AT 2026cex / ZTF26aaedxli is likely an outburst of Gaia star 866940901044573184
ATel #17660; I. Perez-Fournon, F. Poidevin, D. Aguado, A. Lopez-Oramas (IAC and ULL), S. Geier (GRANTECAN and IAC), C. Jimenez Angel (GRANTECAN), D. Cano-Morales, A. E. Hernandez-Diaz, I. Correa-Plasencia, E. Lekaroz-Urriza, and M. Quintana-Ansaldo (ULL)
on 9 Feb 2026; 15:37 UT
Credential Certification: Ismael Perez-Fournon (ipf@iac.es)
Subjects: Optical, Star, Transient
We report on ZTF and TTT1 photometry and analysis of AT 2026cex, a candidate luminous fast blue optical transient (LFBOT) possibly associated with the nearby galaxy NGC 2398 discovered by Tsuboi et al. (ATel #17646), with follow-up optical and near-infrared observations reported by Ramandeep et al. (ATel #17647), Pereyra et al. (ATel #17648), Schneider et al. (ATel #17649), Ma et al. (ATel#17652),
Garton and Steele (ATel #17655), and Lin et al. (ATel #17656), and not detected in X-ray observations of Einstein Probe (Sun et al. ATel #17651).
In ZTF survey observations, AT 2026cex was first detected on MJD = 61069.21404 at a ZTF-r magnitude of 15.218 +/- 0.089 (ZTF26aaedxli).There was no ZTF detection on MJD = 61066.40068 with a ZTF-r limiting magnitude of 17.693. The ZTF coordinates are RA (J2000) = 07:30:08.510, Dec (J2000) = 24:30:05.07. The Gaia star 866940901044573184 is located at only 0.104 arcsec from the ZTF position. We propose that AT 2026cex is likely an outburst of this Gaia star and not an LFBOT associated with NGC 2398. Gaia 866940901044573184 is also detected in multiple large-area surveys (e.g. SDSS, Pan-STARRS, and Legacy Imaging Surveys) with Pan-STARRS magnitudes g = 21.3473 +/- 0.0353, r = 20.5916 +/- 0.0374, i = 19.9086 +/- 0.0139, z = 19.7375 +/- 0.0948, and y = 19.3635 +/- 0.0453.
We observed AT 2026cex with the TTT1 80-cm telescope at Teide Observatory (Tenerife, Canary Islands, Spain), equipped with a QHY411M CMOS camera, with a single 60-sec exposure in the SDSS r filter. We measure an AB magnitude r = 16.91 +/- 0.12 on MJD = 61078.10015 calibrated using Pan-STARRS stars and not corrected for Galactic extinction.
ZTF light curve of AT 2026cex (ZTF26aaedxli), Lasair broker
