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Li, L., Wang, Y., Ryde, F., Pe'er, A., Zhang, B., Guiriec, S., . . . Bhat, P. N. (2023). A Cosmological Fireball with 16% Gamma-Ray Radiative Efficiency. Astrophysical Journal Letters, 944(2), Article ID L57.
Open this publication in new window or tab >>A Cosmological Fireball with 16% Gamma-Ray Radiative Efficiency
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2023 (English)In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 944, no 2, article id L57Article in journal (Refereed) Published
Abstract [en]

Gamma-ray bursts (GRBs) are the most powerful explosions in the universe. How efficiently the jet converts its energy to radiation is a long-standing problem, which is poorly constrained. The standard model invokes a relativistic fireball with a bright photosphere emission component. A definitive diagnosis of GRB radiation components and the measurement of GRB radiative efficiency require prompt emission and afterglow data, with high resolution and wide band coverage in time and energy. Here, we present a comprehensive temporal and spectral analysis of the TeV-emitting bright GRB 190114C. Its fluence is one of the highest for all the GRBs that have been detected so far, which allows us to perform a high-resolution study of the prompt emission spectral properties and their temporal evolutions, down to a timescale of about 0.1 s. We observe that each of the initial pulses has a thermal component contributing similar to 20% of the total energy and that the corresponding temperature and inferred Lorentz factor of the photosphere evolve following broken power-law shapes. From the observation of the nonthermal spectra and the light curve, the onset of the afterglow corresponding to the deceleration of the fireball is considered to start at similar to 6 s. By incorporating the thermal and nonthermal observations, as well as the photosphere and synchrotron radiative mechanisms, we can directly derive the fireball energy budget with little dependence on hypothetical parameters, measuring a similar to 16% radiative efficiency for this GRB. With the fireball energy budget derived, the afterglow microphysics parameters can also be constrained directly from the data.

Place, publisher, year, edition, pages
American Astronomical Society, 2023
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:kth:diva-325092 (URN)10.3847/2041-8213/acb99d (DOI)000937591100001 ()2-s2.0-85149048631 (Scopus ID)
Note

QC 20230329

Available from: 2023-03-29 Created: 2023-03-29 Last updated: 2023-03-29Bibliographically approved
Lesage, S., Ryde, F. & Zaharijas, G. (2023). Fermi-GBM Discovery of GRB 221009A: An Extraordinarily Bright GRB from Onset to Afterglow. Astrophysical Journal Letters, 952(2), Article ID L42.
Open this publication in new window or tab >>Fermi-GBM Discovery of GRB 221009A: An Extraordinarily Bright GRB from Onset to Afterglow
2023 (English)In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 952, no 2, article id L42Article in journal (Refereed) Published
Abstract [en]

We report the discovery of GRB 221009A, the highest flux gamma-ray burst (GRB) ever observed by the Fermi Gamma-ray Burst Monitor (Fermi-GBM). This GRB has continuous prompt emission lasting more than 600 s, which smoothly transitions to afterglow emission visible in the Fermi-GBM energy range (8 keV-40 MeV), and total energetics higher than any other burst in the Fermi-GBM sample. By using a variety of new and existing analysis techniques we probe the spectral and temporal evolution of GRB 221009A. We find no emission prior to the Fermi-GBM trigger time (t (0); 2022 October 9 at 13:16:59.99 UTC), indicating that this is the time of prompt emission onset. The triggering pulse exhibits distinct spectral and temporal properties suggestive of the thermal, photospheric emission of shock breakout, with significant emission up to & SIM;15 MeV. We characterize the onset of external shock at t (0) + 600 s and find evidence of a plateau region in the early-afterglow phase, which transitions to a slope consistent with Swift-XRT afterglow measurements. We place the total energetics of GRB 221009A in context with the rest of the Fermi-GBM sample and find that this GRB has the highest total isotropic-equivalent energy (E ( & gamma;,iso) = 1.0 x 10(55) erg) and second highest isotropic-equivalent luminosity (L ( & gamma;,iso) = 9.9 x 10(53) erg s(-1)) based on its redshift of z = 0.151. These extreme energetics are what allowed us to observe the continuously emitting central engine of Fermi-GBM from the beginning of the prompt emission phase through the onset of early afterglow.

