Central Bureau for Astronomical Telegrams

CBAT "Transient Object Followup Reports"

TCP J21091443-0917104

TCP J21091443-0917104   2025 08 22.8877*  21 09 14.43 -09 17 10.4  12.4 U             Aqr       9 0

2025 08 22.8877

The CV=12.4 transient was found in two dithered wide-field images obtained with the second NMW survey camera (135mm f/2.0 telephoto lens + unfiltered STL-11000M CCD, 13.8"/pix) on 2025-08-22.8877 UTC. It is also visible at CV=12.5 in confirmation images obtained with the same camera 1h32m later on 2025-08-22.9516. A star Gaia DR3 6896395696896704000 (G=14.44, Plx=3.12 +/-0.04 mas) is located 2" from the transient position. It was visible at its normal brightness (CV=14.7 +/-0.2) in previous NMW images obtained on 2025-08-19.8882. The star shows no obvious signs of variability in ASAS-SN and ZTF archival data: https://asas-sn.osu.edu/sky-patrol/coordinate/b1872fed-ee9b-43e1-ab4a-b0bfa744946e https://ztf.snad.space/dr23/view/389210400005479 The event may be a flare of a previously unknown UV Ceti star, however the relatively large 320 pc distance and stable brightness over the 1.5 hours appear somewhat unusual for a flare star. The plate-solved NMW FITS images and finder charts are available at http://scan.sai.msu.ru/~kirx/img/TCPJ21091443-0917104/ The NMW survey is operating at the Astroverty astrofarm in Nizhnii Arkhyz, Karachay-Cherkessia, Russia http://scan.sai.msu.ru/nmw/ https://astrovert.ru/astrofarm/ ---- Kirill Sokolovsky (UIUC), Stanislav Korotkiy (Astroverty, Ka-Dar) for the NMW team, Andrey Tatarnikov (SAI MSU)

2025 08 22.98

Astrometry with the 0.6m telescope + FLI 16803 CCD camera (CAS of SAI) 21:09:14.32 -09:17:11.7 J2000 supports the association of the transient with Gaia DR3 6896395696896704000. Preliminary photometry obtained on 2025-08-22.98 UT (2h20m post-discovery): V=12.49 B-V=-0.09. ---- Andrey Tatarnikov (SAI MSU), Kirill Sokolovsky (UIUC)