Confirmation of SRGt 062340.2-265751 as a nova-like cataclysmic variable with a possible magnetic nature

TL;DR

This study confirms SRGt 062340.2-265751 as a nova-like cataclysmic variable with potential magnetic properties, based on multi-wavelength observations revealing orbital, spin, and short-term variability, and spectral analysis indicating a multi-temperature plasma.

Contribution

First detailed multi-wavelength analysis confirming the nova-like nature and possible magnetic characteristics of SRGt 062340.2-265751, including detection of orbital and spin modulations.

Findings

Orbital period of ~3.6 hours confirmed.

Possible white dwarf magnetic spin period detected.

Spectral analysis shows multi-temperature plasma components.

Abstract

SRGt 062340.2-265751, a cataclysmic variable identified by SRG/eROSITA thanks to its significant X-ray variability, remains poorly characterised despite the multi-wavelength follow-up. We present spectral and timing analyses from the first dedicated X-ray and ultraviolet observations with XMM-Newton, complemented by SRG/eROSITA data from four all-sky surveys (eRASS1-4) and ASAS-SN optical photometry. Our timing analysis reveals a >8$\sigma$ significant modulation at 3.6 $\pm$ 0.5 hours, likely representing the orbital period. Long-term ASAS-SN monitoring confirms the source as a VY Sculptoris-type nova-like system, while short-timescale X-ray and ultraviolet variability, down to a few minutes, suggests a possible underlying magnetic white dwarf. Two additional significant X-ray modulations at 43 $\pm$ 1 min and 36.0 $\pm$ 0.7 min tentatively point to the spin period of an intermediate polar. The best-fit XMM-Newton energy spectra reveal a multi-temperature thermal plasma ($kT$ = 0.23, 0.94, and 5.2 keV), while the SRG/eROSITA spectra are consistent with a single-temperature thermal plasma of a few keV. We estimate unabsorbed X-ray luminosities of $\gtrsim$$10^{32}$ erg s$^{-1}$ (0.2-12 keV). Broadband spectral energy distribution modelling, from near-ultraviolet to infrared, indicates a disc-dominated system consistent with a nova-like classification. We discuss these results in the context of the source's confirmed nova-like classification and its possible magnetic nature, a scenario increasingly supported by discoveries of intermediate polars exhibiting VY Sculptoris-type nova-like features.