The Fermi-LAT collaboration presented the second gamma-ray burst (GRB) catalog covering its first 10 years of operations. A significant fraction of afterglow-phase light curves in this catalog cannot ...be explained by the closure relations of the standard synchrotron forward-shock model, suggesting that there could be an important contribution from another process. In view of the above, we derive the synchrotron self-Compton (SSC) light curves from the reverse shock in the thick- and thin-shell regime for a uniform-density medium. We show that this emission could explain the GeV flares exhibited in some LAT light curves. Additionally, we demonstrate that the passage of the forward shock synchrotron cooling break through the LAT band from jets expanding in a uniform-density environment may be responsible for the late time ( 102 s) steepening of LAT GRB afterglow light curves. As a particular case, we model the LAT light curve of GRB 160509A that exhibited a GeV flare together with a break in the long-lasting emission, and also two very high energy photons with energies of 51.9 and 41.5 GeV observed 76.5 and 242 s after the onset of the burst, respectively. Constraining the microphysical parameters and the circumburst density from the afterglow observations, we show that the GeV flare is consistent with an SSC reverse-shock model, the break in the long-lasting emission with the passage of the synchrotron cooling break through the Fermi-LAT band, and the very energetic photons with SSC emission from the forward shock, when the outflow carries a significant magnetic field (RB 30) and it decelerates in a uniform-density medium with a very low density ( ).
ABSTRACT
Since neutrinos can escape from dense regions without being deflected, they are promising candidates to study the new physics at the sources that produce them. With the increasing ...development of more sensitive detectors in the coming years, we will infer several intrinsic properties from incident neutrinos. In particular, we centralize our study in those produced by thermal processes in short gamma-ray bursts (sGRBs) and their interactions within the central engine’s anisotropic medium. On the one hand, we consider baryonic winds produced with a strong magnetic contribution, and on the other hand, we treat only neutrino-driven winds. First, we obtain the effective neutrino potential considering both baryonic density profiles around the central engine. Then, we get the three-flavour oscillation probabilities in this medium to finally calculate the expected neutrino ratios. We find a stronger angular dependence on the expected neutrino ratios, which, incidentally, contrast from the expected theoretical ratios without considering the winds’ additional contribution. The joint analysis of this observable, together with the sGRB ejected jet angle, might lead to an effective mechanism to discriminate between the involved merger progenitors (black hole-neutron star (BH-NS) or neutron-star neutron-star(NS-NS)), acting as an additional detection channel to gravitational waves.
ABSTRACT One of the most powerful gamma-ray bursts, GRB 130427A was swiftly detected from GeV γ-rays to optical wavelengths. In the GeV band, the Large Area Telescope (LAT) on board the Fermi ...Gamma-Ray Space Telescope observed the highest-energy photon ever recorded of 95 GeV and a bright peak in the early phase followed by emission temporally extended for more than 20 hr. In the optical band, a bright flash with a magnitude of 7.03 0.03 in the time interval from 9.31 to 19.31 s after the trigger was reported by RAPTOR in r band. We study the origin of the GeV γ-ray emission, using the multiwavelength observation detected in X-ray and optical bands. The origin of the temporally extended LAT, X-ray, and optical flux is naturally interpreted as synchrotron radiation, and the 95 GeV photon and the integral flux upper limits placed by the high-altitude water Cerenkov observatory are consistent with synchrotron self-Compton from an adiabatic forward shock propagating into the stellar wind of its progenitor. The extreme LAT peak and the bright optical flash are explained through synchrotron self-Compton and synchrotron emission from the reverse shock, respectively, when the ejecta evolves in the thick-shell regime and carries a significant magnetic field.
