Activity and differential rotation of the early M dwarf Kepler-45 from transit mapping

Zaleski, S. M. and Valio, A. and Carter, B. D. ORCID: and Marsden, S. C. (2020) Activity and differential rotation of the early M dwarf Kepler-45 from transit mapping. Monthly Notices of the Royal Astronomical Society, 492. pp. 5141-5151. ISSN 0035-8711

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Little is known of the activity and differential rotation of low luminosity, early M dwarfs from direct observation. We present the first stellar activity analysis of star-spots and faculae for the hot Jupiter hosting M1V dwarf Kepler-45 from Kepler transit light curves. We find star-spot and facula temperatures contrasting a few hundred degrees with the quiet photosphere, hence similar to other early M dwarfs having a convective envelope surrounding a radiative core. Star-spots are prominent close to the centre of the stellar disc, with faculae prominent towards the limbs, similar to what is observed for the Sun. Star-spot and facula mean sizes are about 40 and 45 × 10^3 km, respectively, and thus faculae occupy a 10 per cent larger surface area than the star-spots. A short-term activity cycle of about 295 d is observed that is reminiscent of those seen for other cool dwarfs. Adopting a solar-type differential rotation profile (faster equatorial rotation than polar rotation), our star-spot and facula temporal mapping indicates a rotation period of 15.520 ± 0.025 d at the transit latitude of −33.2◦. From the mean stellar rotation of 15.762 d, we estimate a rotational shear of 0.031 ± 0.004 rad d^−1, or a relative differential rotation of 7.8 ± 0.9 per cent. Kepler-45’s surface rotational shear is thus consistent with observations and theoretical modelling of other early M dwarfs that indicate a shear of less than 0.045 rad d^−1 and no less than 0.03 rad d^−1 for stars with similar stellar rotation periods.

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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Published version deposited in accordance with the copyright policy of the publisher.
Faculty/School / Institute/Centre: Current - Institute for Advanced Engineering and Space Sciences - Centre for Astrophysics (1 Aug 2018 -)
Faculty/School / Institute/Centre: Current - Faculty of Health, Engineering and Sciences - School of Sciences (6 Sep 2019 -)
Date Deposited: 11 Dec 2020 05:09
Last Modified: 03 Jan 2021 23:47
Uncontrolled Keywords: stars: activity – stars: solar-type – starspots
Fields of Research (2008): 02 Physical Sciences > 0201 Astronomical and Space Sciences > 020110 Stellar Astronomy and Planetary Systems
Fields of Research (2020): 51 PHYSICAL SCIENCES > 5101 Astronomical sciences > 510109 Stellar astronomy and planetary systems
Socio-Economic Objectives (2008): E Expanding Knowledge > 97 Expanding Knowledge > 970102 Expanding Knowledge in the Physical Sciences
Socio-Economic Objectives (2020): 28 EXPANDING KNOWLEDGE > 2801 Expanding knowledge > 280120 Expanding knowledge in the physical sciences
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