GJ 1252 b: a 1.2 R planet transiting an M-dwarf at 20.4 pc

Avi Shporer, Karen A. Collins, Nicola Astudillo-Defru, Jonathan Irwin, Xavier Bonfils, Kevin I. Collins, Elisabeth Matthews, Jennifer G. Winters, David R. Anderson, James D. Armstrong, David Charbonneau, Ryan Cloutier, Tansu Daylan, Tianjun Gan, Maximilian N. Günther, Coel Hellier, Keith Horne, Chelsea X. Huang, Eric L. N. Jensen, John KielkopfEnric Palle, Ramotholo Sefako, Keivan G. Stassun, Thiam-Guan Tan, Andrew Vanderburg, George R. Ricker, David W. Latham, Roland Vanderspek, Sara Seager, Joshua N. Winn, Jon M. Jenkins, Knicole Colon, Courtney D. Dressing, Sébastien Lépine, Philip S. Muirhead, Mark E. Rose, Joseph D. Twicken, Jesus Noel Villasenor

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We report the discovery of GJ 1252 b, a planet with a radius of 1.193 ± 0.074  and an orbital period of 0.52 days around an M3-type star (0.381 ± 0.019 , 0.391 ± 0.020 ) located 20.385 ± 0.019 pc away. We use Transiting Exoplanet Survey Satellite (TESS) data, ground-based photometry and spectroscopy, Gaia astrometry, and high angular resolution imaging to show that the transit signal seen in the TESS data must originate from a transiting planet. We do so by ruling out all false-positive scenarios that attempt to explain the transit signal as originating from an eclipsing stellar binary. Precise Doppler monitoring also leads to a tentative mass measurement of 2.09 ± 0.56 M . The host star proximity, brightness (V = 12.19 mag, K = 7.92 mag), low stellar activity, and the system's short orbital period make this planet an attractive target for detailed characterization, including precise mass measurement, looking for other objects in the system, and planet atmosphere characterization.
Original languageEnglish
JournalAstrophysical Journal
Issue number1
Publication statusPublished - 10 Feb 2020


  • Exoplanet astronomy
  • M dwarf stars
  • Exoplanets


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