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Burgess, J. M. (2019). The rest-frame Golenetskii correlation via a hierarchical Bayesian analysis. Monthly notices of the Royal Astronomical Society, 485(1), 1262-1277
Open this publication in new window or tab >>The rest-frame Golenetskii correlation via a hierarchical Bayesian analysis
2019 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 485, no 1, p. 1262-1277Article in journal (Refereed) Published
Abstract [en]

Gamma-ray bursts (GRBs) are characterized by a strong correlation between the instantaneous luminosity and the spectral peak energy within a burst. This correlation, which is known as the hardness-intensity correlation or the Golenetskii correlation, not only holds important clues to the physics of GRBs but is thought to have the potential to determine redshifts of bursts. In this paper, I use a hierarchical Bayesian model to study the universality of the rest-frame Golenetskii correlation and in particular I assess its use as a redshift estimator for GRBs. I find that, using a power-law prescription of the correlation, the power-law indices cluster near a common value, but have a broader variance than previously reported (similar to 1 - 2). Furthermore, I find evidence that there is a spread in intrinsic rest-frame correlation normalizations for the GRBs in our sample (similar to 10(51)-10(53) erg s(-1)). This points towards variable physical settings of the emission (magnetic field strength, number of emitting electrons, photospheric radius, viewing angle, etc.). Subsequently, these results eliminate the Golenetskii correlation as a useful tool for redshift determination and hence a cosmological probe in its current form. Though, modifications such as the introduction of correction terms similar to supernovae may alleviate these issues. Nevertheless, the Bayesian method introduced in this paper allows for a better determination of the rest-frame properties of the correlation, which in turn allows for more stringent limitations for physical models of the emission to be set.

Place, publisher, year, edition, pages
OXFORD UNIV PRESS, 2019
Keywords
methods: data analysis, methods: statistical, gamma-ray burst: general, LLAPORTAS P, 1995, BIOMETRICS, V51, P1085 loborodov Andrei M., 2010, MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, V407, P1033 R. -J., 2010, ASTROPHYSICAL JOURNAL, V720, P1146 dreon S., 2010, MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, V404, P1922 irlanda G., 2010, ASTRONOMY & ASTROPHYSICS, V510
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:kth:diva-252391 (URN)10.1093/mnras/stx1159 (DOI)000466786400087 ()
Note

QC 20190618

Available from: 2019-06-18 Created: 2019-06-18 Last updated: 2019-06-24Bibliographically approved
Bégué, H. D. & Burgess, J. M. (2016). The anatomy of a long gamma-ray burst: a simple classification scheme for the emission mechanism(s). Astrophysical Journal, 820(1), Article ID 68.
Open this publication in new window or tab >>The anatomy of a long gamma-ray burst: a simple classification scheme for the emission mechanism(s)
2016 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 820, no 1, article id 68Article in journal (Refereed) Published
Abstract [en]

Ultra-relativistic motion and efficient conversion of kinetic energy to radiation are required by gamma-ray burst (GRB) observations, yet they are difficult to simultaneously achieve. Three leading mechanisms have been proposed to explain the observed emission emanating from GRB outflows: radiation from either relativistic internal or external shocks, or thermal emission from a photosphere. Previous works were dedicated to independently treating these three mechanisms and arguing for a sole, unique origin of the prompt emission of GRBs. In contrast, herein, we first explain why all three models are valid mechanisms and that a contribution from each of them is expected in the prompt phase. Additionally, we show that a single parameter, the dimensionless entropy of the GRB outflow, determines which mechanism contributes the most to the emission. More specifically, internal shocks dominate for low values of the dimensionless entropy, external shocks for intermediate values, and finally, photospheric emission for large values. We present a unified framework for the emission mechanisms of GRBs with easily testable predictions for each process.

