We present the fourth in a series of catalogs of gamma-ray bursts (GRBs) observed with Fermi's Gamma-ray Burst Monitor (Fermi-GBM). It extends the six year catalog by four more years, now covering ...the 10 year time period from trigger enabling on 2008 July 12 to 2018 July 11. During this time period GBM triggered almost twice a day on transient events, 2356 of which we identified as cosmic GRBs. Additional trigger events were due to solar flare events, magnetar burst activities, and terrestrial gamma-ray flashes. The intention of the GBM GRB catalog series is to provide updated 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 10-1000 keV, exploiting the full energy range of GBM's low-energy detectors. Furthermore, information is given on the settings of the triggering criteria and exceptional operational conditions during years 7 to 10 in the mission. This fourth 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.
On 2017 August 17 at 12:41:06 UTC the Fermi Gamma-ray Burst Monitor (GBM) detected and triggered on the short gamma-ray burst (GRB) 170817A. Approximately 1.7 s prior to this GRB, the Laser ...Interferometer Gravitational-wave Observatory triggered on a binary compact merger candidate associated with the GRB. This is the first unambiguous coincident observation of gravitational waves and electromagnetic radiation from a single astrophysical source and marks the start of gravitational-wave multi-messenger astronomy. We report the GBM observations and analysis of this ordinary short GRB, which extraordinarily confirms that at least some short GRBs are produced by binary compact mergers.
The capability of the Fermi Gamma-ray Burst Monitor (GBM) to localize gamma-ray bursts (GRBs) is evaluated for two different automated algorithms: the GBM Team's RoboBA algorithm and the ...independently developed BALROG algorithm. Through a systematic study utilizing over 500 GRBs with known locations from instruments like Swift and the Fermi Large Area Telescope, we directly compare the effectiveness of, and accurately estimate the systematic uncertainty for, both algorithms. We show that simple adjustments to the GBM Team's RoboBA, in operation since early 2016, yield significant improvement in the systematic uncertainty, removing the long tail identified in the systematic, and improve the overall accuracy. The systematic uncertainty for the updated RoboBA localizations is 1 8 for 52% of GRBs and 4 1 for the remaining 48%. Both from public reporting by BALROG and our systematic study, we find the systematic uncertainty of 1°-2° quoted in circulars for bright GRBs is an underestimate of the true magnitude of the systematic, which we find to be 2 7 for 74% of GRBs and 33° for the remaining 26%. We show that, once the systematic uncertainty is considered, the RoboBA 90% localization confidence regions can be more than an order of magnitude smaller in area than those produced by BALROG.
ABSTRACT With an instantaneous view of 70% of the sky, the Fermi Gamma-ray Burst Monitor (GBM) is an excellent partner in the search for electromagnetic counterparts to gravitational-wave (GW) ...events. GBM observations at the time of the Laser Interferometer Gravitational-wave Observatory (LIGO) event GW150914 reveal the presence of a weak transient above 50 keV, 0.4 s after the GW event, with a false-alarm probability of 0.0022 (2.9 ). This weak transient lasting 1 s was not detected by any other instrument and does not appear to be connected with other previously known astrophysical, solar, terrestrial, or magnetospheric activity. Its localization is ill-constrained but consistent with the direction of GW150914. The duration and spectrum of the transient event are consistent with a weak short gamma-ray burst (GRB) arriving at a large angle to the direction in which Fermi was pointing where the GBM detector response is not optimal. If the GBM transient is associated with GW150914, then this electromagnetic signal from a stellar mass black hole binary merger is unexpected. We calculate a luminosity in hard X-ray emission between 1 keV and 10 MeV of 1.8 − 1.0 + 1.5 × 10 49 erg s−1. Future joint observations of GW events by LIGO/Virgo and Fermi GBM could reveal whether the weak transient reported here is a plausible counterpart to GW150914 or a chance coincidence, and will further probe the connection between compact binary mergers and short GRBs.
In light of the joint multimessenger detection of a binary neutron star merger as the gamma-ray burst GRB 170817A and in gravitational waves as GW170817, we reanalyze the Fermi Gamma-ray Burst ...Monitor data of one of the closest short gamma-ray bursts (SGRBs): GRB 150101B. We find that this burst is composed of a short hard spike followed by a comparatively long soft tail. This apparent two-component nature is phenomenologically similar to that of GRB 170817A. While GRB 170817A was distinct from the previously known population of SGRBs in terms of its prompt intrinsic energetics, GRB 150101B is not. Despite these differences, GRB 150101B can be modeled as a more on-axis version of GRB 170817A. Identifying a similar signature in two of the closest SGRBs suggests that the soft tail is common, but generally undetectable in more distant events. If so, it will be possible to identify nearby SGRBs from the prompt gamma-ray emission alone, aiding the search for kilonovae.
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 1degrees, 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 3degrees.7 Gaussian with a non-Gaussian tail that contains about 10% of GBM-detected GRBs and extends to approximately 14degrees. 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.
