    Sarkar, R.
    Scotti, V.
    Simon, M.
    Sparvoli, R.
    Spillantini, P.
    Stozhkov, Y. I.
    Vacchi, A.
    Vannuccini, E.
    Vasilyev, G. I.
    Voronov, S. A.
    Yurkin, Y. T.
    Zampa, G.
    Zampa, N.
    Zverev, V. G.
    Measurement of Boron and Carbon Fluxes in Cosmic Rays with the Pamela Experiment2014Ingår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 791, nr 2, s. 93-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The propagation of cosmic rays inside our galaxy plays a fundamental role in shaping their injection spectra into those observed at Earth. One of the best tools to investigate this issue is the ratio of fluxes for secondary and primary species. The boron-to-carbon (B/C) ratio, in particular, is a sensitive probe to investigate propagation mechanisms. This paper presents new measurements of the absolute fluxes of boron and carbon nuclei as well as the B/C ratio from the PAMELA space experiment. The results span the range 0.44-129 GeV/n in kinetic energy for data taken in the period 2006 July to 2008 March.

  • 219. Adriani, O.
    et al.
    Barbarino, G. C.
    Bazilevskaya, G. A.
    Bellotti, R.
    Boezio, M.
    Bogomolov, E. A.
    Bongi, M.
    Bonvicini, V.
    Bottai, S.
    Bruno, A.
    Cafagna, F.
    Campana, D.
    Carlson, Per
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Casolino, M.
    Castellini, G.
    De Donato, C.
    De Santis, C.
    De Simone, N.
    Di Felice, V.
    Formato, V.
    Galper, A. M.
    Giaccari, U.
    Karelin, A. V.
    Koldashov, S. V.
    Koldobskiy, S.
    Krutkov, S. Y.
    Kvashnin, A. N.
    Leonov, A.
    Malakhov, V.
    Marcelli, L.
    Martucci, M.
    Mayorov, A. G.
    Menn, W.
    Merge, M.
    Mikhailov, V. V.
    Mocchiutti, E.
    Monaco, A.
    Mori, N.
    Munini, R.
    Osteria, G.
    Palma, F.
    Panico, B.
    Papini, P.
    Pearce, Mark
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Picozza, P.
    Ricci, M.
    Ricciarini, S. B.
    Sarkar, R.
    Scotti, V.
    Simon, M.
    Sparvoli, R.
    Spillantini, P.
    Stozhkov, Y. I.
    Vacchi, A.
    Vannuccini, E.
    Vasilyev, G. I.
    Voronov, S. A.
    Yurkin, Y. T.
    Zampa, G.
    Zampa, N.
    SEARCH FOR ANISOTROPIES IN COSMIC-RAY POSITRONS DETECTED BY THE PAMELA EXPERIMENT (vol 811, 21, 2015)2016Ingår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 818, nr 1, artikel-id 100Artikel i tidskrift (Refereegranskat)
  • 220. Adriani, O.
    et al.
    Barbarino, G. C.
    Bazilevskaya, G. A.
    Bellotti, R.
    Boezio, M.
    Bogomolov, E. A.
    Bongi, M.
    Bonvicini, V.
    Bottai, S.
    Bruno, A.
    Cafagna, F.
    Campana, D.
    Carlson, Per
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik. AlbaNova Univ Ctr, Oskar Klein Ctr Cosmoparticle Phys, Stockholm, Sweden.
    Casolino, M.
    Castellini, G.
    De Donato, C.
    De Santis, C.
    De Simone, N.
    Di Felice, V.
    Formato, V.
    Galper, A. M.
    Karelin, A. V.
    Koldashov, S. V.
    Koldobskiy, S.
    Krutkov, S. Y.
    Kvashnin, A. N.
    Leonov, A.
    Malakhov, V.
    Marcelli, L.
    Martucci, M.
    Mayorov, A. G.
    Menn, W.
    Merge, M.
    Mikhailov, V. V.
    Mocchiutti, E.
    Monaco, A.
    Mori, N.
    Munini, R.
    Osteria, G.
    Palma, F.
    Panico, B.
    Papini, P.
    Pearce, Mark
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Picozza, P.
    Ricci, M.
    Ricciarini, S. B.
    Sarkar, R.
    Scotti, V.
    Simon, M.
    Sparvoli, R.
    Spillantini, P.
    Stozhkov, Y. I.
    Vacchi, A.
    Vannuccini, E.
    Vasilyev, G. I.
    Voronov, S. A.
    Yurkin, Y. T.
    Zampa, G.
    Zampa, N.
    Reentrant albedo proton fluxes measured by the PAMELA experiment2015Ingår i: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 120, nr 5, s. 3728-3738Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present a precise measurement of downward going albedo proton fluxes for kinetic energy above similar to 70 MeV performed by the Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA) experiment at an altitude between 350 and 610 km. On the basis of a trajectory tracing simulation, the analyzed protons were classified into quasi-trapped, concentrating in the magnetic equatorial region, and untrapped spreading over all latitudes, including both short-lived (precipitating) and long-lived (pseudotrapped) components. In addition, features of the penumbra region around the geomagnetic cutoff were investigated in detail. PAMELA results significantly improve the characterization of the high-energy albedo proton populations at low-Earth orbits.

  • 221. Adriani, O.
    et al.
    Barbarino, G. C.
    Bazilevskaya, G. A.
    Bellotti, R.
    Boezio, M.
    Bogomolov, E. A.
    Bongi, M.
    Bonvicini, V.
    Bottai, S.
    Bruno, A.
    Cafagna, F.
    Campana, D.
    Carlson, Per
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik. AlbaNova Univ Ctr, Oskar Klein Ctr Cosmoparticle Phys, Stockholm, Sweden.
    Casolino, M.
    Castellini, G.
    De Donato, C.
    De Santis, C.
    De Simone, N.
    Di Felice, V.
    Formato, V.
    Galper, A. M.
    Karelin, A. V.
    Koldashov, S. V.
    Koldobskiy, S.
    Krutkov, S. Y.
    Kvashnin, A. N.
    Leonov, A.
    Malakhov, V.
    Marcelli, L.
    Martucci, M.
    Mayorov, A. G.
    Menn, W.
    Merge, M.
    Mikhailov, V. V.
    Mocchiutti, E.
    Monaco, A.
    Mori, N.
    Munini, R.
    Osteria, G.
    Palma, F.
    Panico, B.
    Papini, P.
    Pearce, Mark
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik. AlbaNova Univ Ctr, Oskar Klein Ctr Cosmoparticle Phys, Stockholm, Sweden.
    Picozza, P.
    Ricci, M.
    Ricciarini, S. B.
    Sarkar, R.
    Scotti, V.
    Simon, M.
    Sparvoli, R.
    Spillantini, P.
    Stozhkov, Y. I.
    Vacchi, A.
    Vannuccini, E.
    Vasilyev, G.
    Voronov, S. A.
    Yurkin, Y. T.
    Zampa, G.
    Zampa, N.
    MEASUREMENTS OF COSMIC-RAY HYDROGEN AND HELIUM ISOTOPES WITH THE PAMELA EXPERIMENT2016Ingår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 818, nr 1, artikel-id 68Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The cosmic-ray hydrogen and helium (H-1, H-2, He-3, He-4) isotopic composition has been measured with the satellite-borne experiment PAMELA, which was launched into low-Earth orbit on board the Resurs-DK1 satellite on 2006 June 15. The rare isotopes H-2 and He-3 in cosmic rays are believed to originate mainly from the interaction of high-energy protons and helium with the galactic interstellar medium. The isotopic composition was measured between 100 and 1100 MeV/n for hydrogen and between 100 and 1400 MeV/n for helium isotopes using two different detector systems over the 23rd solar minimum from 2006 July to 2007 December.

  • 222. Adriani, O.
    et al.
    Barbarino, G. C.
    Carlson, Per
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Gillard, William
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Pearce, Mark
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Rossetto, Laura
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Wu, Juan
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Zampa, G.
    Zampa, N.
    Zverev, V. G.
    Cosmic-Ray Electron Flux Measured by the PAMELA Experiment between 1 and 625 GeV2011Ingår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 106, nr 20, s. 201101-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Precision measurements of the electron component in the cosmic radiation provide important information about the origin and propagation of cosmic rays in the Galaxy. Here we present new results regarding negatively charged electrons between 1 and 625 GeV performed by the satellite-borne experiment PAMELA. This is the first time that cosmic-ray e(-) have been identified above 50 GeV. The electron spectrum can be described with a single power-law energy dependence with spectral index -3.18 +/- 0.05 above the energy region influenced by the solar wind (> 30 GeV). No significant spectral features are observed and the data can be interpreted in terms of conventional diffusive propagation models. However, the data are also consistent with models including new cosmic-ray sources that could explain the rise in the positron fraction.

