[vsnet-grb-info 14926] GRB 140502A: ISON-NM early optical limit

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  16221
SUBJECT: GRB 140502A: ISON-NM early optical limit
DATE:    14/05/07 20:16:19 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen at iki.rssi.ru>

L. Elenin (KIAM),  A. Volnova (IKI), I. Molotov (KIAM), A. Pozanenko 
(IKI) report on behalf of larger GRB  follow-up collaboration:

We observed of  the field of  Swift GRB GRB 140502A  with 0.4-m 
telescope of ISON-NM observatory starting on May, 02 (UT)  08:31:32, 
i.e. 72 s after BAT trigger (Swenson et al.,  GCN 16202). We took series 
of unfiltered images of 30 s - 60 s exposures.  A bright star (USNO-B1.0 
1389-0392112) already mentioned (Oates et al.,  GCN 16210) lies within 
enhanced XRT error circle (Goad et al.,  GCN 16206). We investigate 
variability of  a possible OT  in presence in near vicinity of the 
bright star. The upper limit of possible variation of the OT is 16.6m 
within any of 60 s interval of our observations between (UT)  08:31:32 
and 09:24:25 which can be considered as an upper limit on the OT 
associated with GRB 140502A.

Formal photometry and limiting magnitude of point-like source in the 
observed field is following

UT start   t-T0        Exp.    Filter   OT   UL(3 sigma)
           (mid.,days)  (s)
08:31:32  0.00383      10*30   None     n/d  18.8

and based on nearby USNO-B1.0 stars, R2 magnitudes.