VizieR Online Data Catalog: A combined Chandra & LAMOST study of stellar activity (He+, 2019)

To estimate the X-ray-to-bolometric luminosity ratio (R_X=L of different stellar types, we first cross-matched the Chandra point-source catalog (Wang+ 2016, J/ApJS/224/40) and the LAMOST database (DR4, V/153), using a radius of 3". This led to 2638 unique Chandra sources with 3502 LAMOST spectral observations.

In order to have a reliable estimation of stellar parameters, we only used spectra with signal-to-noise ratio (S/N) higher than 7 in the r-band. After further exclusions of sources based on their SIMBAD classification (see Section 2.1), we obtain 1086 unique X-ray sources with 1479 LAMOST spectral observations (R~1800; 3690-9100Å).

We also collected the V-band magnitude from the UCAC4 catalog (I/322). For objects without a UCAC4 V-band magnitude, we calculated it using the g- and r-band magnitudes from Pan-STARRS (see II/349).

Finally our sample is composed of 484 sources for which the optical magnitude and complete stellar parameters (Teff, logg, E(B-V), distance) can be obtained, and therefore a R_X value was estimated.

(5 data files).