GCN Circular 45998
Subject
EP261015a: Follow-up with the 1.3m DFOT
Event
Date
2026-10-20T15:08:00Z (23 days ago)
Edited On
2026-10-20T15:22:03Z (23 days ago)
From
pawarpankaj1492@gmail.com
Edited By
Vidushi Sharma at NASA GSFC/UMBC <vidushi.sharma@nasa.gov> on behalf of pawarpankaj1492@gmail.com
Via
Web form
Pankaj Pawar, Sarvesh Yadav, Anshika Gupta, Debalina Kar, Dhruv Jain, Yash Sharma, Kuntal Misra and Shashi B. Pandey (ARIES, Nainital, India) report:
We observed the field of the Einstein Probe transient EP261015a
(Li et al., GCN 45956) with the 1.3-m Devasthal Fast Optical Telescope
(DFOT), India, on 2026 October 17. Observations started at 18:29:19 UT,
approximately 53.23 hours after the event onset. We obtained six 300-s
exposures in the R filter.
We detect a source at the position of the candidate optical counterpart
reported by Corcoran et al. (GCN 45955). Our preliminary PSF photometry
of the stacked image, obtained using AutoPhOT (Brennan & Fraser 2022,
A&A, 667, A62), is:
Mid-time (UT) Tmid-T0 (d) Filter Exposure (s) Mag (Vega)
2026-10-17 18:44:31 2.22842 R 6 x 300 22.18 +/- 0.19
T0 is 2026-10-15 13:15:36 UT, the start of the EP-WXT event
(Li et al., GCN 45956). Photometry was calibrated against 26 nearby
Gaia DR3 XP stars using synthetic Johnson-Cousins R magnitudes on the
Vega system. The magnitude is not corrected for Galactic extinction.
Our photometry was performed on unsubtracted images and is contaminated
by the underlying galaxy noted by Ma et al. (GCN 45963). The reported
measurement includes galaxy light and is not a galaxy-subtracted
transient magnitude.
Our observation predates the optical rebrightening reported by Fortin
et al. (GCN 45991). The galaxy contribution and different passbands prevent
a direct comparison with their template-subtracted r-band photometry.