J. S. Bloom (UC Berkeley), W. Li (UC Berkeley), A. J. Levan (U.
Warwick), D. A. Perley (UCB), N. R. Tanvir (U. Leicester), N. R. Butler
(UCB), H-W. Chen (U. Chicago), R. Chornock (UCB), J. X. Prochaska
(UCO/Lick), C. D. Bailyn (Yale), A. Bunker (U. Exeter), R. Chornock
(UCB), B. Cobb (Yale), P. B. Hall (York U.), A. V. Filippenko (UCB), N.
Gehrels (NASA/GSFC), K. Glazebrook (Swinburne), J. Granot (U.
Hertfordshire), K. C. Hurley (UCB), D. Kocevski (UCB), B. Metzger (UCB),
M. Modjaz (UCB), A. Miller (UCB), W. Lee (I. de Astronomia), S. Lopez
(U. Chile), J. Norris (NASA/Ames), P. E. Nugent (LBNL), M. Pettini (U.
Cambridge), D. Poznanski (UCB), A. L. Piro (UCB), E. Quataert (UCB), E.
Ramirez-Ruiz (UCSC), J. Shiode (UCB), and T. Sakamoto (GSFC/UMBC) report:
Under Director's Discretionary Proposal (#11551), we acquired
observations of GRB 080503 (Mao et al., GCN 7665) with the Hubble Space
Telescope (HST+WFPC2), starting at 15:08 and lasting until 20:45 (UT
2008-05-08), approximately 5.2 days after the GRB. The total
integration time was 2x1200s + 2x1100s (2 orbits) in F606W, 3x700s (1
orbit) in F814W, and 3x700s (1 orbit) in F450W. The data were collected
in a small dither pattern around the WFALL position to mitigate against
We clearly detect a point source at a location consistent with the
optical transient (Perley et al., GCN 7678) in F606W, and marginally
detect a source at this position in 450W. The transient is not detected
in F814W. We report the following preliminary magnitudes:
F450W_AB = 26.95 +/- 0.27
F606W_AB = 26.86 +/- 0.15
F814W_AB > 26.6
The nearby source s1 (see Perley et al., GCN 7667) is also detected, and
appears visibly extended, though this extension does not reach s2. Two
other faint, extended sources ("s3" and "s4") are detected about 1
arcsecond to the northwest and southeast of the transient, respectively.
There is no obviously extended source detected at the position of s2.
The source is significantly fainter than observed in our Gemini
measurements, which may suggest a break (as expected from an off-axis
jet) or an exponential decline (as expected from an LP mini-supernova).
However, LP mini-SN models also predict a red late-time color, which
is not observed. We note also the detection of an X-ray afterglow in
late-time Chandra observations (Butler et al., GCN in prep.)
An additional epoch of HST imaging will be obtained starting 15:05
An preliminary image with less-than-optimal cosmic ray reduction is
We are grateful to all the people STSCI that made such a rapid ToO possible.