Constraining the GRB collimation with a survey for orphan afterglows

Free access article

Issue		A&A Volume 449, Number 1, April I 2006


Page(s)		79 - 88
Section		Extragalactic astronomy
DOI		http://dx.doi.org/10.1051/0004-6361:20054317

A&A 449, 79-88 (2006)
DOI: 10.1051/0004-6361:20054317

Constraining the GRB collimation with a survey for orphan afterglows

A. Rau¹, J. Greiner¹ and R. Schwarz²

¹ Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse, 85748 Garching, Germany
e-mail: arau@mpe.mpg.de
² Astrophysikalisches Institut Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany

(Received 7 October 2005 / Accepted 22 November 2005)

Abstract
Gamma-ray bursts are believed to be produced in highly-relativistic collimated outflows. Support for this comes among others from the association of the times of detected breaks in the decay of afterglow light curves with the collimation angle of the jets. An alternative approach to estimate a limit on the collimation angle uses GRB afterglows without detected prompt-emission counterparts. Here we report on the analysis of a dedicated survey for the search of these orphan afterglows using the Wide Field Imager at the 2.2 m MPI/ESO telescope at La Silla, Chile. We monitored ~12 deg² in up to 25 nights typically spaced by one to two nights with a limiting magnitude of R=23. Four previously unknown optical transients were discovered and three of these associated with a flare star, a cataclysmic variable and a dwarf nova. The fourth source shows indications for an extragalactic origin but the sparse sampling of the light curve prevents a reliable classification. We discuss the results in the context of the collimation of GRBs.

Key words: gamma rays: bursts -- surveys

SIMBAD Objects

What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access. An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.

If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
You can define your own OpenURL resolver with your EDPS Account. In this case your choice will be given priority over that of your library.
You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.