2009A&A...503..771V


C.D.S. - SIMBAD4 rel 1.7 - 2020.07.14CEST00:05:15

2009A&A...503..771V - Astronomy and Astrophysics, volume 503, 771-781 (2009/9-1)

Statistics and characteristics of MgII absorbers along GRB lines of sight observed with VLT-UVES.

VERGANI S.D., PETITJEAN P., LEDOUX C., VREESWIJK P., SMETTE A. and MEURS E.J.A.

Abstract (from CDS):

We analyze the properties of MgII absorption systems detected along the sightlines toward GRBs using a sample of 10 GRB afterglow spectra obtained with VLT-UVES over the past six years. The signal-to-noise ratio is high enough that we can extend previous studies to smaller equivalent widths (typically Wr>0.3Å). Over a pathlength of Δz∼14, we detect 9 intervening MgII systems with Wr>1Å and 9 weaker MgII systems (0.3< Wr<1.0Å) when about 4 and 7, respectively, are expected from observations of QSO sightlines. The number of weak absorbers is similar along GRB and QSO lines of sight, while the number of strong systems is higher along GRB lines of sight with a 2σ significance. Using intermediate and low-resolution observations reported in the literature, we increase the absorption length for strong systems to Δz=31.5 (about twice the path length of previous studies) and find that the number density of strong MgII systems is a factor of 2.1±0.6 higher (about 3σ significance) toward GRBs than towards QSOs, about twice less, however, than previously reported. We divide the sample into three redshift bins and find that the number density of strong MgII is greater in the low-redshift bins. We investigate in detail the properties of strong MgII systems observed with UVES, deriving an estimate of both the HI column density and the associated extinction. Both the estimated dust extinction in strong GRB MgII systems and the equivalent width distribution are consistent with what is observed for standard QSO systems. We also find that the number density of (sub)-DLAs per unit redshift in the UVES sample is probably twice more than what is expected from QSO sightlines, which confirms the peculiarity of GRB lines of sight. These results indicate that neither a dust extinction bias nor different beam sizes of the sources are viable explanations for the excess. It is still possible that the current sample of GRB lines of sight is biased by a subtle gravitational lensing effect. More data and larger samples are needed to test this hypothesis.

Abstract Copyright:

Journal keyword(s): quasars: absorption lines - gamma rays: bursts

Simbad objects: 26

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Number of rows : 26

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 GRB 071031 gB 00 25 37.40 -58 03 33.9           ~ 142 0
2 GRB 021004 gB 00 26 54.68 +18 55 41.6           ~ 515 1
3 GRB 050908 gB 01 21 50.750 -12 57 17.20           ~ 157 1
4 GRB 991216 gB 05 09 31.2983 +11 17 07.262           ~ 406 1
5 GRB 050505 gB 09 27 03.300 +30 16 23.70     20.74     ~ 170 1
6 GRB 030323 gB 11 06 09.4 -21 46 13           ~ 125 1
7 GRB 011211 gB 11 15 16 -21 56.0           ~ 285 1
8 GRB 030226 gB 11 33 04.9 +25 53 56           ~ 186 2
9 GRB 030328 gB 12 10 48.4 -09 20 51           ~ 136 2
10 GRB 030429 gB 12 13 07.495 -20 54 49.54           ~ 120 1
11 GRB 060206 gB 13 31 43.420 +35 03 03.60   19.99 17.09     ~ 282 1
12 GRB 020405 gB 13 58 03.12 -31 22 22.2   21.9 21.5     ~ 236 1
13 GRB 050730 gB 14 08 17.090 -03 46 18.90   20.32 17.68     ~ 282 1
14 GRB 080319B gB 14 31 41.04 +36 18 09.2           ~ 421 0
15 GRB 080310 gB 14 40 13.89 -00 10 30.4           ~ 161 0
16 GRB 010222 gB 14 52 12.55 +43 01 06.3           ~ 335 2
17 GRB 060526 gB 15 31 18.360 +00 17 04.90   18.31 17.16     ~ 233 0
18 GRB 060418 gB 15 45 42.600 -03 38 20.00 15.73 16.19 14.98     ~ 322 1
19 GRB 000926 gB 17 04 15 +51 46.0           ~ 341 2
20 GRB 080413A gB 19 09 11.73 -27 40 39.6           ~ 123 0
21 GRB 020813A gB 19 46 41.874 -19 36 04.81           ~ 285 1
22 GRB 071003 gB 20 07 24.50 +10 56 48.8           ~ 139 0
23 GRB 050922C gB 21 09 33.000 -08 45 30.10 15.15 15.86 14.69     ~ 250 0
24 GRB 060607 gB 21 58 50.400 -22 29 46.70 18.49 16.67 15.09     ~ 258 1
25 GRB 050820A gB 22 29 38.110 +19 33 37.10 18.33 19.00 18.47     ~ 338 1
26 GRB 051111A gB 23 12 33.170 +18 22 28.80 19.77 20.08 19.50     ~ 185 1

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2020.07.14-00:05:15

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