THE ORIGIN OF ENHANCED ACTIVITY IN THE SUNS OF M67
- Institut fuer Astrophysik, Georg-August-Universitaet, Friedrich-Hund-Platz 1, 37077 Goettingen (Germany)
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 sin iapprox< 2-3 km s{sup -1}) 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 v sin i = 4 +- 0.5 km s{sup -1}, 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.
- OSTI ID:
- 21389307
- Journal Information:
- Astrophysical Journal, Vol. 707, Issue 1; Other Information: DOI: 10.1088/0004-637X/707/1/852; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
Similar Records
ROTATION AND MAGNETIC ACTIVITY IN A SAMPLE OF M-DWARFS
Outer atmospheres of cool stars. V. IUE observations of Capella: The rotation-activity connection