AT 2025ajgh is Likely Not a Nova in M31
ATel #17567; K. Hornoch (Ondrejov), H. Kucakova (Charles University), A. W. Shafter (SDSU)
on 31 Dec 2025; 05:53 UT
Distributed as an Instant Email Notice Novae
Credential Certification: Allen W. Shafter (ashafter@sdsu.edu)
Subjects: Optical, Nova, Transient
F. Castellani et al. reported a discovery of a probable nova AT 2025ajgh discovered on a co-added 3600-s unfiltered CCD frame taken on 2025 Dec. 28.765 UT. The new object has R = 18.9 mag (measured on the unfiltered CCD image using GAIA DR3 catalogue).
We observed the central region of M31 during our survey using the 0.65-m telescope at Ondrejov on Dec. 28.695 UT (we obtained a co-added 980-s R-band CCD frame) and did not detect any new object at the position of AT 2025ajgh down to R = 20.3 mag. After we noticed the discovery report of AT 2025ajgh we took another set of R-band images with the same instrumentation on 28.964 UT. There is nothing visible on a co-added 490-s R-band CCD frame down to R = 20.4 mag. To go even deeper, we then co-added both series of our images (1470-s of total exposure time, see link to the image below) with the same result - there is nothing visible down to R = 20.6 mag.
Based on the available observations we conclude that the object discovered by F. Castellani et al. is likely not a nova but probably other type of variable star, perhaps a foreground red dwarf flare star. Additional observations at the reported position of this object are encouraged.
R-band image
