AAS 201st Meeting, January, 2003
Session 12. Activity in Cool Stars
Poster, Monday, January 6, 2003, 9:20am-6:30pm, Exhibit Hall AB

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[12.01] ROSAT View of Hipparcos F Stars

A.A. Suchkov (STScI), V.V. Makarov (USNO)

In this paper we analyse a sample of ~2000 F stars within ~200~pc for which we have found X-ray counterparts in the ROSAT All Sky Survey. We have isolated a population of stars with enhanced X-ray emission, which appear to be very young, possibly pre-mainsequence, and are characterized by high metallicity and high temperature. Many of these strong emitters are located in or near the known regions of ongoing star formation that are abundant at ~130 to ~170 pc. Another group of strong emitters has been found among overluminous stars whose optical luminosity is too high for their temperature and surface gravity (as derived from uvby photometry). This group comprises the oldest F stars, therefore their strong X-ray emission looks quite puzzling. We discuss the X-ray properties of various physical groups of F stars as related to stellar evolution, duplicity, and specific stellar parameters such as mass, metallicity, and effective temperature.

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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.