A super-Earth and sub-Neptune transiting the late-type M dwarf LP 791-18. (arXiv:1906.09267v1 [astro-ph.EP])

A super-Earth and sub-Neptune transiting the late-type M dwarf LP 791-18. (arXiv:1906.09267v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Crossfield_I/0/1/0/all/0/1">Ian J. M. Crossfield</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Waalkes_W/0/1/0/all/0/1">William Waalkes</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Newton_E/0/1/0/all/0/1">Elisabeth R. Newton</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Narita_N/0/1/0/all/0/1">Norio Narita</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Muirhead_P/0/1/0/all/0/1">Philip Muirhead</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ment_K/0/1/0/all/0/1">Kristo Ment</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Matthews_E/0/1/0/all/0/1">Elisabeth Matthews</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kraus_A/0/1/0/all/0/1">Adam Kraus</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kostov_V/0/1/0/all/0/1">Veselin Kostov</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kosiarek_M/0/1/0/all/0/1">Molly R. Kosiarek</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kane_S/0/1/0/all/0/1">Stephen R. Kane</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Isaacson_H/0/1/0/all/0/1">Howard Isaacson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Halverson_S/0/1/0/all/0/1">Sam Halverson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gonzales_E/0/1/0/all/0/1">Erica Gonzales</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Everett_M/0/1/0/all/0/1">Mark Everett</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dragomir_D/0/1/0/all/0/1">Diana Dragomir</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Collins_K/0/1/0/all/0/1">Karen A. Collins</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chontos_A/0/1/0/all/0/1">Ashley Chontos</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Berardo_D/0/1/0/all/0/1">David Berardo</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Winters_J/0/1/0/all/0/1">Jennifer G. Winters</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Winn_J/0/1/0/all/0/1">Joshua N. Winn</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Scott_N/0/1/0/all/0/1">Nicholas J. Scott</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rojas_Ayala_B/0/1/0/all/0/1">Barbara Rojas-Ayala</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rizzuto_A/0/1/0/all/0/1">Aaron C. Rizzuto</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Petigura_E/0/1/0/all/0/1">Erik A. Petigura</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Peterson_M/0/1/0/all/0/1">Merrin Peterson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mocnik_T/0/1/0/all/0/1">Teo Mocnik</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mikal_Evans_T/0/1/0/all/0/1">Thomas Mikal-Evans</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mehrle_N/0/1/0/all/0/1">Nicholas Mehrle</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Matson_R/0/1/0/all/0/1">Rachel Matson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kuzuhara_M/0/1/0/all/0/1">Masayuki Kuzuhara</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Irwin_J/0/1/0/all/0/1">Jonathan Irwin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Huber_D/0/1/0/all/0/1">Daniel Huber</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Huang_C/0/1/0/all/0/1">Chelsea Huang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Howell_S/0/1/0/all/0/1">Steve Howell</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Howard_A/0/1/0/all/0/1">Andrew W. Howard</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hirano_T/0/1/0/all/0/1">Teruyuki Hirano</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Fulton_B/0/1/0/all/0/1">Benjamin J. Fulton</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dupuy_T/0/1/0/all/0/1">Trent Dupuy</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dressing_C/0/1/0/all/0/1">Courtney D. Dressing</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dalba_P/0/1/0/all/0/1">Paul A. Dalba</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Charbonneau_D/0/1/0/all/0/1">David Charbonneau</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Burt_J/0/1/0/all/0/1">Jennifer Burt</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Berta_Thompson_Z/0/1/0/all/0/1">Zachory Berta-Thompson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Benneke_B/0/1/0/all/0/1">Björn Benneke</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Watanabe_N/0/1/0/all/0/1">Noriharu Watanabe</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Twicken_J/0/1/0/all/0/1">Joseph D. Twicken</a>, et al. (13 additional authors not shown)

Planets occur most frequently around cool dwarfs, but only a handful of
specific examples are known to orbit the latest-type M stars. Using TESS
photometry, we report the discovery of two planets transiting the low-mass star
called LP 791-18 (identified by TESS as TOI 736). This star has spectral type
M6V, effective temperature 2960 K, and radius 0.17 R_Sun, making it the
third-coolest star known to host planets. The two planets straddle the radius
gap seen for smaller exoplanets; they include a 1.1 R_Earth planet on a 0.95
day orbit and a 2.3 R_Earth planet on a 5 day orbit. Because the host star is
small the loss of light during these planets’ transits is fairly large (0.4%
and 1.7%). This has allowed us to detect both planets’ transits from
ground-based photometry, refining their radii and orbital ephemerides. In the
future, radial velocity observations and transmission spectroscopy can both
probe these planets’ bulk interior and atmospheric compositions, and additional
photometric monitoring would be sensitive to even smaller transiting planets.

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