J/AJ/170/51ivo://CDS.VizieR/J/AJ/170/51CDSTeng H.-Y.Dai F.Howard A.W.Halverson S.Isaacson H.Kokubo E.,Rubenzahl R.A.Fulton B.Householder A.Lubin J.Giacalone S.,Handley L.Van Zandt J.Petigura E.A.Ong J.M.J.Premnath P.Yu H.,Gibson S.R.Rider K.Roy A.Baker A.Edelstein J.Smith C.,Walawender J.Lee B.-C.Liu Y.-J.Winn J.N.2026-04-29T14:10:05Z2026-04-29T15:02:06ZCDS support team

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

cds-question@unistra.frexoplanetsradial-velocityspectroscopyvisible-astronomyWe report an observation of the Rossiter-McLaughlin (RM) effect of the transiting planet HD 93963 Ac, a mini-Neptune planet orbiting a G0-type star with an orbital period of P_c_=3.65d, accompanied by an inner super-Earth planet with P_b_=1.04d. We observed a full transit of planet c on 2024 May 3 UT with the Keck/Keck Planet Finder. The observed RM effect has an amplitude of ~1m/s and implies a sky-projected obliquity of {lambda}=14_-19_^+17^ degrees for HD 93963 Ac. Our dynamical analysis suggests that the two inner planets are likely well aligned with the stellar spin, to within a few degrees, thus allowing both to transit. Along with WASP-47, 55 Cnc, and HD 3167, HD 93963 is the fourth planetary system with an ultrashort-period planet and obliquity measurement(s) of any planet(s) in the system. HD 93963, WASP-47, and 55 Cnc favor largely coplanar orbital architectures, whereas HD 3167 has been reported to have a large mutual inclination (~100{deg}) between its transiting planets b and c. In this configuration, the probability that both planets transit is low. Moreover, one planet would quickly evolve to be nontransiting due to nodal precession. Future missions such as ESO/PLATO should detect the resulting transit duration variations. We encourage additional obliquity measurements of the HD 3167 system to better constrain its orbital architecture.2025AJ....170...51Thttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/AJ/170/51CatalogResearchIsServedByTAP VizieR generic servicerelated-toI/350 : Gaia EDR3 (Gaia Collaboration, 2020)I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)VI/120 : High-resolution synthetic stellar library (Coelho+, 2005)J/ApJS/159/141 : Spectroscopic properties of cool stars. I. (Valenti+, 2005)J/ApJ/757/18 : RVs for 16 hot Jupiter host stars (Albrecht+, 2012)J/ApJ/790/146 : Planets in Kepler's multi-transiting systems (Fabrycky+, 2014)J/ApJ/787/47 : 106 Kepler ultra-short-period planets (Sanchis-Ojeda+, 2014)J/ApJ/821/47 : KOI transit proba. of multi-planet syst. (Brakensiek+, 2016)J/AJ/154/109 : California-Kepler Surv. (CKS). III. Planet radii (Fulton+, 2017)J/ApJ/844/102 : KIC star plxs from asteroseismology vs Gaia (Huber+, 2017)J/AJ/154/107 : California-Kepler Survey (CKS). I. 1305 stars (Petigura+, 2017)J/ApJ/836/77 : A library of high-S/N optical spectra of FGKM stars (Yee+, 2017)J/AJ/156/264 : California-Kepler Survey. VII. Planet radius gap (Fulton+, 2018)J/AJ/155/48 : California-Kepler Survey (CKS). V. Masses & radii (Weiss+, 2018)J/A+A/667/A1 : HD93963 CHEOPS light curves (Serrano+, 2022)J/AJ/166/33 : The TESS-Keck Survey. XV. 108 TESS Planets (MacDougall+, 2023)J/AJ/168/109 : Resonant and ultra-short-period planet systems (Schmidt+, 2024)J/AJ/169/235 : TESS-Keck Survey. XXIV. 47 distant giants RVs (Van Zandt+, 2025)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/AJ/170/51https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/AJ/170/51http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/AJ/170/51https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/AJ/170/51https://vizier.iucaa.in/viz-bin/votable?-source=J/AJ/170/51http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/AJ/170/51GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticaldefaultJ/AJ/170/51/table1Keck/KPF radial velocity data during transitrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintBJD[3433.72/3433.93] Barycentric Julian Date - 2457000 (1)dtime.epochdoubleRVel[-2.69/3.23] Radial velocitym/sspect.dopplerVelocfloate_RVel[0.33/0.55] Uncertainty in RVm/sstat.error;spect.dopplerVelocfloat