Identification of SRGt 062340.2-265715 as a bright, strongly variable, novalike cataclysmic variable

Abstract

We report the identification and follow-up of the transient SRG 062340.2-265715 detected with both instruments on board the Spektrum-Roentgen-Gamma mission. Optical spectroscopy of the G=12.5 counterpart firmly classifies the object as a novalike cataclysmic variable (CV) at a distance of 495 pc. A highly significant TESS period of 3.941 hours, tentatively identified with the orbital period of the binary, could not be found when the object was reobserved with TESS two years later. The newer high-cadence TESS data revealed quasi-periodic oscillations around 25 min, while ground-based photometry indicated periodic variability at 32 min. Located in very sparsely populated regions of color-magnitude diagrams involving X-ray and optical magnitudes and colors, the new object could be an X-ray underluminous magnetic CV, an intermediate polar, or an overluminous nonmagnetic CV. The lack of uniquely identified spin and orbital periods prevents a final classification. The site of X-ray production in the system, L(X, bol) = 4.8 x 10^{32} erg/s, remains to be understood given its high variability on long and short timescales.

9 pages, 16 figures, to appear on A&A, Special Issue: The Early Data Release of eROSITA and Mikhail Pavlinsky ART-XC on the SRG Mission

References in corpus (13)

• Estimating distances from parallaxes. V: Geometric and photogeometric distances to 1.47 billion stars in Gaia Early Data Release 3
• HI4PI: A full-sky HI survey based on EBHIS and GASS
• The Zwicky Transient Facility: Data Processing, Products, and Archive
• The All-Sky Automated Survey for Supernovae (ASAS-SN) Light Curve Server v1.0
• Assessing statistical significance of periodogram peaks
• The SRG X-ray orbital observatory, its telescopes and first scientific results
• The eROSITA Final Equatorial Depth Survey (eFEDS): The X-ray catalog
• The Wide Field Spectrograph (WiFeS): Performance and Data Reduction
• The ART-XC telescope on board the SRG observatory
• Accretion Flows in Nonmagnetic White Dwarf Binaries as Observed in X-rays
• The structure of accretion flows in nova-like cataclysmic variables: RW Sextantis and 1RXS J064434.5+334451
• X-ray observations of VY Scl type nova-like binaries in the high and low state
• An Overview of the Bowen Survey; detecting donor star signatures in Low Mass X-ray Binaries

Cited by in corpus (7)

• The SRG X-ray orbital observatory, its telescopes and first scientific results
• Compact white-dwarf binaries in the combined SRG/eROSITA/SDSS eFEDS survey
• X-ray properties of the white dwarf pulsar eRASSU J191213.9-441044
• 1RXH J082623.6-505741: a new long-period cataclysmic variable with an evolved donor and a low mass transfer rate
• The eROSITA DR1 variability catalogue
• Confirmation of SRGt 062340.2-265751 as a nova-like cataclysmic variable with a possible magnetic nature
• XMM-Newton follow-up of two eROSITA X-ray binary candidates