Evolution of X-Ray Activity in < 25 Myr Old Pre-main Sequence Stars

Getman, Konstantin V.; Feigelson, Eric D.; Garmire, Gordon P.; Broos, Patrick S.; Kuhn, Michael A.; Preibisch, Thomas und Airapetian, Vladimir S. (2022): Evolution of X-Ray Activity in < 25 Myr Old Pre-main Sequence Stars. In: Astrophysical Journal, Bd. 935, Nr. 1, 43

Abstract

Measuring the evolution of X-ray emission from pre-main-sequence (PMS) stars gives insight into two issues: the response of magnetic dynamo processes to changes in the interior structure, and the effects of high-energy radiation on protoplanetary disks and primordial planetary atmospheres. We present a sample of 6003 stars with ages 7-25 Myr in 10 nearby open clusters from Chandra X-ray and Gaia-EDR3 surveys. Combined with previous results in large samples of younger (less than or similar to 5 Myr) stars in MYStIX and SFiNCs star-forming regions, mass-stratified activity-age relations are derived for the early phases of stellar evolution. X-ray luminosity (L (X) ) is constant during the first few Myr, possibly due to the presence of extended X-ray coronas insensitive to temporal changes in stellar size. L (X) then decays during the 7-25 Myr period, more rapidly as stellar mass increases. This decay is interpreted as decreasing efficiency of the alpha (2) dynamo as radiative cores grow and a solar-type alpha omega dynamo emerges. For more massive 3.5-7 M (circle dot) fully radiative stars, the X-ray emission plummets-indicating the lack of an effective magnetic dynamo. The findings provide improved measurements of high-energy radiation effects on circumstellar material, first for the protoplanetary disk and then for the atmospheres of young planets. The observed X-ray luminosities can be so high that an inner Earth-mass rocky, unmagnetized planet around a solar-mass PMS star might lose its primary and secondary atmospheres within a few (several) million years. PMS X-ray emission may thus have a significant impact on the evolution of early-planetary atmospheres and the conditions promoting the rise of habitability.

• Dokumententyp: Zeitschriftenartikel
• Fakultät: Physik
• Themengebiete: 500 Naturwissenschaften und Mathematik > 530 Physik
• ISSN: 0004-637X
• Sprache: Englisch
• DFG: Gefördert durch die Deutsche Forschungsgemeinschaft (DFG) - 362051796