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CHROMOSPHERICALLY ACTIVE STARS in the RAVE SURVEY. II. YOUNG DWARFS in the SOLAR NEIGHBORHOOD

Accepted version
Peer-reviewed

Type

Article

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Abstract

jats:titleABSTRACT</jats:title> jats:pA large sample of over 38,000 chromospherically active candidate solar-like stars and cooler dwarfs from the RAVE survey is addressed in this paper. An improved activity identification with respect to the previous study was introduced to build a catalog of field stars in the solar neighborhood with an excess emission flux in the calcium infrared triplet wavelength region. The central result of this work is the calibration of the age–activity relation for main-sequence dwarfs in a range from a few jats:inline-formula jats:tex-math

</jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjaa501aieqn1.gif" xlink:type="simple" /> </jats:inline-formula> up to a few Gyr. It enabled an order of magnitude age estimation of the entire active sample. Almost 15,000 stars are shown to be younger than jats:inline-formula jats:tex-math

</jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjaa501aieqn2.gif" xlink:type="simple" /> </jats:inline-formula> and ∼2000 younger than jats:inline-formula jats:tex-math

</jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjaa501aieqn3.gif" xlink:type="simple" /> </jats:inline-formula>. The young age of the most active stars is confirmed by their position off the main sequence in the jats:italicJ</jats:italic> − jats:italicK</jats:italic> versus jats:inline-formula jats:tex-math

</jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjaa501aieqn4.gif" xlink:type="simple" /> </jats:inline-formula> diagram showing strong ultraviolet excess, mid-infrared excess in the jats:italicJ</jats:italic> − jats:italicK</jats:italic> versus jats:inline-formula jats:tex-math

</jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjaa501aieqn5.gif" xlink:type="simple" /> </jats:inline-formula> diagram, and very cool temperatures (jats:inline-formula jats:tex-math

</jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjaa501aieqn6.gif" xlink:type="simple" /> </jats:inline-formula>). They overlap with the reference pre-main-sequence RAVE stars often displaying X-ray emission. The activity level increasing with the color reveals their different nature from the solar-like stars and probably represents an underlying dynamo-generating magnetic fields in cool stars. Of the RAVE objects from DR5, 50% are found in the TGAS catalog and supplemented with accurate parallaxes and proper motions by jats:italicGaia</jats:italic>. This makes the database of a large number of young stars in a combination with RAVE’s radial velocities directly useful as a tracer of the very recent large-scale star formation history in the solar neighborhood. The data are available online in the Vizier database.</jats:p>

Description

Keywords

catalogs, stars: activity, stars: chromospheres, stars: emission-line, Be, stars: evolution, stars: pre-main sequence

Journal Title

Astrophysical Journal

Conference Name

Journal ISSN

0004-637X
1538-4357

Volume Title

835

Publisher

American Astronomical Society