Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Evolution of X-ray Activity in <25 Myr Old Pre-Main Sequence Stars   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 interior structure and the effects of high-energy radiation on
protoplanetary disks and primordial planetary atmospheres. We present a sample
of 6,003 stars with ages [7-25] Myr in ten 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 early phases of stellar
evolution. X-ray luminosity (Lx) is constant during the first few Myr, possibly
due to the presence of extended X-ray coronas insensitive to temporal changes
in stellar size. Lx 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 [2-7] Msun fully radiative stars, the X-ray emission
plummets indicating lack of an effective magnetic dynamos. The findings provide
improved measurements of high energy radiation effects on circumstellar
material, first the protoplanetary disk and then 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 evolution of early
planetary atmospheres and the conditions promoting the rise of habitability.

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The categories of this paper are: nlin
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The categories of this paper are: physics
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The categories of this paper are: hep-ex
32
The categories of this paper are: atom-ph
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The categories of this paper are: math-ph
30
The categories of this paper are: q-alg
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The categories of this paper are: cond-mat
21
The categories of this paper are: adap-org
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The categories of this paper are: gr-qc
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The categories of this paper are: eess
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The categories of this paper are: nucl-th
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The categories of this paper are: patt-sol
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The categories of this paper are: nucl-ex
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The categories of this paper are: cs
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The categories of this paper are: acc-phys
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The categories of this paper are: q-fin