Abstract
Gamma-ray bursts (GRBs) are fascinating events due to their panchromatic nature. Their afterglow emission is observed from sub-TeV energies to radio wavelengths. We investigate GRBs that ...present an optical plateau, leveraging on the resemblance with the X-ray plateau shown in many GRB light curves (LCs). We comprehensively analyze all published GRBs with known redshifts and optical plateau observed mostly by the Neil Gehrels Swift Observatory (Swift). We fit 267 optical LCs and show the existence of the plateau in 102 cases, which is the largest compilation so far of optical plateaus. For 56 Swift GRBs with optical and X-ray plateaus, we compare the rest-frame end time at both wavelengths (
,
), and conclude that the plateau is achromatic between
and
. We also confirm the existence of the two-dimensional relations between
and the optical luminosity at the end of the plateau emission, which resembles the same luminosity–time correlation in X-rays (Dainotti et al. 2013). The existence of this optical correlation has been demonstrated for the largest sample of optical plateaus in the literature to date. The squared scatter in this optical correlation is smallest for the subset of the Gold GRBs with a decrease in the scatter equivalent to 52.4% when compared to the scatter of the entire GRB sample.
Abstract
A large fraction of gamma-ray burst (GRB) lightcurves (LCs) show X-ray plateaus. We analyze all GRBs with known redshifts presenting plateaus observed by The Neil Gehrels Swift Observatory ...from its launch until 2019 August. The fundamental plane relation between the rest-frame time and X-ray luminosity at the end of the plateau emission and the peak prompt luminosity holds for all the GRB classes when selection biases and cosmological evolutions are applied. We have discovered two important findings: (1) a new class of long GRBs with good data coverage: the platinum sample; and (2) the platinum, the SNe-LGRB, and the KN-SGRB samples, yield the smallest intrinsic scatter with
σ
platinum
,
GRB−SNe
= 0.22 ± 0.10 and
σ
KN−SGRB
= 0.24 ± 0.12. The SNe-LGRBs are composed of GRBs associated spectroscopically with the SNe Ib,c, the KN-SGRBs are composed by eight GRBs associated with kilonovae or where there could have been such an association. The highest correlation coefficients are yielded for the SN-LGRB-ABC sample, which includes GRBs spectroscopically associated with SNe Ib/c or with a clear optical bump in the LC resembling the SNe Ib/c, (
), the SN-LGRBs (
), and the KN-SGRBs (
) when the redshift evolution is considered. These category planes are reliable candidates to use as cosmological tools. Furthermore, the distance from the gold fundamental plane is a crucial discriminant among classes. In fact, we find that the distributions of the distances of the SNe-LGRB, SNe-LGRB-ABC, KN-SGRB, and SGRB samples from the gold fundamental plane are statistically different from the distribution of the gold GRBs’ distances from the gold fundamental plane with and without considering evolution cases.
Binary neutron star mergers are believed to eject significant masses with a diverse range of velocities. Once these ejected materials begin to be decelerated by a homogeneous medium, relativistic ...electrons are mainly cooled down by synchrotron radiation, generating a multiwavelength long-lived afterglow. Analytic and numerical methods illustrate that the outermost matter, the merger shock-breakout material, can be parametrized by power-law velocity distributions . Considering that the shock-breakout material is moving on-axis toward the observer and the relativistic jet off-axis, we compute the light curves during the relativistic and the lateral expansion phase. As a particular case, we successfully describe the X-ray, optical, and radio light curves alongside the spectral energy distribution from the recently discovered gravitational-wave transient GW170817, when the merger shock-breakout material moves with mildly relativistic velocities and achieves the near-Newtonian phase and the jet moves with relativistic velocities. Future electromagnetic counterpart observations of this binary system could be able to evaluate different properties of these light curves.
ABSTRACT
Gamma-Ray Bursts (GRBs) are panchromatic, highly energetic transients whose energy emission mechanism is still debated. One of the possible explanations is the standard fireball model, which ...can be tested with the closure relations (CRs), or relations between the temporal and spectral indices of a GRB. To test these, we compile an extensive sample of radio afterglow light curves (LCs) that span from 1997 to 2020, the most comprehensive analysis of GRBs with radio observations to date. We fit 202 LCs from 82 distinct GRBs with a broken power law, obtaining a sample of 26 that display a clear break and a sub-sample of 14 GRBs that present a radio plateau. We test these samples against CRs corresponding to a constant-density interstellar medium (ISM) or a stellar wind medium in both fast- and slow-cooling regimes, as well as three additional density profiles, k = 1, 1.5, 2.5, following n ∝r−k, and consider sets of CRs both with and without energy injection. We find that 12 of the 26 GRBs (46 per cent), of which 7/12 present a radio plateau, fulfill at least one CR in the sets tested, suggesting our data are largely incompatible with the standard fireball model. Of the fulfilled CRs, the most preferred environment is the ISM, SC, νm < ν < νc without energy injection. Our results are consistent with previous studies that test the standard fireball model via the CRs in radio.