  • 223. Adriani, O.
    et al.
    Carlson, Per
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Gillard, William
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Pearce, Mark
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Rossetto, Laura
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Wu, Juan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zverev, V. G.
    et al.,
    The discovery of geomagnetically trapped cosmic-ray antiprotons2011Ingår i: Astrophysical Journal Letters, ISSN 2041-8205, Vol. 737, nr 2, s. L29-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The existence of a significant flux of antiprotons confined to Earth's magnetosphere has been considered in several theoretical works. These antiparticles are produced in nuclear interactions of energetic cosmic rays with the terrestrial atmosphere and accumulate in the geomagnetic field at altitudes of several hundred kilometers. A contribution from the decay of albedo antineutrons has been hypothesized in analogy to proton production by neutron decay, which constitutes the main source of trapped protons at energies above some tens of MeV. This Letter reports the discovery of an antiproton radiation belt around the Earth. The trapped antiproton energy spectrum in the South Atlantic Anomaly (SAA) region has been measured by the PAMELA experiment for the kinetic energy range 60-750 MeV. A measurement of the atmospheric sub-cutoff antiproton spectrum outside the radiation belts is also reported. PAMELA data show that the magnetospheric antiproton flux in the SAA exceeds the cosmic-ray antiproton flux by three orders of magnitude at the present solar minimum, and exceeds the sub-cutoff antiproton flux outside radiation belts by four orders of magnitude, constituting the most abundant source of antiprotons near the Earth.

  • 224. Adriani, O.
    et al.
    Carlson, Per
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Pearce, Mark
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Vos, E.E.
    et al.,
    TIME DEPENDENCE of the e- FLUX MEASURED by PAMELA during the 2006 July-2009 DECEMBER SOLAR MINIMUM2015Ingår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 810, nr 2Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Precision measurements of the electron component of cosmic radiation provide important information about the origin and propagation of cosmic rays in the Galaxy not accessible from the study of cosmic-ray nuclear components due to their differing diffusion and energy-loss processes. However, when measured near Earth, the effects of propagation and modulation of Galactic cosmic rays in the heliosphere, particularly significant for energies up to at least 30 GeV, must be properly taken into account. In this paper the electron (e-) spectra measured by the Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics down to 70 MeV from 2006 July to 2009 December over six-month time intervals are presented. Fluxes are compared with a state-of-the-art three-dimensional model of solar modulation that reproduces the observations remarkably well.

  • 225. Adriani, O.
    et al.
    Carlson, Per
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Pearce, Mark
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zampa, N.
    et. al.,
    PAMELA's measurements of geomagnetic cutoff variations during the 14 December 2006 storm2016Ingår i: Space Weather: The International Journal of Research and Application, E-ISSN 1542-7390, Vol. 14, nr 3, s. 210-220Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Data from the Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA) satellite experiment were used to measure the geomagnetic cutoff for high-energy ( 80MeV) protons during the 14 December 2006 geomagnetic storm. The variations of the cutoff latitude as a function of rigidity were studied on relatively short timescales, corresponding to spacecraft orbital periods (approximate to 94 min). Estimated cutoff values were compared with those obtained by means of a trajectory-tracing approach based on a dynamical empirical modeling of the Earth's magnetosphere. We found significant variations in the cutoff latitude, with a maximum suppression of approximate to 7 degrees at lowest rigidities during the main phase of the storm. The observed reduction in the geomagnetic shielding and its temporal evolution were related to the changes in the magnetospheric configuration, investigating the role of interplanetary magnetic field, solar wind, and geomagnetic parameters. PAMELA's results represent the first direct measurement of geomagnetic cutoffs for protons with kinetic energies in the sub-GeV and GeV region.

  • 226. Adriani, O.
    et al.
    Carlson, Per
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik. the Oskar Klein Centre for Cosmoparticle Physics, AlbaNova University Centre.
    Pearce, Mark
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik. the Oskar Klein Centre for Cosmoparticle Physics, AlbaNova University Centre.
    Zverev, V. G.
    et al.,
    TRAPPED proton fluxes at low earth orbits measured by the PAMELA experiment2015Ingår i: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 799, nr 1, s. L4-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report an accurate measurement of the geomagnetically trapped proton fluxes for kinetic energy above similar to 70 MeV performed by the PAMELA mission at low Earth orbits (350 divided by 610 km). Data were analyzed in the frame of the adiabatic theory of charged particle motion in the geomagnetic field. Flux properties were investigated in detail, providing a full characterization of the particle radiation in the South Atlantic Anomaly region, including locations, energy spectra, and pitch angle distributions. PAMELA results significantly improve the description of the Earth's radiation environment at low altitudes, placing important constraints on the trapping and interaction processes, and can be used to validate current trapped particle radiation models.

  • 227. Adriani, O.
    et al.
    Galper, A. M.
    Bonvicini, V.
    Topchiev, N. P.
    Aptekar, R. L.
    Arkhangelskaja, I. V.
    Arkhangelskiy, A. I.
    Bergstrom, L.
    Berti, E.
    Bigongiari, G.
    Bobkov, S. G.
    Boezio, M.
    Bogomolov, E. A.
    Bonechi, S.
    Bongi, M.
    Bottai, S.
    Boyarchuk, K. A.
    Castellini, G.
    Cattaneo, P. W.
    Cumani, P.
    Dedenko, G. L.
    De Donato, C.
    Dogiel, V. A.
    Gorbunov, M. S.
    Gusakov, Y. U. V.
    Hnatyk, B. I.
    Kadilin, V. V.
    Kaplin, V. A.
    Kaplun, A. A.
    Kheymits, M. D.
    Korepanov, V. E.
    Larsson, Josefin
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Leonov, A. A.
    Loginov, V. A.
    Longo, F.
    Maestro, P.
    Marrocchesi, P. S.
    Mikhailov, V. V.
    Mocchiutti, E.
    Moiseev, A. A.
    Mori, N.
    Moskalenko, I. V.
    Naumov, P. Y. U.
    Papini, P.
    Pearce, M.
    Picozza, P.
    Popov, A. V.
    Rappoldi, A.
    Ricciarini, S.
    Runtso, M. F.
    Ryde, F.
    Serdin, O. V.
    Sparvoli, R.
    Spillantini, P.
    Suchkov, S. I.
    Tavani, M.
    Taraskin, A. A.
    Tiberio, A.
    Tyurin, E. M.
    Ulanov, M. V.
    Vacchi, A.
    Vannuccini, E.
    Vasilyev, G. I.
    Yurkin, Y. U. T.
    Zampa, N.
    Zirakashvili, V. N.
    Zverev, V. G.
    The gamma-400 space observatory: Status and perspectives2014Ingår i: Proceedings of Science, Sissa Medialab Srl , 2014Konferensbidrag (Refereegranskat)
    Abstract [en]

    The present design of the new space observatory GAMMA-400 is presented in this paper. The instrument has been designed for the optimal detection of gamma rays in a broad energy range (from ∼100 MeV up to 3 TeV), with excellent angular and energy resolution. The observatory will also allow precise and high statistic studies of the electron component in the cosmic rays up to the multi TeV region, as well as protons and nuclei spectra up to the knee region. The GAMMA-400 observatory will allow to address a broad range of science topics, like search for signatures of dark matter, studies of Galactic and extragalactic gamma-ray sources, Galactic and extragalactic diffuse emission, gamma-ray bursts and charged cosmic rays acceleration and diffusion mechanism up to the knee. 

  • 228.
    Adriani, O.
    et al.
    Universitá di Firenze and Istituto Nazionale di Fisica Nucleare, Sezione di Firenze, Firenze, Italy.
    Pearce, Mark
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Ryde, Felix
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zhu, K. J.
    Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, China.
    Gamma-ray performance study of the HERD payload2022Ingår i: 37th International Cosmic Ray Conference, ICRC 2021, Sissa Medialab Srl , 2022, artikel-id 651Konferensbidrag (Refereegranskat)
    Abstract [en]

    The High Energy cosmic-Radiation Detection (HERD) facility has been proposed as a space astronomy payload onboard the future China's Space Station. HERD is planned for operation starting around 2027 for about 10 years In addition to the unprecedented sensitivity for dark matter searches and cosmic-ray measurements up to the knee energy, it should perform gamma-ray monitoring and full sky survey from few hundred MeV up to tens of TeV. We present the first study of the HERD gamma-ray performance obtained with full simulations of the whole detector geometry. HERD will be a cubic detector composed with 5 active faces. We present a study conducted inside the HERD analysis software package, which includes a detailed description of the detector materials. In this work we present the HERD effective area, the point spread function and the resulting gamma-ray sensitivity.