Place, publisher, year, edition, pages
IOP Publishing Ltd, 2023
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:kth:diva-338931 (URN)10.3847/2041-8213/ace5b4 (DOI)001042049400001 ()2-s2.0-85167911401 (Scopus ID)
Note

QC 20231101

Available from: 2023-11-01 Created: 2023-11-01 Last updated: 2023-11-01Bibliographically approved
Samuelsson, F. & Ryde, F. (2023). Observational Characteristics of Radiation-mediated Shocks in Photospheric Gamma-Ray Burst Emission. Astrophysical Journal, 956(1), Article ID 42.
Open this publication in new window or tab >>Observational Characteristics of Radiation-mediated Shocks in Photospheric Gamma-Ray Burst Emission
2023 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 956, no 1, article id 42Article in journal (Refereed) Published
Abstract [en]

Emission from the photosphere in gamma-ray burst jets can be substantially affected by subphotospheric energy dissipation, which is typically caused by radiation-mediated shocks. We study the observational characteristics of such emission, in particular the spectral signatures. Relevant shock initial conditions are estimated using a simple internal collision framework, which then serve as inputs for a radiation-mediated shock model that generates synthetic photospheric spectra. Within this framework, we find that if the free fireball acceleration starts at r 0 similar to 1010 cm, in agreement with hydrodynamical simulations, then the typical spectrum consists of a broad, soft power-law segment with a cutoff at high energies and a hardening in X-rays. The synthetic spectra are generally well fitted with a standard cutoff power-law (CPL) function, as the hardening in X-rays is commonly outside the observable energy range of current detectors. The CPL-fits yield values for the low-energy index, alpha, and the peak energy, E peak, that are centered around similar to -0.8 and similar to 220 keV, respectively, similar to typical observed values. We also identify a nonnegligible parameter region for what we call optically shallow shocks: shocks that do not accumulate enough scatterings to reach a steady-state spectrum before decoupling and thereby produce more complex spectra. These occur for optical depths tau less than or similar to 55uu-2 , where u u = gamma u beta u is the dimensionless specific momentum of the upstream as measured in the shock rest frame.

Place, publisher, year, edition, pages
American Astronomical Society, 2023
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:kth:diva-338729 (URN)10.3847/1538-4357/ace441 (DOI)001079214700001 ()2-s2.0-85175078690 (Scopus ID)
Note

QC 20231024

Available from: 2023-10-24 Created: 2023-10-24 Last updated: 2023-11-08Bibliographically approved
Dereli-Begue, H., Pe'er, A., Ryde, F., Oates, S. R., Zhang, B. & Dainotti, M. G. (2022). A wind environment and Lorentz factors of tens explain gamma-ray bursts X-ray plateau. Nature Communications, 13(1), Article ID 5611.
Open this publication in new window or tab >>A wind environment and Lorentz factors of tens explain gamma-ray bursts X-ray plateau
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2022 (English)In: Nature Communications, E-ISSN 2041-1723, Vol. 13, no 1, article id 5611Article in journal (Refereed) Published
Abstract [en]

The origin of the plateau observed in the early X-ray light curves of gamma ray bursts (GRBs) is debated. Here, the authors show that the observed plateau can be explained within the classical GRB model by considering expanding shell with initial Lorentz factor of a few tens. Gamma-ray bursts (GRBs) are known to have the most relativistic jets, with initial Lorentz factors in the order of a few hundreds. Many GRBs display an early X-ray light-curve plateau, which was not theoretically expected and therefore puzzled the community for many years. Here, we show that this observed signal is naturally obtained within the classical GRB fireball model, provided that the initial Lorentz factor is rather a few tens, and the expansion occurs into a medium-low density wind. The range of Lorentz factors in GRB jets is thus much wider than previously thought and bridges an observational gap between mildly relativistic jets inferred in active galactic nuclei, to highly relativistic jets deduced in few extreme GRBs. Furthermore, long GRB progenitors are either not Wolf-Rayet stars, or the wind properties during the final stellar evolution phase are different than at earlier times. Our model has predictions that can be tested to verify or reject it in the future, such as lack of GeV emission, lack of strong thermal component and long (few seconds) variability during the prompt phase characterizing plateau bursts.

