Stellar Characterization and a Chromospheric Activity Analysis of a K2 Sample of Planet-Hosting Stars

By Keith Cowing
Status Report
May 15, 2024
Filed under , , , , , ,
Stellar Characterization and a Chromospheric Activity Analysis of a K2 Sample of Planet-Hosting Stars
Kiel diagram for the sample stars. The gray dashed lines represent solar metallicity 4.6 and 10 Gyr old stellar evolution tracks from Yonsei-Yale. The colors of the circles indicate stellar activity as measured by the log R ′ HK indicator (Section 4) and corresponding to the color bar. The main sequence stars and the evolved stars are separated by the black dashed line. — astro-ph.SR

Effective temperatures, surface gravities, and iron abundances were derived for 109 stars observed by the K2 mission using equivalent width measurements of Fe I and Fe II lines. Calculations were carried out in LTE using Kurucz model atmospheres.

Stellar masses and radii were derived by combining the stellar parameters with Gaia DR3 parallaxes, V-magnitudes, and isochrones. The derived stellar and planetary radii have median internal precision of 1.8%, and 2.3%, respectively. The radius gap near Rplanet∼1.9R was detected in this K2 sample. Chromospheric activity was measured from the Ca II H and K lines using the Values of logR′HK were investigated as a function of stellar rotational period (Prot) and we found that chromospheric activity decreases with increasing Prot, although there is a large scatter in logR′HK (∼0.5) for a given Prot. Activity levels in this sample reveal a paucity of F & G dwarfs with intermediate activity levels (Vaughan-Preston gap).

The effect that stellar activity might have on the derivation of stellar parameters was investigated by including magnetically-sensitive Fe I lines in the analysis and we find no significant differences between parameters with and without magnetically-sensitive lines, although the more active stars (logR′HK>−5.0) exhibit a larger scatter in the differences in Teff and [Fe/H].

V. Loaiza-Tacuri, Katia Cunha, Verne V. Smith, F. Quispe-Huaynasi, Ellen Costa-Almeida, Luan Ghezzi, Jorge Melendez

Comments: 19 pages, 13 figures, 5 tables
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP); Astrophysics of Galaxies (astro-ph.GA)
Cite as: arXiv:2405.08128 [astro-ph.SR] (or arXiv:2405.08128v1 [astro-ph.SR] for this version)
Submission history
From: Verónica Loaiza Tacuri
[v1] Mon, 13 May 2024 19:12:51 UTC (464 KB)

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