  • 229. Agarwal, Abhishek
    et al.
    Lipstein, Arthur E.
    Young, Donovan
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Scattering amplitudes of massive N = 2 gauge theories in three dimensions2014Ingår i: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 89, nr 4, s. 045020-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We study the scattering amplitudes of mass-deformed Chern-Simons theories and Yang-Mills-Chern-Simons theories with N = 2 supersymmetry in three dimensions. In particular, we derive the on-shell supersymmetry algebras which underlie the scattering matrices of these theories. We then compute various 3 and 4-point on-shell tree-level amplitudes in these theories. For the mass-deformed Chern-Simons theory, odd-point amplitudes vanish and we find that all of the 4-point amplitudes can be encoded elegantly in superamplitudes. For the Yang-Mills-Chern-Simons theory, we obtain all of the 4-point tree-level amplitudes using a combination of perturbative techniques and algebraic constraints and we comment on difficulties related to computing amplitudes with external gauge fields using Feynman diagrams. Finally, we propose a Britto-Cachazo-Feng-Witten recursion relation for mass-deformed theories in three dimensions and discuss the applicability of this proposal to mass-deformed N = 2 theories.

  • 230.
    Agarwal, Sahil
    et al.
    Yale Univ, Program Appl Math, New Haven, CT 06520 USA..
    Wettlaufer, John
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. Yale Univ, Program Appl Math, New Haven, CT 06520 USA.;Royal Inst Technol, Nordita, SE-10691 Stockholm, Sweden.;Stockholm Univ, SE-10691 Stockholm, Sweden..
    Minimal Data Fidelity for Stellar Feature and Companion Detection2022Ingår i: Astronomical Journal, ISSN 0004-6256, E-ISSN 1538-3881, Vol. 163, nr 1, s. 6-, artikel-id 6Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Technological advances in instrumentation have led to an exponential increase in exoplanet detection and scrutiny of stellar features such as spots and faculae. While the spots and faculae enable us to understand the stellar dynamics, exoplanets provide us with a glimpse into stellar evolution. While the ubiquity of noise (e.g., telluric, instrumental, or photonic) is unavoidable, combining this with increased spectrographic resolution compounds technological challenges. To account for these noise sources and resolution issues, we use a temporal multifractal framework to study data from the Spot Oscillation And Planet 2.0 tool, which simulates a stellar spectrum in the presence of a spot, a facula or a planet. Given these controlled simulations, we vary the resolution as well as the signal-to-noise ratio (S/N) to obtain a lower limit on the resolution and S/N required to robustly detect features. We show that a spot and a facula with a 1% coverage of the stellar disk can be robustly detected for a S/N (per pixel) of 35 and 60, respectively, for any spectral resolution above 20,000, while a planet with a radial velocity of 10 m s(-1) can be detected for a S/N (per pixel) of 600. Rather than viewing noise as an impediment, our approach uses noise as a source of information.

  • 231. Aghamin, N.
    et al.
    Bracco, Andrea
    Nordita SU.
    Zonca, A.
    et al.,
    Planck 2018 results: XII. Galactic astrophysics using polarized dustemission2020Ingår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 641, artikel-id A12Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Observations of the submillimetre emission from Galactic dust, in both total intensity I and polarization, have received tremendous interest thanks to the Planck full-sky maps. In this paper we make use of such full-sky maps of dust polarized emission produced from the third public release of Planck data. As the basis for expanding on astrophysical studies of the polarized thermal emission from Galactic dust, we present full-sky maps of the dust polarization fraction p, polarization angle psi, and dispersion function of polarization angles ?. The joint distribution (one-point statistics) of p and N-H confirms that the mean and maximum polarization fractions decrease with increasing N-H. The uncertainty on the maximum observed polarization fraction,(max) = 22.0(-1.4)(+3.5)pmax= 22 .0- 1.4+ 3.5% at 353 GHz and 80 ' resolution, is dominated by the uncertainty on the Galactic emission zero level in total intensity, in particular towards diffuse lines of sight at high Galactic latitudes. Furthermore, the inverse behaviour between p and ? found earlier is seen to be present at high latitudes. This follows the ?proportional to p(-1) relationship expected from models of the polarized sky (including numerical simulations of magnetohydrodynamical turbulence) that include effects from only the topology of the turbulent magnetic field, but otherwise have uniform alignment and dust properties. Thus, the statistical properties of p, psi, and ? for the most part reflect the structure of the Galactic magnetic field. Nevertheless, we search for potential signatures of varying grain alignment and dust properties. First, we analyse the product map ?xp, looking for residual trends. While the polarization fraction p decreases by a factor of 3-4 between N-H=10(20) cm(-2) and N-H=2x10(22) cm(-2), out of the Galactic plane, this product ?xp only decreases by about 25%. Because ? is independent of the grain alignment efficiency, this demonstrates that the systematic decrease in p with N-H is determined mostly by the magnetic-field structure and not by a drop in grain alignment. This systematic trend is observed both in the diffuse interstellar medium (ISM) and in molecular clouds of the Gould Belt. Second, we look for a dependence of polarization properties on the dust temperature, as we would expect from the radiative alignment torque (RAT) theory. We find no systematic trend of ?xp with the dust temperature T-d, whether in the diffuse ISM or in the molecular clouds of the Gould Belt. In the diffuse ISM, lines of sight with high polarization fraction p and low polarization angle dispersion ? tend, on the contrary, to have colder dust than lines of sight with low p and high ?. We also compare the Planck thermal dust polarization with starlight polarization data in the visible at high Galactic latitudes. The agreement in polarization angles is remarkable, and is consistent with what we expect from the noise and the observed dispersion of polarization angles in the visible on the scale of the Planck beam. The two polarization emission-to-extinction ratios, R-P/p and R-S/V, which primarily characterize dust optical properties, have only a weak dependence on the column density, and converge towards the values previously determined for translucent lines of sight. We also determine an upper limit for the polarization fraction in extinction, p(V)/E(B-V), of 13% at high Galactic latitude, compatible with the polarization fraction p approximate to 20% observed at 353 GHz. Taken together, these results provide strong constraints for models of Galactic dust in diffuse gas.

