A Decade of Gamma-Ray Bursts Observed by Fermi-LAT: The Second GRB Catalog

Abstract

The Large Area Telescope (LAT) aboard the Fermi spacecraft routinely observes high-energy emission from gamma-ray bursts (GRBs). Here we present the second catalog of LAT-detected GRBs, covering the first 10 yr of operations, from 2008 to 2018 August 4. A total of 186 GRBs are found; of these, 91 show emission in the range 30-100 MeV (17 of which are seen only in this band) and 169 are detected above 100 MeV. Most of these sources were discovered by other instruments (Fermi/GBM, Swift/BAT, AGILE, INTEGRAL) or reported by the Interplanetary Network (IPN); the LAT has independently triggered on four GRBs. This catalog presents the results for all 186 GRBs. We study onset, duration, and temporal properties of each GRB, as well as spectral characteristics in the 100 MeV-100 GeV energy range. Particular attention is given to the photons with the highest energy. Compared with the first LAT GRB catalog, our rate of detection is significantly improved. The results generally confirm the main findings of the first catalog: the LAT primarily detects the brightest GBM bursts, and the high-energy emission shows delayed onset as well as longer duration. However, in this work we find delays exceeding 1 ks and several GRBs with durations over 10 ks. Furthermore, the larger number of LAT detections shows that these GRBs not only cover the high-fluence range of GBM-detected GRBs but also sample lower fluences. In addition, the greater number of detected GRBs with redshift estimates allows us to study their properties in both the observer and rest frames. Comparison of the observational results with theoretical predictions reveals that no model is currently able to explain all results, highlighting the role of LAT observations in driving theoretical models.

Magnetohydrodynamic simulations of binary neutron star mergers in general relativity: Effects of magnetic field orientation on jet launching

“…Here B and ρ 0 are the strength of the magnetic field and the rest-mass density, respectively. As in the BHNS case, the lifetime of the jet and its associated Poynting luminosity are consistent with typical sGRBs [20][21][22][23], as well as with the BZ mechanism. Note that in the GRMHD simulations reported in [31][32][33], where the magnetic field is confined to the NS interior, neither an outgoing outflow nor a jet were observed.…”

Two-component Jets of GRB 160623A as Shocked Jet Cocoon Afterglow

“…the collapsar jet case; Peng et al (2005)) and the identical micro-physical parameters (n, ǫ B , and ǫ e ) to the wide jet (Nakar, & Piran 2017) with the synchrotron slope of p ∼ 2 (based on the X-ray spectrum) and the narrow jet opening angle of 5.5 • , we confirmed that the expected narrow jet components in X-ray and radio bands can describe the observed light curves (Figure 2). Considering the prompt phase of GRB160623A missed by Fermi/LAT (Figure 1), the huge total energy (∼ 8.5 × 10 53 erg) is likely reasonable as same as other energitic (> 10 54 erg) Fermi/LAT events (e.g., Abdo et al 2009;Urata et al 2012;Ajello et al 2019). In fact, even the late phase radiation in 100MeV-10GeV reached (2.4 ± 0.3) × 10 52 erg (Ajello et al 2019).…”

“…Considering the prompt phase of GRB160623A missed by Fermi/LAT (Figure 1), the huge total energy (∼ 8.5 × 10 53 erg) is likely reasonable as same as other energitic (> 10 54 erg) Fermi/LAT events (e.g., Abdo et al 2009;Urata et al 2012;Ajello et al 2019). In fact, even the late phase radiation in 100MeV-10GeV reached (2.4 ± 0.3) × 10 52 erg (Ajello et al 2019). This result therefore implies that the GRB160623A radio afterglow originated from a relativistic cocoon afterglow.…”

“…The highest-energy photon within the 2500 1 http://cgbm.calet.jp/cgbm trigger/flight/ sec time coverage was ∼3.4 GeV at 1315 sec after the burst, which was considerably after the main pulse observed with CALET and Konus-Wind. According to the Fermi/LAT GRB catalog (Ajello et al 2019), the energetic photon at 18 GeV was also observed at 12038.53 sec after the burst. Figure 1 shows the light curves obtained by CALET/SGM (100-230 keV), Fermi/GBM (10-1000 keV), and Fermi/LAT (> 100 MeV) along with the photon energy distribution for an energy higher than 100 MeV.…”

Origin for the Prompt Spectral Evolution Characteristics and High Energy Emission during the X-Ray Flare in GRB 180720B

“…2 For the LAT data, we also used the gtBurst code to make unbinned maximum likelihood analysis. According to Ajello et al (2019), we selected the Pass 8 P8R2 TRANSIENT020E V6 event class and the corresponding response function for the time window starting at the trigger time T 0 and ending at 100 s after the GBM trigger (bottom panel in Figure 1). Another time window starting at the trigger time T 0 and ending at 10000 s after the GBM trigger, we selected the Pass 8 P8R2 TRANSIENT010E V6 event class and the corresponding response function (Table 1).…”