GCN Circular 42951
Subject
EP251130a: continued NOT optical observations indicate steep fading phase
Event
Date
2025-12-02T15:26:45Z (10 months ago)
From
Gregory Corcoran at University College Dublin <gregory.corcoran@ucdconnect.ie>
Via
Web form
G. Corcoran (UCD), A. Martin-Carrillo (UCD), D. B. Malesani (DAWN/NBI and Radboud), P. G. Jonker (Radboud), R. H. Rasmussen (NOT and Aarhus) report on behalf of a larger collaboration.
We continued the monitoring of the optical counterpart (Dornic et al., GCN 42904; Evans et al., GCN 42908; He et al., GCN 42914; Gupta et al., GCN 42916; Zheng et al., GCN 42917; van Dalen et al., GCN 42918; Moskvitin et al., GCN 42919; Aryan et al., GCN 42921; Volnova et al., GCN 42922; Ma et al., GCN 42940) of EP251130a (Wu et al., GCN 42903; Zhang et al., GCN 42915) with the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera.
Observations consisted of two epochs, the first consisting of 3 x 300 s exposures in SDSS-i and 5 x 200 s exposures in SDSS-z starting at 2025-12-01T23:32:00, with the second epoch being a repeat of the first i-band observation starting at 2025-12-02T05:56:48. The source was detected in all stacked images. We calibrated our photometry using nearby stars from the Pan-STARRS catalog and did not correct for Galactic extinction. We obtain the following i-band photometry:
epoch 1: i = 20.84 +/- 0.07 (mid time: 2025-12-01T23:42:39, ~1.52 days post trigger);
epoch 2: i = 21.23 +/- 0.04 (mid time: 2025-12-02T06:07:27, ~1.79 days post trigger).
These measurements show that the re-brightening reported by Zheng et al. (GCN 42917), van Dalen et al. (GCN 42918) and Moskvitin et al. (GCN 42919) seems to have finished and the light curve is fading quickly with a power-law decay index of ~2.2.
Further observations are planned and encouraged.