This study investigates the X-ray emission from Cepheid variable stars using data from the eROSITA telescope onboard the SRG mission. Cepheids are crucial ‘‘standard candles’’ due to their well-known period-luminosity relationship. While some Cepheids, like Cephei, have shown pulsation-phase-dependent X-ray emission, others, such as Polaris and V473 Lyrae, exhibit X-ray emission independent of pulsation, often attributed to low-mass companions. Previous targeted observations with Chandra and XMM-Newton were limited. The all-sky X-ray survey by eROSITA provides an unprecedented opportunity for a comprehensive study. We cross-matched a combined catalog of 15620 Cepheids from Gaia DR3 and the ‘‘Classical Cepheids in Milky Way’’ catalog with the eRASS1 X-ray catalog. Our analysis yielded 107 potential Cepheid-X-ray source matches. A detailed examination of identification ambiguity using Gaia data reduced the number of robust candidates to 18. We present preliminary results, highlighting 3 highly probable and 12 probable X-ray emitting Cepheids, while 89 cases require further investigation.
Matrokhin et al. (Mon,) studied this question.