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.
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.
We present the spectroscopic and photometric late-time follow-up of the host galaxy of the long-duration Swift {gamma}-ray burst GRB140506A at z=0.889. The optical and near-infrared afterglow of this GRB had a peculiar spectral energy distribution (SED) with a strong flux-drop at 8000{AA} (4000{AA} rest-frame) suggesting an unusually steep extinction curve. By analysing the contribution and physical properties of the host galaxy, we here aim at providing additional information on the properties and origin of this steep, non-standard extinction.We find that the strong flux-drop in the GRB afterglow spectrum at <8000{AA} and rise at <4000{AA} (observers frame) is well explained by the combination of a steep extinction curve along the GRB line of sight and contamination by the host galaxy light at short wavelengths so that the scenario with an extreme 2175{AA} extinction bump can be excluded. We localise the GRB to be at a projected distance of approximately 4kpc from the centre of the host galaxy. Based on emission-line diagnostics of the four detected nebular lines, H{alpha}, H{beta}, [OII] and [OIII], we find the host to be a modestly star forming (SFR=1.34+/-0.04M_{sun}_/yr) and relatively metal poor (Z=0.35^+0:15^_0.11_Z_{sun}_) galaxy with a large dust content, characterised by a measured visual attenuation of AV=1.74+/-0.41mag. We compare the host to other GRB hosts at similar redshifts and find that it is unexceptional in all its physical properties. We model the extinction curve of the host-corrected afterglow and show that the standard dust properties causing the reddening seen in the Local Group are inadequate in describing the steep drop. We thus conclude that the steep extinction curve seen in the afterglow towards the GRB is of exotic origin and is sightline-dependent only, further confirming that this type of reddening is present only at very local scales and that it is solely a consequence of the circumburst environment.
We observed GRB190114C (redshift z=0.4245), the first gamma-ray burst (GRB) ever detected at TeV energies, at optical and near-infrared wavelengths with several ground-based telescopes and the Hubble Space Telescope, with the primary goal of studying its underlying supernova, SN 2019jrj. The monitoring spanned the time interval between 1.3 and 370 days after the burst, in the observer frame. We find that the afterglow emission can be modelled with a forward shock propagating in a uniform medium modified by time-variable extinction along the line of sight. A jet break could be present after 7 rest-frame days, and accordingly the maximum luminosity of the underlying supernova (SN) ranges between that of stripped-envelope core-collapse SNe of intermediate luminosity and that of the luminous GRB-associated SN 2013dx. The observed spectral absorption lines of SN 2019jrj are not as broad as in classical GRB SNe and are instead more similar to those of less-luminous core-collapse SNe. Taking the broad-lined stripped-envelope core-collapse SN 2004aw as an analogue, we tentatively derive the basic physical properties of SN 2019jrj. We discuss the possibility that a fraction of the TeV emission of this source might have had a hadronic origin and estimate the expected high-energy neutrino detection level with IceCube.
We reveal multiple components of an interacting galaxy system at z~3.35 through a detailed analysis of the exquisite high-resolution Keck/HIRES spectrum of the afterglow of a gamma-ray burst (GRB). Through Voigt-profile fitting of absorption lines from the Lyman-series, we constrain the neutral hydrogen column density to N_HI_<=10^18.35^cm^-2^ for the densest of four distinct systems at the host redshift of GRB 080810, among the lowest NHI ever observed in a GRB host, despite the line of sight passing within a projected 5kpc of the galaxy centres. By detailed analysis of the corresponding metal absorption lines, we derive chemical, ionic and kinematic properties of the individual absorbing systems, and thus build a picture of the host as a whole. Striking differences between the systems imply that the line of sight passes through several phases of gas: the star-forming regions of the GRB host; enriched material in the form of a galactic outflow; the hot and ionised halo of a second, interacting galaxy falling towards the host at a line-of-sight velocity of 700km/s; and a cool, metal-poor cloud which may represent one of the best candidates yet for the inflow of metal-poor gas from the intergalactic medium.
High frequency water maser and HI spectra are available through this web service. The water maser phenomena are found in active galactic nuclei (AGN) and have been surveyed with the NRAO Green Bank Telescope. HI spectra are measured mostly from galaxies in the local Universe.
