J/A+A/675/A168ivo://CDS.VizieR/J/A+A/675/A168doi:10.26093/cds/vizier.36750168CDSMignon L.Meunier N.Delfosse X.Bonfils X.Santos N.C.Forveille T.,Gaisne G.Astudillo-Defru N.Lovis C.Udry S.2024-11-06T20:04:58Z2023-07-18T09:01:44ZCDS support team

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

cds-question@unistra.frm-starsspectroscopyphotometryvisible-astronomyM dwarfs are active stars that exhibit variability in chromospheric emission and photometry at short and long timescales, including long cycles that are related to dynamo processes. This activity also impacts the search for exoplanets because it affects the radial velocities. We analysed a large sample of 177 M dwarfs observed with HARPS during the period 2003-2020 in order to characterise the long-term variability of these stars. We compared the variability obtained in three chromospheric activity indices (Ca-II H & K, the Na D doublet, and H{alpha}) and with ASAS photometry. We focused on the detailed analysis of the chromospheric emission based on linear, quadratic, and sinusoidal models. We used various tools to estimate the significance of the variability and to quantify the improvement brought by the models. In addition, we analysed complementary photometric time series for the most variable stars to be able to provide a broader view of the long-term variability in M dwarfs. We find that most stars are significantly variable, even the quietest stars. Most stars in our sample (75%) exhibit a long-term variability, which manifests itself mostly through linear or quadratic variability, although the true behaviour may be more complex. We found significant variability with estimated timescales for 24 stars, and estimated the lower limit for a possible cycle period for an additional 9 stars that were not previously published. We found evidence of complex variability because more than one long-term timescale may be present for at least 12 stars, together with significant differences between the behaviour of the three activity indices. This complexity may also be the source of the discrepancies observed between previous publications. We conclude that long-term variability is present for all spectral types and activity level in M dwarfs, without a significant trend with spectral type or mean activity level.2023A&A...675A.168Mhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/675/A168CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toI/311 : Hipparcos, the New Reduction (van Leeuwen, 2007)I/344 : The URAT Parallax Catalog (UPC). Update 2018 (Finch+, 2018)I/345 : Gaia DR2 (Gaia Collaboration, 2018)II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)II/237 : Stellar photometry in Johnson's 11-color systemJ/MNRAS/403/1949 : UBV(RcIc)JHK photometry of HIP nearby stars (Koen+, 2010)J/AJ/152/24 : Trigonometric parallaxes of 134 low-mass starshttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/675/A168https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/675/A168http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/675/A168https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/675/A168https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/675/A168http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/675/A168GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/675/A168/tableb1 (Stellar properties of our 177 stars)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/675/A168/tableb1?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/675/A168/tableb1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/675/A168/tableb1?GETtext/xml+votable180.050000true118.5453447-25.30317280.0055555555555555566/115 131 546 4157 4366 4444 4651 8343 8394 8440 8739 10278 12440 16391 16758 16847 16910 17288 17455 17870 18496 18569 18666 18856 19064 19466 20100 20867 20896 21171 21271 21473 21527 21777 21953 22014 22222 22309 22626 22645 22700 22807 22959 22964 23137 23238 23363 23731 23735 24227 24713 24995 25009 25125 25388 25426 25516 25639 25989 26495 26560 26583 26772 26972 27201 27392 27462 27484 27912 28548 28955 29170 29665 29684 30321 30429 30505 30522 30625 30735 30771 30893 30931 31013-31014 31031 31035 31191 31216 31495 31781 32335 33441 33702 33758 33849 33966 34181 34301 34448 34514 34767 34924 34975 35057 35324-35325 35388 35499 35670 36078 36133 36614 36732 36892 36910 37379 37654 37942 38152 38456 38464 38551 38675 38744 38913 39059 39080 39807 39912 40250 40341 40359 40436 40505 40513 40811 41252 41455 41591 42054 42101 42209 42255 42290 42314 42429 42459 42471 42544 42652 42784 42982 43187 43203 43336 43723 43970 44728 44921 45322 45497 46128 46218 46275 46566 46632 46699 47121 47183 47337 47347 47414 47758 48274 48906 49101https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/675/A168?format=asciiOpticaldefaultJ/A+A/675/A168/tableb1Stellar properties of our 177 starsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameStar namemeta.id;meta.maincharV-KV-K colour index (1)magphot.color;em.opt.V;em.IR.Kfloatn_V-K[d] d indicates calculated V-K (1)meta.notecharTeff? Effective temperature, from CDSKphys.temperature.effectiveintnullableMassMass (2)solMassphys.massfloatDistDistance (3)pcpos.distancefloatNnightsNumber of nightsmeta.numberintlogR'HKAveraged LogR'HKphot.colorfloatrmsR'HKrms R'HK x 10^5^stat.errorfloatSeason[X] X indicates star in the season subsamplemeta.codecharSimbadSimbad column added by the CDSmeta.ref.urlchar_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