GCN Circular 7678
Subject
GRB 080503: Late-time Optical rebrightening (possible mini-SN)
Date
2008-05-05T04:49:49Z (17 years ago)
From
Daniel Perley at U.C. Berkeley <dperley@astro.berkeley.edu>
D. A. Perley, J. S. Bloom (UC Berkeley), and J. X. Prochaska (UCO/Lick)
report:
Further to Bloom et al. (GCN 7667), we acquired additional imaging of
the probable short-hard (Ukwatta et al., GCN 7677) GRB 080503 (Mao et
al., GCN 7665) with extended emission the night after the burst. A
total of 10 exposures of 180 seconds each were taken in r-band between
UT 14:08 and 14:46 (2008-05-04), 26 hours after the BAT trigger, using
GMOS on Gemini-North. In addition, we report analysis of additional
imaging taken between 1.0-2.5 hours after the burst in g, r, i, and z
filters.
The source noted in our previous circular, s1, does not appear to be
variable between images, and no other sources are detected in the XRT
error circle to a very deep limit of r >~ 26.5 during the first night.
However, a new source ("s2") appears in the second night's observation
that was not detected in our r-band imaging during the first night. If
this source is associated with GRB 080319B this would be extremely
unusual behavior for a short gamma-ray burst. It is possible that the
rebrightening is the first example of the detection of a Li-Paczynski
"mini"-supernova (1998ApJ...507L..59L; see also Kulkarni
astro-ph/0510256). More tentatively, we note that s1 may the host galaxy
(we note that all previous SHB's with extended emission have been seen
at small offset from their host galaxies: Troja et al., astro-ph/0711.3034).
The source is located near the center of the enhanced XRT error circle
(Goad et al, GCN 7669) at:
RA=19:06:28.766 Dec=+68:47:35.53 (J2000)
(uncertainty is 250 mas in both coordinates relative to the ICRS)
And can be seen at the following links:
http://lyra.berkeley.edu/~jbloom/grb080503-comp.png
http://lyra.berkeley.edu/~jbloom/grb080503-rebrightening.mpeg
http://lyra.berkeley.edu/~dperley/080503/080503_s2b.png
We report the following photometry, calibrated relative to USNO-B1.0:
Acquisition r-band image (t=0.98 hr)
s1: R = 25.56 +/- 0.33
s2: R > 25.6
First night r-band stack (t=1.5 hr)
s1: R = 26.00 +/- 0.18
s2: R >~ 26.5
Second night r-band stack (t=26.0 hr)
s1: R = 25.70 +/- 0.12
s2: R = 25.28 +/- 0.09
UT_start exposure filter magnitude
13:23 1x180 r R = 24.8 +/- 0.3
13:38 1x30+2x300 R R > 25.5 (2-sigma)
13:47 5x180 r R = 25.4 +/- 0.2
Photometric uncertainties do not include calibration uncertainties
relative to USNO-B1.0, which are at the level of 0.1 magnitude. (This
does not affect the relative magnitudes between the images).
In our images in other filters, s2 is not detected in i-band or z-band
during the first night. It may be marginally detected in g-band imaging
near the limiting magnitude of that observation.
Further observations of this source are planned and strongly encouraged.