Strong H-alpha emission detected from recent M31 nova candidates AT 2025agmm, AT 2025ahwf and AT 2025ahch
ATel #17550; A. Valcheva (Sofia University, Bulgaria) and D. Stefanova (IANAO, BAS, Bulgaria)
on 18 Dec 2025; 21:56 UT
Credential Certification: Antoniya Valcheva (valcheva@phys.uni-sofia.bg)
Subjects: Optical, Nova, Transient
We report optical observations of the recent M31 nova candidates AT 2025agmm, AT 2025agwf, and AT 2025ahch and the detection of their strong H-alpha emission. AT 2025agmm (= Vend78) (= PNV J00421476+4117284) (= M31N 2025-12b) was discovered by R. Fidrich on 2025 Dec. 11.775 UT. AT 2025agwf (= PNV J00431764+4114201) (= M31N 2025-12c) (= Vend79) was independently discovered by Castellani et al. on 2025 Dec 14.746 UT and Hornoch et al. on 2025 Dec. 15.023 (ATel #17543). AT 2025ahch (= PSP25W) (= PNV J00422038+4114207) (= M31N 2025-12d) (= PNV J00422066+4114212) was independently discovered by Hornoch et al. on 2025 Dec. 16.025 UT (ATel #17545) and Xingming Observatory Sky Survey (XOSS) on 2025 Dec 16.528 UT.
Our observations were carried out with the focal reducer FoReRo2 mounted at the 2m RCC telescope at Rozhen NAO, Bulgaria, in H-alpha (FWHM of 3 nm) and R filter. The images can be seen
here and
here, and the magnitudes are summarized below:
Name | Date [UT] | Filter | Mag ± Err | Exposure
=======================================================================
AT 2025agmm | 2025 Dec. 17.815 | R | 16.67±0.01 | 5x120 sec
| 2025 Dec. 17.829 | Ha | 15.09±0.02 | 3x300 sec
AT 2025agwf | 2025 Dec. 17.851 | R | 17.19±0.01 | 5x120 sec
| 2025 Dec. 17.840 | Ha | 15.09±0.02 | 3x300 sec
AT 2025ahch | 2025 Dec. 17.815 | R | 15.89±0.01 | 5x120 sec
| 2025 Dec. 17.829 | Ha | 15.31±0.02 | 3x300 sec
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All three transients show strong H-alpha emission and a very bright optical maximum. Follow-up ppotometric and spectroscopic observations are encouraged.
The study was supported by the National RI Roadmap Project D01-109/30.06.2025 with the Ministry of Education and Science of the Republic of Bulgaria.
