The high A_V Quasar Survey: A z=2.027 metal-rich damped Lyman-alpha absorber towards a red quasar at z=3.21

To fully exploit the potential of quasars as probes of cosmic chemical evolution and the internal gas dynamics of galaxies it is important to understand the selection effects behind the quasar samples and in particular if the selection criteria exclude foreground galaxies with certain properties (most importantly a high dust content). Here we present spectroscopic follow-up from the 10.4-m GTC telescope of a dust-reddened quasar, eHAQ0111+0641, from the extended High A_V Quasar (HAQ) survey. We find that the z=3.21 quasar has a foreground Damped Lyman-alpha Absorber (DLA) at z=2.027 along the line of sight. The DLA has very strong metal lines due to a moderately high metallicity (with an inferred lower limit of 25% of the solar metallicity), but a very large gas column density along the line-of-sight in its host galaxy. This discovery is further evidence that there is a dust bias affecting the census of metals, caused by the combined effect of dust obscuration and reddening, in existing samples of z>2 DLAs. The case of eHAQ0111+0641 illustrates that dust bias is not only caused by dust obscuration, but also dust reddening.Comment: 7 pages, 4 figures. Accepted for publication in A&A. A few typos have been correcte

The properties of the 2175AA extinction feature discovered in GRB afterglows

The unequivocal, spectroscopic detection of the 2175 bump in extinction curves outside the Local Group is rare. To date, the properties of the bump have been examined in only two GRB afterglows (GRB 070802 and GRB 080607). In this work we analyse in detail the detections of the 2175 extinction bump in the optical spectra of the two further GRB afterglows: GRB 080605 and 080805. We gather all available optical/NIR photometric, spectroscopic and X-ray data to construct multi-epoch SEDs for both GRB afterglows. We fit the SEDs with the Fitzpatrick & Massa (1990) model with a single or broken PL. We also fit a sample of 38 GRB afterglows, known to prefer a SMC-type extinction curve, with the same model. We find that the SEDs of GRB 080605 and GRB 080805 at two epochs are fit well with a single PL with a derived extinction of A_V = 0.52(+0.13 -0.16) and 0.50 (+0.13 -0.10), and 2.1(+0.7-0.6) and 1.5+/-0.2 respectively. While the slope of the extinction curve of GRB 080805 is not well-constrained, the extinction curve of GRB 080605 has an unusual very steep far-UV rise together with the 2175 bump. Such an extinction curve has previously been found in only a small handful of sightlines in the MW. One possible explanation of such an extinction curve may be dust arising from two different regions with two separate grain populations, however we cannot distinguish the origin of the curve. We finally compare the four 2175 bump sightlines to the larger GRB afterglow sample and to Local Group sightlines. We find that while the width and central positions of the bumps are consistent with what is observed in the Local Group, the relative strength of the detected bump (A_bump) for GRB afterglows is weaker for a given A_V than for almost any Local Group sightline. Such dilution of the bump strength may offer tentative support to a dual dust-population scenario.Comment: 9 pages, 8 figures, 3 tables, accepted to Ap

The Highly Energetic Expansion of SN2010bh Associated with GRB 100316D

We present the spectroscopic and photometric evolution of the nearby (z = 0.059) spectroscopically confirmed type Ic supernova, SN 2010bh, associated with the soft, long-duration gamma-ray burst (X-ray flash) GRB 100316D. Intensive follow-up observations of SN 2010bh were performed at the ESO Very Large Telescope (VLT) using the X-shooter and FORS2 instruments. Owing to the detailed temporal coverage and the extended wavelength range (3000--24800 A), we obtained an unprecedentedly rich spectral sequence among the hypernovae, making SN 2010bh one of the best studied representatives of this SN class. We find that SN 2010bh has a more rapid rise to maximum brightness (8.0 +/- 1.0 rest-frame days) and a fainter absolute peak luminosity (L_bol~3e42 erg/s) than previously observed SN events associated with GRBs. Our estimate of the ejected (56)Ni mass is 0.12 +/- 0.02 Msun. From the broad spectral features we measure expansion velocities up to 47,000 km/s, higher than those of SNe 1998bw (GRB 980425) and 2006aj (GRB 060218). Helium absorption lines He I lambda5876 and He I 1.083 microm, blueshifted by ~20,000--30,000 km/s and ~28,000--38,000 km/s, respectively, may be present in the optical spectra. However, the lack of coverage of the He I 2.058 microm line prevents us from confirming such identifications. The nebular spectrum, taken at ~186 days after the explosion, shows a broad but faint [O I] emission at 6340 A. The light-curve shape and photospheric expansion velocities of SN 2010bh suggest that we witnessed a highly energetic explosion with a small ejected mass (E_k ~ 1e52 erg and M_ej ~ 3 Msun). The observed properties of SN 2010bh further extend the heterogeneity of the class of GRB supernovae.Comment: 37 pages and 12 figures (one-column pre-print format), accepted for publication in Ap

