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Pearce, M., Eliasson, L., Iyer, N., Kiss, M., Kushwah, R., Larsson, J., . . . Xie, E. (2019). Science prospects for SPHiNX - A small satellite GRB polarimetry mission. Astroparticle physics, 104, 54-63
Open this publication in new window or tab >>Science prospects for SPHiNX - A small satellite GRB polarimetry mission
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2019 (English)In: Astroparticle physics, ISSN 0927-6505, E-ISSN 1873-2852, Vol. 104, p. 54-63Article in journal (Refereed) Published
Abstract [en]

Gamma-ray bursts (GRBs) are exceptionally bright electromagnetic events occurring daily on the sky. The prompt emission is dominated by X-/gamma-rays. Since their discovery over 50 years ago, GRBs are primarily studied through spectral and temporal measurements. The properties of the emission jets and underlying processes are not well understood. A promising way forward is the development of missions capable of characterising the linear polarisation of the high-energy emission. For this reason, the SPHiNX mission has been developed for a small-satellite platform. The polarisation properties of incident high-energy radiation (50-600 keV) are determined by reconstructing Compton scattering interactions in a segmented array of plastic and Gd3Al2Ga3O12(Ce) (GAGG(Ce)) scintillators. During a two-year mission, similar to 200 GRBs will be observed, with similar to 50 yielding measurements where the polarisation fraction is determined with a relative error <= 10%. This is a significant improvement compared to contemporary missions. This performance, combined with the ability to reconstruct GRB localisation and spectral properties, will allow discrimination between leading classes of emission models. 

Place, publisher, year, edition, pages
ELSEVIER SCIENCE BV, 2019
Keywords
Polarimetry, X-ray, Gamma-ray burst, Small satellite
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-238522 (URN)10.1016/j.astropartphys.2018.08.007 (DOI)000447479300004 ()
Funder
Swedish National Space Board, 232/16
Note

QC 20181106

Available from: 2018-11-06 Created: 2018-11-06 Last updated: 2018-11-06Bibliographically approved
Pearce, M., Eliasson, L., Iyer, N., Kiss, M., Kushwah, R., Larsson, J., . . . Xie, F. (2019). Science prospects for SPHiNX – A small satellite GRB polarimetry mission. Astroparticle physics, 104, 54-63
Open this publication in new window or tab >>Science prospects for SPHiNX – A small satellite GRB polarimetry mission
Show others...
2019 (English)In: Astroparticle physics, ISSN 0927-6505, E-ISSN 1873-2852, Vol. 104, p. 54-63Article in journal (Refereed) Published
Abstract [en]

Gamma-ray bursts (GRBs) are exceptionally bright electromagnetic events occurring daily on the sky. The prompt emission is dominated by X-/γ-rays. Since their discovery over 50 years ago, GRBs are primarily studied through spectral and temporal measurements. The properties of the emission jets and underlying processes are not well understood. A promising way forward is the development of missions capable of characterising the linear polarisation of the high-energy emission. For this reason, the SPHiNX mission has been developed for a small-satellite platform. The polarisation properties of incident high-energy radiation (50–600 keV) are determined by reconstructing Compton scattering interactions in a segmented array of plastic and Gd3Al2Ga3O12(Ce) (GAGG(Ce)) scintillators. During a two-year mission, ∼ 200 GRBs will be observed, with ∼ 50 yielding measurements where the polarisation fraction is determined with a relative error ≤ 10%. This is a significant improvement compared to contemporary missions. This performance, combined with the ability to reconstruct GRB localisation and spectral properties, will allow discrimination between leading classes of emission models.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Gamma-ray burst, Polarimetry, Small satellite, X-ray, Ellipsometry, Polarimeters, Polarization, Satellites, Stars, X rays, Gamma ray bursts, Gamma-ray bursts (GRBs), High energy emission, High energy radiation, Linear polarisation, Scattering interactions, Small-satellite, Temporal measurements, Gamma rays
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-236345 (URN)10.1016/j.astropartphys.2018.08.007 (DOI)2-s2.0-85052499332 (Scopus ID)
Funder
Swedish National Space Board, 232/16
Note

