Space Weather

Constraints On The History of the Stellar Radiation Environment Of Planets Orbiting Low-mass Stars

By Keith Cowing
May 6, 2022
Filed under
Constraints On The History of the Stellar Radiation Environment Of Planets Orbiting Low-mass Stars
The semi-amplitude of variability as a function of rotation period. The teal circles show rotation periods determined using MEarth data presented in Newton et al. (2016), M20, and this work. The purple circles show the rotation periods measured in this work and M20 using TESS data. The two blue plus symbols represent stars that did not use MEarth or TESS data for the determination of the rotation periods of Gl 54.1 and LEP 2211+4059. Red stars denote known transiting planet hosts. Magenta stars denote members of young moving groups discussed in section 6.6. We see no relationship between the rotation period and the semi-amplitude of variability.

We present a study of the relationship between galactic kinematics, flare rates, chromospheric magnetic activity, and rotation periods for a volume-complete, nearly all-sky sample of 219 single stars within 15 parsecs and with masses between 0.1−0.3 M⊙ observed during the primary mission of TESS.

We find that all targeted stars are consistent with a common value of α=1.984 ± 0.019 for the exponent of the flare frequency distribution. From multi-epoch high-resolution spectroscopy, we determine the stellar radial velocity which, when combined with Gaia astrometry, permits us to determine the galactic UVW space motions.

We find that 64% of our stars are members of the thin disk in the Galaxy, 5% belong to the thick disk, and for the remaining 31%, we cannot confidently assign membership to either component. If we assume that star formation has been constant in the thin disk for the past 8 Gyr, then based on the fraction that we observe to be active, we estimate the average age at which these stars transition from the saturated to the unsaturated flaring regime to be 2.4 ± 0.3 Gyr. This is consistent with the ages that we assign from galactic kinematics:

We find that stars with Prot < 10 days (which have yet to spin down) have a mean age of 2.0 ± 1.2 Gyr, whereas stars with 10 < Prot ≤ 90 days have a mean age of 5.6 ± 2.7 Gyr, and stars with Prot > 90 days have a mean age of 12.9 ± 3.5 Gyr. When we divide our sample by mass, we find that the average age of stars with Prot < 10 days increases from 0.6 ± 0.3 Gyr (0.2 - 0.3 M⊙) to 2.3 ± 1.3 Gyr (0.1--0.2 M⊙). Galactic Kinematics and Observed Flare Rates of a Volume-Complete Sample of Mid-to-Late M-dwarfs: Constraints on the History of the Stellar Radiation Environment of Planets Orbiting Low-mass Stars

Amber A. Medina, Jennifer G. Winters, Jonathan M. Irwin, David Charbonneau

Comments: Submitted to AAS Journals
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP); Astrophysics of Galaxies (astro-ph.GA)
Cite as: arXiv:2205.02331 [astro-ph.SR] (or arXiv:2205.02331v1 [astro-ph.SR] for this version)
Submission history
From: Amber Medina
[v1] Wed, 4 May 2022 21:18:47 UTC (2,905 KB)

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