The latest two GRB detected by Hete-2: GRB 051022 and GRB 051028
- Instituto de Astrofisica de Andalucia (IAA-CSIC), P.O. Box 3.004, E-18.080 Granada (Spain)
- Astrophysics Missions Division, RSSD, ESA-ESTEC, Noordwijk, The Netherlands (Netherlands)
- Institute de Radioastronomie Milimetrique (IRAM), 38406 Saint Martin d'Heres (France)
- Instituto de Astrofisica de Canarias (IAC), 38205 La Laguna, Tenerife (Spain)
- Thueringer Landessternwarte Tautenburg, Sternwarte 5, D-07778 Tautenburg (Germany)
- Max-Planck Institut fuer Astronomie, Koennigstuhl 17, D-69117 Heidelberg (Germany)
- ARIES, Manora Peak, Nainital 263 129 (India)
- Indian Institute of Astrophysics, 560034 Bangalore (India)
We present multiwavelength observations of the latest two GRB detected by Hete-2 in 2005. For GRB 051022, no optical/nIR afterglow has been detected, in spite of the strong gamma-ray emission and the reported X-ray afterglow discovered by Swift. A mm afterglow was discovered at PdB confirming the association of this event with a luminous (MV = - 21.5) galaxy within the X-ray error box. Spectroscopy of this galaxy shows strong a strong [O II] emission line at z = 0.807, besides weaker [O III] emission. The X-ray spectrum showed evidence of considerable absorption by neutral gas with NH,X-ray = 4.5 x 1022 cm2 (at rest frame). ISM absorption by dust in the host galaxy at z = 0.807 cannot certainly account for the non-detection of the optical afterglow, unless the dust-to-gas ratio is quite different than that seen in our Galaxy. It is possible then that GRB 051022 was produced in an obscured, stellar forming region in its parent host galaxy.For GRB 051028, the data can be interpreted by collimated emission (a jet model with p = 2.4) moving in an homogeneous ISM and with a cooling frequency vc still above the X-rays at 0.5 days after the burst onset. GRB 051028 can be classified as a 'gray' or 'potentially dark' GRB. The Swift/XRT data are consistent with the interpretation that the reason for the optical dimness is not extra absorption in the host galaxy, but rather the GRB taking place at high-redshift.
- OSTI ID:
- 20798713
- Journal Information:
- AIP Conference Proceedings, Journal Name: AIP Conference Proceedings Journal Issue: 1 Vol. 836; ISSN APCPCS; ISSN 0094-243X
- Country of Publication:
- United States
- Language:
- English
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