Work

The optical photometric and spectroscopic periodicities of the cataclysmic variable SRGt 062340.2-265751

Year: 2026

Type: article

Abstract: Context. We report on optical spectroscopic and photometric follow-up observations of the eROSITA discovered transient SRGt 062340.2-265751 and show that it displays the characteristics of a nova-like cataclysmic variable (CV), with possible indications of being a magnetic system. Aims. We try to put better constraints on the classification of SRGt 062340.2-265751 using optical time-resolved spectroscopic and photometric observations to find any periodicities in the system. From these periodicities we can classify the CV sub-type that it belongs to. Methods. Time-resolved photometric and spectroscopic observations were obtained at the South African Astronomical Observatory (SAAO), using the 1.9 m and the two 1.0 m telescopes. High-resolution spectra were also taken using the Southern African Large Telescope (SALT), to study the morphology of the emission lines seen in the system. Archival photometric data was also analysed in this study, including ASAS-SN, CRTS, and TESS observations. Results. Spectroscopic observations revealed a very low amplitude, K ∼ 14 km s −1 , in the radial velocity of the H β and H γ emission lines, suggesting that the system is likely observed at a low inclination angle. High-speed photometric observations revealed highly stochastic variability, characteristic of many magnetic cataclysmic variable systems. A probable 3.645 ± 0.006 hour orbital period was found by applying Lomb-Scargle period analysis to the H β and H γ emission line radial velocities. A 24.905 ± 0.065 min period was found from photometric observations, which we associate with the white dwarf spin. However, it was also found that the photometry revealed multiple periodicities from night to night. TESS observations in three sectors did not reveal any of the periodicities found from ground-based observations, but did show a prominent period in only one sector, which might be attributed to a positive superhump period. These multiple periodicities as well as the He II λ 4686 and Bowen blend emission lines seen in the spectra indicate that SRGt 062340.2-265751 is likely a nova-like CV, and might belong to the VY Scl sub-type.

Source: Astronomy and Astrophysics

DOI: 10.1051/0004-6361/202557005