Mamajek, Eric E. and Hillenbrand, Lynne A. (2008) Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics. Astrophysical Journal, 687 (2). pp. 1264-1293. ISSN 0004-637X. doi:10.1086/591785. https://resolver.caltech.edu/CaltechAUTHORS:20091006-203424650
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Abstract
While the strong anticorrelation between chromospheric activity and age has led to the common use of the Ca II H and K emission index (R'_(HK) = L_(HK)/L_(bol)) as an empirical age estimator for solar-type dwarfs, existing activity-age relations produce implausible ages at both high and low activity levels.We have compiled R'_(HK) HK data from the literature for young stellar clusters, richly populating for the first time the young end of the activity-age relation. Combining the cluster activity data with modern cluster age estimates and analyzing the color dependence of the chromospheric activity age index,we derive an improved activity-age calibration for F7-K2 dwarfs (0:5 mag < B - V < 0.9 mag). We also present a more fundamentally motivated activity-age calibration that relies on conversion of R'_(HK) values through the Rossby number to rotation periods and then makes use of improved gyrochronology relations. We demonstrate that our new activity-age calibration has typical age precision of ~0.2 dex for normal solar-type dwarfs aged between the Hyades and the Sun (~0.6-4.5 Gyr). Inferring ages through activity-rotation-age relations accounts for some color-dependent effects and systematically improves the age estimates (albeit only slightly). We demonstrate that coronal activity as measured through the fractional X-ray luminosity (R_X = L_X/L_(bol)) has nearly the same age- and rotation inferring capability as chromospheric activity measured through R'_(HK). As a first application of our calibrations, we provide new activity-derived age estimates for a volume-limited sample of the 108 solar-type field dwarfs within 16 pc.
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| Additional Information: | © 2008 The American Astronomical Society. Received 2008 April 26, accepted for publication 2008 July 10. We thank Mark Giampapa, David Soderblom, John Stauffer, Jason Wright, Debra Fischer, Sallie Baliunas, Søren Meibom, and Sydney Barnes for discussions and input. We acknowledge Greg Henry for allowing us access to his rotation period data for young MS stars in advance of publication. E. M. is supported through a Clay Postdoctoral Fellowship from the Smithsonian Astrophysical Observatory. | |||||||||
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| Subject Keywords: | stars: activity — stars: chromospheres — stars: coronae — stars: fundamental parameters — stars: rotation — X-rays: stars | |||||||||
| Issue or Number: | 2 | |||||||||
| DOI: | 10.1086/591785 | |||||||||
| Record Number: | CaltechAUTHORS:20091006-203424650 | |||||||||
| Persistent URL: | https://resolver.caltech.edu/CaltechAUTHORS:20091006-203424650 | |||||||||
| Official Citation: | Title: Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics Author(s): Eric E. Mamajek and Lynne A. Hillenbrand Affiliation(s): Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138; Clay Postdoctoral Fellow; Current address: Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627-0171; Department of Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125 Publication date: 2008 November 10 Volume: 687 Start page: 1264 Publication: The Astrophysical Journal URL: http://stacks.iop.org/0004-637X/687/1264 Abstract: While the strong anticorrelation between chromospheric activity and age has led to the common use of the Ca II H and K emission index ( <IMG SRC="eq-00001.gif" ALT="R^{\prime }_{\mathrm{HK}\,}=L_{\mathrm{HK}\,}/L_{\mathrm{bol}\,}"/> R'HK = LHK/Lbol) as an empirical age estimator for solar-type dwarfs, existing activity-age relations produce implausible ages at both high and low activity levels. We have compiled <IMG SRC="eq-00002.gif" ALT="R^{\prime }_{\mathrm{HK}\,}"/> R'HK data from the literature for young stellar clusters, richly populating for the first time the young end of the activity-age relation. Combining the cluster activity data with modern cluster age estimates and analyzing the color dependence of the chromospheric activity age index, we derive an improved activity-age calibration for F7-K2 dwarfs ( <IMG SRC="eq-00003.gif" ALT="0.5\ \mathrm{mag}\, < B-V < 0.9\ \mathrm{mag}\,"/> 0.5 mag < B − V < 0.9 mag ). We also present a more fundamentally motivated activity-age calibration that relies on conversion of <IMG SRC="eq-00004.gif" ALT="R^{\prime }_{\mathrm{HK}\,}"/> R'HK values through the Rossby number to rotation periods and then makes use of improved gyrochronology relations. We demonstrate that our new activity-age calibration has typical age precision of ~0.2 dex for normal solar-type dwarfs aged between the Hyades and the Sun (~0.6-4.5 Gyr). Inferring ages through activity-rotation-age relations accounts for some color-dependent effects and systematically improves the age estimates (albeit only slightly). We demonstrate that coronal activity as measured through the fractional X-ray luminosity ( <IMG SRC="eq-00005.gif" ALT="R_{\mathrm{X}\,}=L_{\mathrm{X}\,}/L_{\mathrm{bol}\,}"/> RX = LX/Lbol) has nearly the same age- and rotation-inferring capability as chromospheric activity measured through <IMG SRC="eq-00006.gif" ALT="R^{\prime }_{\mathrm{HK}\,}"/> R'HK. As a first application of our calibrations, we provide new activity-derived age estimates for a volume-limited sample of the 108 solar-type field dwarfs within 16 pc. | |||||||||
| Usage Policy: | No commercial reproduction, distribution, display or performance rights in this work are provided. | |||||||||
| ID Code: | 16206 | |||||||||
| Collection: | CaltechAUTHORS | |||||||||
| Deposited By: | Joy Painter | |||||||||
| Deposited On: | 07 Oct 2009 17:57 | |||||||||
| Last Modified: | 08 Nov 2021 23:25 |
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