  • 232. Aharonian, F.
    et al.
    Akhperjanian, A. G.
    Anton, G.
    Barres De Almeida, U.
    Bazer-Bachi, A. R.
    Becherini, Y.
    Behera, B.
    Bernloehr, K.
    Boisson, C.
    Bochow, A.
    Borrel, V.
    Brion, E.
    Brucker, J.
    Brun, P.
    Buehler, R.
    Bulik, T.
    Buesching, I.
    Boutelier, T.
    Chadwick, P. M.
    Charbonnier, A.
    Chaves, R. C. G.
    Cheesebrough, A.
    Chounet, L. -M
    Clapson, A. C.
    Coignet, G.
    Dalton, M.
    Daniel, M. K.
    Davids, I. D.
    Degrange, B.
    Deil, C.
    Dickinson, H. J.
    Djannati-Ata, A.
    Domainko, W.
    O'C. Drury, L.
    Dubois, F.
    Dubus, G.
    Dyks, J.
    Dyrda, M.
    Egberts, K.
    Emmanoulopoulos, D.
    Espigat, P.
    Farnier, C.
    Feinstein, F.
    Fiasson, A.
    Foerster, A.
    Fontaine, G.
    Fuessling, M.
    Gabici, S.
    Gallant, Y. A.
    Gerard, L.
    Giebels, B.
    Glicenstein, J. F.
    Glueck, B.
    Goret, P.
    Goehring, D.
    Hauser, D.
    Hauser, M.
    Heinz, S.
    Heinzelmann, G.
    Henri, G.
    Hermann, G.
    Hinton, J. A.
    Hoffmann, A.
    Hofmann, W.
    Holleran, M.
    Hoppe, S.
    Horns, D.
    Jacholkowska, A.
    De Jager, O. C.
    Jahn, C.
    Jung, I.
    Katarzyński, K.
    Katz, U.
    Kaufmann, S.
    Kendziorra, E.
    Kerschhaggl, M.
    Khangulyan, D.
    Khélifi, B.
    Keogh, D.
    Kluzniak, W.
    Komin, N.
    Kosack, K.
    Lamanna, G.
    Lenain, J. -P
    Lohse, T.
    Marandon, V.
    Martin, J. M.
    Martineau-Huynh, O.
    Marcowith, A.
    Maurin, D.
    McComb, T. J. L.
    Medina, M. C.
    Moderski, R.
    Moulin, E.
    Naumann-Godo, M.
    De Naurois, M.
    Nedbal, D.
    Nekrassov, D.
    Niemiec, J.
    Nolan, S. J.
    Ohm, S.
    Olive, J. -F
    De Wilhelmi, E.
    Orford, K. J.
    Ostrowski, M.
    Panter, M.
    Arribas, M. P.
    Pedaletti, G.
    Pelletier, G.
    Petrucci, P. -O
    Pita, S.
    Paehlhofer, G.
    Punch, M.
    Quirrenbach, A.
    Raubenheimer, B. C.
    Raue, M.
    Rayner, S. M.
    Renaud, M.
    Rieger, F.
    Ripken, J.
    Rob, L.
    Rosier-Lees, S.
    Rowell, G.
    Rudak, B.
    Rulten, C. B.
    Ruppel, J.
    Sahakian, V.
    Santangelo, A.
    Schlickeiser, R.
    Schock, F. M.
    Schröder, R.
    Schwanke, U.
    Schwarzburg, S.
    Schwemmer, S.
    Shalchi, A.
    Sikora, M.
    Skilton, J. L.
    Sol, H.
    Spangler, D.
    Stawarz, Ł.
    Steenkamp, R.
    Stegmann, C.
    Superina, G.
    Szostek, A.
    Tam, P. H.
    Tavernet, J. -P
    Terrier, R.
    Tibolla, O.
    Van Eldik, C.
    Vasileiadis, G.
    Venter, C.
    Venter, L.
    Vialle, J. P.
    Vincent, P.
    Vivier, M.
    Vaelk, H. J.
    Volpe, F.
    Wagner, S. J.
    Ward, M.
    Zdziarski, A. A.
    Zech, A.
    Abdo, A. A.
    Ackermann, M.
    Ajello, M.
    Atwood, W. B.
    Axelsson, Magnus
    Department of Astronomy, Stockholm University.
    Baldini, L.
    Ballet, J.
    Barbiellini, G.
    Baring, M. G.
    Bastieri, D.
    Battelino, Milan
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Baughman, B. M.
    Bechtol, K.
    Bellazzini, R.
    Berenji, B.
    Bloom, E. D.
    Bonamente, E.
    Borgland, A. W.
    Bregeon, J.
    Brez, A.
    Brigida, M.
    Bruel, P.
    Caliandro, G. A.
    Cameron, R. A.
    Caraveo, P. A.
    Casandjian, J. M.
    Cavazzuti, E.
    Cecchi, C.
    Charles, E.
    Chekhtman, A.
    Chen, A. W.
    Cheung, C. C.
    Chiang, J.
    Ciprini, S.
    Claus, R.
    Cohen-Tanugi, J.
    Colafrancesco, S.
    Conrad, Jan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Costamante, L.
    Cutini, S.
    Dermer, C. D.
    De Angelis, A.
    De Palma, F.
    Digel, S. W.
    Do Couto E Silva, E.
    Drell, P. S.
    Dubois, R.
    Dumora, D.
    Favuzzi, C.
    Fegan, S. J.
    Ferrara, E. C.
    Fleury, P.
    Focke, W. B.
    Frailis, M.
    Fukazawa, Y.
    Funk, S.
    Fusco, P.
    Gargano, F.
    Gasparrini, D.
    Gehrels, N.
    Germani, S.
    Giglietto, N.
    Giordano, F.
    Grondin, M. -H
    Grove, J. E.
    Guillemot, L.
    Guiriec, S.
    Hanabata, Y.
    Harding, A. K.
    Hayashida, M.
    Hays, E.
    Horan, D.
    Jóhannesson, G.
    Johnson, A. S.
    Johnson, R. P.
    Johnson, W. N.
    Kadler, M.
    Kamae, T.
    Katagiri, H.
    Kataoka, J.
    Kerr, M.
    Knödlseder, J.
    Kuehn, F.
    Kuss, M.
    Lande, J.
    Latronico, L.
    Lee, S. -H
    Lemoine-Goumard, M.
    Longo, F.
    Loparco, F.
    Lott, B.
    Lovellette, M. N.
    Madejski, G. M.
    Makeev, A.
    Mazziotta, M. N.
    McEnery, J. E.
    Meurer, C.
    Michelson, P. F.
    Mitthumsiri, W.
    Mizuno, T.
    Moiseev, A. A.
    Monte, C.
    Monzani, M. E.
    Morselli, A.
    Moskalenko, I. V.
    Murgia, S.
    Nolan, P. L.
    Nuss, E.
    Ohsugi, T.
    Omodei, N.
    Orlando, E.
    Ormes, J. F.
    Paneque, D.
    Panetta, J. H.
    Parent, D.
    Pelassa, V.
    Pepe, M.
    Pesce-Rollins, M.
    Piron, F.
    Porter, T. A.
    Rainò, S.
    Razzano, M.
    Reimer, A.
    Reimer, O.
    Reposeur, T.
    Ritz, S.
    Rodriguez, A. Y.
    Ryde, Felix
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Sadrozinski, H. F. -W
    Sanchez, D.
    Sander, A.
    Scargle, J. D.
    Schalk, T. L.
    Sellerholm, A.
    Sgro, C.
    Shaw, M.
    Smith, D. A.
    Spandre, G.
    Spinelli, P.
    Starck, J. -L
    Strickman, M. S.
    Tajima, H.
    Takahashi, H.
    Takahashi, T.
    Tanaka, T.
    Thayer, J. G.
    Thompson, D. J.
    Tibaldo, L.
    Torres, D. F.
    Tosti, G.
    Tramacere, A.
    Uchiyama, Y.
    Usher, T. L.
    Vilchez, N.
    Villata, M.
    Vitale, V.
    Waite, A. P.
    Wood, K. S.
    Ylinen, Tomi
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Ziegler, M.
    Simultaneous observations of pks 2155-304 with hess, fermi, rxte, and atom: Spectral energy distributions and variability in a low state2009Ingår i: Astrophysical Journal Letters, ISSN 2041-8205, Vol. 696, nr 2 PART 2, s. L150-L155Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report on the first simultaneous observations that cover the optical, X-ray, and high-energy gamma-ray bands of the BL Lac object PKS 2155-304. The gamma-ray bands were observed for 11 days, between 2008 August 25 and 2008 September 6 (MJD 54704-54715), jointly with the Fermi Gamma-ray Space Telescope and the HESS atmospheric Cherenkov array, providing the first simultaneous MeV-TeV spectral energy distribution (SED) with the new generation of gamma-ray telescopes. The ATOM telescope and the RXTE and Swift observatories provided optical and X-ray coverage of the low-energy component over the same time period. The object was close to the lowest archival X-ray and very high energy (VHE; > 100 GeV) state, whereas the optical flux was much higher. The light curves show relatively little (similar to 30%) variability overall when compared to past flaring episodes, but we find a clear optical/VHE correlation and evidence for a correlation of the X-rays with the high-energy spectral index. Contrary to previous observations in the flaring state, we do not find any correlation between the X-ray and VHE components. Although synchrotron self-Compton models are often invoked to explain the SEDs of BL Lac objects, the most common versions of these models are at odds with the correlated variability we find in the various bands for PKS 2155-304.

  • 233.
    Ahlgren, Björn
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Investigating subphotospheric dissipation in gamma-ray bursts by fitting a physical model2019Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Ladda ner fulltext (pdf)
    Thesis
  • 234.
    Ahlgren, Björn
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Subphotospheric dissipation in gamma-ray bursts observed by the Fermi Gamma-ray Space Telescope2016Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Gamma-ray bursts (GRBs) are the brightest events in the Universe, for a short time outshining the rest of the Universe combined, as they explode with isotropic equivalent luminosities up to $10^{54}$ erg s$^{-1}$. These events are believed to be connected to supernovae and to binary compact object mergers, such as binary neutron stars or neutron star -- black hole systems. The origin of the so-called prompt emission in GRBs remains an unsolved problem, although some progress is being made. Spectral analysis of prompt emission has traditionally been performed with the Band function, an empirical model with no physical interpretation, and it is just recently that physical models have started to be fitted to data. This thesis presents spectral analysis of GRB data from the Fermi Gamma-ray Space Telescope using a physical model for subphotospheric dissipation. The model is developed using a numerical code and implemented as a table model in {\scriptsize XSPEC}. Paper \rom{1} presents the model and provides a proof-of-concept of fitting GRB data with such a model. Specifically, two GRBs are fitted and compared with the corresponding Band function fits. In paper \rom{2}, a sample of 37 bursts are fitted with an extended version of the model and improved analysis tools. Overall, about a third of the fitted spectra can be described by the model. From these fits it is concluded that the scenario of subphotospheric dissipation can describe all spectral shapes present in the sample. The key characteristic of the spectra that are not fitted by the model is that they are very luminous. Within the context of the model, this suggests that the assumption of internal shocks as a dissipation mechanism cannot explain the full population of GRBs. Alternatively, additional emission components may required. The thesis concludes that subphotospheric dissipation is viable as a possible origin of GRB prompt emission. Furthermore, it shows the importance of using physically motivated models when analysing GRBs.

    Ladda ner fulltext (pdf)
    fulltext
  • 235.
    Ahlgren, Björn
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Subphotospheric dissipation in GRBs: fits to Fermi data constrain the dissipation scenario and reveal correlationsManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

     The emission mechanisms that give rise to the prompt emission in gamma-ray bursts (GRBs) is one of the main open questions in understanding these extreme explosions.

    We consider a model for subphotospheric dissipation which produces non-thermal spectra from the photosphere, by letting kinetic energy of the outow dissipate below the photosphere using a dissipation mechanism based on internal shocks. Building on the work of Ahlgren et al. (2015), we expand the model parameter space, compensate for adiabatic cooling, and improve the analysis tools. We create two table models for two dierent scenarios regarding the magnetisation, corresponding to no and moderate synchrotron emission, respectively. We t the models to time-resolved spectra of a sample of 37 Fermi GRBs and nd that  approximately a third of the spectra can be described by the models. From these ts we conclude that the scenario of subphotospheric dissipation can describe all spectral shapes present in the sample. However, we are not able to discriminate between no and moderate synchrotron emission. The key characteristic of spectra which are not tted by the model is that they are very luminous. Within the context of our model, we conclude that this is due to the assumption of internal shocks as a dissipation mechanism. Alternatively, some of these luminous bursts may require additional emission components.

