J/AJ/165/88ivo://CDS.VizieR/J/AJ/165/88doi:10.26093/cds/vizier.51650088CDSBrinkman C.L.Weiss L.M.Dai F.Huber D.Kite E.S.Valencia D.,Bean J.L.Beard C.Behmard A.Blunt S.Brady M.Fulton B.,Giacalone S.Howard A.W.Isaacson H.Kasper D.Lubin J.,MacDougall M.Akana Murphy J.M.Plotnykov M.Polanski A.S.Rice M.,Seifahrt A.Stefansson G.Sturmer J.2024-02-12T10:51:16Z2023-06-16T07:12:55ZCDS support team

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

cds-question@unistra.frexoplanetschemically-peculiar-starsvisible-astronomyspectroscopyradial-velocityTOI-561 is a galactic thick-disk star hosting an ultra-short-period (0.45-day-orbit) planet with a radius of 1.37R{Earth}, making it one of the most metal-poor ([Fe/H]=-0.41) and oldest ({~10Gyr) sites where an Earth-sized planet has been found. We present new simultaneous radial velocity (RVel) measurements from Gemini-N/MAROON-X and Keck/HIRES, which we combined with literature RVels to derive a mass of Mb=2.24{+/-}0.20M{Earth}. We also used two new sectors of TESS photometry to improve the radius determination, finding Rb=1.37{+/-}0.04R{Earth} and confirming that TOI-561b is one of the lowest-density super-Earths measured to date ({rho}b=4.8{+/-}0.5g/cm^3^). This density is consistent with an iron-poor rocky composition reflective of the host star's iron and rock-building element abundances; however, it is also consistent with a low-density planet with a volatile envelope. The equilibrium temperature of the planet ({~2300K) suggests that this envelope would likely be composed of high mean molecular weight species, such as water vapor, carbon dioxide, or silicate vapor, and is likely not primordial. We also demonstrate that the composition determination is sensitive to the choice of stellar parameters and that further measurements are needed to determine whether TOI-561b is a bare rocky planet, a rocky planet with an optically thin atmosphere, or a rare example of a nonprimordial envelope on a planet with a radius smaller than 1.5R{Earth}.2023AJ....165...88Bhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/AJ/165/88CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/ApJS/210/20 : Small Kepler planets radial velocities (Marcy+, 2014)J/ApJ/800/135 : HARPS-N radial velocities of KOI-69 (Dressing+, 2015)J/ApJ/822/86 : False positive probabilities Q1-Q17 DR24 KOIs (Morton+, 2016)J/AJ/154/109 : California-Kepler Survey. III. Planet radii (Fulton+, 2017)J/ApJ/844/102 : KICstar parallaxes from asteroseismology vs Gaia (Huber+, 2017)J/AJ/153/136 : Planets and host stars with Gaia parallaxes (Stassun+, 2017)J/A+A/653/A41 : L 98-59 (TOI-175) ESPRESSO observations (Demangeon+, 2021)J/AJ/161/56 : The TESS-Keck Survey. II. RVs of TOI-561 (Weiss+, 2021)J/AJ/162/55 : 65 Transit-timing variation planets properties (Yee+, 2021)J/MNRAS/511/4551 : TOI-561 CHEOPS light curves (Lacedelli+, 2022)J/AJ/163/168 : Photometry and radial velocity of LTT 1445A (Winters+, 2022)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/AJ/165/88https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/AJ/165/88http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/AJ/165/88https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/AJ/165/88https://vizier.iucaa.in/viz-bin/votable?-source=J/AJ/165/88http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/AJ/165/88GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticaldefaultJ/AJ/165/88/table3Radial velocitiesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintBJD[2458599/2459650] Barycentric Julian Datedtime.epochdoubleRVel[-12.4/12.6] Radial velocitym/sphys.veloc;pos.heliocentricfloate_RVel[0.6/6] Uncertainty in RVelm/sstat.error;spect.dopplerVelocfloatInstSpectrograph; HARPS, HIRES, or MAROONmeta.id;instrchar