J/AJ/158/133ivo://CDS.VizieR/J/AJ/158/133doi:10.26093/cds/vizier.51580133CDSHamann A.Montet B.T.Fabrycky D.C.Agol E.Kruse E.2019-11-06T07:50:42Z2019-11-06T08:41:13ZCDS support team

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

cds-question@unistra.frdwarf-starsm-starsphotometryexoplanetsK2-146 is a mid-M dwarf (M_*_=0.331+/-0.009 M_{sun}_; R_*_=0.330+/-0.010 R_{sun}_), observed in Campaigns 5, 16, and 18 of the K2 mission. In Campaign 5 data, a single planet was discovered with an orbital period of 2.6 days and large transit timing variations due to an unknown perturber. Here, we analyze data from Campaigns 16 and 18, detecting the transits of a second planet, c, with an orbital period of 4.0 days, librating in a 3:2 resonance with planet b. Large, anticorrelated timing variations of both planets exist due to their resonant perturbations. The planets have a mutual inclination of 2.40{deg}+/-0.25{deg}, which torqued planet c more closely into our line of sight. Planet c was grazing in Campaign 5 and thus missed in previous searches; it is fully transiting in Campaigns 16 and 18, and its transit depth is three times larger. We improve the stellar properties using data from Gaia DR2 (Cat. I/345), and use dynamical fits to find that both planets are sub-Neptunes: their masses are 5.77+/-0.18 and 7.50+/-0.23 M_{Earth}_, and their radii are 2.04+/-0.06 and 2.19+/-0.07 R_{Earth}_, respectively. These mass constraints set the precision record for small exoplanets (a few gas giants have comparable relative precision). These planets lie in the photoevaporation valley when viewed in Radius-Period space, but due to the low-luminosity M-dwarf host star, they lie among the atmosphere-bearing planets when viewed in Radius-Irradiation space. This, along with their densities being 60-80% that of Earth, suggests that they may both have retained a substantial gaseous envelope.2019AJ....158..133Hhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/AJ/158/133CatalogResearchIsServedByTAP VizieR generic servicerelated-toI/345 : Gaia DR2 (Gaia Collaboration, 2018)J/PASP/124/1279 : Q3 Kepler's combined photometry (Christiansen+, 2012)J/ApJS/224/2 : K2 EPIC stellar properties for 138600 targets (Huber+, 2016)J/AJ/154/207 : K2 planetary systems orbiting low-mass starsJ/AJ/155/21 : Planet candidates from K2 campaigns 5-8 (Petigura+, 2018)J/AJ/156/22 : Planetary candidates from K2 Campaign 16 (Yu+, 2018)J/AJ/156/277 : Sixty validated planets from K2 campaigns 5-8https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/AJ/158/133https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/AJ/158/133http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/AJ/158/133https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/AJ/158/133https://vizier.iucaa.in/viz-bin/votable?-source=J/AJ/158/133http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/AJ/158/133GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapdefaultJ/AJ/158/133/table4Differential Evolution Markov Chain Monte Carlo (DEMCMC) dynamical samplesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintrho*[6.44887750696/12.4918984765] Stellar density, relative to the Sun, {rho}_*_Sunphot.mag.sb;phys.density;arith.ratiodoublePb[2.64439278952/2.64481606882] Period for planet bdtime.perioddoubleT0b[3371.58808107/3371.59223826] Time of a sample transit for planet b (BKJD)dtime.epochdoublesecwb[0.01181286323/0.33187384921] sqrt(e)cos{omega} for planet bsrc.orbital.eccentricitydoubleseswb[-0.39092356579/-0.23995868521] sqrt(e)sin{omega} for planet bsrc.orbital.eccentricitydoubleib[88.5693239327/89.4510052858] Inclination for planet bdegsrc.orbital.inclinationdoubleOmegab[0] Longitude of periastron {Omega} for planet bdegsrc.orbital.periastronintMb[0.01729664139/0.01873442648] Mass of planet b(1.898187x10+27kg)phys.massdoubleRb[0.0554467/0.0592313] Radius of planet b, relative to starphys.size;arith.ratiodoublePc[4.00457876322/4.0053746211] Period for planet cdtime.perioddoubleT0c[3371.12891058/3371.13425933] Time of a sample transit for planet c (BKJD)dtime.epochdoublesecwc[-0.29730700286/-0.00691265158] sqrt(e)cos{omega} for planet csrc.orbital.eccentricitydoubleseswc[0.0494574229/0.2858422551] sqrt(e)sin{omega} for planet csrc.orbital.eccentricitydoubleic[87.4198453867/87.65620229] Inclination for planet cdegsrc.orbital.inclinationdoubleOmegac[0.8118583802/2.95924502312] Longitude of periastron {Omega} for planet cdegsrc.orbital.periastrondoubleMc[0.02243419248/0.02433098732] Mass of planet c(1.898187x10+27kg)phys.massdoubleRc[0.0573228/0.0648858] Radius of planet c, relative to starphys.size;arith.ratiodoubleJ/AJ/158/133/transitPredicted transit times for planet b (table 5) and planet c (table 6)N[0/610] Transit numbermeta.idintPlanetPlanet b/cmeta.code.multipcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintt[3371.13159/4992.44805] Transit time (BKJD)dtime.epochdoublee_t[0.36/20.0592] Uncertainty in tminstat.errorfloatJ/AJ/158/133/fig1aLong cadence light curve for K2-146 during C16recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTime[2306.61/4985.3] Observation date (BKJD) (Time (BKJD))dtime.epoch;obsdoubleFlux[-0.597158/1.02738] Relative flux (Relative Flux)phot.flux;arith.ratiodoubleJ/AJ/158/133/fig1bShort cadence light curve for K2-146 during C16recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTime[2306.61/4985.3] Observation date (BKJD) (Time (BKJD))dtime.epoch;obsdoubleFlux[-0.597158/1.02738] Relative flux (Relative Flux)phot.flux;arith.ratiodoubleJ/AJ/158/133/fig1cLong cadence light curve for K2-146 during C18recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTime[2306.61/4985.3] Observation date (BKJD) (Time (BKJD))dtime.epoch;obsdoubleFlux[-0.597158/1.02738] Relative flux (Relative Flux)phot.flux;arith.ratiodoubleJ/AJ/158/133/fig1dShort cadence light curve for K2-146 during C18recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTime[2306.61/4985.3] Observation date (BKJD) (Time (BKJD))dtime.epoch;obsdoubleFlux[-0.597158/1.02738] Relative flux (Relative Flux)phot.flux;arith.ratiodoubleJ/AJ/158/133/fig1eLong cadence light curve for K2-146 during C5recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTime[2306.61/4985.3] Observation date (BKJD) (Time (BKJD))dtime.epoch;obsdoubleFlux[-0.597158/1.02738] Relative flux (Relative Flux)phot.flux;arith.ratiodouble