  • 236.
    Ahlgren, Björn
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Larsson, Josefin
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    A Search for Lensed Gamma-Ray Bursts in 11 yr of Observations by Fermi GBM2020Ingår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 897, nr 2, artikel-id 178Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Macrolensing of gamma-ray bursts (GRBs) is expected to manifest as a GRB recurring with the same light curve and spectrum as a previous one, but with a different flux and a slightly offset position. Identifying such lensed GRBs may give important information about the lenses, the cosmology, and the GRBs themselves. Here we present a search for lensed GRBs among similar to 2700 GRBs observed by the Fermi Gamma-ray Burst Monitor during 11 yr of operations. To identify lensed GRBs, we perform initial cuts on position, time-averaged spectral properties, and relative duration. We then use the cross-correlation function to assess the similarity of light curves, and finally we analyze the time-resolved spectra of the most promising candidates. We find no convincing lens candidates. The most similar pairs are single-pulsed GRBs with relatively few time bins for the spectral analysis. This is best explained by similarities within the GRB population rather than lensing. However, the null result does not rule out the presence of macrolensed GRBs in the sample. In particular, we find that observational uncertainties and Poisson fluctuations can lead to significant differences within a pair of lensed GRBs.

  • 237.
    Ahlgren, Björn
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Larsson, Josefin
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Ahlberg, Erik
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lundman, Christoffer
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Ryde, Felix
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Pe'er, Asaf
    Testing a model for subphotospheric dissipation in GRBs: fits to Fermi data constrain the dissipation scenario2019Ingår i: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 485, s. 474-497Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    It has been suggested that the prompt emission in gamma-ray bursts (GRBs) could be described by radiation from the photosphere in a hot fireball. Such models must be tested by directly fitting them to data. In this work we use data from the Fermi Gamma-ray Space Telescope and consider a specific photospheric model, in which the kinetic energy of a low-magnetization outflow is dissipated locally by internal shocks below the photosphere. We construct a table model with a physically motivated parameter space and fit it to time-resolved spectra of the 36 brightest Fermi GRBs with a known redshift. We find that about two-thirds of the examined spectra cannot be described by the model, as it typically underpredicts the observed flux. However, since the sample is strongly biased towards bright GRBs, we argue that this fraction will be significantly lowered when considering the full population. From the successful fits we find that the model can reproduce the full range of spectral slopes present in the sample. For these cases we also find that the dissipation consistently occurs at a radius of ∼1012 cm and that only a few per cent efficiency is required. Furthermore, we find a positive correlation between the fireball luminosity and the Lorentz factor. Such a correlation has been previously reported by independent methods. We conclude that if GRB spectra are due to photospheric emission, the dissipation cannot only be the specific scenario we consider here.

  • 238.
    Ahlgren, Björn
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Larsson, Josefin
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Valan, Vlasta
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Mortlock, Daniel
    Ryde, Felix
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Pe'er, Asaf
    Constraining subphotospheric dissipation in Gamma-ray Bursts using joint Fermi-Swift observationsManuskript (preprint) (Övrigt vetenskapligt)
  • 239.
    Ahlgren, Björn
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Larsson, Josefin
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Valan, Vlasta
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Mortlock, Daniel
    Imperial Coll London, Dept Math, Stat Sect, London SW7 2AZ, England.;Imperial Coll London, Astrophys Grp, Blackett Lab, Prince Consort Rd, London SW7 2AZ, England.;Stockholm Univ, Dept Astron, SE-10691 Stockholm, Sweden.;Oscar Klein Ctr Alballova, SE-10691 Stockholm, Sweden..
    Ryde, Felix
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Pe'er, Asaf
    Univ Coll Cork, Phys Dept, Cork, Ireland..
    Investigating Subphotospheric Dissipation in Gamma-Ray Bursts Using Joint Fermi-Swift Observations2019Ingår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 880, nr 2, artikel-id 76Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The jet photosphere has been proposed as the origin for the gamma-ray burst (GRB) prompt emission. In many such models, characteristic features in the spectra appear below the energy range of the Fermi Gamma-ray Burst Monitor (GBM) detectors, so joint fits with X-ray data are important in order to assess the photospheric scenario. Here we consider a particular photospheric model which assumes localized subphotospheric dissipation by internal shocks in a non-magnetized outflow. We investigate it using Bayesian inference and a sample of eight GRBs with known redshifts which are observed simultaneously with Fermi GBM and the Swift X-ray Telescope (XRT). This provides us with an energy range of 0.3. keV-40. MeV and much tighter parameter constraints. We analyze 32 spectra and find that 16 are well described by the model. We also find that the estimates of the bulk Lorentz factor, Gamma, and the fireball luminosity, L-0,L-52, decrease while the fraction of dissipated energy, epsilon(d), increases in the joint fits compared to GBM-only fits. These changes are caused by a small excess of counts in the XRT data, relative to the model predictions from fits to GBM-only data. The fact that our limited implementation of the physical scenario yields 50% accepted spectra is promising, and we discuss possible model revisions in the light of the new data. Specifically, we argue that the inclusion of significant magnetization, as well as removing the assumption of internal shocks, will provide better fits at low energies.

  • 240.
    Ahlström Kjerrgren, Anders
    et al.
    KTH.
    Mortsell, Edvard
    Stockholm Univ, Oskar Klein Ctr, Dept Phys, SE-10691 Stockholm, Sweden..
    On the use of galaxies as clocks and the universal expansion2023Ingår i: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 518, nr 1, s. 585-591Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We set out to rederive the 8 Hubble parameter values obtained from estimated relative galaxy ages by Simon et al. We find that to obtain the level of precision claimed in H(z), unrealistically small galaxy age uncertainties have to be assumed. Also, some parameter values will be correlated. In our analysis we find that the uncertainties in the Hubble parameter values are significantly larger when 8 independent H(z) are obtained using Monte Carlo sampling. Smaller uncertainties can be obtained using Gaussian processes, but at the cost of strongly correlated results. We do not obtain any useful constraints on the Hubble parameter from the galaxy data employed.

  • 241.
    Ahnen, M. L.
    et al.
    Swiss Fed Inst Technol, CH-8093 Zurich, Switzerland..
    Jóhannesson, Gudlaugur
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Larsson, Stefan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Yassine, M.
    Ist Nazl Fis Nucl, Sez Trieste, I-34127 Trieste, Italy.;Univ Trieste, Dipartimento Fis, I-34127 Trieste, Italy..
    et al.,
    MAGIC and Fermi-LAT gamma-ray results on unassociated HAWC sources2019Ingår i: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 485, nr 1, s. 356-366Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The HAWC Collaboration released the 2HWC catalogue of TeV sources, in which 19 show no association with any known high-energy (HE; E greater than or similar to 10 GeV) or very-high-energy (VHE; E greater than or similar to 300 GeV) sources. This catalogue motivated follow-up studies by both the Major Atmospheric Gamma-ray Imaging Cherenkov (MAGIC) and Fermi-LAT (Large Area Telescope) observatories with the aim of investigating gamma-ray emission over a broad energy band. In this paper, we report the results from the first joint work between High Altitude Water Cherenkov (HAWC), MAGIC, and Fermi-LAT on three unassociated HAWC sources: 2HWC J2006+341, 2HWC J1907+084*, and 2HWC J1852+013*. Although no significant detection was found in the HE and VHE regimes, this investigation shows that a minimum 1 degrees extension (at 95 per cent confidence level) and harder spectrum in the GeV than the one extrapolated from HAWC results are required in the case of 2HWC J1852+013*, whilst a simply minimum extension of 0.16 degrees (at 95 per cent confidence level) can already explain the scenario proposed by HAWC for the remaining sources. Moreover, the hypothesis that these sources are pulsar wind nebulae is also investigated in detail.

  • 242. Ahnen, Max L.
    et al.
    Larsson, Stefan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik. Oskar Klein Centre for Cosmoparticle Physics, AlbaNova, Stockholm, Sweden.
    Li, Liang
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik. Oskar Klein Centre for Cosmoparticle Physics, AlbaNova, Stockholm, Sweden.
    Zottmann, N.
    et al.,
    VERY HIGH ENERGY γ-RAYS from the UNIVERSE'S MIDDLE AGEMAGIC: DETECTION of the z = 0.940 BLAZAR PKS 1441+25 with MAGIC2015Ingår i: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 815, nr 2, artikel-id L23Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The flat-spectrum radio quasar PKS 1441+25 at a redshift of z = 0.940 is detected between 40 and 250 GeV with a significance of 25.5σ using the MAGIC telescopes. Together with the gravitationally lensed blazar QSO B0218+357 (z = 0.944), PKS 1441+25 is the most distant very high energy (VHE) blazar detected to date. The observations were triggered by an outburst in 2015 April seen at GeV energies with the Large Area Telescope on board Fermi. Multi-wavelength observations suggest a subdivision of the high state into two distinct flux states. In the band covered by MAGIC, the variability timescale is estimated to be 6.4 ±1.9 days. Modeling the broadband spectral energy distribution with an external Compton model, the location of the emitting region is understood as originating in the jet outside the broad-line region (BLR) during the period of high activity, while being partially within the BLR during the period of low (typical) activity. The observed VHE spectrum during the highest activity is used to probe the extragalactic background light at an unprecedented distance scale for ground-based gamma-ray astronomy.

