The LHS 1678 system: two earth-sized transiting planets and an astrometric companion orbiting an M dwarf near the convective boundary at 20 pc

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

doi:10.3847/1538-3881/ac32e3

The LHS 1678 system: two earth-sized transiting planets and an astrometric companion orbiting an M dwarf near the convective boundary at 20 pc

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

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Abstract

We present the Transiting Exoplanet Survey Satellite (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 ± 0.04 R⊕ and 0.98 ± 0.06 R⊕ in 0.86 day and 3.69 day orbits, respectively. Both planets are validated and characterized via ground-based follow-up observations. High Accuracy Radial Velocity Planet Searcher RV monitoring yields 97.7 percentile mass upper limits of 0.35 M⊕ and 1.4 M⊕ for planets b and c, respectively. The astrometric companion detected by the Cerro Tololo Inter-American Observatory/Small and Moderate Aperture Telescope System 0.9 m 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 James Webb Space Telescope and mass measurements via extreme-precision radial velocity. A third planet candidate of radius 0.9 ± 0.1 R⊕ in a 4.97 day orbit is also identified in multicycle 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.

Original language	English
Article number	151
Number of pages	31
Journal	Astronomical Journal
Volume	163
Issue number	4
Early online date	7 Mar 2022
DOIs	https://doi.org/10.3847/1538-3881/ac32e3
Publication status	Published - 1 Apr 2022

Keywords

Exoplanet systems
Transit photometry
Low mass stars
M dwarf stars
Astrometric binary stars

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Copyright © 2022. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
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https://arxiv.org/abs/2110.12079

Astronomy at St Andrews 2018-2021: Astronomy at St Andrews 2018-2021
Jardine, M. M. (PI), Bonnell, I. A. (CoI), Cameron, A. C. (CoI), Cyganowski, C. J. (CoI), Dominik, M. (CoI), Helling, C. (CoI), Horne, K. D. (CoI), Scholz, A. (CoI), Tojeiro, R. (CoI), Weijmans, A.-M. (CoI), Wild, V. (CoI), Woitke, P. (CoI), Wood, K. (CoI) & Zhao, H. (CoI)
1/04/18 → 31/03/22
Project: Standard

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Silverstein, M. L., Schlieder, J. E., Barclay, T., Hord, B. J., Jao, W.-C., Vrijmoet, E. H., Henry, T. J., Cloutier, R., Kostov, V. B., Kruse, E., Winters, J. G., Irwin, J. M., Kane, S. R., Stassun, K. G., Huang, C., Kunimoto, M., Tey, E., Vanderburg, A., Astudillo-Defru, N., ... Wang, G. (2022). The LHS 1678 system: two earth-sized transiting planets and an astrometric companion orbiting an M dwarf near the convective boundary at 20 pc. Astronomical Journal, 163(4), Article 151. https://doi.org/10.3847/1538-3881/ac32e3

@article{a2c04c8bc5194532b232e09549cdbd79,

title = "The LHS 1678 system: two earth-sized transiting planets and an astrometric companion orbiting an M dwarf near the convective boundary at 20 pc",

abstract = "We present the Transiting Exoplanet Survey Satellite (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 (VJ = 12.5, Ks = 8.3) M2 dwarf at 19.9 pc. The two TESS-detected planets are of radius 0.70 ± 0.04 R⊕ and 0.98 ± 0.06 R⊕ in 0.86 day and 3.69 day orbits, respectively. Both planets are validated and characterized via ground-based follow-up observations. High Accuracy Radial Velocity Planet Searcher RV monitoring yields 97.7 percentile mass upper limits of 0.35 M⊕ and 1.4 M⊕ for planets b and c, respectively. The astrometric companion detected by the Cerro Tololo Inter-American Observatory/Small and Moderate Aperture Telescope System 0.9 m 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 James Webb Space Telescope and mass measurements via extreme-precision radial velocity. A third planet candidate of radius 0.9 ± 0.1 R⊕ in a 4.97 day orbit is also identified in multicycle 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.",

keywords = "Exoplanet systems, Transit photometry, Low mass stars, M dwarf stars, Astrometric binary stars",

