J/A+A/695/A89ivo://CDS.VizieR/J/A+A/695/A89doi:10.26093/cds/vizier.36950089CDSAdebali O.Strassmeier K.G.Ilyin I.V.Weber M.Gruner D.Kovari Zs.2025-08-05T20:01:00Z2025-03-11T09:32:44ZCDS support team

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

cds-question@unistra.frspectroscopic-binary-starsradial-velocityvisible-astronomyStarspots on a rotating stellar surface impact the measured radial velocities and thereby limit the determination of precise orbital elements as well as astrophysical stellar parameters and even jeopardize the detection and characterization of (exo)planets. We quantify the effect of starspots for the orbital elements of the spotted RS CVn binary {lambda} And and present an empirical correction. The aim is a more precise orbital solution that can be used to better study the system's severe orbital-rotational asynchronism. Phase-resolved high-resolution optical spectra were recorded over the course of 522 days in 2021-2022. We employed two facilities with medium and high resolution spectroscopy for the multiple activity analyses. Doppler imaging is used to reconstruct {lambda} And's starspots with high resolution (R=250000) and high signal-to-noise ratio spectra. Optimized cross-correlation functions are used to measure precise radial velocities at a few ten's of m/s level. The spot-corrected radial velocities enable on average a three-fold increase of precision of the individual orbital elements. The residual velocity jitter with a full range of 500m/s is modulated by the rotation period of {lambda} And of 54.4+/-0.3d. Our logarithmic gravity from spectrum synthesis of 2.8+/-0.2 together with the interferometrically determined stellar radius suggest a most-likely mass of the primary of ~1.4M_{sun}_. The small orbital mass function then implies a secondary mass of just ~0.1M_{sun}_, appropriate for an L-class brown dwarf. The Doppler image reconstructs a dominating cool spot with an umbral temperature difference of ~1000K with respect to the photosphere of 4660K and is likely surrounded by a moat-like velocity field. Three more but weaker spots add to the total surface spottedness of up to 25% of the visible surface. Seven optical chromospheric tracers show rotational modulation of their emission line fluxes in phase with the cool spots. This surface configuration appeared to have been stable for the 522d of our observations. We also redetermine the carbon isotope ratio to ^12^C/^13^C=30+/-5 and measure a contemporaneous disk-integrated mean longitudinal magnetic field of polarity Plus/Minus up to 2.70+/-0.35G from Stokes-V line profiles.2025A&A...695A..89Ahttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/695/A89CatalogResearchIsServedByTAP VizieR generic servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/695/A89https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/695/A89http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/695/A89https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/695/A89https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/695/A89http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/695/A89GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticaldefaultJ/A+A/695/A89/stellarvSTELLA radial velocities (table A1)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintObs.DateCoordinated Universal Time of observationobs.param;obsnullableBJDBarycenteric Julian Date of observationdtime.epochdoubleRVRadial velocitykm/sphys.veloc;pos.heliocentricfloatRVresResidual of radial velocitym/sstat.fit.residual;phys.velocdoublee_RVError of radial velocitym/sstat.errorfloatPhaseorbOrbital phase of the startime.phasedoublePhaserotRotational phase of the startime.phasedoubleRVcActivity corrected radial velocitykm/sspect.dopplerVelocdoubleJ/A+A/695/A89/pepsirvPEPSI radial velocities (table A2)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintObs.DateCoordinated Universal Time of observationobs.param;obsnullableBJDBarycenteric Julian Date of observationdtime.epochdoubleRVRadial velocitykm/sphys.veloc;pos.heliocentricfloatRVresResidual of radial velocitym/sstat.fit.residual;phys.velocdoublee_RVError of radial velocitym/sstat.errorfloatPhaseorbOrbital phase of the startime.phasedoublePhaserotRotational phase of the startime.phasedoubleRVcActivity corrected radial velocitykm/sspect.dopplerVelocdouble