The X-shooter GRB afterglow legacy sample (XS-GRB)

Abstract

In this work we present spectra of all γ-ray burst (GRB) afterglows that have been promptly observed with the X-shooter spectrograph until 31/03/2017. In total, we obtained spectroscopic observations of 103 individual GRBs observed within 48 hours of the GRB trigger. Redshifts have been measured for 97 per cent of these, covering a redshift range from 0.059 to 7.84. Based on a set of observational selection criteria that minimize biases with regards to intrinsic properties of the GRBs, the follow-up effort has been focused on producing a homogeneous sample of 93 afterglow spectra for GRBs discovered by the Swift satellite. We here provide a public release of all the reduced spectra, including continuum estimates and telluric absorption corrections. For completeness, we also provide reductions for the 18 late-time observations of the underlying host galaxies. We provide an assessment of the degree of completeness with respect to the parent GRB population, in terms of the X-ray properties of the bursts in the sample and find that the sample presented here is representative of the full Swift sample. We constrain the fraction of dark bursts to be < 28 per cent and we confirm previous results that higher optical darkness is correlated with increased X-ray absorption. For the 42 bursts for which it is possible, we provide a measurement of the neutral hydrogen column density, increasing the total number of published HI column density measurements by ∼ 33 per cent. This dataset provides a unique resource to study the ISM across cosmic time, from the local progenitor surroundings to the intervening universe.Article number, page 19 of 43 A&A proofs: manuscript no. XSGRB_sample_arxiv Cité, 10, Rue Alice Domon et Léonie Duquet, 75205,

Lowly Polarized Light from a Highly Magnetized Jet of GRB 190114C

“…Latter observations started at T 0 + 67 s, T 0 + 74 s and T 0 + 201 s with the Swift X-ray Telescope (XRT; D'Elia et al 2019), the 0.3-m Ultraviolet/Optical Telescope (UVOT; Siegel & Gropp 2019) and the 2-m Liverpool Telescope (see Section 2.1), respectively. A spectroscopic redshift of 0.4245 ± 0.0005 was measured by the 10.4-m GTC telescope and confirmed by the 2.5-m Nordic Optical Telescope (Selsing et al 2019;Castro-Tirado et al 2019). Additionally, a supernova component was detected 15 days after the burst, confirming a collapsar origin for GRB 190114C (Melandri et al 2019).…”

A comparison between short GRB afterglows and kilonova AT2017gfo: shedding light on kilonovae properties

“…Here we list the references for the redshift. GRB 060614 (Price et al 2006); GRB 100816A (Tanvir et al 2010); GRB 150423A (Selsing et al 2019); GRB 150424A (Castro-Tirado et al 2015); GRB 160410A (Selsing et al 2019); GRB 160624A (Cucchiara & Levan 2016); GRB 160821B ; GRB 170428A (Izzo et al 2017). c new redshift from Selsing et al (2018).…”

Synchrotron Self-Compton Emission from External Shocks as the Origin of the Sub-TeV Emission in GRB 180720B and GRB 190114C

“…HESS started to observe GRB 180720B at about 10 hr after the burst and detected 100 − 440 GeV photons at such late times (Ruiz-Velasco 2019). Both GRBs have relatively low redshifts, with z = 0.4245 and z = 0.653 for GRB 190114C and GRB 180720B respectively (Selsing et al 2019;Vreeswijk et al 2019) . They are also bright bursts with the isotropic energies of 3 × 10 53 erg and 6 × 10 53 erg, respectively (Hamburg et al 2019;Frederiks et al 2018).…”