GRB 001011

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 #846
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 ) 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 #847
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 ). 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."

GRB001011 BeppoSAX/WFC refined position

Refined  coordinates of GRB001011 from WFC are:

R.A.(2000)= 275.768
DEC.(2000)= -50.899

The error radius is 2'.

A BeppoSAX/NFI follow-up observation is not feasible due to the presence
of the moon in one of the startrackers of the satellite.

G. Gandolfi
on behalf of BeppoSAX Mission Scientist

BeppoSAX ALERT: GRB001011

On Oct. 11, 15:54:50 U.T. a GRB (GRB001011) has been detected
simultaneosly by the GRBM and WFC2 aboard BeppoSAX.

Preliminary  coordinates from WFC are:

R.A.(2000)= 275.865
DEC(2000)= -50.902

The error radius at this stage of analysis is 5'.

We are planning a BeppoSAX-NFI observation.


G. Gandolfi on behalf of
BeppoSAX Mission Scientist