The weak transient detected by the Fermi Gamma-ray Burst Monitor (GBM) 0.4 s after GW150914 has generated much speculation regarding its possible association with the black hole binary merger. ...Investigation of the GBM data by Connaughton et al. revealed a source location consistent with GW150914 and a spectrum consistent with a weak, short gamma-ray burst. Greiner et al. present an alternative technique for fitting background-limited data in the low-count regime, and call into question the spectral analysis and the significance of the detection of GW150914-GBM presented in Connaughton et al. The spectral analysis of Connaughton et al. is not subject to the limitations of the low-count regime noted by Greiner et al. We find Greiner et al. used an inconsistent source position and did not follow the steps taken in Connaughton et al. to mitigate the statistical shortcomings of their software when analyzing this weak event. We use the approach of Greiner et al. to verify that our original spectral analysis is not biased. The detection significance of GW150914-GBM is established empirically, with a false-alarm rate (FAR) of Hz. A post-trials false-alarm probability (FAP) of ( ) of this transient being associated with GW150914 is based on the proximity in time to the gravitational-wave event of a transient with that FAR. The FAR and the FAP are unaffected by the spectral analysis that is the focus of Greiner et al.
Aims: In this paper we examine gamma-ray and optical data of GRB 091024, a gamma-ray burst (GRB) with an extremely long duration of T90 $\approx$ 1020 s, as observed with the Fermi Gamma-ray Burst ...Monitor (GBM). Methods: We present spectral analysis of all three distinct emission episodes using data from Fermi/GBM. Because of the long nature of this event, many ground-based optical telescopes slewed to its location within a few minutes and thus were able to observe the GRB during its active period. We compare the optical and gamma-ray light curves. Furthermore, we estimate a lower limit on the bulk Lorentz factor from the variability and spectrum of the GBM light curve and compare it with that obtained from the peak time of the forward shock of the optical afterglow. Results: From the spectral analysis we note that, despite its unusually long duration, this burst is similar to other long GRBs, i.e. there is spectral evolution (both the peak energy and the spectral index vary with time) and spectral lags are measured. We find that the optical light curve is highly anti-correlated to the prompt gamma-ray emission, with the optical emission reaching the maximum during an epoch of quiescence in the prompt emission. We interpret this behavior as the reverse shock (optical flash), expected in the internal-external shock model of GRB emission but observed only in a handful of GRBs so far. The lower limit on the initial Lorentz factor deduced from the variability time scale (Γmin = 195_-110+90) is consistent within the error to the one obtained using the peak time of the forward shock (Γ0 = 120) and is also consistent with Lorentz factors of other long GRBs.
Aims. In this paper we study the main spectral and temporal properties of gamma-ray bursts (GRBs) observed by Fermi/GBM. We investigate these key properties of GRBs in the rest-frame of the ...progenitor and test for possible intra-parameter correlations to better understand the intrinsic nature of these events. Methods. Our sample comprises 32 GRBs with measured redshift that were observed by GBM until August 2010. 28 of them belong to the long-duration population and 4 events were classified as short/hard bursts. For all of these events we derive, where possible, the intrinsic peak energy in the νFν spectrum (Ep,rest), the duration in the rest-frame, defined as the time in which 90% of the burst fluence was observed (T90,rest) and the isotropic equivalent bolometric energy (Eiso). Results. The distribution of Ep,rest has mean and median values of 1.1 MeV and 750 keV, respectively. A log-normal fit to the sample of long bursts peaks at ~800 keV. No high-Ep population is found but the distribution is biased against low Ep values. We find the lowest possible Ep that GBM can recover to be ≈ 15 keV. The T90,rest distribution of long GRBs peaks at ~10 s. The distribution of Eiso has mean and median values of 8.9 × 1052 erg and 8.2 × 1052 erg, respectively. We confirm the tight correlation between Ep,rest and Eiso (Amati relation) and the one between Ep,rest and the 1-s peak luminosity (Lp) (Yonetoku relation). Additionally, we observe a parameter reconstruction effect, i.e. the low-energy power law index α gets softer when Ep is located at the lower end of the detector energy range. Moreover, we do not find any significant cosmic evolution of neither Ep,rest nor T90,rest.
THE FIVE YEAR FERMI/GBM MAGNETAR BURST CATALOG Collazzi, A. C.; Kouveliotou, C.; Horst, A. J. van der ...
The Astrophysical journal. Supplement series,
05/2015, Letnik:
218, Številka:
1
Journal Article
Recenzirano
Odprti dostop
ABSTRACT Since launch in 2008, the Fermi Gamma-ray Burst Monitor (GBM) has detected many hundreds of bursts from magnetar sources. While the vast majority of these bursts have been attributed to ...several known magnetars, there is also a small sample of magnetar-like bursts of unknown origin. Here, we present the Fermi/GBM magnetar catalog, providing the results of the temporal and spectral analyses of 440 magnetar bursts with high temporal and spectral resolution. This catalog covers the first five years of GBM magnetar observations, from 2008 July to 2013 June. We provide durations, spectral parameters for various models, fluences, and peak fluxes for all the bursts, as well as a detailed temporal analysis for SGR J1550-5418 bursts. Finally, we suggest that some of the bursts of unknown origin are associated with the newly discovered magnetar 3XMM J185246.6+0033.7.
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