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Low-resolution VLT Spectroscopy of GRBs 991216, 011211, 021211 and 030328

Authors :
Vreeswijk, P. M
Smette, A
Fruchter, A. S
Palazzi, E
Rol, E
Wijers, R. A. M. J
Kouveliotou, C
Kaper, L
Pian, E
Masetti, N
Publication Year :
2005
Publisher :
United States: NASA Center for Aerospace Information (CASI), 2005.

Abstract

We present low-resolution VLT spectroscopy of the aftergiow position of the gamma ray bursts 991216, 011211, 021211 and 030328. The spectmm of GRB 991216 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, more uncertain, system may be detected at z = 0.77. HST imaging of the field obtained 4 months later, show two amorphous regions of emission, one at the projected OT position, the presumed host galaxy at z = 1.02, and the other 0"6 away. All significant lines in the spectrum of GRB 011211 are identified with lines originating in a single absorption system at z = 2.142 plus or minus 0.002, the redshift of the GRB 011211 host galaxy. We also detect Lya in the host, for which we fit a neutral hydrogen column density of log N(HI)=20.4 plus or minus 0.2, which indicates that it is a damped Lya system. For GRB021211, we detect a single emission line in a spectrum tens of days after the burst, which we identify as [OII] at z = 1.006. The galaxy l"5 away from the afterglow location has z = 0.800, and is therefore unrelated to the GRB. Finally, for GRB030328 at least two absorption systems are required to explain all significant lines: one at z = 1.522, the likely redshift of the GRB, and the other at z = 1.295. For the latter system we only detect two lines, and we consider the reality of this system to be uncertain.

Subjects

Subjects :
Astronomy

Details

Language :
English
Database :
NASA Technical Reports
Publication Type :
Report
Accession number :
edsnas.20050092392
Document Type :
Report