Place, publisher, year, edition, pages
Springer Nature, 2022
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:kth:diva-319752 (URN)10.1038/s41467-022-32881-1 (DOI)000858076500004 ()36153328 (PubMedID)2-s2.0-85138458307 (Scopus ID)
Note

QC 20221007

Available from: 2022-10-07 Created: 2022-10-07 Last updated: 2023-03-28Bibliographically approved
Samuelsson, F., Lundman, C. & Ryde, F. (2022). An Efficient Method for Fitting Radiation-mediated Shocks to Gamma-Ray Burst Data: The Kompaneets RMS Approximation. Astrophysical Journal, 925(1), 65, Article ID 65.
Open this publication in new window or tab >>An Efficient Method for Fitting Radiation-mediated Shocks to Gamma-Ray Burst Data: The Kompaneets RMS Approximation
2022 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 925, no 1, p. 65-, article id 65Article in journal (Refereed) Published
Abstract [en]

Shocks that occur below a gamma-ray burst (GRB) jet photosphere are mediated by radiation. Such radiation-mediated shocks (RMSs) could be responsible for shaping the prompt GRB emission. Although well studied theoretically, RMS models have not yet been fitted to data owing to the computational cost of simulating RMSs from first principles. Here we bridge the gap between theory and observations by developing an approximate method capable of accurately reproducing radiation spectra from mildly relativistic (in the shock frame) or slower RMSs, called the Kompaneets RMS approximation (KRA). The approximation is based on the similarities between thermal Comptonization of radiation and the bulk Comptonization that occurs inside an RMS. We validate the method by comparing simulated KRA radiation spectra to first-principle radiation hydrodynamics simulations, finding excellent agreement both inside the RMS and in the RMS downstream. The KRA is then applied to a shock scenario inside a GRB jet, allowing for fast and efficient fitting to GRB data. We illustrate the capabilities of the developed method by performing a fit to a nonthermal spectrum in GRB 150314A. The fit allows us to uncover the physical properties of the RMS responsible for the prompt emission, such as the shock speed and the upstream plasma temperature.

Place, publisher, year, edition, pages
American Astronomical Society, 2022
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:kth:diva-308564 (URN)10.3847/1538-4357/ac332a (DOI)000746980200001 ()2-s2.0-85125833696 (Scopus ID)
Note

QC 20220215

Available from: 2022-02-15 Created: 2022-02-15 Last updated: 2022-06-25Bibliographically approved
Pacini, L., Pearce, M., Ryde, F., Zhu, K. J. & et al., . (2022). Design and expected performances of the large acceptance calorimeter for the HERD space mission. In: 37th International Cosmic Ray Conference, ICRC 2021: . Paper presented at 37th International Cosmic Ray Conference, ICRC 2021, Virtual, Berlin, Germany, Jul 12 2021 - Jul 23 2021. Sissa Medialab Srl, Article ID 066.
Open this publication in new window or tab >>Design and expected performances of the large acceptance calorimeter for the HERD space mission
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2022 (English)In: 37th International Cosmic Ray Conference, ICRC 2021, Sissa Medialab Srl , 2022, article id 066Conference paper, Published paper (Refereed)
Abstract [en]

The High Energy cosmic-Radiation Detection (HERD) is a future space experiment which will be installed on the China’s Space Station around 2027. The main goal of the experiment is the measurement of cosmic rays up to energies which are not explored by the instruments currently operating in space, in particular protons with energies up to PeV, nuclei up to hundreds of TeV per nucleon and electrons up to tens of TeV. HERD will consist of silicon charge detectors, anti-coincidence scintillators, scintillating fiber trackers, a transition radiation detector and a calorimeter. The latter is a homogeneous, deep, 3D segmented calorimeter made of about 7500 LYSO cubic crystals: thanks to this innovative design, it will achieve large acceptance, good energy resolution and excellent electron/proton discrimination. In order to increase both energy calibration capabilities and redundancy of the instrument, the LYSO scintillation light will be read-out by two independent systems: the first is made of wave-length shifting fibers coupled with imaged intensified CMOS cameras, and the second one consists of photodiodes with different active areas connected to a custom front-end electronics. Both read-out systems are designed to have a large dynamic range, up to 107, and a low power consumption. The design of the calorimeter is validated by several Monte Carlo simulations and beam test results obtained with detector prototypes. In this paper we describe the anticipated performances of the calorimeter and the current status of the double read-out system, and we discuss the recent developments of both the HERD prototype and the flight model design.

