Search

Start Over Subject gamma-ray astronomy
151. GRB 100814A GROND and UVOT light curves
ID:
ivo://CDS.VizieR/J/A+A/562/A29
Title:
GRB 100814A GROND and UVOT light curves
Short Name:
J/A+A/562/A29
Date:
21 Oct 2021
Publisher:
CDS
Description:
In the past few years the number of well-sampled optical to near-infrared (NIR) light curves of long gamma-ray bursts (GRBs) has greatly increased, particularly due to simultaneous multi-band imagers such as GROND. Combining these densely sampled ground-based data sets with the Swift UVOT and XRT space observations unveils a much more complex afterglow evolution than what was predicted by the most commonly invoked theoretical models. GRB 100814A represents a remarkable example of these interesting well-sampled events, showing a prominent late-time rebrightening in the optical to NIR bands and a complex spectral evolution. This represents a unique laboratory to test the different afterglow emission models. Here we study the nature of the complex afterglow emission of GRB 100814A in the framework of different theoretical models. Moreover, we compare the late-time chromatic rebrightening with those observed in other well-sampled long GRBs.
152. GRB 111209A GROND and UVOT light curves
ID:
ivo://CDS.VizieR/J/A+A/617/A122
Title:
GRB 111209A GROND and UVOT light curves
Short Name:
J/A+A/617/A122
Date:
21 Oct 2021
Publisher:
CDS
Description:
Afterglows of Gamma-Ray Bursts (GRBs) are simple in the most basic model, but can show many complex features. The ultra-long duration GRB 111209A, one of the longest GRBs ever detected, also has the best-monitored afterglow in this rare class of GRBs. We want to address the question whether GRB 111209A was a special event beyond its extreme duration alone, and whether it is a classical GRB or another kind of high-energy transient. The afterglow may yield significant clues. We present afterglow photometry obtained in seven bands with the GROND imager as well as in further seven bands with the UVOT telescope on-board the Neil Gehrels Swift Observatory. The light curve is analysed by multi-band modelling and joint fitting with power-laws and broken power-laws, and we use the contemporaneous GROND data to study the evolution of the spectral energy distribution. We compare the optical afterglow to a large ensemble we have analysed in earlier works, and especially to that of another ultra-long event, GRB 130925A. We furthermore undertake a photometric study of the host galaxy. We find a strong, chromatic rebrightening event at ~0.8-days after the GRB, during which the spectral slope becomes redder. After this, the light curve decays achromatically, with evidence for a break at about 9 days after the trigger. The afterglow luminosity is found to not be exceptional. We find that a double-jet model is able to explain the chromatic rebrightening. The afterglow features have been detected in other events and are not unique. The duration aside, the GRB prompt emission and afterglow parameters of GRB 111209A are in agreement with the known distributions for these parameters. While the central engine of this event may differ from that of classical GRBs, there are multiple lines of evidence pointing to GRB 111209A resulting from the core-collapse of a massive star with a stripped envelope.
153. GRB 130925A GROND light curves
ID:
ivo://CDS.VizieR/J/A+A/568/A75
Title:
GRB 130925A GROND light curves
Short Name:
J/A+A/568/A75
Date:
21 Oct 2021
Publisher:
CDS
Description:
Prompt or early optical emission in gamma-ray bursts (GRBs) is notoriously difficult to measure, and observations of the dozen cases show a large variety of properties. Yet, such early emission promises to help us achieve a better understanding of the GRB emission process(es). We performed dedicated observations of the ultra-long duration (T90 about 7000s) Swift GRB 130925A in the optical/near-infrared with the 7-channel Gamma-Ray burst Optical and Near-infrared Detector (GROND) at the 2.2m MPG/ESO telescope. We detect an optical/near-infrared flare with an amplitude of nearly 2mag which is delayed with respect to the keV-MeV prompt emission by about 300-400s. The decay time of this flare is shorter than the duration of the flare (500s) or its delay. While we cannot offer a straightforward explanation, we discuss the implications of the flare properties and suggest ways toward understanding it.