Place, publisher, year, edition, pages
The American Astronomical Society, 2016
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:kth:diva-184433 (URN)10.3847/0004-637X/820/1/68 (DOI)000372787000067 ()2-s2.0-84961601423 (Scopus ID)
Note

QC 20160419

Available from: 2016-03-31 Created: 2016-03-31 Last updated: 2017-11-30Bibliographically approved
Bhat, P. N., Meegan, C. A., von Kienlin, A., Paciesas, W. S., Briggs, M. S., Burgess, J. M., . . . Zhang, B. (2016). THE THIRD FERMI GBM GAMMA-RAY BURST CATALOG: THE FIRST SIX YEARS. Astrophysical Journal Supplement Series, 223(2), Article ID 28.
Open this publication in new window or tab >>THE THIRD FERMI GBM GAMMA-RAY BURST CATALOG: THE FIRST SIX YEARS
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2016 (English)In: Astrophysical Journal Supplement Series, ISSN 0067-0049, E-ISSN 1538-4365, Vol. 223, no 2, article id 28Article in journal (Refereed) Published
Abstract [en]

Since its launch in 2008, the Fermi Gamma-ray Burst Monitor (GBM) has triggered and located on average approximately two.-ray bursts (GRBs) every three days. Here, we present the third of a series of catalogs of GRBs detected by GBM, extending the second catalog by two more years through the middle of 2014 July. The resulting list includes 1405 triggers identified as GRBs. The intention of the GBM GRB catalog is to provide information to the community on the most important observables of the GBM-detected GRBs. For each GRB, the location and main characteristics of the prompt emission, the duration, peak flux, and fluence are derived. The latter two quantities are calculated for the 50-300 keV energy band where the maximum energy release of GRBs in the instrument reference system is observed, and also for a broader energy band from 10 to 1000 keV, exploiting the full energy range of GBM's low-energy [NaI[Tl)] detectors. Using statistical methods to assess clustering, we find that the hardness and duration of GRBs are better fit by a two-component model with short-hard and long-soft bursts than by a model with three components. Furthermore, information is provided on the settings and modifications of the triggering criteria and exceptional operational conditions during years five and six in the mission. This third catalog is an official product of the Fermi GBM science team, and the data files containing the complete results are available from the High-Energy Astrophysics Science Archive Research Center.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2016
Keywords
catalogs, gamma-ray burst: general
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:kth:diva-187825 (URN)10.3847/0067-0049/223/2/28 (DOI)000375304600010 ()2-s2.0-84964842282 (Scopus ID)
Note

QC 20160531

Available from: 2016-05-31 Created: 2016-05-30 Last updated: 2017-11-30Bibliographically approved
Burgess, J. M. & Ryde, F. (2015). Are GRB blackbodies an artefact of spectral evolution?. Monthly notices of the Royal Astronomical Society, 447(4), 3087-3094
Open this publication in new window or tab >>Are GRB blackbodies an artefact of spectral evolution?
2015 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 447, no 4, p. 3087-3094Article in journal (Refereed) Published
Abstract [en]

The analysis of gamma-ray burst (GRB) spectra with multicomponent emission models has become an important part of the field. In particular, multicomponent analysis where one component is a blackbody representing emission from a photosphere has enabled both a more detailed understanding of the energy content of the jet as well as the ability to examine the dynamic structure of the outflow. While the existence of a blackbody-like component has been shown to be significant and not a byproduct of background fluctuations, it is very possible that it can be an artefact of spectral evolution of a single component that is being poorly resolved in time. Herein, this possibility is tested by simulating a single component evolving in time and then folding the spectra through the Fermi detector response to generate time-tagged event Gamma-ray Burst Monitor (GBM) data. We then fit both the time-integrated and -resolved generated spectral data with a multicomponent model using standard tools. It is found that in time-integrated spectra, a blackbody can be falsely identified due to the spectral curvature introduced by the spectral evolution. However, in a time-resolved analysis defined by time bins that can resolve the evolution of the spectra, the significance of the falsely identified blackbody is very low. Additionally, the evolution of the artificial blackbody parameters does not match the recurring behaviour that has been identified in the actual observations. These results reinforce the existence of the blackbody found in time-resolved analysis of GRBs and stress the point that caution should be taken when using time-integrated spectral analysis for identifying physical properties of GRBs.

