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

Konstantin V. Getman, Eric D. Feigelson, Gordon P. Garmire, Patrick S. Broos, Michael A. Kuhn, Thomas Preibisch, Vladimir S. Airapetian

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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 (≲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 α 2 dynamo as radiative cores grow and a solar-type αΩ dynamo emerges. For more massive 3.5-7 M 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.
Original languageEnglish
Article number43
Number of pages29
JournalThe Astrophysical Journal
Volume935
Early online date1 Aug 2022
DOIs
Publication statusPublished - 10 Aug 2022

Keywords

  • Pre-main sequence stars
  • Planetary atmospheres
  • Protoplanetary disks
  • Stellar x-ray flares
  • Single x-ray stars
  • X-ray stars
  • 1290
  • 1244
  • 1300
  • 1637
  • 1461
  • 1823
  • Astrophysics - Solar and Stellar Astrophysics
  • Astrophysics - Earth and Planetary Astrophysics
  • Astrophysics - High Energy Astrophysical Phenomena
  • High Energy Physics - Phenomenology

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