154. GRB 161023A light curves and EW
ID:
ivo://CDS.VizieR/J/A+A/620/A119
Title:
GRB 161023A light curves and EW
Short Name:
J/A+A/620/A119
Date:
21 Oct 2021
Publisher:
CDS
Description:
Long gamma-ray bursts (GRBs) are produced during the dramatic deaths of massive stars with very short lifetimes, meaning that they explode close to the birth place of their progenitors. Over a short period they become the most luminous objects observable in the Universe, being perfect beacons to study high-redshift star-forming regions. We aim to use the afterglow of GRB161023A at a redshift z=2.710 as a background source to study the environment of the explosion and the intervening systems along its line of sight. For the first time, we complement ultraviolet (UV), optical and near-infrared (NIR) spectroscopy with millimetre spectroscopy using the Atacama Large Millimeter Array (ALMA), which allows us to probe the molecular content of the host galaxy. The X-shooter spectrum shows a plethora of absorption features including fine-structure and metastable transitions of Fe, Ni, Si, C, and O. We present photometry ranging from 43s to over 500 days after the burst
155. GRB 081007 and GRB 090424 light curves
ID:
ivo://CDS.VizieR/J/ApJ/774/114
Title:
GRB 081007 and GRB 090424 light curves
Short Name:
J/ApJ/774/114
Date:
21 Oct 2021
Publisher:
CDS
Description:
We discuss the results of the analysis of multi-wavelength data for the afterglows of GRB 081007 and GRB 090424, two bursts detected by Swift. One of them, GRB 081007, also shows a spectroscopically confirmed supernova, SN 2008hw, which resembles SN 1998bw in its absorption features, while the maximum magnitude may be fainter, up to 0.7mag, than observed in SN 1998bw. Bright optical flashes have been detected in both events, which allows us to derive solid constraints on the circumburst-matter density profile. This is particularly interesting in the case of GRB 081007, whose afterglow is found to be propagating into a constant-density medium, yielding yet another example of a gamma-ray burst (GRB) clearly associated with a massive-star progenitor which did not sculpt the surroundings with its stellar wind. There is no supernova component detected in the afterglow of GRB 090424, likely due to the brightness of the host galaxy, comparable to the Milky Way. We show that the afterglow data are consistent with the presence of both forward- and reverse-shock emission powered by relativistic outflows expanding into the interstellar medium. The absence of optical peaks due to the forward shock strongly suggests that the reverse-shock regions should be mildly magnetized. The initial Lorentz factor of outflow of GRB 081007 is estimated to be {Gamma}~200, while for GRB 090424 a lower limit of {Gamma}>170 is derived. We also discuss the prompt emission of GRB 081007, which consists of just a single pulse. We argue that neither the external forward-shock model nor the shock-breakout model can account for the prompt emission data and suggest that the single-pulse-like prompt emission may be due to magnetic energy dissipation of a Poynting-flux-dominated outflow or to a dissipative photosphere.
156. GRB 190829A/SN 2019oyw spectra
ID:
ivo://CDS.VizieR/J/A+A/646/A50
Title:
GRB 190829A/SN 2019oyw spectra
Short Name:
J/A+A/646/A50
Date:
21 Oct 2021
Publisher:
CDS
Description:
Gamma-ray burst (GRB) 190829A (z=0.0785) was detected by Fermi and Swift and also at very high energy (VHE) by the High-Energy Stereoscopic System (H.E.S.S.) telescopes. The prompt emission displayed two emission episodes separated by a quiescent gap of ~40s. We present the 10.4m Gran Telescopio CANARIAS (GTC) observations of the afterglow of GRB 190829A and its underlying supernova. We also compare GRB190829A to GRB180728A, a GRB with similar behaviour, and discuss the implications on underlying physical mechanisms producing these two GRBs. We present multi-band photometric data along with spectroscopic follow-up observations taken with the 10.4m GTC telescope. Together with the data from the prompt emission, the 10.4m GTC data are used to understand the emission mechanisms and possible progenitor. A detailed analysis of the multi-band observations of the afterglow requires the cooling frequency to pass between the optical and X-ray bands at early epochs. The afterglow then transitions to the underlying supernova (SN) 2019oyw, which dominates later on. Although the prompt emission temporal properties of GRB 190829A and GRB 180728A are similar, the two pulses are different in the spectral domain. We find that SN 2019oyw associated with GRB 190829A is powered by Ni decay and is a Type Ic-BL SN. The spectroscopic and photometric properties of this SN are consistent with those observed for SN 1998bw, but evolved earlier.
157. GRB 140506A spectra
ID:
ivo://CDS.VizieR/J/A+A/572/A12
Title:
GRB 140506A spectra
Short Name:
J/A+A/572/A12
Date:
21 Oct 2021
Publisher:
CDS
Description:
Gamma-ray burst (GRB) afterglows probe sightlines to star-forming regions in distant star-forming galaxies. Here we present a study of the peculiar afterglow spectrum of the z=0.889 Swift GRB 140506A. Our aim is to understand the origin of the very unusual properties of the absorption along the line of sight. We analyse spectroscopic observations obtained with the X-shooter spectrograph mounted on the ESO/VLT at two epochs 8.8h and 33h after the burst, and with imaging from the GROND instrument. We also present imaging and spectroscopy of the host galaxy obtained with the Magellan telescope.