Keywords
radiation mechanisms: thermal, methods: data analysis
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:kth:diva-163442 (URN)10.1093/mnras/stu2670 (DOI)000350273400009 ()
Note

QC 20150408

Available from: 2015-04-08 Created: 2015-04-07 Last updated: 2017-12-04Bibliographically approved
Larsson, J., Racusin, J. L. & Burgess, J. M. (2015). Evidence for jet launching close to the black hole in GRB 101219b: A Fermi grb dominated by thermal emission. Astrophysical Journal Letters, 800(2), Article ID L34.
Open this publication in new window or tab >>Evidence for jet launching close to the black hole in GRB 101219b: A Fermi grb dominated by thermal emission
2015 (English)In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 800, no 2, article id L34Article in journal (Refereed) Published
Abstract [en]

We present observations by the Fermi Gamma-Ray Space Telescope Gamma-Ray Burst Monitor (GBM) of the nearby (z = 0.55) GRB 101219B. This burst is a long GRB, with an associated supernova and with a blackbody (BB) component detected in the early afterglow observed by the Swift X-ray Telescope (XRT). Here we show that the prompt gamma-ray emission has a BB spectrum, making this the second such burst observed by Fermi GBM. The properties of the BB, together with the redshift and our estimate of the radiative efficiency makes it possible to calculate the absolute values of the properties of the outflow. We obtain an initial Lorentz factor G = 138 +/- 8, a photospheric radius r(phot) = 4.4 +/- 1.9 x 10(11) cm, and a launch radius r(0) = 2.7 +/- 1.6 x 10(7) cm. The latter value is close to the black hole and suggests that the jet has a relatively unobstructed path through the star. There is no smooth connection between the BB components seen by GBM and XRT, ruling out the scenario that the late emission is due to high-latitude effects. In the interpretation that the XRT BB is prompt emission due to late central engine activity, the jet either has to be very wide or have a clumpy structure where the emission originates from a small patch. Other explanations for this component, such as emission from a cocoon surrounding the jet, are also possible.

Keywords
gamma-ray burst, general, gamma-ray burst, individual (GRB 101219B), radiation mechanisms, thermal
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:kth:diva-161955 (URN)10.1088/2041-8205/800/2/L34 (DOI)000349692900015 ()2-s2.0-84923641901 (Scopus ID)
Note

QC 20150408

Available from: 2015-04-08 Created: 2015-03-20 Last updated: 2017-12-04Bibliographically approved
Iyyani, S., Ryde, F., Ahlgren, B., Burgess, J. M., Larsson, J., Pe'er, A., . . . McGlynn, S. (2015). Extremely narrow spectrum of GRB110920A: further evidence for localized, subphotospheric dissipation. Monthly notices of the Royal Astronomical Society, 450(2), 1651-1663
Open this publication in new window or tab >>Extremely narrow spectrum of GRB110920A: further evidence for localized, subphotospheric dissipation
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2015 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 450, no 2, p. 1651-1663Article in journal (Refereed) Published
Abstract [en]

Much evidence points towards that the photosphere in the relativistic outflow in GRBs plays an important role in shaping the observed MeV spectrum. However, it is unclear whether the spectrum is fully produced by the photosphere or whether a substantial part of the spectrum is added by processes far above the photosphere. Here we make a detailed study of the. ray emission from single pulse GRB110920A which has a spectrum that becomes extremely narrow towards the end of the burst. We show that the emission can be interpreted as Comptonization of thermal photons by cold electrons in an unmagnetized outflow at an optical depth of tau similar to 20. The electrons receive their energy by a local dissipation occurring close to the saturation radius. The main spectral component of GRB110920A and its evolution is thus, in this interpretation, fully explained by the emission from the photosphere including localized dissipation at high optical depths.

National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-170964 (URN)10.1093/mnras/stv636 (DOI)000356338500039 ()
Note

QC 20150713

Available from: 2015-07-13 Created: 2015-07-13 Last updated: 2017-12-04Bibliographically approved
Connaughton, V., Briggs, M. S., Goldstein, A., Meegan, C. A., Paciesas, W. S., Preece, R. D., . . . Zhang, B. B. (2015). Localization of Gamma-Ray Bursts Using the Fermi Gamma-Ray Burst Monitor. Astrophysical Journal Supplement Series, 216(2), Article ID 32.
Open this publication in new window or tab >>Localization of Gamma-Ray Bursts Using the Fermi Gamma-Ray Burst Monitor
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2015 (English)In: Astrophysical Journal Supplement Series, ISSN 0067-0049, E-ISSN 1538-4365, Vol. 216, no 2, article id 32Article in journal (Refereed) Published
Abstract [en]