We present a grid of computed non-local thermodynamic equilibrium (NLTE) equivalent widths (EW) and NLTE abundance corrections for four Ba II lines: 4554, 5853, 6141, and 6496{AA}. The grid can be useful in deriving the NLTE barium abundance in stars having parameters in the following ranges: effective temperature from 4000K to 6500K, surface gravity log g from 0 to 5, microturbulent velocity 0km/s to 3km/s, metallicity [Fe/H] from -2 to +0.5, and [Ba/Fe] from -0.4 to +0.6. The NLTE abundance can be either derived by EW interpolation (using the observed Ba II line EW) or by using the NLTE correction applied to a previously determined LTE abundance. Ba II line equivalent widths and the NLTE corrections were calculated using the updated MULTI code and the Ba II atomic model that was previously applied to determine the NLTE barium abundance in different types of stars. The grid is available on-line through the web, and we find that the grid Ba NLTE corrections are almost as accurate as direct NLTE profile fitting (to within 0.05-0.08dex). For the weakest Ba II line (5853{AA}) the LTE abundances almost agree with the NLTE abundances, whereas the other three Ba II lines, 4554, 6141, and 6496{AA}, need NLTE corrections even at the highest metallicities tested here. The 4554{AA} line is extremely strong and should not be used for abundance analysis above [Fe/H]=-1. Furthermore, we tested the impact of different model atmospheres and spectrum synthesis codes and found average differences of 0.06 dex and 0.09 dex, respectively, for all four lines. At these metallicities we find an average Delta NLTE of +/-0.1dex for the three useful Ba lines for subsolar cool dwarfs.
A new grid of detailed atmosphere model spectra for hot and moderately cool subdwarf stars is presented. High-resolution spectra and synthetic photometry are calculated in the range from 1000{AA} to 10,000{AA} using Non-LTE fully line- blanketed atmosphere structures. Our grid covers eight temperatures within 10000<Teff[K]<65000, three surface gravities in the range 4.5<logg[cgs]<6.5, two helium abundances matching two extreme helium-rich and helium-poor scenarios, and two limiting metallicity boundaries regarding both solar ([Fe/H]=0) and Galactic halo ([Fe/H]=-1.5 and [alpha/Fe]=+0.4). Besides its application in the determination of fundamental parameters of subdwarfs in isolation and in binaries, the resulting database is also of interest for population synthesis procedures in a wide variety of stellar systems.
Grids of ATLAS9 Model Atmospheres and MOOG spectra
Short Name:
VI/134
Date:
21 Oct 2021
Publisher:
CDS
Description:
A grid of ATLAS9 model atmospheres has been computed, spanning Teff in 3500--8000K, log.g in 0.0--5.0, [Fe/H] in -4.0--0.0, [{alpha}/Fe] in -0.08--1.2. These parameters are appropriate for stars in the red giant branch, subgiants, and the lower main sequence. The main difference from a previous, similar grid (Castelli & Kurucz 2003, "Modelling of Stellar Atmospheres", 210, astro-ph/0405087) is the range of [{alpha}/Fe] values. A grid of synthetic spectra, calculated from the model atmospheres, is also presented. The fluxes are computed every 0.02{AA} from 630nm to 910nm. The microturbulent velocity is given by a relation to the surface gravity. This relation is appropriate for giants, but not for subgiants or dwarfs. Therefore, caution is urged for the synthetic spectra with log.g>3.5.
Grism Lens-Amplified Survey from Space (GLASS). I.
Short Name:
J/ApJ/812/114
Date:
21 Oct 2021
Publisher:
CDS
Description:
We give an overview of the Grism Lens Amplified Survey from Space (GLASS), a large Hubble Space Telescope program aimed at obtaining grism spectroscopy of the fields of 10 massive clusters of galaxies at redshift z=0.308-0.686, including the Hubble Frontier Fields (HFF). The Wide Field Camera 3 (WFC3) yields near-infrared spectra of the cluster cores covering the wavelength range 0.81-1.69{mu}m through grisms G102 and G141, while the Advanced Camera for Surveys in parallel mode provides G800L spectra of the infall regions of the clusters. The WFC3 spectra are taken at two almost orthogonal position angles in order to minimize the effects of confusion. After summarizing the scientific drivers of GLASS, we describe the sample selection as well as the observing strategy and data processing pipeline. We then utilize MACS J0717.5+3745, a HFF cluster and the first one observed by GLASS, to illustrate the data quality and the high-level data products. Each spectrum brighter than H_AB_=23 is visually inspected by at least two co-authors and a redshift is measured when sufficient information is present in the spectra. Furthermore, we conducted a thorough search for emission lines through all of the GLASS WFC3 spectra with the aim of measuring redshifts for sources with continuum fainter than H_AB_=23. We provide a catalog of 139 emission-line-based spectroscopic redshifts for extragalactic sources, including three new redshifts of multiple image systems (one probable, two tentative).
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