The LHS 1678 System: Two Earth-Sized Transiting Planets and an Astrometric Companion Orbiting an M Dwarf Near the Convective Boundary at 20 pc - Archive ouverte HAL Access content directly
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The LHS 1678 System: Two Earth-Sized Transiting Planets and an Astrometric Companion Orbiting an M Dwarf Near the Convective Boundary at 20 pc

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Michele L. Silverstein
  • Function : Author
Benjamin J. Hord
  • Function : Author
Wei-Chun Jao
  • Function : Author
Eliot Halley Vrijmoet
  • Function : Author
Todd J. Henry
  • Function : Author
Ryan Cloutier
Veselin B. Kostov
  • Function : Author
Jennifer G. Winters
  • Function : Author
Jonathan M. Irwin
  • Function : Author
Stephen R. Kane
  • Function : Author
Keivan G. Stassun
  • Function : Author
Chelsea Huang
Michelle Kunimoto
  • Function : Author
Evan Tey
  • Function : Author
Andrew Vanderburg
Nicola Astudillo-Defru
C. E. Brasseur
  • Function : Author
David Charbonneau
David R. Ciardi
  • Function : Author
Karen A. Collins
  • Function : Author
Kevin I. Collins
  • Function : Author
Dennis M. Conti
  • Function : Author
Ian J. M. Crossfield
  • Function : Author
Tansu Daylan
John P. Doty
  • Function : Author
Courtney D. Dressing
  • Function : Author
Emily A. Gilbert
  • Function : Author
Keith Horne
  • Function : Author
Jon M. Jenkins
  • Function : Author
David W. Latham
  • Function : Author
Andrew W. Mann
  • Function : Author
Elisabeth Matthews
Leonardo A. Paredes
  • Function : Author
Samuel N. Quinn
  • Function : Author
George R. Ricker
  • Function : Author
Richard P. Schwarz
  • Function : Author
Sara Seager
Ramotholo Sefako
  • Function : Author
Avi Shporer
Jeffrey C. Smith
  • Function : Author
Christopher Stockdale
  • Function : Author
Thiam-Guan Tan
Guillermo Torres
  • Function : Author
Joseph D. Twicken
  • Function : Author
Roland Vanderspek
Gavin Wang
Joshua N. Winn
  • Function : Author

Abstract

We present the TESS discovery of the LHS 1678 (TOI-696) exoplanet system, comprised of two approximately Earth-sized transiting planets and a likely astrometric brown dwarf orbiting a bright ($V_J$=12.5, $K_s$=8.3) M2 dwarf at 19.9 pc. The two TESS-detected planets are of radius 0.70$\pm$0.04 $R_\oplus$ and 0.98$\pm$0.06 $R_\oplus$ in 0.86-day and 3.69-day orbits, respectively. Both planets are validated and characterized via ground-based follow-up observations. HARPS RV monitoring yields 97.7 percentile mass upper limits of 0.35 $M_\oplus$ and 1.4 $M_\oplus$ for planets b and c, respectively. The astrometric companion detected by the CTIO/SMARTS 0.9m has an orbital period on the order of decades and is undetected by other means. Additional ground-based observations constrain the companion to being a high-mass brown dwarf or smaller. Each planet is of unique interest; the inner planet has an ultra-short period, and the outer planet is in the Venus zone. Both are promising targets for atmospheric characterization with the JWST and mass measurements via extreme-precision radial velocity. A third planet candidate of radius 0.9$\pm$0.1 $R_\oplus$ in a 4.97-day orbit is also identified in multi-Cycle TESS data for validation in future work. The host star is associated with an observed gap in the lower main sequence of the Hertzsprung-Russell diagram. This gap is tied to the transition from partially- to fully-convective interiors in M dwarfs, and the effect of the associated stellar astrophysics on exoplanet evolution is currently unknown. The culmination of these system properties makes LHS 1678 a unique, compelling playground for comparative exoplanet science and understanding the formation and evolution of small, short-period exoplanets orbiting low-mass stars.

Dates and versions

insu-03458317 , version 1 (30-11-2021)

Identifiers

Cite

Michele L. Silverstein, Joshua E. Schlieder, Thomas Barclay, Benjamin J. Hord, Wei-Chun Jao, et al.. The LHS 1678 System: Two Earth-Sized Transiting Planets and an Astrometric Companion Orbiting an M Dwarf Near the Convective Boundary at 20 pc. 2021. ⟨insu-03458317⟩
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