Place, publisher, year, edition, pages
Sissa Medialab Srl, 2022
Series
Proceedings of Science, ISSN 1824-8039 ; 395
National Category
Accelerator Physics and Instrumentation
Identifiers
urn:nbn:se:kth:diva-331630 (URN)2-s2.0-85144102310 (Scopus ID)
Conference
37th International Cosmic Ray Conference, ICRC 2021, Virtual, Berlin, Germany, Jul 12 2021 - Jul 23 2021
Note

QC 20230713

Available from: 2023-07-13 Created: 2023-07-13 Last updated: 2023-07-13Bibliographically approved
Perrina, C., Pearce, M., Ryde, F., Zhu, K. J. & et al., . (2022). FIT: the scintillating fiber tracker of the HERD space mission. In: 37th International Cosmic Ray Conference, ICRC 2021: . Paper presented at 37th International Cosmic Ray Conference, ICRC 2021, Virtual, Berlin, Germany, Jul 12 2021 - Jul 23 2021. Sissa Medialab Srl, Article ID 067.
Open this publication in new window or tab >>FIT: the scintillating fiber tracker of the HERD space mission
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2022 (English)In: 37th International Cosmic Ray Conference, ICRC 2021, Sissa Medialab Srl , 2022, article id 067Conference paper, Published paper (Refereed)
Abstract [en]

The High Energy cosmic-Radiation Detection (HERD) facility is a space payload proposed to be installed onboard the China’s Space Station (CSS). The aims of HERD are the indirect detection of dark matter, the direct detection of cosmic rays towards the “knee” of the spectrum (∼ 1 PeV) and the monitoring of the full gamma-ray sky from 100 MeV. The HERD core is a calorimeter capable of accepting particles incident on its top and four lateral sides, each equipped with a sector of the scintillating fiber tracker: FIT. The FIT sectors host 7 tracking planes made of modules. The module, composed of a fiber mat and three arrays of silicon photomultipliers (SiPMs), is the elementary brick of FIT. Several FIT modules have been built and tested with particle beams at CERN. A FIT demonstrator, made of two partially instrumented tracking planes, has been assembled and sent through vibration tests. The results of the performed tests as well as the current design of FIT are presented in this contribution.

Place, publisher, year, edition, pages
Sissa Medialab Srl, 2022
Series
Proceedings of Science, ISSN 1824-8039 ; 395
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-331632 (URN)2-s2.0-85144453181 (Scopus ID)
Conference
37th International Cosmic Ray Conference, ICRC 2021, Virtual, Berlin, Germany, Jul 12 2021 - Jul 23 2021
Note

QC 20230713

Available from: 2023-07-13 Created: 2023-07-13 Last updated: 2023-07-13Bibliographically approved
Adriani, O., Pearce, M., Ryde, F. & Zhu, K. J. (2022). Gamma-ray performance study of the HERD payload. In: 37th International Cosmic Ray Conference, ICRC 2021: . Paper presented at 37th International Cosmic Ray Conference, ICRC 2021, Virtual, Berlin, Germany, Jul 12 2021 - Jul 23 2021. Sissa Medialab Srl, Article ID 651.
Open this publication in new window or tab >>Gamma-ray performance study of the HERD payload
2022 (English)In: 37th International Cosmic Ray Conference, ICRC 2021, Sissa Medialab Srl , 2022, article id 651Conference paper, Published paper (Refereed)
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.

Place, publisher, year, edition, pages
Sissa Medialab Srl, 2022
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:kth:diva-333505 (URN)2-s2.0-85145019544 (Scopus ID)
Conference
37th International Cosmic Ray Conference, ICRC 2021, Virtual, Berlin, Germany, Jul 12 2021 - Jul 23 2021
Note

QC 20230802

Available from: 2023-08-02 Created: 2023-08-02 Last updated: 2023-08-02Bibliographically approved
Ryde, F., Iyyani, S., Ahlgren, B., Peer, A., Sharma, V., Lundman, C. & Axelsson, M. (2022). Onset of Particle Acceleration during the Prompt Phase in Gamma-Ray Bursts as Revealed by Synchrotron Emission in GRB 160821A. Astrophysical Journal Letters, 932(2), L15, Article ID L15.
Open this publication in new window or tab >>Onset of Particle Acceleration during the Prompt Phase in Gamma-Ray Bursts as Revealed by Synchrotron Emission in GRB 160821A
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2022 (English)In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 932, no 2, p. L15-, article id L15Article in journal (Refereed) Published
Abstract [en]

