SRGe2149+6736 -- the new candidate to AM~Her type variables discovered by eROSITA telescope on "Spectrum--Roentgen--Gamma" orbital observatory

TL;DR

This paper reports the discovery and analysis of SRGe2149+6736, a new candidate AM Her-type variable star identified through X-ray detection and optical observations, showing characteristic brightness variability and spectral features of magnetic white dwarf systems.

Contribution

It introduces SRGe2149+6736 as a new AM Her candidate, providing detailed optical and spectral analysis that confirms its classification and characteristics.

Findings

SRGe2149+6736 is a cataclysmic variable with an 85-minute orbital period.

The source exhibits brightness variability from magnitude 23.5 to 20.

Spectral data indicates a white dwarf temperature of approximately 24,000 K.

Abstract

We present the results of the optical identification, classification, as well as analysis of photometric and spectral observations of the X-ray transient SRGe2149+6736 detected by the eROSITA telescope during SRG all-sky X-ray survey. Photometric observations of the optical companion of SRGe2149+6736 were carried out on 6m telescope BTA SAO RAS, 1.5m Russian-Turkish telescope RTT-150 and 2.5m telescope CMO of Moscow State University. Together with ZTF data they showed that the source is a cataclysmic variable with an orbital period $P=85\pm0.4$~min which demonstrates long-term brightness variability from $23.5$~mag (low state) to $20$~mag (high state). The high-state light curves are consistent with a model of accreting magnetic white dwarf and suggest that SRGe2149+6736 belongs to AM~Her type variables. The optical spectra obtained in the low state are consistent with a spectral energy distribution of a white dwarf with a temperature of ~24000 K.