The Environment of the Binary Neutron Star Merger GW170817

We present Hubble Space Telescope (HST) and Chandra imaging, combined with Very Large Telescope MUSE integral field spectroscopy of the counterpart and host galaxy of the first binary neutron star merger detected via gravitational-wave emission by LIGO and Virgo, GW170817. The host galaxy, NGC 4993, is an S0 galaxy at z - 0.009783. There is evidence for large, face-on spiral shells in continuum imaging, and edge-on spiral features visible in nebular emission lines. This suggests that NGC 4993 has undergone a relatively recent (less than or similar to 1 Gyr) "dry" merger. This merger may provide the fuel for a weak active nucleus seen in Chandra imaging. At the location of the counterpart, HST imaging implies there is no globular or young stellar cluster, with a limit of a few thousand solar masses for any young system. The population in the vicinity is predominantly old with less than or similar to 1% of any light arising from a population with ages <500 Myr. Both the host galaxy properties and those of the transient location are consistent with the distributions seen for short-duration gamma-ray bursts, although the source position lies well within the effective radius (r(e) similar to 3 kpc), providing an r(e)-normalized offset that is closer than similar to 90% of short GRBs. For the long delay time implied by the stellar population, this suggests that the kick velocity was significantly less than the galaxy escape velocity. We do not see any narrow host galaxy interstellar medium features within the counterpart spectrum, implying low extinction, and that the binary may lie in front of the bulk of the host galaxy.We thank the referee for a prompt and highly constructive report that improved the content and clarity of the manuscript. We also thank the editor, Fred Rasio, for helpful comments. Based on observations made with ESO Telescopes at the La Silla Paranal Observatory under programme ID 099.D-0668 (A.J.L.), and on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5-26555. These observations are associated with programs GO 14771 (N.R.T.), GO 14804 (A.J.L.), and GO 14850 (E.T.). We thank the staff at ESO and STScI for their excellent support of these observations. A.J.L. acknowledges that this project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement No. 725246) A.J.L., D.S., and J.D.L. acknowledge support from STFC via grant ST/P000495/1. N.R.T., K.W., P.T.O., J.L.O., and S.R. acknowledge support from STFC. J.H. was supported by a VILLUM FONDEN Investigator grant (project number 16599). A.d.U.P., C.T., Z.C., and D.A.K. acknowledge support from the Spanish project AYA 2014-58381-P. Z.C. also acknowledges support from the Juan de la Cierva Incorporacion fellowship IJCI-2014-21669, and D.A.K. from Juan de la Cierva Incorporacion fellowship IJCI-2015-26153. M.I. was supported by the NRFK grant, No. 2017R1A3A3001362. E.T. acknowledges support from grants GO718062A and HSTG014850001A. S.R. has been supported by the Swedish Research Council (VR) under grant number 2016-03657_3, by the Swedish National Space Board under grant number Dnr. 107/16 and by the research environment grant "Gravitational Radiation and Electromagnetic Astrophysical Transients (GREAT)" funded by the Swedish Research council (VR) under Dnr 2016-06012. P.A.E. acknowledges UKSA support.Peer Reviewe

Photometric and Spectroscopic Observations of GRB 190106A: Emission from Reverse and Forward Shocks with Late-time Energy Injection

Early optical observations of gamma-ray bursts can significantly contribute to the study of the central engine and physical processes therein. However, of the thousands observed so far, only a few have data at optical wavelengths in the first minutes after the onset of the prompt emission. Here we report on GRB 190106A, whose afterglow was observed in optical bands just 36 s after the Swift/BAT trigger, i.e., during the prompt emission phase. The early optical afterglow exhibits a bimodal structure followed by a normal decay, with a faster decay after ∼ T _0 + 1 day. We present optical photometric and spectroscopic observations of GRB 190106A. We derive the redshift via metal absorption lines from Xinglong 2.16 m/BFOSC spectroscopic observations. From the BFOSC spectrum, we measure z = 1.861 ± 0.002. The double-peak optical light curve is a significant feature predicted by the reverse-forward external-shock model. The shallow decay followed by a normal decay in both the X-ray and optical light curves is well explained with the standard forward-shock model with late-time energy injection. Therefore, GRB 190106A offers a case study for GRB emission from both reverse and forward shocks

A long-duration gamma-ray burst of dynamical origin from the nucleus of an ancient galaxy

The majority of long-duration (&gt;2 s) gamma-ray bursts (GRBs) arise from the collapse of massive stars, with a small proportion created from the merger of compact objects. Most of these systems form via standard stellar evolution pathways. However, a fraction of GRBs may result from dynamical interactions in dense environments. These channels could also contribute substantially to the samples of compact object mergers detected as gravitational wave sources. Here we report the case of GRB 191019A, a long GRB (a duration of T 90 = 64.4 ± 4.5 s), which we pinpoint close (⪅100 pc projected) to the nucleus of an ancient (&gt;1 Gyr old) host galaxy at z = 0.248. The lack of evidence for star formation and deep limits on any supernova emission disfavour a massive star origin. The most likely route for progenitor formation is via dynamical interactions in the dense nucleus of the host. The progenitor, in this case, could be a compact object merger. These may form in dense nuclear clusters or originate in a gaseous disc around the supermassive black hole. Identifying, to the best of our knowledge, a first example of a dynamically produced GRB demonstrates the role that such bursts may have in probing dense environments and constraining dynamical fractions in gravitational wave populations.</p