J/AJ/159/100ivo://CDS.VizieR/J/AJ/159/100doi:10.26093/cds/vizier.51590100CDSStefansson G.Canas C.Wisniewski J.Robertson P.Mahadevan S.,Maney M.Kanodia S.Beard C.Bender C.F.Brunt P.Clemens J.C.,Cochran W.Diddams S.A.Endl M.Ford E.B.Fredrick C.Halverson S.,Hearty F.Hebb L.Huehnerhoff J.Jennings J.Kaplan K.Levi E.,Lubar E.Metcalf A.J.Monson A.Morris B.Ninan J.P.Nitroy C.,Ramsey L.Roy A.Schwab C.Sigurdsson S.Terrien R.Wright J.T.2021-06-18T13:41:03Z2020-10-08T09:40:43ZCDS support team

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

cds-question@unistra.frexoplanetsdwarf-starsvariable-starsinfrared-photometryvisible-astronomyradial-velocitystellar-massesstellar-agesWe validate the discovery of a 2-Earth-radii sub-Neptune-sized planet around the nearby high-proper-motion M2.5 dwarf G9-40 (EPIC212048748), using high-precision, near-infrared (NIR) radial velocity (RV) observations with the Habitable-zone Planet Finder (HPF), precision diffuser-assisted ground-based photometry with a custom narrowband photometric filter, and adaptive optics imaging. At a distance of d=27.9pc, G9-40b is the second-closest transiting planet discovered by K2 to date. The planet's large transit depth (~3500ppm), combined with the proximity and brightness of the host star at NIR wavelengths (J=10, K=9.2), makes G9-40b one of the most favorable sub-Neptune-sized planets orbiting an M dwarf for transmission spectroscopy with James Webb Space Telescope, ARIEL, and the upcoming Extremely Large Telescopes. The star is relatively inactive with a rotation period of ~29days determined from the K2 photometry. To estimate spectroscopic stellar parameters, we describe our implementation of an empirical spectral-matching algorithm using the high-resolution NIR HPF spectra. Using this algorithm, we obtain an effective temperature of Teff=3404{+/-}73K and metallicity of [Fe/H]=-0.08{+/-}0.13. Our RVs, when coupled with the orbital parameters derived from the transit photometry, exclude planet masses above 11.7M{Earth} with 99.7% confidence assuming a circular orbit. From its radius, we predict a mass of M=5.0_-1.9_^+3.8^M_{Earth}_ and an RV semiamplitude of K=4.1_-1.6_^+3.1^m/s, making its mass measurable with current RV facilities. We urge further RV follow-up observations to precisely measure its mass, to enable precise transmission spectroscopic measurements in the future.2020AJ....159..100Shttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/AJ/159/100CatalogResearchIsServedByTAP VizieR generic servicerelated-toII/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)I/289 : UCAC2 Catalogue (Zacharias+ 2004)I/298 : LSPM-North Catalog (Lepine+ 2005)II/328 : AllWISE Data Release (Cutri+ 2013)IV/34 : K2 Ecliptic Plane Input Catalog (EPIC) (Huber+, 2017)I/345 : Gaia DR2 (Gaia Collaboration, 2018)J/AJ/128/463 : A preliminary 20pc census from the NLTT cat. (Reid+,2004)J/AJ/135/907 : Variables in Praesepe identified with KELT (Pepper+,2008)J/ApJS/200/15 : HARPS-TERRA project. I. (Anglada-Escude+, 2012)J/AJ/143/93 : Rotational velocities in early-M stars (Reiners+, 2012)J/ApJ/757/161 : Spectroscopy of 56 exoplanet host stars (Torres+, 2012)J/ApJ/775/L11 : Stellar rotation periods for KOIs (McQuillan+, 2013)J/ApJS/224/2 : K2 EPIC stellar properties, 138600 targets (Huber+, 2016)J/ApJ/825/19 : Mass-radius relation for planets Rp<4 (Wolfgang+, 2016)J/ApJ/834/17 : Mass & radius planets, moons, low mass stars (Chen+,2017)J/AJ/154/207 : K2 planetary syst. orbit. low-mass stars (Dressing+,2017)J/AJ/154/109 : CKS. III. Planet radii (Fulton+, 2017)J/AJ/153/71 : Kepler follow-up obs. program. I. Imaging (Furlan+, 2017)J/ApJ/836/77 : Library of high-S/N opt. spectra FGKM stars (Yee+, 2017)J/A+A/612/A49 : 324 CARMENES M dwarfs velocities (Reiners+, 2018)J/other/Nat/563.365 : Barnard's star radial velocity curve (Ribas+, 2018)J/AJ/156/22 : Planetary candidates from K2 Campaign 16 (Yu+, 2018)J/A+A/629/A111 : L 98-59 (TOI 175) HARPS observations (Cloutier+, 2019)J/AJ/158/87 : 86 cool dwarfs obs. during K2 Campaigns (Dressing+, 2019)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/AJ/159/100https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/AJ/159/100http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/AJ/159/100https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/AJ/159/100https://vizier.iucaa.in/viz-bin/votable?-source=J/AJ/159/100http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/AJ/159/100GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticalInfrareddefaultJ/AJ/159/100/table6Radial velocities of G 9-40 from Habitable-zone Planet Finder (HPF)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSNR[103/149] Spectrum signal-to-noisestat.snrfloatBJD[2458543/2458591] Barycentric Julian date of HPF observation, in TDB (1)dtime.epochdoubleRVel[-10.9/11.3] Habitable zone Planet Finder Radial Velocitym/sphys.veloc;pos.heliocentricfloate_RVel[5.96/10.5] Total RVel uncertainty, including RVel-d in quadraturem/sstat.error;spect.dopplerVelocfloatRVel-d[0.02/0.31] estimated RVel drift errorm/sphys.veloc;pos.heliocentricfloatJ/AJ/159/100/fig7K2 and ground-based diffuser-assisted photometry of G 9-40recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintBJD[2458497/2458498] Barycentric Julian date of diffuser observation, in TDBdtime.epochdoublefluxn[0.99/1.01] Normalized flux, not detrendedphot.flux;arith.ratiodoublefluxd[0.99/1.01] Detrended flux; same as flux after taking out a linephot.flux;arith.ratiodoublee_fluxd[0.001/0.002] Error in flux, includes scintillation error estimatestat.errordoubleres[-0.004/0.005] Residual, detrended-model (flux-d - flux-m)stat.fit.residualdoublefluxm[0.99/1] Best fit model fluxphot.flux;arith.ratiodoubleairmass[1.04/1.56] Airmass of the observationobs.airMassdouble