J/A+A/673/A43ivo://CDS.VizieR/J/A+A/673/A43doi:10.26093/cds/vizier.36730043CDSLiebing F.Jeffers S.V.Zechmeister M.Reiners A.2024-11-28T20:03:24Z2023-05-03T07:45:39ZCDS support team

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

cds-question@unistra.frgiant-starsspectroscopyradial-velocityvisible-astronomyWith the advent of extreme precision radial velocity (RV) surveys, seeking to detect planets at RV semi-amplitudes of 10cm/s, intrinsic stellar variability is the biggest challenge to detecting small exoplanets. To overcome the challenge we must first thoroughly understand all facets of stellar variability. Among those, convective blueshift caused by stellar granulation and its suppression through magnetic activity plays a significant role in covering planetary signals in stellar jitter. Previously we found that for main sequence stars, convective blueshift as an observational proxy for the strength of convection near the stellar surface strongly depends on effective temperature. In this work we investigate 242 post main sequence stars, covering the subgiant, red giant, and asymptotic giant phases and empirically determine the changes in convective blueshift with advancing stellar evolution. We used the third signature scaling approach to fit a solar model for the convective blueshift to absorption-line shift measurements from a sample of coadded HARPS spectra, ranging in temperature from 3750K to 6150K. We compare the results to main sequence stars of comparable temperatures but with a higher surface gravity. We show that convective blueshift becomes significantly stronger for evolved stars compared to main sequence stars of a similar temperature. The difference increases as the star becomes more evolved, reaching a 5x increase below 4300K for the most evolved stars. The large number of stars in the sample, for the first time, allowed for us to empirically show that convective blueshift remains almost constant among the entire evolved star sample at roughly solar convection strength with a slight increase from the red giant phase onward. We discover that the convective blueshift shows a local minimum for subgiant stars, presenting a sweet spot for exoplanet searches around higher mass stars, by taking advantage of their spin-down during the subgiant transition.2023A&A...673A..43Lhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/673/A43CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toI/345 : Gaia DR2 (Gaia Collaboration, 2018)J/A+A/636/A74 : HARPS radial velocity database (Trifonov+, 2020)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/673/A43https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/673/A43http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/673/A43https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/673/A43https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/673/A43http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/673/A43GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/673/A43/tablec2 (Stellar parameters and results indices for each galaxy)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/673/A43/tablec2?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/673/A43/tablec2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/673/A43/tablec2?GETtext/xml+votable180.050000true109.1458033-27.88117920.0055555555555555566/120 341 4268 12482 16496 16691 16837 16883 17266 17496 17568 17721 17731 18102 18172 18276 18428 18466 18539 18688 19237 19426 19797 19815 20043 20486 20503 20529 20642 20664 20981 21223 21523 21531 21539 21612 21738 21806 21989 22040 22059 22753 23066 23533 23538 23574 23695 24715 24752 24799 24820 25304 25454 25538 25981 26120 26552 26727 27040 27881 28044 28274 28322 28773 28776 29269 29280 29558 30215 30278 30294 30339 30419 30439 30770 31048 31809 31812-31814 31842 32297 32785 32873 32922 32969 33018 33059 33122 33221-33222 33383 33509 33589 33655 33675 33731 33749 34064 34132 34199 34288 34343 34392 34414 34510 34520 34616 34646 34664 34777 34869 34890 35025 35115 35130 35170 35185 35191 35264 35344 35351 35396 35415 35494 35532 35639 35673 35811 35958 36115 36221 36224 36414 36433 36462 36579 36689 36693 36714 36723 36759 36784 37252 37349 37412 37498 37507 37583 37648 37664 37873 37920 37933 37944 38242 38248 38378 38452 39001 39026 39090 39336 39340 39446 39569 39672 39675 39742 39813 39839 39888 40048 40104 40202 40210 40588 40696 40965 41039 41524 41834 41986 42051 42080 42274 42281 42318 42361 42527 43143 43280 43310 43893 44015 44191 44364 44474 44554 44883 45164 45613 45682 45752 46112 46171 46176 46248 46582 46793 47113 47157 47181 47207 47237 47263 47354 47424 47514 47715 47991 47997 48065 48147 48175 48183 48296 49060https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/673/A43?format=asciiOpticaldefaultJ/A+A/673/A43/tablec1Modeled CBS reference valuesTeff[4100/6000] Effective TemperatureKphys.temperature.effectiveintrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintScale[0.76/1.53] Solar-relative CBS scale factorarith.factorfloatConvBS[-546.8/-275.5] Convective blueshift velocity (1)m/sphys.velocfloatJ/A+A/673/A43/tablec2Stellar parameters and results indices for each galaxyEvoEvolutionary Phase (4)meta.codecharvsini[0.00/6.79]? Projected rotational velocity (3)m/sphys.veloc.rotatfloatnullablerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameName of the starmeta.id;meta.maincharGaiaDR2Gaia DR2 star ID (1)meta.idTeff[3797/6105] Effective temperature (1)Kphys.temperature.effectiveintGMAG[-8.54/3.85] Absolute Gaia G magnitude (2)magphys.magAbsfloatlogg[0.05/4.01] Surface gravity (4)log(cm.s**-2)phys.gravityfloatNcoadd[1/724] Number of coadded spectrameta.numberintS/N[36/5651] Signal-to-Noise ratiostat.snrintNlines[897/1223] Number of fitted linesmeta.numberintchi2P[0.01/652.34] Pearson Chi-square of fitmeta.notefloatScale[-0.15/3.49] Solar-relative CBS scale factorarith.factorfloate_Scale[0.02/0.24] Error on CBS scale factorstat.error;instr.scalefloatSimbadNameSimbad column added by the CDSmeta.idcharnullable_RARight Ascension (J2000) from SIMBAD (not part of the original data)degpos.eq.ra;meta.main_DEDeclination (J2000) from SIMBAD (not part of the original data)degpos.eq.dec;meta.main