J/AJ/161/23ivo://CDS.VizieR/J/AJ/161/23doi:10.26093/cds/vizier.51610023CDSMent K.Irwin J.Charbonneau D.Winters J.G.Medina A.Cloutier R.,Diaz M.R.Jenkins J.S.Ziegler C.Law N.Mann A.W.Ricker G.,Vanderspek R.Latham D.W.Seager S.Winn J.N.Jenkins J.M.Goeke R.F.,Levine A.M.Rojas-Ayala B.Rowden P.Ting E.B.Twicken J.D.2022-09-30T21:45:21Z2021-03-12T09:09:17ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frexoplanetsdwarf-starsvisible-astronomyspectroscopyphotometryradial-velocityWe present the discovery of TOI540b, a hot planet slightly smaller than Earth orbiting the low-mass star 2MASSJ05051443-4756154. The planet has an orbital period of P=1.239149 days({+/-}170ms) and a radius of r=0.903{+/-}0.052R{Earth}, and is likely terrestrial based on the observed mass- radius distribution of small exoplanets at similar insolations. The star is 14.008pc away and we estimate its mass and radius to be M=0.159{+/-}0.014M{sun} and R=0.1895{+/-}0.0079R{sun}, respectively. The star is distinctive in its very short rotational period of Prot=17.4264{+/-}0.0094hr and correspondingly small Rossby number of 0.007 as well as its high X-ray-to-bolometric luminosity ratio of L_X_/L_bol_=0.0028 based on a serendipitous XMM-Newton detection during a slew operation. This is consistent with the X-ray emission being observed at a maximum value of L_X_/L_bol_~10^-3^ as predicted for the most rapidly rotating M dwarfs. TOI540b may be an alluring target to study atmospheric erosion due to the strong stellar X-ray emission. It is also among the most accessible targets for transmission and emission spectroscopy and eclipse photometry with the James Webb Space Telescope, and may permit Doppler tomography with high-resolution spectroscopy during transit. This discovery is based on precise photometric data from the Transiting Exoplanet Survey Satellite and ground-based follow-up observations by the MEarth team.2021AJ....161...23Mhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/AJ/161/23CatalogResearchIsServedByTAP VizieR generic servicerelated-toI/345 : Gaia DR2 (Gaia Collaboration, 2018)VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)J/ApJ/757/112 : Stellar diameters. II. K and M-stars (Boyajian+, 2012)J/ApJS/208/9 : Intrinsic colors and temperatures of PMS stars (Pecaut+, 2013)J/AJ/148/119 : UCAC4 nearby star survey (Finch+, 2014)J/ApJ/807/45 : Potentially habitable planets orbiting dwarfs (Dressing+,2015)J/ApJ/800/135 : HARPS-N radial velocities of KOI-69 (Dressing+, 2015)J/ApJ/804/64 : Empirical and model parameters of 183 M dwarfs (Mann+, 2015)J/A+A/584/A72 : A transiting rocky planet at 6.5pc from Sun (Motalebi+, 2015)J/AJ/152/141 : Solar neighborhood. XXXVII. RVs for M dwarfs (Benedict+, 2016)J/A+A/588/A103 : Second ROSAT all-sky survey source catalog (Boller+, 2016)J/ApJ/829/23 : Stellar flares from Q0-Q17 Kepler LCs (Davenport, 2016)J/ApJ/821/93 : Rotation & Galactic kinematics of mid M dwarfs (Newton+, 2016)J/AJ/154/109 : California-Kepler Survey. III. Planet radii (Fulton+, 2017)J/A+A/618/A142 : Radial velocity for GJ 1132 (Bonfils+, 2018)J/A+A/618/A20 : Limb-darkening for TESS, Kepler, Corot, MOST (Claret, 2018)J/ApJ/856/23 : BANYAN. XI. The BANYAN {Sigma} algorithm (Gagne+, 2018)J/AJ/156/140 : 4 new eclipsing mid M-dwarf systems from MEarth (Irwin+, 2018)J/AJ/156/217 : Stellar properties for M dwarfs in MEarth-South (Newton+,2018)J/AJ/156/102 : TESS Input Catalog and Candidate Target List (Stassun+, 2018)J/A+A/629/A111 : L 98-59 (TOI 175) HARPS observations (Cloutier+, 2019)J/A+A/628/A39 : Radial velocities of GJ 357 (Luque+, 2019)J/AJ/160/3 : Radial velocities M-dwarf LTT3780 with HARPS (Cloutier+, 2020)J/AJ/159/211 : Exoplanets parameters from Kepler and K2 (Cloutier+, 2020)J/AJ/160/22 : TOI-1235 Radial velocities & optical spectro. (Cloutier+,2020)J/AJ/159/290 : RVs of 12 spectroscopic binaries M-dwarfs (Winters+, 2020)J/AJ/159/19 : SOAR TESS survey. I. (Ziegler+, 2020)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/AJ/161/23https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/AJ/161/23http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/AJ/161/23https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/AJ/161/23https://vizier.iucaa.in/viz-bin/votable?-source=J/AJ/161/23http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/AJ/161/23GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticaldefaultJ/AJ/161/23/table1RV data for TOI 540recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintBJDBarycentric Julian Date at TBDdtime.epochdoubleRVel[18.34/18.91] Barycentric Radial Velocitykm/sphys.veloc;pos.heliocentricfloate_RVel[0.12/0.2] Uncertainty in RVelkm/sstat.error;phys.veloc;pos.heliocentricfloatInstInstrument (1)meta.id;instrcharJ/AJ/161/23/fig1TESS photometry of TOI 540 from Sectors 4-6recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintBJDBarycentric Julian Datedtime.epochdoubleindexedFluxFlux (magnitude difference)magphot.flux.density;em.optdoublee_FluxUncertainty in Fluxmagstat.error;phot.fluxdoubleJ/AJ/161/23/fig2Follow-up photometry of TOI 540 from all 8 MEarth telescopes by nightrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintBJDBarycentric Julian Datedtime.epochdoubleindexedFluxFlux (magnitude difference)magphot.flux.density;em.optdoublee_FluxUncertainty in Fluxmagstat.error;phot.fluxdouble