  • 243. Ahumada, T.
    et al.
    Singer, L. P.
    Anand, S.
    Coughlin, M. W.
    Kasliwal, M. M.
    Ryan, G.
    Andreoni, I.
    Cenko, S. B.
    Fremling, C.
    Kumar, H.
    Pang, P. T. H.
    Burns, E.
    Cunningham, V.
    Dichiara, S.
    Dietrich, T.
    Svinkin, D. S.
    Almualla, M.
    Castro-Tirado, A. J.
    De, K.
    Dunwoody, R.
    Gatkine, P.
    Hammerstein, E.
    Iyyani, S.
    Mangan, J.
    Perley, D.
    Purkayastha, S.
    Bellm, E.
    Bhalerao, V.
    Bolin, B.
    Bulla, Mattia
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Cannella, C.
    Chandra, P.
    Duev, D. A.
    Frederiks, D.
    Gal-Yam, A.
    Graham, M.
    Ho, A. Y. Q.
    Hurley, K.
    Karambelkar, V.
    Kool, E. C.
    Kulkarni, S. R.
    Mahabal, A.
    Masci, F.
    McBreen, S.
    Pandey, S. B.
    Reusch, S.
    Ridnaia, A.
    Rosnet, P.
    Rusholme, B.
    Carracedo, A. S.
    Smith, R.
    Soumagnac, M.
    Stein, R.
    Troja, E.
    Tsvetkova, A.
    Walters, R.
    Valeev, A. F.
    Discovery and confirmation of the shortest gamma-ray burst from a collapsar2021Ingår i: Nature Astronomy, E-ISSN 2397-3366, Vol. 5, nr 9, s. 917-927Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Gamma-ray bursts (GRBs) are among the brightest and most energetic events in the Universe. The duration and hardness distribution of GRBs has two clusters1, now understood to reflect (at least) two different progenitors2. Short-hard GRBs (SGRBs; T90 < 2 s) arise from compact binary mergers, and long-soft GRBs (LGRBs; T90 > 2 s) have been attributed to the collapse of peculiar massive stars (collapsars)3. The discovery of SN 1998bw/GRB 980425 (ref. 4) marked the first association of an LGRB with a collapsar, and AT 2017gfo (ref. 5)/GRB 170817A/GW170817 (ref. 6) marked the first association of an SGRB with a binary neutron star merger, which also produced a gravitational wave. Here, we present the discovery of ZTF20abwysqy (AT2020scz), a fast-fading optical transient in the Fermi satellite and the Interplanetary Network localization regions of GRB 200826A; X-ray and radio emission further confirm that this is the afterglow. Follow-up imaging (at rest-frame 16.5 days) reveals excess emission above the afterglow that cannot be explained as an underlying kilonova, but which is consistent with being the supernova. Although the GRB duration is short (rest-frame T90 of 0.65 s), our panchromatic follow-up data confirm a collapsar origin. GRB 200826A is the shortest LGRB found with an associated collapsar; it appears to sit on the brink between a successful and a failed collapsar. Our discovery is consistent with the hypothesis that most collapsars fail to produce ultra-relativistic jets.

  • 244. Ajello, M.
    et al.
    Albert, A.
    Allafort, A.
    Baldini, L.
    Barbiellini, G.
    Bastieri, D.
    Bellazzini, R.
    Bissaldi, E.
    Bonamente, E.
    Brandt, T. J.
    Bregeon, J.
    Brigida, M.
    Bruel, P.
    Buehler, R.
    Buson, S.
    Caliandro, G. A.
    Cameron, R. A.
    Caraveo, P. A.
    Cecchi, C.
    Charles, E.
    Chekhtman, A.
    Chiang, J.
    Chiaro, G.
    Ciprini, S.
    Claus, R.
    Cohen-Tanugi, J.
    Cominsky, L. R.
    Conrad, J.
    Cutini, S.
    D'Ammando, F.
    de Palma, F.
    Dermer, C. D.
    Desiante, R.
    Digel, S. W.
    do Couto e Silva, E.
    Drell, P. S.
    Drlica-Wagner, A.
    Favuzzi, C.
    Focke, W. B.
    Franckowiak, A.
    Fukazawa, Y.
    Fusco, P.
    Gargano, F.
    Gasparrini, D.
    Germani, S.
    Giglietto, N.
    Giommi, P.
    Giordano, F.
    Giroletti, M.
    Glanzman, T.
    Godfrey, G.
    Grenier, I. A.
    Grove, J. E.
    Guiriec, S.
    Hadasch, D.
    Hayashida, M.
    Hays, E.
    Horan, D.
    Hou, X.
    Hughes, R. E.
    Inoue, Y.
    Jackson, Miranda S.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Jogler, T.
    Johannesson, G.
    Johnson, A. S.
    Johnson, W. N.
    Kamae, T.
    Knoedlseder, J.
    Kocevski, D.
    Kuss, M.
    Lande, J.
    Larsson, S.
    Latronico, L.
    Longo, F.
    Loparco, F.
    Lott, B.
    Lovellette, M. N.
    Lubrano, P.
    Mayer, M.
    Mazziotta, M. N.
    McEnery, J. E.
    Michelson, P. F.
    Mizuno, T.
    Moiseev, A. A.
    Monte, C.
    Monzani, M. E.
    Morselli, A.
    Moskalenko, I. V.
    Murgia, S.
    Murphy, R.
    Nakamori, T.
    Nemmen, R.
    Nuss, E.
    Ohno, M.
    Ohsugi, T.
    Omodei, N.
    Orienti, M.
    Orlando, E.
    Ormes, J. F.
    Paneque, D.
    Panetta, J. H.
    Perkins, J. S.
    Pesce-Rollins, M.
    Petrosian, V.
    Piron, F.
    Pivato, G.
    Porter, T. A.
    Raino, S.
    Rando, R.
    Razzano, M.
    Reimer, A.
    Reimer, O.
    Roth, M.
    Schulz, A.
    Sgro, C.
    Siskind, E. J.
    Spandre, G.
    Spinelli, P.
    Takahashi, H.
    Thayer, J. G.
    Thayer, J. B.
    Thompson, D. J.
    Tibaldo, L.
    Tinivella, M.
    Tosti, G.
    Troja, E.
    Usher, T. L.
    Vandenbroucke, J.
    Vasileiou, V.
    Vianello, G.
    Vitale, V.
    Werner, M.
    Winer, B. L.
    Wood, D. L.
    Wood, K. S.
    Yang, Z.
    Impulsive and long duration high-energy gamma-ray emission from the very bright 2012 march 7 solar flares2014Ingår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 789, nr 1, s. 20-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Fermi Large Area Telescope (LAT) detected gamma-rays up to 4 GeV from two bright X-class solar flares on 2012 March 7, showing both an impulsive and temporally extended emission phases. The gamma-rays appear to originate from the same active region as the X-rays associated with these flares. The >100 MeV gamma-ray flux decreases monotonically during the first hour (impulsive phase) followed by a slower decrease for the next 20 hr. A power law with a high-energy exponential cutoff can adequately describe the photon spectrum. Assuming that the gamma rays result from the decay of pions produced by accelerated protons and ions with a power-law spectrum, we find that the index of that spectrum is similar to 3, with minor variations during the impulsive phase. During the extended phase the photon spectrum softens monotonically, requiring the proton index varying from similar to 4 to >5. The >30 MeV proton flux observed by the GOES satellites also shows a flux decrease and spectral softening, but with a harder spectrum (index similar to 2-3). Based on these observations, we explore the relative merits of prompt or continuous acceleration scenarios, hadronic or leptonic emission processes, and acceleration at the solar corona or by the fast coronal mass ejections. We conclude that the most likely scenario is continuous acceleration of protons in the solar corona that penetrate the lower solar atmosphere and produce pions that decay into gamma rays. However, acceleration in the downstream of the shock cannot be definitely ruled out.