Abstract
Gamma-ray bursts (GRBs) are one of the most promising transient events for studying multiwavelength observations in extreme conditions. Observation of GeV photons from bursts would provide ...crucial information on GRB physics, including the off-axis emission. The Second Gamma-ray Burst Catalog (2FLGC) has been announced by the Fermi Large Area Telescope (Fermi-LAT) Collaboration. This catalog includes 29 bursts with photon energy higher than 10 GeV. While the synchrotron forward-shock model has well explained the afterglow data of GRBs, photon energies greater than 10 GeV are very difficult to interpret within this framework. To study the spectral and temporal indices of those bursts described in 2FLGC, Fraija et al. (2022a) proposed the closure relations (CRs) of the synchrotron self-Compton (SSC) emission of GRBs emitted from an on-axis jet, which decelerates in stellar-wind and constant-density medium. In this paper, we extend the CRs of the SSC afterglow from an on-axis scenario to an off-axis scenario, including the synchrotron afterglow radiation that seems to be off-axis. In order to investigate the spectral and temporal index evolution of those bursts reported in 2FLGC, we consider hydrodynamical evolution with energy injection in the adiabatic and radiative regimes for an electron distribution with a spectral index of 1 <
p
< 2 and 2 <
p
. The results show that the most likely scenario for synchrotron emission corresponds to the stellar wind whether or not there is energy injection and that the most likely scenario for SSC emission corresponds to the constant density when there is no energy injection and to the stellar wind when there is energy injection.
ABSTRACT
Cosmological models and their corresponding parameters are widely debated because of the current discrepancy between the results of the Hubble constant, H0, obtained by SNe Ia, and the ...Planck data from the cosmic microwave background radiation. Thus, considering high redshift probes like gamma-ray bursts (GRBs) is a necessary step. However, using GRB correlations between their physical features to infer cosmological parameters is difficult because GRB luminosities span several orders of magnitude. In our work, we use a three-dimensional relation between the peak prompt luminosity, the rest-frame time at the end of the X-ray plateau, and its corresponding luminosity in X-rays: the so-called 3D Dainotti fundamental plane relation. We correct this relation by considering the selection and evolutionary effects with a reliable statistical method, obtaining a lower central value for the intrinsic scatter, σint = 0.18 ± 0.07 (47.1 per cent) compared to previous results, when we adopt a particular set of GRBs with well-defined morphological features, called the platinum sample. We have used the GRB fundamental plane relation alone with both Gaussian and uniform priors on cosmological parameters and in combination with SNe Ia and BAO measurements to infer cosmological parameters like H0, the matter density in the universe (ΩM), and the dark energy parameter w for a wCDM model. Our results are consistent with the parameters given by the Lambda cold dark matter model but with the advantage of using cosmological probes detected up to z = 5, much larger than the one observed for the furthest SNe Ia.
ABSTRACT
The detection of a prolonged flaring activity from blazar TXS 0506+056 in temporal and spatial coincidence with the energetic neutrino IceCube-170922A provided evidence about the ...photohadronic interactions in this source. However, analysis of the archival neutrino and multiwavelength data from the direction of this blazar between 2014 September and 2015 March revealed a ‘neutrino flare’ without observing quasi-simultaneous activity in the gamma-ray bands, posing challenges to established models. Electron–positron (e±) pairs generated from the accretion discs have been amply proposed as a mechanism of bulk acceleration of sub-relativistic and relativistic jets. These pairs annihilate inside the source producing a line around the electron mass, which is blueshifted in the observed frame (on Earth) and redshifted in the frame of the dissipation region of the jet. The redshifted photons in the dissipation region interact with accelerated protons, producing high-energy neutrinos that contribute significantly to the diffuse neutrino flux in the ∼10–20 TeV energy range in connection with gamma-rays from the photopion process, which can be detected by future MeV orbiting satellites. Based on this phenomenological model, we can explain the ‘neutrino flare’ reported in 2014–1015.
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