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GCN Circular 156

Subject
GRB980425 Optical Follow-up
Date
1998-10-22T05:47:13Z (26 years ago)
From
Jules Halpern at Columbia U. <jules@astro.columbia.edu>
J. P. Halpern, Columbia University, reports:

I obtained optical spectra of objects in the error circle of the variable
X-ray source 1SAXJ1935.3-5252 (Pian et al. GCN 61,69) using the CTIO 1.5m 
telescope on Oct. 17-21.  A total of 24 objects in the original error circle
(Pian et al. GCN 61) and the revised error circle (Piro et al. GCN 155) were
observed, completing this spectroscopic survey to a limiting magnitude of 18.
No compelling candidate for identification was found at this level.  Thus,
1SAXJ1935.3-5252 remains a plausible candidate for the afterglow of
GRB980425.

The brightest galaxy in this field, of approximate magnitude 17.5, has narrow 
emission lines of H-alpha and [N II] 658 nm at z = 0.142, but no evidence of 
nuclear activity.  Its position is RA = 19h35m27.6s, Dec = -52o53'00" (J2000), 
which is within both the old and the new error circles.

Deeper spectroscopy in this field using larger telescopes would be worthwhile,
since the optical counterpart of 1SAXJ1935.3-5252 could easily be fainter than 
the limit surveyed here.   If a definitive identification cannot be obtained,
more X-ray observations of 1SAXJ1935.3-5252 are needed to determine if this
X-ray source recurs.
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