QC 20181108

Available from: 2018-11-08 Created: 2018-11-08 Last updated: 2018-11-08Bibliographically approved
Pearce, M., Eliasson, L., Iyer, N., Kiss, M., Kushwah, R., Larsson, J., . . . Xie, F. (2019). Science prospects for SPHiNX - A small satellite GRB polarimetry mission. Astroparticle physics, 104, 54-63
Open this publication in new window or tab >>Science prospects for SPHiNX - A small satellite GRB polarimetry mission
Show others...
2019 (English)In: Astroparticle physics, ISSN 0927-6505, E-ISSN 1873-2852, Vol. 104, p. 54-63Article in journal (Refereed) Published
Abstract [en]

Gamma-ray bursts (GRBs) are exceptionally bright electromagnetic events occurring daily on the sky. The prompt emission is dominated by X-/gamma-rays. Since their discovery over 50 years ago, GRBs are primarily studied through spectral and temporal measurements. The properties of the emission jets and underlying processes are not well understood. A promising way forward is the development of missions capable of characterising the linear polarisation of the high-energy emission. For this reason, the SPHiNX mission has been developed for a small-satellite platform. The polarisation properties of incident high-energy radiation (50-600 keV) are determined by reconstructing Compton scattering interactions in a segmented array of plastic and Gd3Al2Ga3O12(Ce) (GAGG(Ce)) scintillators. During a two-year mission, similar to 200 GRBs will be observed, with similar to 50 yielding measurements where the polarisation fraction is determined with a relative error <= 10%. This is a significant improvement compared to contemporary missions. This performance, combined with the ability to reconstruct GRB localisation and spectral properties, will allow discrimination between leading classes of emission models.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE BV, 2019
Keywords
Polarimetry, X-ray, Gamma-ray burst, Small satellite
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-238104 (URN)10.1016/j.astropartphys.2018.08.007 (DOI)000447479300004 ()2-s2.0-85052499332 (Scopus ID)
Note

QC 20190111

Available from: 2019-01-11 Created: 2019-01-11 Last updated: 2019-01-11Bibliographically approved
Ahlgren, B., Larsson, J., Ahlberg, E., Lundman, C., Ryde, F. & Pe'er, A. (2019). Testing a model for subphotospheric dissipation in GRBs: fits to Fermi data constrain the dissipation scenario. Monthly notices of the Royal Astronomical Society, 485, 474-497
Open this publication in new window or tab >>Testing a model for subphotospheric dissipation in GRBs: fits to Fermi data constrain the dissipation scenario
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2019 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 485, p. 474-497Article in journal (Refereed) Published
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.

Keywords
gamma-ray burst
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Physics
Identifiers
urn:nbn:se:kth:diva-245227 (URN)10.1093/mnras/stz110 (DOI)
Note

QC 20190308

Available from: 2019-03-07 Created: 2019-03-07 Last updated: 2019-03-08Bibliographically approved
Larsson, J., D'Ammando, F., Falocco, S., Giroletti, M., Orienti, M., Piconcelli, E. & Righini, S. (2018). FBQS J1644+2619: multiwavelength properties and its place in the class of gamma-ray emitting Narrow Line Seyfert 1s. Monthly notices of the Royal Astronomical Society, 476(1), 43-55
Open this publication in new window or tab >>FBQS J1644+2619: multiwavelength properties and its place in the class of gamma-ray emitting Narrow Line Seyfert 1s
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2018 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 476, no 1, p. 43-55Article in journal (Refereed) Published
Abstract [en]

A small fraction of Narrow Line Seyfert 1s (NLSy1s) are observed to be gamma-ray emitters. Understanding the properties of these sources is of interest since the majority of NLSy1s are very different from typical blazars. Here, we present a multifrequency analysis of FBQS J1644+2619, one of the most recently discovered gamma-ray emitting NLSy1s. We analyse an similar to 80 ks XMM-Newton observation obtained in 2017, as well as quasi-simultaneous multi-wavelength observations covering the radio-gamma-ray range. The spectral energy distribution of the source is similar to the other gamma-ray NLSy1s, confirming its blazar-like nature. The X-ray spectrum is characterized by a hard photon index (Gamma = 1.66) above 2 keV and a soft excess at lower energies. The hard photon index provides clear evidence that inverse Compton emission from the jet dominates the spectrum, while the soft excess can be explained by a contribution from the underlying Seyfert emission. This contribution can be fitted by reflection of emission from the base of the jet, as well as by Comptonization in a warm, optically thick corona. We discuss our results in the context of the other gamma-ray NLSy1s and note that the majority of them have similar X-ray spectra, with properties intermediate between blazars and radio-quiet NLSy1s.