158. GRB 100621A unusual afterglow
ID:
ivo://CDS.VizieR/J/A+A/560/A70
Title:
GRB 100621A unusual afterglow
Short Name:
J/A+A/560/A70
Date:
21 Oct 2021
Publisher:
CDS
Description:
With the afterglow of GRB 100621A being the brightest detected so far in X-rays, and superb GROND coverage in the optical/near-infrared during the first few hours, an observational verification of basic fireball predictions seemed possible. In order to constrain the broad-band spectral energy distribution of the afterglow of GRB 100621A, dedicated observations were performed in the optical/near-infrared with the 7-channel Gamma-Ray Burst Optical and Near-infrared Detector (GROND) at the 2.2m MPG/ESO telescope, in the sub-millimeter band with the large bolometer array LABOCA at APEX, and at radio frequencies with ATCA. Utilizing also Swift X-ray observations, we attempt an interpretation of the observational data within the fireball scenario.
159. GRB 160509A VLA monitoring campain results
ID:
ivo://CDS.VizieR/J/ApJ/833/88
Title:
GRB 160509A VLA monitoring campain results
Short Name:
J/ApJ/833/88
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the second multi-frequency radio detection of a reverse shock in a {gamma}-ray burst. By combining our extensive radio observations of the Fermi-Large Area Telescope {gamma}-ray burst 160509A at z=1.17 up to 20 days after the burst with Swift X-ray observations and ground-based optical and near-infrared data, we show that the afterglow emission comprises distinct reverse shock and forward shock contributions: the reverse shock emission dominates in the radio band at <~10 days, while the forward shock emission dominates in the X-ray, optical, and near-infrared bands. Through multi-wavelength modeling, we determine a circumburst density of n_0_~10^-3^cm^-3^, supporting our previous suggestion that a low-density circumburst environment is conducive to the production of long-lasting reverse shock radiation in the radio band. We infer the presence of a large excess X-ray absorption column, N_H_~1.5x10^22^cm^-2^, and a high rest-frame optical extinction, A_V_~3.4mag. We identify a jet break in the X-ray light curve at t_jet_~6days, and thus derive a jet opening angle of {theta}_jet_~4{deg}, yielding a beaming-corrected kinetic energy and radiated {gamma}-ray energy of E_K_~4x10^50^erg and E_{gamma}_~1.3x10^51^erg (1-10^4^keV, rest frame), respectively. Consistency arguments connecting the forward shocks and reverse shocks suggest a deceleration time of t_dec_~460s~T_90_, a Lorentz factor of {Gamma}(t_dec_)~330, and a reverse-shock-to-forward-shock fractional magnetic energy density ratio of R_B_={epsilon}_B,RS_/{epsilon}_B,FS_~8. Our study highlights the power of rapid-response radio observations in the study of the properties and dynamics of {gamma}-ray burst ejecta.
160. GRB 130606A VLT/X-shooter spectroscopy
ID:
ivo://CDS.VizieR/J/A+A/580/A139
Title:
GRB 130606A VLT/X-shooter spectroscopy
Short Name:
J/A+A/580/A139
Date:
21 Oct 2021
Publisher:
CDS
Description:
The reionisation of the Universe is a process that is thought to have ended around z~6, as inferred from spectroscopy of distant bright background sources, such as quasars (QSO) and gamma-ray burst (GRB) afterglows. Furthermore, spectroscopy of a GRB afterglow provides insight in its host galaxy, which is often too dim and distant to study otherwise. For the Swift GRB 130606A at z=5.913 we have obtained a high S/N spectrum covering the full optical and near-IR wavelength region at intermediate spectral resolution with VLT/X-Shooter. We aim to measure the degree of ionisation of the intergalactic medium (IGM) between z=5.02-5.84 and to study the chemical abundance pattern and dust content of its host galaxy. We estimated the UV continuum of the GRB afterglow using a power-law extrapolation, then measured the flux decrement due to absorption at Ly{alpha},{beta}, and {gamma} wavelength regions. Furthermore, we fitted the shape of the red damping wing of Ly{alpha}. The hydrogen and metal absorption lines formed in the host galaxy were fitted with Voigt profiles to obtain column densities. We investigated whether ionisation corrections needed to be applied.