[vsnet-grb-info 6521] SGR 0501+4516: MDM Optical Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8129
SUBJECT: SGR 0501+4516: MDM Optical Observations
DATE:    08/08/24 23:55:33 GMT
FROM:    Jules Halpern at Columbia U.  <jules at astro.columbia.edu>

I observed the Swift XRT location of SGR 0501+4516 (Holland et al., GCN #8112;
Barthelmy et al., GCN #8113) in the R-band using the MDM 2.4m telescope
on the nights of Aug. 23 and 24 UT.  Preliminary flux calibration was
performed with Landolt standard stars.  In a sequence of 90 s exposures from
Aug. 24 09:55 UT to 11:49 UT, I find variability of the star noted by
Denisenko (GCN #8114) as variable between POSS epochs.  It began at R = 17.16,
remaining at plateau for the first hour, then declined monotonically to
R = 17.35 over the next hour.  Within a radius of 10" of the XRT position,
there is no new object that is not on the POSS to a limit of R = 23.0 in the
summed images from Aug. 24.

I also obtained a series of 10 s exposures that bracketed the time
of the large flare on Aug. 23 11:27:35 UT (Gehrels et al., GCN #8124),
but unfortunately did not include it.  No optical increase is seen
in the Denisenko star in an exposure beginning 16 s after the burst
to a limit of 0.05 magnitudes.  No new object appears in the vicinity
of the XRT position to a limit of R = 20.5 in this image.