  • 245. Ajello, M.
    et al.
    Albert, A.
    Atwood, W. B.
    Barbiellini, G.
    Bastieri, D.
    Bechtol, K.
    Bellazzini, R.
    Bissaldi, E.
    Blandford, R. D.
    Bloom, E. D.
    Bonino, R.
    Bottacini, E.
    Brandt, T. J.
    Bregeon, J.
    Bruel, P.
    Buehler, R.
    Buson, S.
    Caliandro, G. A.
    Cameron, R. A.
    Caputo, R.
    Caragiulo, M.
    Carave, P. A.
    Cecchi, C.
    Chekhtman, A.
    Chiang, J.
    Chiaro, G.
    Ciprini, S.
    Cohen-Tanugi, J.
    Cominsky, L. R.
    Conrad, J.
    Cutini, S.
    D'Ammando, F.
    de Angelis, A.
    de Palma, F.
    Desiante, R.
    Di Venere, L.
    Drell, P. S.
    Favuzzi, C.
    Ferrara, E. C.
    Fusco, P.
    Gargano, F.
    Gasparrini, D.
    Giglietto, N.
    Giommi, P.
    Giordano, F.
    Giroletti, M.
    Glanzman, T.
    Godfrey, G.
    Gomez-Vargas, G. A.
    Grenier, I. A.
    Guiriec, S.
    Gustafsson, M.
    Harding, A. K.
    Hewitt, J. W.
    Hill, A. B.
    Horan, D.
    Jogler, T.
    Johannesson, G.
    Johnson, A. S.
    Kamae, T.
    Karwin, C.
    Knoedlseder, J.
    Kuss, M.
    Larsson, Stefan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Latronico, L.
    Li, J.
    Li, L.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Longo, F.
    Loparco, F.
    Lovellette, M. N.
    Lubrano, P.
    Magill, J.
    Maldera, S.
    Malyshev, D.
    Manfreda, A.
    Mayer, M.
    Mazziotta, M. N.
    Michelson, P. F.
    Mitthumsiri, W.
    Mizuno, T.
    Moiseev, A. A.
    Monzani, M. E.
    Morselli, A.
    Moskalenko, I. V.
    Murgia, S.
    Nuss, E.
    Ohno, M.
    Ohsugi, T.
    Omodei, N.
    Orlando, E.
    Ormes, J. F.
    Paneque, D.
    Pesce-Rollins, M.
    Piron, F.
    Pivato, G.
    Porter, T. A.
    Raino, S.
    Rando, R.
    Razzano, M.
    Reimer, A.
    Reimer, O.
    Ritz, S.
    Sanchez-Conde, M.
    Parkinson, P. M. Saz
    Sgro, C.
    Siskind, E. J.
    Smith, D. A.
    Spada, F.
    Spandre, G.
    Spinelli, P.
    Suson, D. J.
    Tajima, H.
    Takahashi, H.
    Thayer, J. B.
    Torres, D. F.
    Tosti, G.
    Troja, E.
    Uchiyama, Y.
    Vianello, G.
    Winer, B. L.
    Wood, K. S.
    Zaharijas, G.
    Zimmer, S.
    FERMI-LAT OBSERVATIONS OF HIGH-ENERGY gamma-RAY EMISSION TOWARD THE GALACTIC CENTER2016Ingår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 819, nr 1, artikel-id 44Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Fermi Large Area Telescope (LAT) has provided the most detailed view to date of the emission toward the Galactic center (GC) in high-energy gamma-rays. This paper describes the analysis of data taken during the first 62 months of the mission in the energy range 1-100 GeV from a 15 degrees x 15 degrees region about the direction of the GC. Specialized interstellar emission models (IEMs) are constructed to enable the separation of the.-ray emissions produced by cosmic ray particles interacting with the interstellar gas and radiation fields in the Milky Way into that from the inner similar to 1 kpc surrounding the GC, and that from the rest of the Galaxy. A catalog of point sources for the 15 degrees x 15 degrees region is self-consistently constructed using these IEMs: the First Fermi-LAT Inner Galaxy Point Source Catalog (1FIG). The spatial locations, fluxes, and spectral properties of the 1FIG sources are presented, and compared with gamma-ray point sources over the same region taken from existing catalogs. After subtracting the interstellar emission and point-source contributions a residual is found. If templates that peak toward the GC are used to model the positive residual the agreement with the data improves, but none of the additional templates tried account for all of its spatial structure. The spectrum of the positive residual modeled with these templates has a strong dependence on the choice of IEM.

  • 246.
    Ajello, M.
    et al.
    Clemson Univ, Dept Phys & Astron, Kinard Lab Phys, Clemson, SC 29634 USA..
    Arimoto, M.
    Kanazawa Univ, Inst Sci & Engn, Fac Math & Phys, Kanazawa, Ishikawa 9201192, Japan..
    Axelsson, Magnus
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Jóhannesson, Gudlaugur
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Larsson, Stefan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Ryde, Felix
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    De Pasquale, M.
    Fermi and Swift Observations of GRB 190114C: Tracing the Evolution of High-energy Emission from Prompt to Afterglow2020Ingår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 890, nr 1, artikel-id 9Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report on the observations of gamma-ray burst (GRB) 190114C by the Fermi Gamma -ray Space Telescope and the Neil Gehrels Swift Observatory. The prompt gamma-ray emission was detected by the Fermi GRB Monitor (GBM), the Fermi Large Area Telescope (LAT), and the Swift Burst Alert Telescope (BAT) and the long-lived afterglow emission was subsequently observed by the GBM, LAT, Swift X-ray Telescope (XRT), and Swift UV Optical Telescope. The early -time observations reveal multiple emission components that evolve independently, with a delayed power-law component that exhibits significant spectral attenuation above 40 MeV in the first few seconds of the burst. This power-law component transitions to a harder spectrum that is consistent with the afterglow emission observed by the XRT at later times. This afterglow component is clearly identifiable in the GBM and BAT light curves as a slowly fading emission component on which the rest of the prompt emission is superimposed. As a result, we are able to observe the transition from internal-shock- to external-shock-dominated emission. We find that the temporal and spectral evolution of the broadband afterglow emission can be well modeled as synchrotron emission from a forward shock propagating into a wind -like circumstellar environment. We estimate the initial bulk Lorentz factor using the observed high-energy spectral cutoff. Considering the onset of the afterglow component, we constrain the deceleration radius at which this forward shock begins to radiate in order to estimate the maximum synchrotron energy as a function of time. We find that even in the LAT energy range, there exist high-energy photons that are in tension with the theoretical maximum energy that can be achieved through synchrotron emission from a shock. These violations of the maximum synchrotron energy are further compounded by the detection of very high-energy (VHE) emission above 300 GeV by MAGIC concurrent with our observations. We conclude that the observations of VHE photons from GRB 190114C necessitates either an additional emission mechanism at very high energies that is hidden in the synchrotron component in the LAT energy range, an acceleration mechanism that imparts energy to the particles at a rate that is faster than the electron synchrotron energy -loss rate, or revisions of the fundamental assumptions used in estimating the maximum photon energy attainable through the synchrotron process.

  • 247. Ajello, M.
    et al.
    Atwood, W. B.
    Axelsson, Magnus
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Baldini, L.
    Barbiellini, G.
    Baring, M. G.
    Bastieri, D.
    Bellazzini, R.
    Berretta, A.
    Bissaldi, E.
    Blandford, R. D.
    Bonino, R.
    Bregeon, J.
    Bruel, P.
    Buehler, R.
    Burns, E.
    Buson, S.
    Cameron, R. A.
    Caraveo, P. A.
    Cavazzuti, E.
    Chen, S.
    Cheung, C. C.
    Chiaro, G.
    Ciprini, S.
    Costantin, D.
    Crnogorcevic, M.
    Cutini, S.
    D’Ammando, F.
    de la Torre Luque, P.
    de Palma, F.
    Digel, S. W.
    Di Lalla, N.
    Di Venere, L.
    Dirirsa, F. F.
    Fukazawa, Y.
    Funk, S.
    Fusco, P.
    Gargano, F.
    Giglietto, N.
    Gill, R.
    Giordano, F.
    Giroletti, M.
    Granot, J.
    Green, D.
    Grenier, I. A.
    Griffin, S.
    Guiriec, S.
    Hays, E.
    Horan, D.
    Jóhannesson, Gudlaugur
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Kerr, M.
    Kovačević, M.
    Kuss, M.
    Larsson, Stefan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Latronico, L.
    Li, J.
    Longo, F.
    Loparco, F.
    Lovellette, M. N.
    Lubrano, P.
    Maldera, S.
    Manfreda, A.
    Martí-Devesa, G.
    Mazziotta, M. N.
    McEnery, J. E.
    Mereu, I.
    Michelson, P. F.
    Mizuno, T.
    Monzani, M. E.
    Morselli, A.
    Moskalenko, I. V.
    Negro, M.
    Omodei, N.
    Orienti, M.
    Orlando, E.
    Paliya, V. S.
    Paneque, D.
    Pei, Z.
    Pesce-Rollins, M.
    Piron, F.
    Poon, H.
    Porter, T. A.
    Principe, G.
    Racusin, J. L.
    Rainò, S.
    Rando, R.
    Rani, B.
    Razzaque, S.
    Reimer, A.
    Reimer, O.
    Parkinson, P. M. S.
    Scargle, J. D.
    Scotton, L.
    Serini, D.
    Sgrò, C.
    Siskind, E. J.
    Spandre, G.
    Spinelli, P.
    Tajima, H.
    Takahashi, M. N.
    Tak, D.
    Torres, D. F.
    Tosti, G.
    Troja, E.
    Wadiasingh, Z.
    Wood, K.
    Yassine, M.
    Yusafzai, A.
    Zaharijas, G.
    High-energy emission from a magnetar giant flare in the Sculptor galaxy2021Ingår i: Nature Astronomy, E-ISSN 2397-3366, Vol. 5, nr 4, s. 385-391Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Magnetars are the most highly magnetized neutron stars in the cosmos (with magnetic field 1013–1015 G). Giant flares from magnetars are rare, short-duration (about 0.1 s) bursts of hard X-rays and soft γ rays1,2. Owing to the limited sensitivity and energy coverage of previous telescopes, no magnetar giant flare has been detected at gigaelectronvolt (GeV) energies. Here, we report the discovery of GeV emission from a magnetar giant flare on 15 April 2020 (refs. 3,4 and A. J. Castro-Tirado et al., manuscript in preparation). The Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope detected GeV γ rays from 19 s until 284 s after the initial detection of a signal in the megaelectronvolt (MeV) band. Our analysis shows that these γ rays are spatially associated with the nearby (3.5 megaparsecs) Sculptor galaxy and are unlikely to originate from a cosmological γ-ray burst. Thus, we infer that the γ rays originated with the magnetar giant flare in Sculptor. We suggest that the GeV signal is generated by an ultra-relativistic outflow that first radiates the prompt MeV-band photons, and then deposits its energy far from the stellar magnetosphere. After a propagation delay, the outflow interacts with environmental gas and produces shock waves that accelerate electrons to very high energies; these electrons then emit GeV γ rays as optically thin synchrotron radiation. This observation implies that a relativistic outflow is associated with the magnetar giant flare, and suggests the possibility that magnetars can power some short γ-ray bursts.

