[vsnet-grb-info 5317] GRB071021: MARGE Optical Limits

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  7007
SUBJECT: GRB071021: MARGE Optical Limits
DATE:    07/10/26 15:23:36 GMT
FROM:    Heather Swan at U.of Michigan/ROTSE  <hflewell at umich.edu>

H. Swan (U Mich), I. Smith (Rice), C. Akerlof (U Mich), E. Rykoff (UCSB)
and M. Skinner (Boeing) report on behalf of the MARGE collaboration:

The AEOS Burst Camera (ABC) on the AEOS telescope, located at the Maui
Space Surveillance System on Haleakala, observed the field of GRB071021
(Swift trigger 294974 (T. Sakamoto et al, GCN 6958)). The images are
unfiltered 10s exposures that started ~10 minutes after the trigger and
ended ~ 2 hour later.  We calibrated our images to the USNO-B1 R2
catalog.  We do not see the NIR counterpart observed by A. J.
Castro-Tirado et al. (GCN 6968), down to the following limiting
magnitudes.  We have not corrected for the galactic extinction, which is
E(B-V)= 0.074 mag, according to the NED Extinction calculator.


start UT       end UT      t_exp(s)   mlim   t_start-tGRB(s)  Coadd?
--------------------------------------------------------------------
09:51:24.7   09:57:32.2      367.5     22.6           591.7      Y
09:51:24.7   12:09:06.9     8262.3     23.7           591.7      Y


The ABC is an unfiltered camera, with enhanced sensitivity in the red
end of the spectrum.  This sensitivity to the red end of the spectrum
allows us to see high (z < 6) bursts. The relatively deep upper limits
we have obtained may assist efforts to better determine the redshift for
this unusual event.