The Fermi Gamma-ray Burst Monitor (GBM) has detected over 1400 gamma-ray bursts (GRBs) since it began science operations in 2008 July. We use a subset of over 300 GRBs localized by instruments such as Swift, the Fermi Large Area Telescope, INTEGRAL, and MAXI, or through triangulations from the InterPlanetary Network, to analyze the accuracy of GBM GRB localizations. We find that the reported statistical uncertainties on GBM localizations, which can be as small as 1°, underestimate the distance of the GBM positions to the true GRB locations and we attribute this to systematic uncertainties. The distribution of systematic uncertainties is well represented (68% confidence level) by a 3.°7 Gaussian with a non-Gaussian tail that contains about 10% of GBM-detected GRBs and extends to approximately 14°. A more complex model suggests that there is a dependence of the systematic uncertainty on the position of the GRB in spacecraft coordinates, with GRBs in the quadrants on the Y axis better localized than those on the X axis.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2015
Keywords
GBM
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:kth:diva-184444 (URN)10.1088/0067-0049/216/2/32 (DOI)000350899000011 ()2-s2.0-84923384641 (Scopus ID)
Note

QC 20160408

Available from: 2016-03-31 Created: 2016-03-31 Last updated: 2017-11-30Bibliographically approved
Troja, E., Piro, L., Vasileiou, V., Omodei, N. & Burgess, J. M. (2015). Swift and Fermi observations of X-ray flares: the case of Late Internal Shock. Astrophysical Journal, 803(1)
Open this publication in new window or tab >>Swift and Fermi observations of X-ray flares: the case of Late Internal Shock
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2015 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 803, no 1Article in journal (Refereed) Published
Abstract [en]

Simultaneous Swift and Fermi observations of gamma-ray bursts (GRBs) offer a unique broadband view of their afterglow emission, spanning more than 10 decades in energy. We present the sample of X-ray flares observed by both Swift and Fermi during the first three years of Fermi operations. While bright in the X-ray band, X-ray flares are often undetected at lower (optical), and higher (MeV to GeV) energies. We show that this disfavors synchrotron self-Compton processes as the origin of the observed X-ray emission. We compare the broadband properties of X-ray flares with the standard late internal shock model, and find that in this scenario, X-ray flares can be produced by a late-time relativistic (Γ > 50) outflow at radii R ∼ 1013-1014 cm. This conclusion holds only if the variability timescale is significantly shorter than the observed flare duration, and implies that X-ray flares can directly probe the activity of the GRB central engine.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2015
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:kth:diva-184447 (URN)10.1088/0004-637X/803/1/10 (DOI)000353015400010 ()2-s2.0-84927591081 (Scopus ID)
Note

QC 20160331

Available from: 2016-03-31 Created: 2016-03-31 Last updated: 2017-11-30Bibliographically approved
Yu, H.-F., Greiner, J., van Eerten, H., Burgess, J. M., Bhat, P. N., Briggs, M. S., . . . Zhang, B.-B. (2015). Synchrotron cooling in energetic gamma-ray bursts observed by the Fermi Gamma-Ray Burst Monitor. Astronomy and Astrophysics, 573, Article ID A81.
Open this publication in new window or tab >>Synchrotron cooling in energetic gamma-ray bursts observed by the Fermi Gamma-Ray Burst Monitor
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2015 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 573, article id A81Article in journal (Refereed) Published
Abstract [en]

