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GCN Circular 849

Subject
The Likely Optical/Infrared Afterglow of GRB 001011
Date
2000-10-14T12:03:42Z (24 years ago)
From
Javier Gorosabel at LAEFF-INTA, Madrid <jgu@laeff.esa.es>
The Likely Optical/Infrared Afterglow of GRB 001011


J. Gorosabel (DSRI, Copenhagen), J. Hjorth (U. of Copenhagen 
and OMP, Toulouse), H. Pedersen, B. L. Jensen (U. of Copenhagen), 
J. P. U. Fynbo (ESO), M. I. Andersen (U. of Oulu), J. Greiner 
(AIP, Potsdam), A. J. Castro-Tirado (LAEFF-INTA, Madrid and 
IAA-CSIC, Granada), E. Pian (Astr. Obs., Trieste and ITESRE-CNR, 
Bologna), P. Vreeswijk, E. van den Heuvel (U. of Amsterdam), 
M. A. Treyer (LAM, Marseille), G. Mallen-Ornelas (U. of Toronto) 
report on behalf of a joint afterglow network:


"We have performed R, J and Ks-band observations of the GRB 001011
error box (Gandolfi et al. GCN #846Not found
 
 
) with the 1.54-m Danish and the
3.58-m New Technology Telescope (NTT) at ESO, La Silla as follows:

        Date (UT)       Telescope (Instr.)    Texp (s)  Filter
  ------------------------------------------------------------
  Oct. 11.963 - 11.967      NTT (SOFI)        15 x 60     Ks
  Oct. 11.967 - 11.982      NTT (SOFI)        15 x 60     J
  Oct. 11.983 - 12.000      NTT (SOFI)        15 x 60     Ks
  Oct. 11.993 - 12.036    1.54-m (DFOSC)      5 x 600     R 
  Oct. 14.003 - 14.052    1.54-m (DFOSC)      5 x 600     R
  ------------------------------------------------------------

A comparison of the two sets of R-band images reveals a fading object 
(not present in the DSS-2) located at:

  RA(J2000)  =  18h 23m 04.6s
  Dec(J2000) = -50d 54' 16"

with an uncertainty of 2". This location is consistent with the refined
BeppoSAX WFC position (GCN #847Not found
 
 
). Preliminary aperture photometry yields 
for the optical transient:

 R = 20.6 +- 0.1 on Oct. 12.014 UT
 R = 23.5 +- 0.4 on Oct. 14.027 UT

The zero point is based on the USNO-A2.0 star located at 
RA(J2000) = 18h 23m 1.658s, Dec(J2000) = -50d 54' 17.24" with
magnitude R = 18.0.

The object is also clearly detected in the J and Ks-band images.

Given the location of the transient in the WFC error box, its absence in 
the DSS-2, and a power-law decay index of -1.4 which is typical of GRB 
afterglows, it is likely that the transient is the optical/infrared 
afterglow of GRB 001011.

Finding charts can be found at:

http://www.dsri.dk/~jgu/grb001011/

We acknowledge the assistance from L. Vanzi, N. Ageorges, and H. Jones
at La Silla."