[vsnet-alert 25307] The discovery of the photometric variability of a new SR-type variable star in the M31 galaxy, while searching for variable red sources using V and I observations from the Galati Astronomical Observatory

[Gabriel Neagu gabrielneagu874@gmail.com via vsnet-alert]

Authors: Jan Ovidiu Tercu (Galati Astronomical Observatory - C73), Gabriel
Cristian Neagu (Galati Astronomical Observatory - C73)

We report the discovery of a new SR-type variable star located in the M31
galaxy. We cross-identify it as 2MASS J00405619+4045461 = Gaia EDR3
381154123908000512 = [M31] Galati V23. Gaia EDR3 381154123908000512 has
J2000 coordinates R.A. = 00h40m56.206s Decl. = +40d45m46.173s. We report
the following parameters: Max = 19.4 r, Min = 20.1 r from ZTF DR4 and PS1.
The range is about 0.7 magnitudes. During the RSG search in M31 using the
0.4 m Ritchey-Chretien telescope with SBIG STL-6303E CCD camera using 11
exposures of 120s in V and I filters, we observed a very high V-I
difference. V-I  > 0.5 (Galati Observatory). I mag = 17.3 and the star
wasn't detected in V- band observations with the limit mag = 17.8
(transformed from Gaia DR2). Gaia EDR3 BP-RP = 3.08, suggesting a very red
star, confirming our observations. We analyzed the ZTF DR4 and PS1 data in
search of variability using Peranso 3 (CLEANest algorithm) and identified a
824 ± 5 d period. J-K = 1.67 (2MASS), W3-W4 = 2.63 (WISE). The data was
posted on the NGCA variable star catalog's extragalactic findings page (
https://sites.google.com/view/ngca-variable-star-catalog/variable-star-in-andromeda
).