J/AJ/161/56ivo://CDS.VizieR/J/AJ/161/56doi:10.26093/cds/vizier.51610056CDSWeiss L.M.Dai F.Huber D.Brewer J.M.Collins K.A.Ciardi D.R.,Matthews E.C.Ziegler C.Howell S.B.Batalha N.M.Crossfield I.J.M.,Dressing C.Fulton B.Howard A.W.Isaacson H.Kane S.R.Petigura E.A.,Robertson P.Roy A.Rubenzahl R.A.Twicken J.D.Claytor Z.R.,Stassun K.G.MacDougall M.G.Chontos A.Giacalone S.Dalba P.A.,Mocnik T.Hill M.L.Beard C.Akana Murphy J.M.Rosenthal L.J.,Behmard A.Van Zandt J.Lubin J.Kosiarek M.R.Lund M.B.,Christiansen J.L.Matson R.A.Beichman C.A.Schlieder J.E.,Gonzales E.J.Briceno C.Law N.Mann A.W.Collins K.I.Evans P.,Fukui A.Jensen E.L.N.Murgas F.Narita N.Palle E.Parviainen H.,Schwarz R.P.Tan T.-G.Acton J.S.Bryant E.M.Chaushev A.Gill S.,Eigmuller P.Jenkins J.Ricker G.Seager S.Winn J.N.2025-05-05T20:07:35Z2021-04-08T08:04:59ZCDS support team

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

cds-question@unistra.frexoplanetschemically-peculiar-starsvisible-astronomyspectroscopyradial-velocityWe report the discovery of TOI-561, a multiplanet system in the galactic thick disk that contains a rocky, ultra-short-period planet. This bright (V=10.2) star hosts three small transiting planets identified in photometry from the NASA TESS mission: TOI-561b (TOI-561.02, P=0.44days, Rp=1.45{+/-}0.11R{Earth}), c (TOI-561.01, P=10.8days, Rp=2.90{+/-}0.13R{Earth}), and d (TOI-561.03, P=16.3days, Rp=2.32{+/-}0.16R{Earth}). The star is chemically ([Fe/H]=-0.41{+/-}0.05, [{alpha}/Fe]=+0.23{+/-}0.05) and kinematically consistent with the galactic thick-disk population, making TOI-561 one of the oldest (10{+/-}3Gyr) and most metal-poor planetary systems discovered yet. We dynamically confirm planets b and c with radial velocities from the W.M.Keck Observatory High Resolution Echelle Spectrometer. Planet b has a mass and density of 3.2{+/-}0.8M{Earth} and 5.5_-1.6_^+2.0^g/cm^3^, consistent with a rocky composition. Its lower- than-average density is consistent with an iron-poor composition, although an Earth-like iron-to-silicates ratio is not ruled out. Planet c is 7.0{+/-}2.3M{Earth} and 1.6{+/-}0.6g/cm^3^, consistent with an interior rocky core overlaid with a low-mass volatile envelope. Several attributes of the photometry for planet d (which we did not detect dynamically) complicate the analysis, but we vet the planet with high-contrast imaging, ground-based photometric follow-up, and radial velocities. TOI-561b is the first rocky world around a galactic thick-disk star confirmed with radial velocities and one of the best rocky planets for thermal emission studies.2021AJ....161...56Whttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/AJ/161/56CatalogResearchIsServedByTAP VizieR generic servicerelated-toI/345 : Gaia DR2 (Gaia Collaboration, 2018)J/A+A/415/155 : Oxygen abundances in the Galactic disk (Bensby+, 2004)J/A+A/433/185 : Detailed abund. analysis of 102 F and G dwarfs (Bensby+, 2005)J/A+A/512/A54 : Teff and Fbol from Infrared Flux Method (Casagrande+, 2010)J/ApJ/725/875 : Chromospheric activity for CPS stars (Isaacson+, 2010)J/AJ/142/19 : Speckle observations of KOI (Howell+, 2011)J/A+A/545/A32 : Chemical abundances of 1111 FGK stars (Adibekyan+, 2012)J/other/Nat/486.375 : Stellar parameters of KOI stars (Buchhave+, 2012)J/ApJ/776/67 : Rotational tracks (van Saders+, 2013)J/A+A/562/A71 : Chemical abund. of solar neighbourhood dwarfs (Bensby+, 2014)J/ApJ/789/154 : Kepler-10 RV measurements by HARPS-N (Dumusque+, 2014)J/AJ/148/54 : The Hypatia Catalog ((Hinkel+, 2014)J/ApJ/787/47 : 106 Kepler ultra-short-period planets (Sanchis-Ojeda+, 2014)J/ApJS/225/32 : Extended abundance analysis of cool stars (Brewer+, 2016)J/AJ/154/226 : Photometry and radial velocities of K2-131 (Dai+, 2017)J/AJ/153/71 : Kepler follow-up observation program I Imaging (Furlan+, 2017)J/ApJ/844/102 : KIC star plxs from asteroseismology vs Gaia (Huber+, 2017)J/AJ/153/136 : Planets and host stars with Gaia parallaxes (Stassun+, 2017)J/ApJ/836/77 : Library of high-S/N optical spectra of FGKM stars (Yee+, 2017)J/MNRAS/473/2004 : TESS-HERMES Survey Data Release 1 catalog (Sharma+, 2018)J/AJ/156/102 : TESS Input Catalog and Candidate Target List (Stassun+, 2018)J/AJ/155/235 : Speckle interferometry SOAR in 2016 & 2017 (Tokovinin+, 2018)J/AJ/155/48 : California-Kepler Survey V. Masses and radii (Weiss+, 2018)J/A+A/636/A58 : L 168-9 radial velocity curve (Astudillo-Defru+, 2020)J/AJ/159/241 : TESS-Keck Survey. I. HD332231 Radial Velocities (Dalba+, 2020)J/AJ/159/239 : Transmission Spectroscopy Metric of exoplanets (Guo+, 2020)J/AJ/160/138 : 68 Gaia DR2 ultra-short-period planet host stars (Hamer+,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/161/56https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/AJ/161/56http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/AJ/161/56https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/AJ/161/56https://vizier.iucaa.in/viz-bin/votable?-source=J/AJ/161/56http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/AJ/161/56GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticaldefaultJ/AJ/161/56/table2Radial VelocitiesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintBJD[2458599/2459183] Barycentric Julian Datedtime.epochdoubleRVel[-11.3/9.5] Radial velocitym/sphys.veloc;pos.heliocentricfloate_RVel[1.1/1.9] Uncertainty in RVelm/sstat.error;spect.dopplerVelocfloatS-Val[0.12/0.16] Mt. Wilson S-Value (1)meta.codefloate_S-Val[0.001] Uncertainty in SValstat.errorfloat