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GCN Circular 377

Infrared and Optical Observations of GRB990705
1999-07-07T16:28:35Z (25 years ago)
Elena Pian at ITESRE-CNR,Bologna <>
Infrared and Optical Observations of GRB990705

E. Palazzi, N. Masetti, E. Pian, F. Frontera, L. Amati (ITESRE-CNR,
Bologna), M. Mendez, P. Vreeswijk, E. Rol, T. Galama, F. van der Hooft,
M.  van der Klis, M. Heemskerk, (Univ. of Amsterdam), J. van Paradijs
(U. of Amsterdam and U. of Alabama in Huntsville), L.  Hunt (Astr. Obs.
of Arcetri), L.A. Antonelli, G. Marconi (Astr. Obs. of Rome), E.
Kuulkers (SRON, Utrecht), T. Augusteijn, H. Boehnhardt, C. Lidman, L.
Vanzi (ESO), M. Feroci (IAS-CNR, Rome), and C.  Kouveliotou (MSFC/NASA)
report on behalf of a large collaboration:

"We have observed the error box of GRB990705 (BeppoSAX mail # 99/16 and
99/17) at the ESO NTT with SOFI in H filter for 20 minutes starting on 
July 5.94 UT and for 10 minutes starting on July 6.95 UT. An object of 
H = 16.7 +- 0.1 is detected in the first night at RA = 05 09 55.4, Dec
= -72 08 01 (astrometric uncertainty of 1".5), and not in the second  
night, with a 3-sigma upper limit of H >~ 19.  The position of the  
transient is consistent with that of the X-ray transient detected with
the SAX NFIs (Gandolfi, GCN 373).  We propose that the transient source
is the infrared counterpart to GRB 990705.  Assuming a power-law
temporal fading, the measured magnitude and upper limit would imply
that the decay index is < -1.4.

In a 10-minutes exposure taken at the VLT with FORS1 in the V filter on
July 6.40 UT in very bad seeing conditions (~2".5) the source is
detected at 3-sigma confidence level with V ~22.5, linked to the
standard sequence PG 2331+055 (Landolt 1992, AJ 104, 340).

A 7.5-min exposure with the ESO 2.2m telescope at La Silla on July 6.44
UT yields no detection, to a 3-sigma limiting magnitude of B ~22,
linked to the USNO-A1.0 star at RA = 05 09 42.59, Dec = -72 07 41.2
(J2000) which has B = 19.1."

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