Discovery of eclipses in the cataclysmic variable ASASSN-V J090756.65+715859.5

Abstract

I conducted photometric observations of the cataclysmic variable LAMOST J035913.61+405035.0 and discovered previously unknown eclipses. During these observations, I recorded 14 eclipses over two groups of nights separated by 13 months. I accurately determined the orbital period of the system to be P orb = 0.228 343 85 ± 0.000 000 21 d. For the eclipses, I derived an ephemeris which is valid for a long time and suitable for studying changes in the orbital period. The out-of-eclipse magnitude of the star varied between 15.32(±0.02) and 17.25(±0.08) mag. As the brightness decreased, the eclipses became deeper and narrower. The average depth of eclipses was 1.35(±0.10) mag, and the average width at half-depth was 16.9(±0.7) min. I estimated the range of possible orbital inclinations to be between 72.8 • and 76.0 • , and the range of average absolute V -band magnitudes of the disc to be between 5.16(±0.15) and 5.44(±0.15) mag. Although based on the light curve from the ZTF survey, LAMOST J035913.61+405035.0 showed only small outbursts with amplitudes below 1.5 mag, it should be classified as a dwarf nova because the average disc brightness and mass transfer rate were below the limit of thermal instability. However, there have been no significant outbursts in the ZTF light curve over the past 1.6 yr. Instead, a gradual decrease in brightness lasting 120 d suggests that this object may occasionally become a nova-like variable of the VY Scl type.