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

note = "Funding: The MEarth Team gratefully acknowledges funding from the David and Lucile Packard Fellowship for Science and Engineering (awarded to D.C.). This material is based upon work supported by the National Science Foundation under grants AST-0807690, AST-1109468, AST-1004488 (Alan T. Waterman Award), and AST-1616624, and upon work supported by the National Aeronautics and Space Administration under Grant No. 80NSSC18K0476 issued through the XRP Program. This work is made possible by a grant from the John Templeton Foundation. N. A.-D. acknowledges the support of FONDECYT project 3180063. TD acknowledges support from MIT{\textquoteright}s Kavli Institute as a Kavli postdoctoral fellow. KH acknowledges support from STFC grant ST/R000824/1. E.A.G. thanks the LSSTC Data Science Fellowship Program, which is funded by LSSTC, NSF Cybertraining Grant #1829740, the Brinson Foundation, and the Moore Foundation; The material is based upon work supported by NASA under award number 80GSFC21M0002. This work was supported by the lead author{\textquoteright}s appointment to the NASA Postdoctoral Program at the Goddard Space Flight Center, administered by Universities Space Research Association under contract with NASA ",

year = "2022",

month = apr,

day = "1",

doi = "10.3847/1538-3881/ac32e3",

language = "English",

volume = "163",

journal = "Astronomical Journal",

issn = "0004-6256",

publisher = "American Astronomical Society",

number = "4",

}

Silverstein, ML, Schlieder, JE, Barclay, T, Hord, BJ, Jao, W-C, Vrijmoet, EH, Henry, TJ, Cloutier, R, Kostov, VB, Kruse, E, Winters, JG, Irwin, JM, Kane, SR, Stassun, KG, Huang, C, Kunimoto, M, Tey, E, Vanderburg, A, Astudillo-Defru, N, Bonfils, X, Brasseur, CE, Charbonneau, D, Ciardi, DR, Collins, KA, Collins, KI, Conti, DM, Crossfield, IJM, Daylan, T, Doty, JP, Dressing, CD, Gilbert, EA, Horne, K, Jenkins, JM, Latham, DW, Mann, AW, Matthews, E, Paredes, LA, Quinn, SN, Ricker, GR, Schwarz, RP, Seager, S, Sefako, R, Shporer, A, Smith, JC, Stockdale, C, Tan, T-G, Torres, G, Twicken, JD, Vanderspek, R & Wang, G 2022, 'The LHS 1678 system: two earth-sized transiting planets and an astrometric companion orbiting an M dwarf near the convective boundary at 20 pc', Astronomical Journal, vol. 163, no. 4, 151. https://doi.org/10.3847/1538-3881/ac32e3

TY - JOUR

T1 - The LHS 1678 system

T2 - two earth-sized transiting planets and an astrometric companion orbiting an M dwarf near the convective boundary at 20 pc

AU - Silverstein, Michele L.

AU - Schlieder, Joshua E.

AU - Barclay, Thomas

AU - Hord, Benjamin J.

AU - Jao, Wei-Chun

AU - Vrijmoet, Eliot Halley

AU - Henry, Todd J.

AU - Cloutier, Ryan

AU - Kostov, Veselin B.

AU - Kruse, Ethan

AU - Winters, Jennifer G.

AU - Irwin, Jonathan M.

AU - Kane, Stephen R.

AU - Stassun, Keivan G.

AU - Huang, Chelsea

AU - Kunimoto, Michelle

AU - Tey, Evan

AU - Vanderburg, Andrew

AU - Astudillo-Defru, Nicola

AU - Bonfils, Xavier

AU - Brasseur, C. E.

AU - Charbonneau, David

AU - Ciardi, David R.

AU - Collins, Karen A.

AU - Collins, Kevin I.

AU - Conti, Dennis M.

AU - Crossfield, Ian J. M.

AU - Daylan, Tansu

AU - Doty, John P.

AU - Dressing, Courtney D.

AU - Gilbert, Emily A.

