Chromospheric activity in several single late-type stars

AbstractWe present an observational program we started in 1999, to systematically obtain mid-resolution spectra of late-type stars, to study in particular chromospheric activity. In particular, we found cyclic activity in four dM stars, including Prox-Cen. We directly derived the conversion factor that translates the known S index to flux in the Ca II cores, and extend its calibration to a wider spectral range. We investigated the relation between the activity measurements in the calcium and hydrogen lines, and found that the usual correlation observed is the product of the dependence of each flux on stellar color, and it is not always preserved when simultaneous observations of a particular star are considered. We also used our observations to model the chromospheres of stars of different spectral types and activity levels, and found that the integrated chromospheric radiative losses, normalized to the surface luminosity, show a unique trend for G and K dwarfs when plotted against the S index.

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Metallicity effects on the chromospheric activity-age relation for late-type dwarfs

Monthly Notices of the Royal Astronomical Society ◽

10.1046/j.1365-8711.1998.01597.x ◽

1998 ◽

Vol 298 (2) ◽

pp. 332-346 ◽

Cited By ~ 68

Author(s):

H. J. Rocha-Pinto ◽

W. J. Maciel

Keyword(s):

Late Type ◽

Chromospheric Activity ◽

Age Relation

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Chromospheric activity on late-type star DM UMa using high-resolution spectroscopic observations

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stw668 ◽

2016 ◽

Vol 459 (1) ◽

pp. 854-862 ◽

Cited By ~ 7

Author(s):

LiYun Zhang ◽

QingFeng Pi ◽

Xianming L. Han ◽

Liang Chang ◽

Daimei Wang

Keyword(s):

High Resolution ◽

Type Star ◽

Late Type ◽

Spectroscopic Observations ◽

Chromospheric Activity ◽

Late Type Star

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Magnetic activity based on LAMOST medium-resolution spectra and the Kepler survey

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa942 ◽

2020 ◽

Vol 495 (1) ◽

pp. 1252-1270 ◽

Cited By ~ 1

Author(s):

Li-yun Zhang ◽

Liu Long ◽

Jianrong Shi ◽

Hong-peng Lu ◽

Qi Gao ◽

...

Keyword(s):

Rotation Period ◽

Magnetic Activity ◽

Physical Parameters ◽

Late Type ◽

Data Bases ◽

Interesting Phenomenon ◽

Chromospheric Activity ◽

Medium Resolution ◽

Hα Emission ◽

Relationship Of

ABSTRACT Stellar magnetic activity is an interesting phenomenon in late-type stars. We use the medium-resolution spectroscopic observations of 406 069 late-type stars from LAMOST to explore their properties. We perform a statistical analysis on the magnetic activity of the stars and their associated physical parameters. Our samples are cross-matched with other data bases (LAMOST DR5, VSX, and SDSS DR12) to obtain additional observational properties. The equivalent widths (EWs) of Hα lines, an indicator of chromospheric activity, are calculated. According to the EWs of the Hα line, we detect 8816 spectra with apparent Hα emission for a total of 2115 stars among the 2 108 565 spectra analysed. Furthermore, 1521 of these stars show variability in their Hα lines. In addition, we detect 2132 flare events associated with 41 542 stars from the catalogue by cross-matching our LAMOST medium-resolution samples and the Kepler and K2 data bases. We also confirm a weak relationship of the flare amplitude with increasing Rossby number. There is a clear decease in the strength of chromospheric activity (LHα/Lbol) with increasing rotation period. Moreover, the ratio of the flare energy and stellar luminosity is found to decrease with the stellar mass.

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