Place, publisher, year, edition, pages
OXFORD UNIV PRESS, 2018
Keywords
galaxies: active, galaxies: individual (FBQS J1644+2619), galaxies: jets, galaxies: Seyfert, X-rays: general
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:kth:diva-228113 (URN)10.1093/mnras/sty241 (DOI)000429276700004 ()2-s2.0-85043514539 (Scopus ID)
Note

QC 20180518

Available from: 2018-05-18 Created: 2018-05-18 Last updated: 2018-05-18Bibliographically approved
Alp, D., Larsson, J., Fransson, C., Indebetouw, R., Jerkstrand, A., Ahola, A., . . . Wheeler, J. C. (2018). The 30 Year Search for the Compact Object in SN 1987A. Astrophysical Journal, 864(2), Article ID 174.
Open this publication in new window or tab >>The 30 Year Search for the Compact Object in SN 1987A
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2018 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 864, no 2, article id 174Article in journal (Refereed) Published
Abstract [en]

Despite more than 30 years of searching, the compact object in Supernova (SN) 1987A has not yet been detected. We present new limits on the compact object in SN 1987A using millimeter, near-infrared, optical, ultraviolet, and X-ray observations from ALMA, VLT, HST, and Chandra. The limits are approximately 0.1 mJy (0.1 x 10(-26) erg s(-1) cm(-2) Hz(-1)) at 213 GHz, 1 L-circle dot (6 x 10(-29) erg s(-1) cm(-2) Hz(-1)) in the optical if our line of sight is free of ejecta dust, and 10(36) erg s(-1) (2 x 10(-30) erg s(-1) cm(-2) Hz(-1) ) in 2-10 keV X-rays. Our X-ray limits are an order of magnitude less constraining than previous limits because we use a more realistic ejecta absorption model based on three-dimensional neutrino-driven SN explosion models. The allowed bolometric luminosity of the compact object is 22 L-circle dot if our line of sight is free of ejecta dust, or 138L(circle dot) if dust-obscured. Depending on assumptions, these values limit the effective temperature of a neutron star (NS) to <4-8 MK and do not exclude models, which typically are in the range 3-4 MK. For the simplest accretion model, the accretion rate for an efficiency 77 is limited to <10(-11) eta(-1) M-circle dot yr(-1), which excludes most predictions. For pulsar activity modeled by a rotating magnetic dipole in vacuum, the limit on the magnetic field strength (B) for a given spin period (P) is B less than or similar to 10(14) P-2 G s(-2), which firmly excludes pulsars comparable to the Crab. By combining information about radiation reprocessing and geometry, we infer that the compact object is a dust-obscured thermally emitting NS, which may appear as a region of higher-temperature ejecta dust emission.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2018
Keywords
stars: black holes, stars: neutron, supernovae: individual (SN 1987A)
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-235442 (URN)10.3847/1538-4357/aad739 (DOI)000444645600011 ()2-s2.0-85053411220 (Scopus ID)
Funder
Knut and Alice Wallenberg FoundationSwedish Research CouncilEU, European Research Council, 341157-COCO2CASA
Note

QC 20180927

Available from: 2018-09-27 Created: 2018-09-27 Last updated: 2019-01-21Bibliographically approved
Valan, V., Larsson, J. & Ahlgren, B. (2018). Thermal components in the early X-ray afterglows of GRBs: likely cocoon emission and constraints on the progenitors. Monthly notices of the Royal Astronomical Society, 474(2), 2401-2418
Open this publication in new window or tab >>Thermal components in the early X-ray afterglows of GRBs: likely cocoon emission and constraints on the progenitors
2018 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 474, no 2, p. 2401-2418Article in journal (Refereed) Published
Abstract [en]

