A Relationship between Stellar Age and Spot Coverage

Morris, Brett M. (2020). A Relationship between Stellar Age and Spot Coverage. Astrophysical journal, 893(1), p. 67. Institute of Physics Publishing IOP 10.3847/1538-4357/ab79a0

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We investigate starspot distributions consistent with space-based photometry of F, G, and K stars in six stellar associations ranging in age from 10 Myr to 4 Gyr. We show that a simple light-curve statistic called the "smoothed amplitude" is proportional to stellar age as t−1/2, following a Skumanich-like spin-down relation. We marginalize over the unknown stellar inclinations by forward modeling the ensemble of light curves for direct comparison with the Kepler, K2, and TESS photometry. We sample the posterior distributions for spot coverage with approximate Bayesian computation. We find typical spot coverages in the range 1%–10%, which decrease with increasing stellar age. The spot coverage is proportional to tn where n = −0.37 ± 0.16, also statistically consistent with a Skumanich-like t−1/2 decay of starspot coverage with age. We apply two techniques to estimate the spot coverage of young exoplanet-hosting stars likely to be targeted for transmission spectroscopy with the James Webb Space Telescope, and estimate the bias in exoplanet radius measurements due to varying starspot coverage.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Physics Institute > NCCR PlanetS
08 Faculty of Science > Physics Institute > Space Research and Planetary Sciences
08 Faculty of Science > Physics Institute
10 Strategic Research Centers > Center for Space and Habitability (CSH)

UniBE Contributor:

Morris, Brett Michael

Subjects:

500 Science
500 Science > 520 Astronomy
500 Science > 530 Physics

ISSN:

0004-637X

Publisher:

Institute of Physics Publishing IOP

Language:

English

Submitter:

Danielle Zemp

Date Deposited:

13 Apr 2021 15:44

Last Modified:

18 Apr 2021 03:03

Publisher DOI:

10.3847/1538-4357/ab79a0

BORIS DOI:

10.48350/154805

URI:

https://boris.unibe.ch/id/eprint/154805

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