Multi-band optical photometry of novae AT2025qdc and AT2025qsm in M31
ATel #17320; M. Petkova, A. Valcheva, E. Zaharieva, E. Ovcharov (Sofia University, Bulgaria)
on 5 Aug 2025; 06:06 UT
Credential Certification: Antoniya Valcheva (valcheva@phys.uni-sofia.bg)
Subjects: Optical, Nova, Transient
We report BVR photometry of two bright M31 transients: AT2025qdc (= PNV J00425628+4114512) (= M31N 2025-07a) independently discovered by R. Fidrich on 2025 Jul 03.109 UT and Hornoch et al. on 2025 Jul 2.448 UT (ATel #17265), and AT2025qsm (= PNV J00424863+4113513) discovered on 2025 Jul 10.132 UT by J. Zhao. Both are spectroscopically classified as novae by C. Balcon.
The observations were carried out with a 35 cm Schmidt Cassegrain telescope + CCD SBIG STX-16803 and filters at the student Space and Earth Sciences Summer School "Prof. Marin Bachevarov", Pamporovo, Bulgaria on July 19, 2025. The B-, V- and R-band magnitudes were derived from 3x120 sec co-added frames and stars from Massey et al.(2016) were used for photometric calibration.
Additionally, we carried out observations using narrowband H-alpha (FWHM of 3 nm) with the focal reducer FoReRo2 mounted on the 2m RCC telescope at Rozhen NAO, Bulgaria. The magnitudes in H-alpha were derived from 3x300 sec co-added frames. R-band magnitudes from the 2m telescope are also available and are derived from 3x120 sec co-added frames. The photometric calibration was performed using standard stars from Massey et al.(2016).
The following magnitudes were obtained:
AT2025qdc
2025 Jul 19.923 UT, B = 18.10 ± 0.30 mag
2025 Jul 19.928 UT, V = 18.10 ± 0.20 mag
2025 Jul 19.918 UT, R = 17.75 ± 0.15 mag
2025 Jul 26.957 UT, H-alpha = 15.87 ± 0.02 mag
2025 Jul 26.949 UT, R = 18.49 ± 0.05 mag
AT2025qsm
2025 Jul 19.923 UT, B = 17.60 ± 0.20 mag
2025 Jul 19.928 UT, V = 17.50 ± 0.10 mag
2025 Jul 19.918 UT, R = 16.70 ± 0.07 mag
2025 Jul 26.957 UT, H-alpha = 14.62 ± 0.01 mag
2025 Jul 26.949 UT, R = 17.65 ± 0.02 mag
Both transients show strong H-alpha emission and R-band magnitude decline consistent with their classification as novae.
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.
