GCN Circular 41529
Subject
EP triggers 01709200706 and 01709200707: GOTO confirmation of flaring stars
Date
2025-08-24T16:50:29Z (2 months ago)
From
d.s.oneill@bham.ac.uk
Via
Web form
D. O'Neill, A. Kumar, G. Ramsay, B. P. Gompertz, R. Starling, K. Ackley, M. J. Dyer, J. Lyman, K. Ulaczyk, B. Godson, D. Steeghs, D. K. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. P. Breton, L. K. Nuttall, and J. Casares
We report on optical observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022, Dyer et al. 2024) in response to the EP/WXT alerts 01709200706 and 01709200707.
Observation consisted of 4x90s exposures in the GOTO L-band (400-700 nm).
Targeted observations of EP-WXT 01709200706 were taken at 2025-08-24 12:46:36 UT (+3.13h post trigger) and 2025-24-08 14:10:18 UT (+4.53h post trigger). We detect a single new source in difference imaging, consistent with the flaring star UCAC4 277-216984, as identified by Li et al. (GCN 41524). The star is saturated in our unsubtracted frames, meaning we cannot robustly determine the magnitude other than place lower limits of L>11.94 AB mag and L>12.11 AB mag at +3.13h and +4.53h post trigger, respectively.
Targeted observations of EP-WXT 01709200707 were taken at 2025-08-24 12:54:10 UT (+0.22h post trigger) and 2025-08-24 14:02:40 UT (+1.36h post trigger). We identify a new source in differencing imaging consistent with UCAC4 268-197742 identified by Li et al. (GCN 41526). The star reaches a peak magnitude in our unsubtracted frames of L=14.31±0.01 and L=15.16±0.01 AB mag at +0.22h and +1.36h post trigger, respectively.
Images were processed immediately after acquisition using the GOTO pipeline. Difference imaging was performed using deeper template observations.
GOTO (https://goto-observatory.org) is a network of telescopes that is
principally funded by the STFC and operated at the Roque de los Muchachos
Observatory on La Palma, Spain, and Siding Spring Observatory in NSW,
Australia, on behalf of a consortium including the University of Warwick,
Monash University, Armagh Observatory & Planetarium, the University of
Leicester, the University of Sheffield, the National Astronomical Research
Institute of Thailand (NARIT), the University of Turku, the University of
Portsmouth, the University of Manchester and the Instituto de Astrofisica
de Canarias (IAC).