Context. We study the time-resolved spectral properties of energetic gamma-ray bursts (GRBs) with good high-energy photon statistics observed by the Gamma-Ray Burst Monitor ((IBM) onboard the Fermi Gamma-Ray Space Telescope. Aims. We aim to constrain in detail the spectral properties of GRB prompt emission on a time-resolved basis and to discuss the theoretical implications of the fitting results in the context of various prompt emission models. Methods. Our sample comprises eight GRBs observed by the Fermi (IBM in its first five years of mission, with 1 keV-1 MeV fluence f > 1.0 x 10(-4) erg cm(-2) and a signal-to-noise ratio level of S/N >= 10.0 above 900 keV. We performed a time-resolved spectral analysis using a variable temporal binning technique according to optimal S/N criteria, resulting in a total of 299 time-resolved spectra. We performed Band function fits to all spectra and obtained the distributions for the low-energy power-lay index alpha, the high-energy power-law index beta, the peak energy in the observed nu F-nu, spectrum E-p, and the difference between the low- and high-energy power-law indices Delta s = alpha-beta. We also applied a physically motivated synchrotron model, which is a triple power-law with constrained power-law indices and a blackbody component, to test the prompt emission for consistency with a synchrotron origin and obtain the distributions for the two break energies E-b,E-1 and E-b,E-2 the middle segment power-law index beta, and the Planck function temperature kT. Results. The Band function parameter distributions are alpha = -0.73(-0.21)(+0.16), beta = -2.13(-0.56)(+0.28), E-p = 374.47(-187.7)(+307.3) keV (log(10) E-p = 2.577(-0.30)(+0.26)), and Delta s = 1.38(-0.31)(+0.54), with average errors sigma(alpha) similar to 0.1, sigma(beta) similar to 0.2, and sigma(Ep) similar to 0.1E(p). Using the distributions of Delta s and beta, the electron population index p is found to be consistent with the "moderately fast" scenario, in which fast- and slow-cooling scenarios cannot be distinguished. The physically motivated synchrotron-fitting function parameter distributions are E-b,E-1 = 129.6(-32.4)(+132.2) keV, E-b,E-2 = 631.4(-309.6)(+582) keV, beta = 1.721(-0.25)(+0.48), and kT = 10.4(-3.7)(+4.9) keV, with average errors sigma(beta) similar to 0.2, sigma E-b,E-1 similar to 0.1E(b,1), sigma E-b,E-2 similar to 0.4E(b,2,) and sigma(kT) similar to 0.1kT. This synchrotron function requires the synchrotron injection and cooling break (i.e., E-min and E-cool) to be close to each other within a factor of ten, often in addition to a Planck function. Conclusions. A synchrotron model is found that is consistent with most of the time-resolved spectra for eight energetic Fermi (IBM bursts with good high-energy photon statistics as long as both the cooling and injection break are included and the leftmost spectral slope is lifted either by including a thermal component or when an evolving magnetic field is accounted for.

Keywords
gamma rays: stars, gamma-ray burst: general, radiation mechanisms: non-thermal, methods: data analysis
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:kth:diva-161628 (URN)10.1051/0004-6361/201424858 (DOI)000346901300085 ()2-s2.0-84919781951 (Scopus ID)
Note

QC 20150324

Available from: 2015-03-24 Created: 2015-03-13 Last updated: 2017-12-04Bibliographically approved
Iyyani, S., Ryde, F., Burgess, J. M. & Bégué, D. (2015). Synchrotron emission in GRBs observed with Fermi: Its limitations and the role of the photosphere. Monthly notices of the Royal Astronomical Society, 456(2), 2157-2171
Open this publication in new window or tab >>Synchrotron emission in GRBs observed with Fermi: Its limitations and the role of the photosphere
2015 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 456, no 2, p. 2157-2171Article in journal (Refereed) Published
Abstract [en]

It has been suggested that the prompt emission in gamma-ray bursts consists of several components giving rise to the observed spectral shape. Here we examine a sample of the eight brightest, single pulsed Fermi bursts whose spectra are modelled by using synchrotron emission as one of the components. Five of these bursts require an additional photospheric component (blackbody). In particular, we investigate the inferred properties of the jet and the physical requirements set by the observed components for these five bursts, in the context of a baryonic dominated outflow, motivated by the strong photospheric component. We find similar jet properties for all five bursts: the bulk Lorentz factor decreases monotonously over the pulses and lies between 1000 and 100. This evolution is robust and can neither be explained by a varying radiative efficiency nor a varying magnetization of the jet (assuming the photosphere radius is above the coasting radius). Such a behaviour challenges several dissipation mechanisms, e.g. the internal shocks. Furthermore, in all eight cases the data clearly reject a fast-cooled synchrotron spectrum (in which a significant fraction of the emitting electrons have cooled to energies below the minimum injection energy), inferring a typical electron Lorentz factor of 104-107. Such values are much higher than what is typically expected in internal shocks. Therefore, while the synchrotron scenario is not rejected by the data, the interpretation does present several limitations that need to be addressed. Finally, we point out and discuss alternative interpretations.

Place, publisher, year, edition, pages
Oxford University Press, 2015
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:kth:diva-184446 (URN)10.1093/mnras/stv2751 (DOI)000372264200073 ()2-s2.0-84960830793 (Scopus ID)
Funder
Swedish Research Council
Note

QC 20160408

Available from: 2016-03-31 Created: 2016-03-31 Last updated: 2017-11-30Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-3345-9515

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