The physical processes of gamma-ray emission and particle acceleration during the prompt phase in gamma-ray bursts (GRBs) are still unsettled. In order to perform unambiguous physical modeling of observations, a clear identification of the emission mechanism is needed. An instance of a clear identification is the synchrotron emission during the very strong flare in GRB 160821A, which occurred during the prompt phase at 135 s. Here we show that the distribution of the radiating electrons in this flare is initially very narrow but later develops a power-law tail of accelerated electrons. We thus identify for the first time the onset of particle acceleration in a GRB jet. The flare is consistent with a late energy release from the central engine causing an external shock as it encounters a preexisting ring nebula of a progenitor Wolf-Rayet star. Relativistic forward and reverse shocks develop, leading to two distinct emission zones with similar properties. The particle acceleration only occurs in the forward shock, moving into the dense nebula matter. Here, the magnetization also decreases below the critical value, which allows for Fermi acceleration to operate. Using this fact, we find a bulk Lorentz factor of 420 less than or similar to Gamma less than or similar to 770 and an emission radius of R similar to 10(18) cm, indicating a tenuous gas of the immediate circumburst surroundings. The observation of the onset of particle acceleration thus gives new and independent constraints on the properties of the flow as well as on theories of particle acceleration in collisionless astrophysical shocks.

Place, publisher, year, edition, pages
American Astronomical Society, 2022
National Category
Astronomy, Astrophysics and Cosmology Accelerator Physics and Instrumentation Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-315219 (URN)10.3847/2041-8213/ac73fe (DOI)000813322400001 ()2-s2.0-85133026451 (Scopus ID)
Note

QC 20220701

Available from: 2022-07-01 Created: 2022-07-01 Last updated: 2023-03-22Bibliographically approved
Kamogawa, W., Iyer, N., Kiss, M., Pearce, M., Ryde, F., Stana, T.-A. & Yoshida, Y. (2022). Optical performance of the X-ray telescope for the XL-Calibur experiment. In: DenHerder, JWA Nikzad, S Nakazawa, K (Ed.), Space Telescopes And Instrumentation 2022: Ultraviolet To Gamma Ray. Paper presented at Conference on Space Telescopes and Instrumentation - Ultraviolet to Gamma Ray Part of SPIE Astronomical Telescopes and Instrumentation Conference, July 17-22, 2022, Montreal, CANADA. SPIE-Intl Soc Optical Eng, 12181, Article ID 1218171.
Open this publication in new window or tab >>Optical performance of the X-ray telescope for the XL-Calibur experiment
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2022 (English)In: Space Telescopes And Instrumentation 2022: Ultraviolet To Gamma Ray / [ed] DenHerder, JWA Nikzad, S Nakazawa, K, SPIE-Intl Soc Optical Eng , 2022, Vol. 12181, article id 1218171Conference paper, Published paper (Refereed)
Abstract [en]

XL-Calibur is a balloon-borne mission for hard X-ray polarimetry. The first launch is currently scheduled from Sweden in summer 2022. Japanese collaborators provide a hard X-ray telescope to the mission. The telescope's design is identical to the Hard X-ray Telescope (HXT, conically-approximated Wolter-I optics) on board ASTRO-H with the same focal length of 12 m and the aperture of 45 cm, which can focus X-rays up to 80 keV. The telescope is divided into three segments in the circumferential direction, and confocal 213 grazing-incidence mirrors are precisely placed in the primary and secondary sections of each segment. The surfaces of the mirrors are coated with Pt/C depth-graded multilayer to reflect hard X-rays efficiently by the Bragg reflection. To achieve the best focus, optical adjustment of all of the segments was performed at the SPring-8/BL20B2 synchrotron radiation facility during 2020. A final performance evaluation was conducted in June 2021 and the experiment yields the effective area of 175 cm(2) and 73 cm(2) at 30 keV and 50 keV, respectively, with its half-power diameter of the point spread function as 2.1 arcmin. The field of view, defined as the full width of the half-maximum of the vignetting curve, is 5.9 arcmin.

Place, publisher, year, edition, pages
SPIE-Intl Soc Optical Eng, 2022
Series
Proceedings of SPIE, ISSN 0277-786X
Keywords
X-ray astronomy, XL-Calibur, polarimetry, X-ray telescope
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:kth:diva-321628 (URN)10.1117/12.2626537 (DOI)000865607100164 ()2-s2.0-85140466992 (Scopus ID)
Conference
Conference on Space Telescopes and Instrumentation - Ultraviolet to Gamma Ray Part of SPIE Astronomical Telescopes and Instrumentation Conference, July 17-22, 2022, Montreal, CANADA
Note

QC 20221121

Part of proceedings: ISBN 978-1-5106-5344-3; 978-1-5106-5343-6

Available from: 2022-11-21 Created: 2022-11-21 Last updated: 2022-11-21Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0002-9769-8016

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