The early X-ray afterglows of gamma-ray bursts (GRBs) are usually well described by absorbed power laws. However, in some cases, additional thermal components have been identified. The origin of this emission is debated, with proposed explanations including supernova shock breakout, emission from a cocoon surrounding the jet, as well as emission from the jet itself. A larger sample of detections is needed in order to place constraints on these different models. Here, we present a time-resolved spectral analysis of 74 GRBs observed by Swift X-ray Telescope in a search for thermal components. We report six detections in our sample, and also confirm an additional three cases that were previously reported in the literature. The majority of these bursts have a narrow range of blackbody radii around similar to 2 x 10(12) cm, despite having a large range of luminosities (L-peak similar to 10(47)-10(51) erg s(-1)). This points to an origin connected to the progenitor stars, and we suggest that emission from a cocoon breaking out from a thick wind may explain the observations. For two of the bursts in the sample, an explanation in terms of late prompt emission from the jet is instead more likely. We also find that these thermal components are preferentially detected when the X-ray luminosity is low, which suggests that they may be hidden by bright afterglows in the majority of GRBs.

Place, publisher, year, edition, pages
Oxford University Press, 2018
Keywords
gamma-ray burst: general, X-rays: bursts
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-223805 (URN)10.1093/mnras/stx2920 (DOI)000424343600068 ()2-s2.0-85042616959 (Scopus ID)
Funder
Knut and Alice Wallenberg Foundation
Note

QC 20180307

Available from: 2018-03-07 Created: 2018-03-07 Last updated: 2018-06-25Bibliographically approved
Alp, D., Larsson, J., Fransson, C., Gabler, M., Wongwathanarat, A. & Janka, H.-T. (2018). X-Ray Absorption in Young Core-collapse Supernova Remnants. Astrophysical Journal, 864(2), Article ID 175.
Open this publication in new window or tab >>X-Ray Absorption in Young Core-collapse Supernova Remnants
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2018 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 864, no 2, article id 175Article in journal (Refereed) Published
Abstract [en]

The material expelled by core-collapse supernova (SN) explosions absorbs X-rays from the central regions. We use SN models based on three-dimensional neutrino-driven explosions to estimate optical depths to the center of the explosion, compare different progenitor models, and investigate the effects of explosion asymmetries. The optical depths below 2 keV for progenitors with a remaining hydrogen envelope are expected to be high during the first century after the explosion due to photoabsorption. A typical optical depth is 100 t(4)(-2 )E(-2), where t(4) is the time since the explosion in units of 10,000 days (similar to 27 years) and E is the energy in units of keV. Compton scattering dominates above 50 keV, but the scattering depth is lower and reaches unity at similar to 1000 days at 1 MeV. The optical depths are approximately an order of magnitude lower for hydrogen-stripped progenitors. The metallicity of the SN ejecta is much higher than that in the interstellar medium, which enhances photoabsorption and makes absorption edges stronger. These results are applicable to young SN remnants in general, but we explore the effects on observations of SN 1987A and the compact object in Cas A in detail. For SN 1987A, the absorption is high and the X-ray upper limits of similar to 100 L-circle dot on a compact object are approximately an order of magnitude less constraining than previous estimates using other absorption models. The details are presented in an accompanying paper. For the central compact object in Cas A, we find no significant effects of our more detailed absorption model on the inferred surface temperature.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2018
Keywords
stars: neutron, supernova remnants, supernovae: general, supernovae: individual (SN 1987A, Cas A), X-rays: ISM
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-235443 (URN)10.3847/1538-4357/aad737 (DOI)000444645600012 ()2-s2.0-85053387396 (Scopus ID)
Note

