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GCN Circular 343

Subject
X-ray/GRB 1SAX J0835.9+5118, Optical Observations
Date
1999-05-23T07:36:56Z (25 years ago)
From
Jules Halpern at Columbia U. <jules@astro.columbia.edu>
J. P. Halpern (Columbia U.), J. Parker (SwRI), L. Allen (U. Michigan),
and E. Costa (IAS/CNR, Rome) report on behalf of the MDM Observatory GRB
follow-up team:

"We imaged the field of the BeppoSAX fast X-ray transient 1SAX J0835.9+5118
(Piro GCN 333; Gandolfi et al., IAUC 7174) in the R band on two consecutive 
nights using the MDM 2.4m telescope.  Total exposure time was 50 minutes on 
May 21.19 UT and 40 minutes on May 22.19 UT.  Seeing was 1.5-1.6 arcsec on
the first night, and 1.8-2.2 arcsec on the second night.  Limiting magnitudes
for 5 sigma detection are R = 23.5 on the first night and R = 22.1 on the
second night.  No variable object is found to the limit of R = 22.1 within
the 3' radius error circle.  Below  we list magnitudes of objects referred
to in previous circulars: the radio source of Frail et al. (GCN 337), and 
the galaxy described by Pedersen et al. (GCN 340).  We adopt here the 
photometric calibration of Henden et al. (GCN 339).

Radio Source     B = 21.58 +/- 0.08 (May 21.15 1.3m)
                 R = 20.81 +/- 0.05 (May 21.19 2.4m)
                 R = 20.69 +/- 0.07 (May 22.19 2.4m)

Pedersen Galaxy  B = 20.62 +/- 0.09 (May 21.15 1.3m)
                 R = 19.63 +/- 0.03 (May 21.19 2.4m)
                 R = 19.62 +/- 0.09 (May 22.19 2.4m)
		
The B magnitude of the radio source differs from the value given in our
GCN 338 in part because of a 0.5 magnitude difference between the USNO-A2.0
values and the new calibration of Henden et al. (GCN 339).  However, the
magnitude of the radio source given as R = 21.21 +/- 0.06 by Luginbuhl et al.
(GCN 341) might indicate a significant discrepancy, assuming that the same 
calibration is being used.

With regard to the morphology of the Pedersen et al. galaxy, although our
images have inferior seeing, the object in question appears consistent in
both magnitude and shape on our May 21 image, including a faint extension 
in the same place as their point-like source.

This message may be cited."
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