J/A+A/687/A118ivo://CDS.VizieR/J/A+A/687/A118doi:10.26093/cds/vizier.36870118CDSNetzel H.Anderson R.I.Viviani G.2024-11-21T20:01:52Z2024-07-12T08:34:53ZCDS support team

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

cds-question@unistra.frvariable-starsradial-velocityvisible-astronomyThe photometric observations from the recent decade revolutionized our view on classical pulsators. Low-amplitude signals have been detected photometrically in addition to the dominant high-amplitude radial mode pulsations in many RR Lyrae stars and classical Cepheids. First overtone pulsators with an additional low-amplitude signal at a period ratio of around 0.61 with the main mode, the so-called 0.61 stars, form the most populous group among these stars. The nature of this signal has been attributed to non-radial pulsations. Another mysterious group are stars, where the additional signal forms a period ratio of around 0.68. These are the 0.68 stars. The origin of the signal remains unknown. Here, we search for similar phenomena in spectroscopic observations of first-overtone classical Cepheids collected as part of the VELOCE project. We performed frequency analysis of several parameters derived from cross-correlation functions (CCFs), including radial velocity (RV), full width at half maximum (FWHM), bisector inverse span (BIS), and CCF depth (contrast). Using standard prewhitening, we searched for additional low-amplitude signals. We identify the location of these stars in various sequences of the Petersen diagram. We detect additional signals in four first-overtone classical Cepheids: BG Cru, QZ Nor, V0391 Nor, and V0411 Lac. We classified BG Cru, QZ Nor, and V0391 Nor as 0.61 stars based on period ratios. V0411 Lac, however, exhibits a ratio of 0.68 between the two modes, and the additional signal has a longer period. This kind of multiperiodicity remains unexplained. VELOCE CCFs yield the first spectroscopic detections of non-radial pulsation modes in classical Cepheids. This opens an asteroseismic window for pursuing a more detailed understanding of these important stars. While the 0.61 signal of BG Cru, QZ Nor, V0391 Nor is understood to originate due to non-radial modes of moderate degrees, the 0.68 signal of V0411 Lac still lacks a physical explanation.2024A&A...687A.118Nhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/687/A118CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/A+A/566/L10 : Cepheid radial velocity amplitude modulations (Anderson, 2014)J/A+A/686/A177 : VELOCE I. Cepheids High-precision RVs (Anderson+, 2024)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/687/A118https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/687/A118http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/687/A118https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/687/A118https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/687/A118http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/687/A118GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/687/A118/table1 (Summary of the data for the four stars)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/687/A118/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/687/A118/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/687/A118/table1?GETtext/xml+votable180.050000true187.9180417-59.42391670.0055555555555555566/14212 41794 42153 43047https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/687/A118?format=asciiOpticaldefaultJ/A+A/687/A118/table1Summary of the data for the four starsSimbadSimbad column added by the CDSmeta.ref.urlcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintVCShow the Radial Velocity curvesmeta.ref.urlcharNameStar namemeta.id;meta.maincharRAJ2000Simbad right ascension (J2000)pos.eq.ra;meta.mainDEJ2000Simbad declination (J2000)pos.eq.dec;meta.mainInstInstrumentmeta.id;instrcharBJD1Lower value of BJD rangedtime.epochintBJD2Upper value of BJD rangedtime.epochint<S/N>Average S/N of the CCF profiles calculated using the tool FAMIAS (Zima, 2008, Communications in Asteroseismology, 157, 387)stat.snrintNobsNumber of observationsmeta.numberintJ/A+A/687/A118/table2Analyzed datarecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameStar namemeta.id;meta.maincharBJDBarycentric Julian date (BJD-2400000)dtime.epochdoubleRVRadial velocitykm/sphys.veloc;pos.heliocentricdoublee_RVRadial velocity errorkm/sstat.errorfloatFWHMFull width at half maximumkm/sspect.line.widthdoubleBISBisector inverse spankm/sphys.velocdoubleContrastRelative depthphot.flux;arith.ratiodouble