We present the discovery of the optical transient of the long-duration gamma-ray burst GRB 000630. The optical transient was detected with the Nordic Optical Telescope 21.1 hours after the burst. At the time of discovery the magnitude of the transient was R = 23.04+/- 0.08. The transient displayed a power-law decline characterized by a decay slope of alpha = -1.035+/- 0.097. A deep image obtained 25 days after the burst shows no indication of a contribution from a supernova or a host galaxy at the position of the transient. The closest detected galaxy is a R=24.68+/- 0.15 galaxy 2.0 arcsec north of the transient. The magnitudes of the optical afterglows of GRB 980329, GRB 980613 and GRB 000630 were all R>~ 23 less than 24 hours from the burst epoch. We discuss the implications of this for our understanding of GRBs without detected optical transients. We conclude that i) based on the gamma-ray properties of the current sample we cannot conclude that GRBs with no detected OTs belong to another class of GRBs than GRBs with detected OTs and ii) the majority (ga 75%) of GRBs for which searches for optical afterglow have been unsuccessful are consistent with no detection if they were similar to bursts like GRB 000630 at optical wavelengths. Based on observations made with the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canaria, and with the German-Spanish Astronomical Centre, Calar Alto, operated by the MPI für Astronomie, Heidelberg, jointly with the Spanish National Commission for Astronomy, and with the TNG, operated on the island of La Palma by the Centro Galileo Galilei of the CNAA at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias.
Detection of the optical afterglow of GRB 000630: Implications for dark bursts
GUIDORZI, Cristiano;MONTANARI, Enrico;
2001
Abstract
We present the discovery of the optical transient of the long-duration gamma-ray burst GRB 000630. The optical transient was detected with the Nordic Optical Telescope 21.1 hours after the burst. At the time of discovery the magnitude of the transient was R = 23.04+/- 0.08. The transient displayed a power-law decline characterized by a decay slope of alpha = -1.035+/- 0.097. A deep image obtained 25 days after the burst shows no indication of a contribution from a supernova or a host galaxy at the position of the transient. The closest detected galaxy is a R=24.68+/- 0.15 galaxy 2.0 arcsec north of the transient. The magnitudes of the optical afterglows of GRB 980329, GRB 980613 and GRB 000630 were all R>~ 23 less than 24 hours from the burst epoch. We discuss the implications of this for our understanding of GRBs without detected optical transients. We conclude that i) based on the gamma-ray properties of the current sample we cannot conclude that GRBs with no detected OTs belong to another class of GRBs than GRBs with detected OTs and ii) the majority (ga 75%) of GRBs for which searches for optical afterglow have been unsuccessful are consistent with no detection if they were similar to bursts like GRB 000630 at optical wavelengths. Based on observations made with the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canaria, and with the German-Spanish Astronomical Centre, Calar Alto, operated by the MPI für Astronomie, Heidelberg, jointly with the Spanish National Commission for Astronomy, and with the TNG, operated on the island of La Palma by the Centro Galileo Galilei of the CNAA at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
