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arXiv · 2607.28066

Cataclysmic variables from SRG/eROSITA: new systems from eRASS1

A. D. Schwope·J. Brink·D. A. H. Buckley·V. A. Cúneo·S. Friedrich·S. Hernández-Díaz·K. Knauff·J. Kurpas·G. Lamer·S. B. Potter·K. G. Pradeep·M. R. Schreiber·B. Stelzer·J. R. Thorstensen·D. Tubin-Arenas
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Abstract

(abridged) Aims. We aim to generate large samples of CVs selected from the SRG/eROSITA surveys to address fundamental questions about binary evolution, the role of magnetic fields in CV evolution and their contribution to the Galactic Ridge X-ray Emission (GRXE). Methods. We have trained a Random Forest (RF) classifier based on combined X-ray and optical properties to select CV candidates from the first eROSITA X-ray all-sky survey (eRASS1). Follow-up spectroscopy to securly identify the objects was performed on a subset of the selected candidates using telescopes at the Northern and the Southern hemisphere. Newly identified CVs were further analyzed to determine their likely subtype with the help of dedicated follow-up photometry, spectroscopy and archival resources. Results. We have identified 156 CVs of almost all subtypes covering a wide range of distances (between 170 pc and several kpc), absolute magnitudes (G= 4.5-12) and X-ray luminosities (log LX (0.2-2.3 keV)= 29.6-33.3 erg/s). For most objects, the nature as a CV is reported here for the first time. For 40 objects periods were determined, which were regarded as their likely orbital periods. These range from 79.2 min, at the CV minimum period, to almost 22 hours. Seven objects were found to be eclipsing, a lower limit to the actual number due to the current lack of dedicated follow-up observations. A further five objects show cyclotron or Zeeman features, that allowed to determine their field strengths. A soft component was found in 14 CVs, all were regarded being magnetic. The sample comprises X-ray luminous objects, excellent candidates for being new Intermediate Polars, that are thought to be main contributors to the GRXE. The new method of selecting CVs from eRASS1 was found to be superior to other methods described in the literature ...

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A. D. Schwope, J. Brink, D. A. H. Buckley, V. A. Cúneo, S. Friedrich, S. Hernández-Díaz, K. Knauff, J. Kurpas, G. Lamer, S. B. Potter, K. G. Pradeep, M. R. Schreiber, B. Stelzer, J. R. Thorstensen, D. Tubin-Arenas. 2026-07-30. Cataclysmic variables from SRG/eROSITA: new systems from eRASS1. https://arxiv.org/abs/2607.28066

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