Low-resolution VLT spectroscopy of GRBs 991216, 011211 and 021211

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dc.creatorVreeswijk, P. M.
dc.creatorSmette, A.
dc.creatorFruchter, A. S.
dc.creatorPalazzi, E.
dc.creatorRol, E.
dc.creatorWijers, R. A. M. J.
dc.creatorKouveliotou, C.
dc.creatorKaper, L.
dc.creatorPian, E.
dc.creatorMasetti, N.
dc.creatorFrontera, F.
dc.creatorHjorth, J.
dc.creatorGorosabel, J.
dc.creatorPiro, L.
dc.creatorFynbo, J. P. U.
dc.creatorJakobsson, P.
dc.creatorWatson, D.
dc.creatorO'Brien, P. T.
dc.creatorLedoux, C.
dc.date2005-10-13
dc.date2005-10-13
dc.date.accessioned2026-07-07T06:43:52Z
dc.date.available2026-07-07T06:43:52Z
dc.descriptionWe present low-resolution VLT spectroscopy of the afterglow of the gamma-ray bursts (GRBs) 991216, 011211 and 021211. Our spectrum of GRB991216 is the only optical spectrum for this afterglow. It shows two probable absorption systems at z=0.80 and z=1.02, where the highest redshift most likely reflects the distance to the host galaxy. A third system may be detected at z=0.77. HST imaging of the field, obtained 4 months after the burst, has resulted in the detection of two amorphous regions of emission, one at the projected afterglow position, and the other 0.6" away. The spectrum shows a depression in flux in between 4000 A and 5500 A. This could be the result of a 2175 A-type extinction feature in the host of GRB991216, but at a rather red wavelength of 2360 A. If this interpretation is correct, it is the first time the extinction feature is seen in a GRB afterglow spectrum. It is centered at a wavelength similar to that of the ultra-violet (UV) bumps inferred from observations of a few UV-strong, hydrogen-poor stars in the Galaxy. All significant absorption lines (except for one) detected in the spectrum of GRB011211 are identified with lines originating in a single absorption system at z=2.142+/-0.002, the redshift of the GRB011211 host galaxy. We also detect the Lyman alpha absorption line in the host, to which we fit a neutral hydrogen column density of log N(HI)=20.4+/-0.2, which indicates that it is a damped Lyman alpha system. Using a curve-of-growth analysis, we estimate the Si, Fe and Al metallicity at the GRB011211 redshift. For GRB021211, we detect a single emission line in a spectrum obtained tens of days after the burst, which we identify as [OII] 3727 at z=1.006. The corresponding unobscured [OII] star-formation rate is 1.4 Msun/yr.
dc.descriptionA&A in press, 13 pages, 7 figures
dc.identifierhttps://arxiv.org/abs/astro-ph/0510404
dc.identifierhttp://arxiv.org/abs/astro-ph/0510404
dc.identifierAstron.Astrophys. 447 (2006) 145-156
dc.identifierdoi:10.1051/0004-6361:20053795
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/102578
dc.subjectAstrophysics
dc.titleLow-resolution VLT spectroscopy of GRBs 991216, 011211 and 021211
dc.typetext

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