What question did this study set out to answer?

This study aims to characterize the physical and dynamical properties of K dwarfs within 33 parsecs.

February 23, 2026Open Access

The Solar Neighborhood LV: Spectral Characterization of an Equatorial Sample of 580 K Dwarfs

Key Points

This study aims to characterize the physical and dynamical properties of K dwarfs within 33 parsecs.
Conducted spectroscopic observations using the CHIRON echelle spectrograph on the SMARTS 1.5 m telescope.
Analyzed 580 K dwarfs using Empirical SpecMatch to derive stellar properties and age indicators.
Investigated chromospheric activity through Hα emission and lithium absorption measurements.
Performed kinematic analysis with BANYAN Σ to identify young stars based on their membership in moving groups.
Identified 51 young and/or active stars, amounting to 8.8% of the sample.
Stellar parameters range from 3600–5500 K in effective temperature and exhibit a metallicity span of −0.60 to +0.55 dex.
Found that 80% of stars are in the thin disk and 18.4% in the thick disk, with a few exceptions.
Only 7.5% of the stars were found to host confirmed exoplanets, suggesting many are ideal for future searches.

Abstract

Abstract We present a spectroscopic characterization of 580 K dwarfs within 33 pc, observed with the CHIRON echelle spectrograph ( R = 80,000) on the SMARTS 1.5 m telescope. This volume-limited sample is part of the RKSTAR survey of ∼4400 K dwarf primaries within 50 pc. Using Empirical SpecMatch and the diagnostic lines H α (6562.8 Å) and Li I (6707.8 Å), we derive stellar properties, activity status, and age indicators calibrated against 35 benchmark K dwarfs with ages from 20 Myr to 5 Gyr. We find that 7.4% (43 stars) exhibit signatures of youth and/or chromospheric activity: 19 stars show lithium absorption indicating ages 25 km s −1 in v sin i . A metal-poor population (Fe/H ≤ −0.50 dex) comprises 4% of the sample. Galactic kinematics place 80% in the thin disk and 18.4% in the thick disk, with one halo member (HD 134439). Young and active stars are predominantly thin disk members, with two thick-disk exceptions. Cross-matching with NASA’s Exoplanet Archive reveals only 7.5% (44 stars) host confirmed planets as of 2025 July. Our results identify 529 mature, inactive K dwarfs as prime targets for terrestrial planet searches, providing a crucial resource for exoplanet habitability studies in the solar neighborhood.

The Solar Neighborhood LV: Spectral Characterization of an Equatorial Sample of 580 K Dwarfs

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Abstract

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