AU - Horne, Keith

AU - Jenkins, Jon M.

AU - Latham, David W.

AU - Mann, Andrew W.

AU - Matthews, Elisabeth

AU - Paredes, Leonardo A.

AU - Quinn, Samuel N.

AU - Ricker, George R.

AU - Schwarz, Richard P.

AU - Seager, Sara

AU - Sefako, Ramotholo

AU - Shporer, Avi

AU - Smith, Jeffrey C.

AU - Stockdale, Christopher

AU - Tan, Thiam-Guan

AU - Torres, Guillermo

AU - Twicken, Joseph D.

AU - Vanderspek, Roland

AU - Wang, Gavin

N1 - Funding: The MEarth Team gratefully acknowledges funding from the David and Lucile Packard Fellowship for Science and Engineering (awarded to D.C.). This material is based upon work supported by the National Science Foundation under grants AST-0807690, AST-1109468, AST-1004488 (Alan T. Waterman Award), and AST-1616624, and upon work supported by the National Aeronautics and Space Administration under Grant No. 80NSSC18K0476 issued through the XRP Program. This work is made possible by a grant from the John Templeton Foundation. N. A.-D. acknowledges the support of FONDECYT project 3180063. TD acknowledges support from MIT’s Kavli Institute as a Kavli postdoctoral fellow. KH acknowledges support from STFC grant ST/R000824/1. E.A.G. thanks the LSSTC Data Science Fellowship Program, which is funded by LSSTC, NSF Cybertraining Grant #1829740, the Brinson Foundation, and the Moore Foundation; The material is based upon work supported by NASA under award number 80GSFC21M0002. This work was supported by the lead author’s appointment to the NASA Postdoctoral Program at the Goddard Space Flight Center, administered by Universities Space Research Association under contract with NASA

PY - 2022/4/1

Y1 - 2022/4/1

N2 - We present the Transiting Exoplanet Survey Satellite (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 (VJ = 12.5, Ks = 8.3) M2 dwarf at 19.9 pc. The two TESS-detected planets are of radius 0.70 ± 0.04 R⊕ and 0.98 ± 0.06 R⊕ in 0.86 day and 3.69 day orbits, respectively. Both planets are validated and characterized via ground-based follow-up observations. High Accuracy Radial Velocity Planet Searcher RV monitoring yields 97.7 percentile mass upper limits of 0.35 M⊕ and 1.4 M⊕ for planets b and c, respectively. The astrometric companion detected by the Cerro Tololo Inter-American Observatory/Small and Moderate Aperture Telescope System 0.9 m 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 James Webb Space Telescope and mass measurements via extreme-precision radial velocity. A third planet candidate of radius 0.9 ± 0.1 R⊕ in a 4.97 day orbit is also identified in multicycle 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.

AB - We present the Transiting Exoplanet Survey Satellite (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 (VJ = 12.5, Ks = 8.3) M2 dwarf at 19.9 pc. The two TESS-detected planets are of radius 0.70 ± 0.04 R⊕ and 0.98 ± 0.06 R⊕ in 0.86 day and 3.69 day orbits, respectively. Both planets are validated and characterized via ground-based follow-up observations. High Accuracy Radial Velocity Planet Searcher RV monitoring yields 97.7 percentile mass upper limits of 0.35 M⊕ and 1.4 M⊕ for planets b and c, respectively. The astrometric companion detected by the Cerro Tololo Inter-American Observatory/Small and Moderate Aperture Telescope System 0.9 m 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 James Webb Space Telescope and mass measurements via extreme-precision radial velocity. A third planet candidate of radius 0.9 ± 0.1 R⊕ in a 4.97 day orbit is also identified in multicycle 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.

KW - Exoplanet systems

KW - Transit photometry

KW - Low mass stars

KW - M dwarf stars

KW - Astrometric binary stars

U2 - 10.3847/1538-3881/ac32e3

DO - 10.3847/1538-3881/ac32e3

M3 - Article

SN - 0004-6256

VL - 163

JO - Astronomical Journal

JF - Astronomical Journal

IS - 4

M1 - 151

ER -

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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