850 SRG/eROSITA Sources in the Pleiades

Using SRG/eROSITA X-ray sky survey data and the optical catalog of 2209 Pleiades cluster members constructed from Gaia data, we have found 850 X-ray sources associated with cluster stars. More than 650 of them have been detected in X-rays for the first time. At the distance of the Pleiades the nominal sensitivity of eROSITA in this sky region corresponds to a $$0.3{-}2.3$$ keV luminosity $$L_{X}\sim 1.6\times 10^{28}$$ erg s $${}^{-1}$$ . The eROSITA sources associated with the Pleiades radiate with a total luminosity $$L_{X,\textrm{total}}\sim 1.3\times 10^{32}$$ erg s $${}^{-1}$$ , which exceeds the X-ray luminosity of the quiet Sun by a million times. A strong, more than a factor of 10, X-ray variability has been recorded for 27 sources. Most of them are known as eruptive optical variable dM stars. $$R_{X}=\log(L_{X}/L_{\textrm{bol}})$$ for Pleiades stars increases with decreasing effective stellar temperature from $$R_{X}\approx{-}5$$ to $$R_{X}\approx{-}2$$ . The $$R_{X}$$ distribution of stars is bimodal. The left peak at $$R_{X}\sim{-}4.3$$ is formed by FGK stars, while the right peak at $$R_{X}\sim{-}3.1$$ is mostly populated by M stars. The dependence of $$R_{X}$$ on the Rossby number $$Ro$$ is different for different spectral types. At small Rossby numbers for K and M stars $$R_{X}\sim{-}3$$ and depends weakly on $$Ro$$ . At $$Ro\gtrsim 0.25$$ a rapid decrease in $$R_{X}$$ is observed for K stars, while there are no M stars with large Rossby numbers in our sample. Most of the F and G stars lie in the range of lower values, $$R_{X}\sim{-}4.5$$ , but the size of our sample is not enough to characterize in more detail the $$R_{X}{-}Ro$$ relation for them.