The Factory And The Beehive. II. Activity And Rotation In Praesepe And The Hyades

dc.contributor.utaustinauthorKraus, Adamen_US
dc.creatorDouglas, S. T.en_US
dc.creatorAgueros, M. A.en_US
dc.creatorCovey, Kevin R.en_US
dc.creatorBowsher, E. C.en_US
dc.creatorBochanski, J. J.en_US
dc.creatorCargile, P. A.en_US
dc.creatorKraus, Adamen_US
dc.creatorLaw, N. M.en_US
dc.creatorLemonias, J. J.en_US
dc.creatorArce, Hector G.en_US
dc.creatorFierroz, D. F.en_US
dc.creatorKundert, A.en_US
dc.description.abstractOpen clusters are collections of stars with a single, well-determined age, and can be used to investigate the connections between angular-momentum evolution and magnetic activity over a star's lifetime. We present the results of a comparative study of the relationship between stellar rotation and activity in two benchmark open clusters: Praesepe and the Hyades. As they have the same age and roughly solar metallicity, these clusters serve as an ideal laboratory for testing the agreement between theoretical and empirical rotation-activity relations at approximate to 600 Myr. We have compiled a sample of 720 spectra-more than half of which are new observations-for 516 high-confidence members of Praesepe; we have also obtained 139 new spectra for 130 high-confidence Hyads. We have also collected rotation periods (P-rot) for 135 Praesepe members and 87 Hyads. To compare H alpha emission, an indicator of chromospheric activity, as a function of color, mass, and Rossby number R-o, we first calculate an expanded set of chi values, with which we can obtain the H alpha to bolometric luminosity ratio, L-H alpha/L-bol, even when spectra are not flux-calibrated and/or stars lack reliable distances. Our. values cover a broader range of stellar masses and colors (roughly equivalent to spectral types from K0 to M9), and exhibit better agreement between independent calculations, than existing values. Unlike previous authors, we find no difference between the two clusters in their H alpha equivalent width or L-H alpha/L-bol distributions, and therefore take the merged H alpha and Prot data to be representative of 600 Myr old stars. Our analysis shows that H alpha activity in these stars is saturated for R-o <= 0.11(-0.03)(+0.02) Above that value activity declines as a power-law with slope beta = -0.73(-0.12,)(+0.06) before dropping off rapidly at Ro approximate to 0.4. These data provide a useful anchor for calibrating the age-activity-rotation relation beyond 600 Myr.en_US
dc.description.sponsorshipNSF AST-1255419, AST-1109612en_US
dc.description.sponsorshipAlfred P. Sloan Foundationen_US
dc.description.sponsorshipParticipating Institutionsen_US
dc.description.sponsorshipU.S. Department of Energy Office of Scienceen_US
dc.identifier.citationDouglas, S. T., M. A. Ag�eros, K. R. Covey, E. C. Bowsher, John J. Bochanski, P. A. Cargile, A. Kraus et al. "The Factory and the Beehive. II. Activity and Rotation in Praesepe and the Hyades." The Astrophysical Journal, Vol. 795, No. 2 (Nov., 2014): 161.en_US
dc.relation.ispartofserialAstrophysical Journalen_US
dc.rightsAdministrative deposit of works to Texas ScholarWorks: This works author(s) is or was a University faculty member, student or staff member; this article is already available through open access or the publisher allows a PDF version of the article to be freely posted online. The library makes the deposit as a matter of fair use (for scholarly, educational, and research purposes), and to preserve the work and further secure public access to the works of the University.en_US
dc.subjectstars: activityen_US
dc.subjectstars: chromospheresen_US
dc.subjectstars: coronaeen_US
dc.subjectstars: evolutionen_US
dc.subjectstars: late-typeen_US
dc.subjectstars: rotationen_US
dc.subjectlow-mass starsen_US
dc.subjectdigital sky surveyen_US
dc.subjectlower main-sequenceen_US
dc.subjectchromospheric activityen_US
dc.subjecthipparcos catalogen_US
dc.subjectopen clustersen_US
dc.subjectastronomy & astrophysicsen_US
dc.titleThe Factory And The Beehive. II. Activity And Rotation In Praesepe And The Hyadesen_US

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