[vsnet-grb-info 5251] GRB 071018: SARA observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  6944
SUBJECT: GRB 071018: SARA observations
DATE:    07/10/19 19:28:57 GMT
FROM:    Adria C. Updike at Clemson U  <aupdike at clemson.edu>

Adria C. Updike, Brian Donehew, Paul Jay Searcy, Ernest Garrison, and 
Dieter H. Hartmann report (on behalf of the Clemson GRB Follow-Up Team):

We observed the field of GRB 071018 (GCN 6932, Krimm et al.) beginning 
1.05 days after the trigger under good weather conditions.  We obtained 
69 minutes of R-band images at high airmass.

Upon comparison to the sources identified by Xin et al. (GCN 6936), we 
find a magnitude of 20.5 ± 0.15 for OT candidate #1.  We note that this 
is brighter than the magnitude reported by Xin et al. half a day 
earlier, so this may indeed be a variable source. 

We also note a source in SDSS images at the location of GCN 6936 OT 
candidate #2.

At the locations of the XRT error circles (GCN 6943, Beardmore et al.), 
we detect no new sources down to a limiting magnitude of 20.8 in the R 
band.

Calibration to the USNO B1.0 catalog was done relative to 10 field stars.

We would like to thank Liping Xin for providing a finder chart and 
additional information on their observations.  We also acknowledge the 
help of Kenneth Rumstay (Valdosta U).

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