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GCN Circular 345

Subject
X-ray/GRB 1SAX J0835.9+5118, TNG V and R observations
Date
1999-05-27T09:53:51Z (25 years ago)
From
Nicola Masetti at ITeSRE,CNR,Bologna <masetti@tesre.bo.cnr.it>
N. Masetti, E. Palazzi, E. Pian, F. Frontera (ITESRE, CNR, Bologna),
D. Gardiol, S. Benetti, A. Zacchei, A. Magazzu' (TNG), M. Della Valle
(Univ. of Padua), E. Costa, M. Feroci and L. Piro (IAS, CNR, Rome) report:

"We imaged the error box of the X-ray transient source SAX J0835.9+5118
(Piro, GCN #333) with TNG plus OIG CCD camera on 1999 May 20.890 - 20.920 
UT (five V frames; seeing 1."2 - 1".5) and on 1999 May 21.934 - 21.955 UT
(one R and two V frames; seeing 0".9). The exposure time was 300s for all
images.

Calibration of V and R frames was performed using the photometry by
Henden et al. (GCN #339).
A limiting magnitude of V ~ 22.5 was obtained in each frame of the first
night, while the limits V ~ 23 and R ~ 23 were reached in the images
acquired on the second night (3-sigma limits).

Comparison among the V frames of May 20 and 21 shows no object which
varied by more than 0.3 magnitudes (at a 3-sigma level) down to V ~ 22.

The optical counterpart (Bloom et al., GCN #335) of the radio source
detected by Frail et al. (GCN #334) appears star-like as earlier noted by
other authors (GCN #336, #338, #341) with magnitudes V = 21.08 +- 0.05 and
R = 20.68 +- 0.05. Some scatter of 0.1 mag around the mean V magnitude of
the object is seen, thus probably indicating the presence of flickering
or of some other optical variability.

The irregular galaxy reported by Pedersen et al. (GCN #340) has 
V = 20.20 +- 0.05 and R = 19.60 +- 0.05 in our frames and does not show
any variability in the V band between the two nights. We see in our images
that the faint knot noted by Pedersen et al. southeast of the galaxy
appears brighter in the R band than in V.

The R magnitudes of both objects are in agreement with the values reported 
by Halpern et al. (GCN #343).


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