  • 248. Ajello, M.
    et al.
    Atwood, W. B.
    Baldini, L.
    Ballet, J.
    Barbiellini, G.
    Bastieri, D.
    Bellazzini, R.
    Bissaldi, E.
    Blandford, R. D.
    Bloom, E. D.
    Bonino, R.
    Bregeon, J.
    Britto, R. J.
    Bruel, P.
    Buehler, R.
    Buson, S.
    Cameron, R. A.
    Caputo, R.
    Caragiulo, M.
    Caraveo, P. A.
    Cavazzuti, E.
    Cecchi, C.
    Charles, E.
    Chekhtman, A.
    Cheung, C. C.
    Chiaro, G.
    Ciprini, S.
    Cohen, J. M.
    Costantin, D.
    Costanza, F.
    Cuoco, A.
    Cutini, S.
    D'Ammando, F.
    de Palma, F.
    Desiante, R.
    Digel, S. W.
    Di Lalla, N.
    Di Mauro, M.
    Di Venere, L.
    Dominguez, A.
    Drell, P. S.
    Dumora, D.
    Favuzzi, C.
    Fegan, S. J.
    Ferrara, E. C.
    Fortin, P.
    Franckowiak, A.
    Fukazawa, Y.
    Funk, S.
    Fusco, P.
    Gargano, F.
    Gasparrini, D.
    Giglietto, N.
    Giommi, P.
    Giordano, F.
    Giroletti, M.
    Glanzman, T.
    Green, D.
    Grenier, I. A.
    Grondin, M. -H
    Grove, J. E.
    Guillemot, L.
    Guiriec, S.
    Harding, A. K.
    Hays, E.
    Hewitt, J. W.
    Horan, D.
    Jóhannesson, Gudlaugur
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Kensei, S.
    Kuss, M.
    La Mura, G.
    Larsson, Stefan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Latronico, L.
    Lemoine-Goumard, M.
    Li, J.
    Longo, F.
    Loparco, F.
    Lott, B.
    Lubrano, P.
    Magill, J. D.
    Maldera, S.
    Manfreda, A.
    Mazziotta, M. N.
    McEnery, J. E.
    Meyer, M.
    Michelson, P. F.
    Mirabal, N.
    Mitthumsiri, W.
    Mizuno, T.
    Moiseev, A. A.
    Monzani, M. E.
    Morselli, A.
    Moskalenko, I. V.
    Negro, M.
    Nuss, E.
    Ohsugi, T.
    Omodei, N.
    Orienti, M.
    Orlando, E.
    Palatiello, M.
    Paliya, V. S.
    Paneque, D.
    Perkins, J. S.
    Persic, M.
    Pesce-Rollins, M.
    Piron, F.
    Porter, T. A.
    Principe, G.
    Raino, S.
    Rando, R.
    Razzano, M.
    Razzaque, S.
    Reimer, A.
    Reimer, O.
    Reposeur, T.
    Parkinson, P. M. Saz
    Sgro, C.
    Simone, D.
    Siskind, E. J.
    Spada, F.
    Spandre, G.
    Spinelli, P.
    Stawarz, L.
    Suson, D. J.
    Takahashi, M.
    Tak, D.
    Thayer, J. G.
    Thayer, J. B.
    Thompson, D. J.
    Torres, D. F.
    Torresi, E.
    Troja, E.
    Vianello, G.
    Wood, K.
    Wood, M.
    3FHL: The Third Catalog of Hard Fermi-LAT Sources2017Ingår i: Astrophysical Journal Supplement Series, ISSN 0067-0049, E-ISSN 1538-4365, Vol. 232, nr 2, artikel-id 18Artikel i tidskrift (Refereegranskat)
  • 249.
    Ajello, M.
    et al.
    Clemson Univ, Dept Phys & Astron, Kinard Lab Phys, Clemson, SC 29634 USA..
    Axelsson, Magnus
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik. Stockholm Univ, Dept Phys, AlbaNova, SE-10691 Stockholm, Sweden.
    Cameron, R. A.
    Stanford Univ, Dept Phys, Kavli Inst Particle Astrophys & Cosmol, WW Hansen Expt Phys Lab, Stanford, CA 94305 USA.;Stanford Univ, SLAC Natl Accelerator Lab, Stanford, CA 94305 USA..
    Jóhannesson, Gudlaugur
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. Univ Iceland, Sci Inst, IS-107 Reykjavik, Iceland. Stockholm Univ, Roslagstullsbacken 23, SE-10691 Stockholm, Sweden..
    Larsson, Stefan
    KTH, Skolan för teknikvetenskap (SCI), Fysik. Dalarna Univ, Sch Educ Hlth & Social Studies, Nat Sci, SE-79188 Falun, Sweden..
    Zaharijas, G.
    Ist Nazl Fis Nucl, Sez Trieste, I-34127 Trieste, Italy.;Univ Nova Gorica, Ctr Astrophys & Cosmol, Nova Gorica, Slovenia..
    Fermi Large Area Telescope Performance after 10 Years of Operation2021Ingår i: Astrophysical Journal Supplement Series, ISSN 0067-0049, E-ISSN 1538-4365, Vol. 256, nr 1, artikel-id 12Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Large Area Telescope (LAT), the primary instrument for the Fermi Gamma-ray Space Telescope (Fermi) mission, is an imaging, wide field-of-view, high-energy gamma-ray telescope, covering the energy range from 30 MeV to more than 300 GeV. We describe the performance of the instrument at the 10 yr milestone. LAT performance remains well within the specifications defined during the planning phase, validating the design choices and supporting the compelling case to extend the duration of the Fermi mission. The details provided here will be useful when designing the next generation of high-energy gamma-ray observatories.

  • 250.
    Ajello, M.
    et al.
    Clemson Univ, Dept Phys & Astron, Kinard Lab Phys, Clemson, SC 29634 USA..
    Axelsson, Magnus
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Ciprini, S.
    Jóhannesson, Gudlaugur
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Larsson, Stefan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Yassine, M.
    The Fourth Catalog of Active Galactic Nuclei Detected by the Fermi Large Area Telescope2020Ingår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 892, nr 2, artikel-id 105Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The fourth catalog of active galactic nuclei (AGNs) detected by the Fermi Gamma-ray Space Telescope Large Area Telescope (4LAC) between 2008 August 4 and 2016 August 2 contains . It includes 85% more sources than the previous 3LAC catalog based on 4 yr of data. AGNs represent at least 79% of the high-latitude sources in the fourth Fermi-Large Area Telescope Source Catalog (4FGL), which covers the energy range from 50 MeV to 1 TeV. In addition, gamma-ray AGNs are found at low Galactic latitudes. Most of the 4LAC AGNs are blazars (98%), while the remainder are other types of AGNs. The blazar population consists of 24% Flat Spectrum Radio Quasars (FSRQs), 38% BL Lac-type objects, and 38% blazar candidates of unknown types (BCUs). On average, FSRQs display softer spectra and stronger variability in the gamma-ray band than BL Lacs do, confirming previous findings. All AGNs detected by ground-based atmospheric Cerenkov telescopes are also found in the 4LAC.

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