TITLE:   GCN CIRCULAR
NUMBER:  45367
SUBJECT: EP trigger #01709278129 (EP260812b?): NOT optical counterpart
DATE:    26/08/13 00:55:59 GMT
FROM:    Daniele Bjørn Malesani at Cosmic Dawn Center, Niels Bohr Institute <daniele.malesani@nbi.ku.dk>

D. B. Malesani (DAWN/NBI and Radboud), G. Corcoran (UCD), J. Chacon (PUC), P. G. Jonker (Radboud), V. Vuolteenaho (NOT / University of Oulu), K. Kisielowski (ING / University of Groningen), R. Vieliute (ING / University of St Andrews), report on behalf of a larger collaboration:

We observed the field of the EP/WXT trigger #01709278129 (likely EP260812b) with the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Several observations were taken in the r filter, starting on 2026 Aug 12.98964 UT, that is 9.4 min after the EP/WXT trigger. Observations were carried out in “rapid-response mode”, with both triggering and observations carried out robotically and with minimal intervention of the telescope operator.

In our images, a new object, not visible in the Legacy survey archival images, is detected at coordinates:

RA(J2000) = 20:31:10.26
Dec(J2000) = -09:51:42.3

Calibrated against nearby stars from the Pan-STARRS catalog, we measure for this target preliminary magnitudes (not corrected for Galactic extinction):

r = 20.56 +- 0.03  (t_mean = 10.9 min after trigger);
r = 20.26 +- 0.03  (t_mean = 24.7 min after trigger).

This source is thus observed to rebrighten over the course of our observations. This variability, coupled with the lack of any counterpart in deeper archival imaging, suggest that this is in fact the afterglow of the EP trigger #01709278129. Further observations are encouraged.