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GCN Circular 161

Subject
GRB 980326/Host Galaxy
Date
1998-12-23T02:48:56Z (25 years ago)
From
Shri Kulkarni at Caltech <srk@astro.caltech.edu>
J. S. Bloom and S. R. Kulkarni report on behalf of the  Caltech GRB
effort:

"On the nights of 17 and 18, December 1998 we carried out imaging
observations of the field of GRB 980326 with LRIS instrument on Keck
II.  In the R-band we obtained 8 images each with an integration time
of 300 s. These images were debiased, flat-fielded, registered and
median stacked. In the resulting image we do not detect the host galaxy
at the position of the optical transient of this GRB (Groot et al., ApJ
502, L123, 1998). We determined the zero-point calibration using the
reference stars quoted in Groot et al. (1998). The faintest object that
was readily detected and in the general vicinity of the OT was ~27.3
mag (with aperture radius of 1.5 arcsec).  This object and others at
similar brightness levels are clearly visible to the eye in the stacked
image.  We can place a firm lower limit on the magnitude of the host
galaxy at this level.

Previous magnitudes for the the magnitude of the host galaxy were
derived using data when the OT was bright and could have been affected
by the assumed decay model and photometric errors.

The true host of GRB 980326 is thus fainter than R=27.3 mag or that the
OT/GRB is not coincident with its host (e.g. the GRB was ejected from
the host galaxy or is of intergalactic origin).  If the former is true
then the host galaxy of GRB 980326 is by far the faintest host and this
faintness is unlikely due to dust extinction given the detection of
the optical transient in the B band (Groot et al. 1998)."
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