QC 20180927

Available from: 2018-09-27 Created: 2018-09-27 Last updated: 2019-01-21Bibliographically approved
Matsuura, M., Indebetouw, R., Woosley, S., Bujarrabal, V., Abellán, F. J., McCray, R., . . . Yates, J. (2017). ALMA observations of Molecules in Supernova 1987A. Proceedings of the International Astronomical Union (S331), 294-299
Open this publication in new window or tab >>ALMA observations of Molecules in Supernova 1987A
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2017 (English)In: Proceedings of the International Astronomical Union, ISSN 1743-9213, E-ISSN 1743-9221, no S331, p. 294-299Article in journal (Refereed) Published
Abstract [en]

Supernova (SN) 1987A has provided a unique opportunity to study how SN ejecta evolve in 30 years time scale. We report our ALMA spectral observations of SN 1987A, taken in 2014, 2015 and 2016, with detections of CO, 28SiO, HCO+ and SO, with weaker lines of 29SiO. We find a dip in the SiO line profiles, suggesting that the ejecta morphology is likely elongated. The difference of the CO and SiO line profiles is consistent with hydrodynamic simulations, which show that Rayleigh-Taylor instabilities causes mixing of gas, with heavier elements much more disturbed, making more elongated structure. Using 28SiO and its isotopologues, Si isotope ratios were estimated for the first time in SN 1987A. The estimated ratios appear to be consistent with theoretical predictions of inefficient formation of neutron rich atoms at lower metallicity, such as observed in the Large Magellanic Cloud (about half a solar metallicity). The deduced large HCO+ mass and small SiS mass, which are inconsistent to the predictions of chemical model, might be explained by some mixing of elements immediately after the explosion. The mixing might have made some hydrogen from the envelope to sink into carbon and oxygen-rich zone during early days after the explosion, enabling the formation of a substantial mass of HCO+. Oxygen atoms may penetrate into silicon and sulphur zone, suppressing formation of SiS. Our ALMA observations open up a new window to investigate chemistry, dynamics and explosive-nucleosynthesis in supernovae. 

Place, publisher, year, edition, pages
Cambridge University Press, 2017
Keywords
ISM: abundances, ISM: molecules, ISM: supernova remnants, radio lines: ISM, supernovae: individual:Supernova 1987A
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:kth:diva-236786 (URN)10.1017/S1743921317004719 (DOI)2-s2.0-85047135288 (Scopus ID)
Funder
EU, European Research Council
Note

QC 20190109

Available from: 2019-01-09 Created: 2019-01-09 Last updated: 2019-01-09Bibliographically approved
Nandi, S., Jamrozy, M., Roy, R., Larsson, J., Saikia, D. J., Baes, M. & Singh, M. (2017). Tale of J1328+2752: a misaligned double-double radio galaxy hosted by a binary black hole?. Monthly notices of the Royal Astronomical Society, 467(1), L56-L60
Open this publication in new window or tab >>Tale of J1328+2752: a misaligned double-double radio galaxy hosted by a binary black hole?
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2017 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 467, no 1, p. L56-L60Article in journal (Refereed) Published
Abstract [en]

We present a radio and optical study of the double-double radio galaxy J1328+2752 based on new low-frequency Giant Metrewave Radio Telescope observations and Sloan Digital Sky Survey (SDSS) data. The radio data were used to investigate the morphology and to perform a spectral index analysis. In this source, we find that the inner double is misaligned by similar to 30 degrees from the axis of the outer diffuse structure. The SDSS spectrum shows that the central component has double-peaked line profiles with different emission strengths. The average velocity offset of the two components is 235 +/- 10.5 kms(-1). The misaligned radio morphology along with the double-peaked emission lines indicate that this source is a potential candidate binary supermassive black hole. This study further supports mergers as a possible explanation for repeated jet activity in radio sources.

Place, publisher, year, edition, pages
OXFORD UNIV PRESS, 2017
Keywords
line: identification, line: profiles, galaxies: active, galaxies: individual: J1328+2752, galaxies: nuclei, radio continuum: galaxies
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:kth:diva-215485 (URN)10.1093/mnrasl/slw256 (DOI)000410063700012 ()2-s2.0-85018296806 (Scopus ID)
Note

QC 20171013

Available from: 2017-10-13 Created: 2017-10-13 Last updated: 2017-10-23Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-0065-2933

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