GRB 050502

S. Bradley Cenko, Derek B. Fox, and P. Brian Cameron report on behalf of
the Caltech-NRAO-Carnegie GRB Collaboration:

We have imaged the field of GRB050502 (GCN 3323
Loading...
 
 ) with the Large Format
Camera (LFC) mounted on the Palomar 5-m Hale Telescope.  Observations
consisted of 2 x 600 s exposures in the Sloan r' filter.  At a mean
epoch of ~ 11:30 3 May UT (33.3 hours after the burst), we find no
emission at the afterglow position reported by Yost et al. (GCN 3322
Loading...
 
 ).
OUr 3-sigma limiting magnitude, calculated by comparison with several
Guide Star Catalog sources in the field, is approximately r' > 23.5

S. Bradley Cenko, Derek B. Fox, and P. Brian Cameron report on behalf of
the Caltech-NRAO-Carnegie GRB Collaboration:

We have imaged the field of GRB050502 (GCN 3323
Loading...
 
 ) with the Large Format
Camera (LFC) mounted on the Palomar 5-m Hale Telescope.  Observations
consisted of 2 x 600 s exposures in the Sloan r' filter.  At a mean
epoch of ~ 11:30 4 May 2005 UT (57.3 hours after the burst), we find no
emission at the afterglow position reported by Yost et al. (GCN 3322
Loading...
 
 ).
Our 3-sigma limiting magnitude, calculated by comparison with several
Guide Star Catalog sources in the field, is approximately r' > 23.5.

D. Gotz and S. Mereghetti (IASF Milano) on behalf of the IBAS Localization 
Team report:

Further analysis of the IBIS/ISGRI data for GRB 050502 (GCN Circ. n. 3323) 
indicates that the peak flux is 1.8 photons (2.E-07 ergs)/cmsq/s (1 s 
integration time) and the fluence is 14.7 photons (1.4E-6 ergs)/cmsq (21 s 
integration time). Both values refer to the 20-200 keV energy range.

A plot of the light curve can be found at:

http://ibas.mi.iasf.cnr.it/IBAS_Results.html

Note that the data before 02:13:56 UT are missing in the plot because the 
satellite was performing a slew and that the short gap at 02:14:10 UT is 
due to satellite telemetry saturation.

This message can be cited.

Josh Rich, Brian  Schmidt (Australian National University) and Jessie 
Christiansen (UNSW)  report on behalf of a larger collaboration:

"We observed a 5' region covering the BAT position of  the SWIFT burst 
GRB 050502B(GCN#3237
Loading...
 
 )
using the ANU 1m telescope on May 2.40 UT in V band.  Preliminary 
comparison with the DSS shows no OT to V=18.
Further observations are continuing."

C. Blake (Harvard) and J. S. Bloom (UCB) report:

PAIRITEL has continued to image the Yost et al. optical candidate
afterglow (GCN #3322
Loading...
 
 ). We confirm that the IR source (#3326) initially
faded, strongly confirming the hypothesis from Yost et al. In
particular, from T+47min to T+94 min the source faded by ~1.1 mag in
J. But from T+94 min to T+121 min, there is some evidence for
brightening by ~0.1 mag in J-band. A similar result is found in H and
Ks.

Based on an astrometric tie of 2MASS to a 141 sec J-band image from
(start) 2005-05-02 02:52:40 UT, we find

  IRT:  RA = 13:29:46.33, Dec = 42:40:27.3    --Offset to IRT--
  A :   RA = 13:29:42.78, Dec = 42:40:49.2  21.83"   S, 39.19" E
  B:    RA = 13:29:44.23, Dec = 42:38:13.1  134.20"  N, 23.21" E

The uncertainty in the absolute WCS is ~0.5 arcsec.  Sources A and B are
nearby bright sources suitable for blind offset spectroscopy."

J.S. Bloom (UCB) and C. Blake (Harvard) report on behalf of a larger
collaboration:

"The PAIRITEL 1.3m telescope began observations of GRB 050502 (GCN 3323
Loading...
 
 )
during twilight, approximately 31 minutes after the burst. We confirm a
bright point source in our J,H,K images coincident with the location
reported by Yost et al. (GCN 3322
Loading...
 
 ). This source is below the 2MASS
detection limit. Observations and analysis are continuing."

A. Gomboc, I. A. Steele, A. Monfardini, C. J. Mottram, C. Guidorzi,
M.F. Bode, C.G. Mundell (Liverpool JMU) report:

Due to a typing error, we need to correct the position of the transient of
the GRB 050502 to be:
 
RA 13:29:46.25
dec +42:40:27.50.

We apologize for the inconvenience.

A. Gomboc, I. A. Steele, A. Monfardini, C. J. Mottram, C. Guidorzi,
M.F. Bode, C.G. Mundell (Liverpool JMU) report:

The automatic pipeline of the Liverpool Telescope detected an optical
transient at 
RA 13:39:46.25
dec +42:40:27.50.
We measure the approximate magnitude r'~15.6 at ~3 min after the burst.

D. Gotz, S. Mereghetti (IASF, Milano), N. Mowlavi, S. Shaw, M. Beck
(ISDC, Versoix) and J. Borkowski (CAMK, Torun) on behalf of the IBAS
Localization Team report:

A 20 s long GRB has been detected by IBAS in IBIS/ISGRI data at 02:13:57 
UT on May 2. Being at the beginning of a pointing the GRB may last longer. 
Its coordinates (J2000) are:

RA:  202.4392 [degrees]
DEC: +42.6741 [degrees]

with an uncertainty of 2.0 arcmin (90% c.l. radius).

Its preliminary peak flux (20-200 keV, 1s integration time) is about 1.3 
ph (1E-07 erg)/cmsq/s.

This message can be cited.

S.A. Yost, H. Swan (U Mich), B. A. Schaefer (Louisiana State), K. Alatalo
(U Mich) report  on behalf of the ROTSE collaboration:

ROTSE-IIIb, located at McDonald Observatory, Texas, responsed to GRB
050502 (Integral trigger 2484) 23.3 s after the burst (5.0s after the GCN
notice time), in conditions of variable clouds across the field. The
unfiltered images are calibrated relative to USNO A2.0. Despite the
changes in limiting magnitude due to the clouds, we see a 14.3rd
magnitude, definitely fading source at:

	13:29:46.3 +42:40:27.7 (J2000)

The source is not visible in DSS (2nd epoch), 2MASS, or the MPChecker
database. It is at ~14.3 mag, around 23.3 s after the burst in an image
with a limiting magnitude of approximately 14.9. It is presently at ~
18.5th mag, ~ 1000 sec post-burst.

Continuing observations are in progress.