The Origin of Enhanced Activity in the Suns of M67

Abstract

We report the results of the analysis of high resolution photospheric line spectra obtained with the UVES instrument on the VLT for a sample of 15 solar-type stars selected from a recent survey of the distribution of H and K chromospheric line strengths in the solar-age open cluster M67. We find upper limits to the projected rotation velocities that are consistent with solar-like rotation (i.e., v sini ~< 2-3 km/s) for objects with Ca II chromospheric activity within the range of the contemporary solar cycle. Two solar-type stars in our sample exhibit chromospheric emission well in excess of even solar maximum values. In one case, Sanders 1452, we measure a minimum rotational velocity of vsini = 4 +/- 0.5 km/s, or over twice the solar equatorial rotational velocity. The other star with enhanced activity, Sanders 747, is a spectroscopic binary. We conclude that high activity in solar-type stars in M67 that exceeds solar levels is likely due to more rapid rotation rather than an excursion in solar-like activity cycles to unusually high levels. We estimate an upper limit of 0.2% for the range of brightness changes occurring as a result of chromospheric activity in solar-type stars and, by inference, in the Sun itself. We discuss possible implications for our understanding of angular momentum evolution in solar-type stars, and we tentatively attribute the rapid rotation in Sanders 1452 to a reduced braking efficiency.

accepted by ApJ

References in corpus (4)

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Cited by in corpus (10)

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• Lithium in M67: From the main sequence to the red giant branch
• Search for giant planets in M67 IV: survey results
• Is it possible to detect planets around young active G and K dwarfs?
• Ultraviolet stellar population of the old open cluster M67 (NGC 2682)
• No "Maunder minimum" candidates in M67: mitigating interstellar contamination of chromospheric emission lines
• A Revised Gyro-Age for M 67 from Kepler/K2-Campaign-5 Light Curves
• A multi-wavelength view of the open cluster NGC 2527: Discovery of active stars