Zodiacal Exoplanets in Time (ZEIT) XII: A Directly-Imaged Planetary-Mass Companion to a Young Taurus M Dwarf Star

Author(s): Eric Gaidos, T. Hirano, A. L. Kraus, M. Kuzuhara, Z. Zhang
Abstract: We report the discovery of a resolved (0″.9) substellar companion to a member of the 1-5 Myr Taurus star-forming region. The host star (2M0437) is a single mid-M type (T_eff≍3100 K) dwarf with a position, space motion, and color-magnitude that support Taurus membership, and possible affiliation with a ~2.5 Myr-old sub-group. A comparison with stellar models suggests a 2-5 Myr age and a mass of 0.15-0.18M_⊙. Although K2 detected quasi-periodic dimming from close-in circumstellar dust, the star lacks detectable excess infrared emission from a circumstellar disk and its Hα emission is not commensurate with accretion. Astrometry based on three years of AO imaging shows that the companion (2M0437b) is co-moving, while photometry of two other sources at larger separation indicates they are likely heavily-reddened background stars. A comparison of the luminosity of 2M0437b with models suggests a mass of 3-5 M_JUP , well below the deuterium burning limit, and an effective temperature of 1400-1500 K, characteristic of a late L spectral type. The H-K color is redder than the typical L dwarf, but comparable to other directly detected young planets, e.g. those around HR 8799. The discovery of a super-Jupiter around a very young, very low mass star challenges models of planet formation by either core accretion (which requires time) or disk instability (which requires mass). We also detected a second, co-moving, widely-separated (75″) object which appears to be a heavily-extincted star. This is certainly a fellow member of this Taurus sub-group and statistically likely to be a bound companion.
Organisation(s): Department of Astrophysics
External organisation(s): University of Hawaii at Manoa, Universität Bern, National Institutes of Natural Sciences (NINS), University of Texas, Austin
Journal: Monthly Notices of the Royal Astronomical Society
Volume: 512
Pages: 583-601
No. of pages: 19
ISSN: 0035-8711
DOI: https://doi.org/10.1093/mnras/stab3069
Publication date: 05-2022
Peer reviewed: Yes
Austrian Fields of Science 2012: 103003 Astronomy, 103004 Astrophysics
Keywords
ASJC Scopus subject areas: Astronomy and Astrophysics, Space and Planetary Science
Portal url: https://ucrisportal.univie.ac.at/en/publications/6e8845ea-34ab-4240-8ebd-171b019f7fe5

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