Stellar chromospheric activities revealed from the LAMOST-K2 time-domain survey

Abstract

By using the LAMOST time-domain survey data, we study stellar activities based on the ${\mathrm{H}}_{\alpha }$ lines for about 2000 stars in four $K$2 plates. Two indices, $R_{\mathrm{H}\alpha }^{{}^{\prime }}$ and $R_{\mathrm{H}\alpha }^{+}$, are computed from LAMOST spectra, the former of which is derived by excluding the photospheric contributions to the ${\mathrm{H}}_{\alpha }$ lines, while the latter is derived by further subtracting the non-dynamo driven chromospheric emission. Meanwhile, the periodicity and variation amplitudes are computed from \emph{K2} light curves. Both the $R_{\mathrm{H}\alpha }^{{}^{\prime }}$-Ro relation and $R_{\mathrm{H}\alpha }^{+}$-Ro relation show complicated profiles in the non-saturated decay region. Hot stars show flatter slopes and higher activity level than cool stars, and the behaviour is more notable in the $R_{\mathrm{H}\alpha }^{+}$-$R_o$ relation. This is consistent with recent studies using other activity proxies, including $L_{\mathrm{x}}/L_{\mathrm{bol}}$, $R_{\mathrm{HK}}^{{}^{\prime }}$ and amplitudes of optical light curves. % This may suggest different kinds of stars follow different power laws in the decay region. Most of our targets have multiple observations, and some of them exhibit significant variability of $\mathrm{H}\alpha$ emissions, which may cause the large scatters shown in the decay region. We find three targets exhibiting positive correlation in rotational phase, possibly indicating that their optical light curves are dominated by hot faculae rather than cool starspots.

20 pages, 34 figures, accepted for publication in ApJS

References in corpus (16)

• Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics
• The H$\alpha$ emission of nearby M dwarfs and its relation to stellar rotation
• Generalized investigation of the rotation-activity relation: Favouring rotation period instead of Rossby number
• Fluxes in Hαand Ca II H and K for a sample of Southern stars
• The Factory and The Beehive II. Activity and Rotation in Praesepe and the Hyades
• The flare catalog and the flare activity in the Kepler mission
• Self-consistent Stellar Radial Velocities from LAMOST Medium-Resolution Survey (MRS) DR7
• Stellar rotation periods from K2 Campaigns 0-18 -- Evidence for rotation period bimodality and simultaneous variability decrease
• The EPOCH Project: I. Periodic variable stars in the EROS-2 LMC database
• Rotational modulation in TESS B stars
• Magnetic Activity of F-, G-, and K-type Stars in the LAMOST-Kepler Field
• LAMOST Time-Domain Survey: First Results of four $K$2 plates
• Rotating Convective Core Excites Non-Radial Pulsations to Cause Rotational Modulations in Early-Type Stars
• A spectroscopic test of the rotational modulation origin of periodic \emph{Kepler} photometric variability of A-type stars
• Association of Plages With Sunspots: A multi wavelength Study Using Kodaikanal Ca $\text{II}$ K and Greenwich sunspot area Data
• Stellar activity with LAMOST. III. Temporal variability pattern in Pleiades, Praesepe, and Hyades

Cited by in corpus (5)

• $\mathrm{H}\alpha$ chromospheric activity of F-, G-, and K-type stars observed by the LAMOST Medium-Resolution Spectroscopic Survey
• Stellar X-ray activity and habitability revealed by ROSAT sky survey
• Stellar Chromospheric Activity Database of Solar-like Stars Based on the LAMOST Low-Resolution Spectroscopic Survey: II. the bolometric and photospheric calibration
• Rotation and activity in late-type members of the young cluster ASCC 123
• Stellar Characterization and a Chromospheric Activity Analysis of a K2 Sample of Planet-Hosting Stars