J/A+A/690/A36ivo://CDS.VizieR/J/A+A/690/A36doi:10.26093/cds/vizier.36900036CDSSu W.Charpinet S.Latour M.Zong W.Green E.M.Li G.2025-02-18T20:01:30Z2024-09-27T10:22:08ZCDS support team

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

cds-question@unistra.frmultiple-starsvisible-astronomyspectroscopyasteroseismologyThe Transiting Exoplanet Survey Satellite (TESS) performs high-precision photometry over almost the whole sky primarily in search of exoplanet transits. It also provides exquisite data to study stellar variability, in particular for pulsating hot B subdwarf (sdB) stars. We present the detailed analysis of a new hybrid (p- and g-mode) sdB pulsator, TIC 441725813 (TYC 4427-1021-1), discovered and monitored by TESS over 670 days. The TESS light curves available for this star were analyzed using prewhitening techniques to extract mode frequencies accurately. The pulsation spectrum was then interpreted through methods that include asymptotic period spacing relationships and the identification of rotational multiplets. We also exploited a high signal-to-noise ratio (S/N), low-resolution spectrum of TIC 441725813 using grids of non-local thermodynamic equilibrium (NLTE) model atmospheres to derive its atmospheric parameters. The light curve analysis reveals that frequencies are mostly found in the g-mode region, but several p-modes are also detected, indicating that TIC 441725813 is a hybrid sdB pulsator. We identify 25 frequencies that can be associated with l=1 g-modes, 15 frequencies corresponding to l=2 g-modes, and six frequencies characteristic of p-modes. Interestingly, several frequency multiplets interpreted as rotational splittings of deep-probing g-modes indicate a slow rotation period of at least 85.3+/-3.6 day, while splittings of mostly envelope-probing p-modes suggest a significantly shorter rotation period of 17.9+/-0.7 day, which implies the core (mainly the helium mantle with possibly the deeper partially mixed helium-burning core that it surrounds) rotates at least 4.7 times slower than the envelope. The radial velocity curves indicate that TIC 441725813 is in a close binary system with a low-luminosity companion, possibly a white dwarf. While elusive in the available TESS photometry, a low-frequency signal that would correspond to a period of ~6.7 h is found, albeit at a low S/N. Furthermore, we estimate the inclination angle to be ~60{deg} by two independent means. TIC 441725813 is a particularly interesting sdB star whose envelope rotates faster than the core. We hypothesise that this might be caused by the effects of a tidal interaction with a companion, although in the present case, the presence of such a companion will have to be further investigated. This analysis paves the way towards a more detailed seismic probing of TIC 441725813 using optimisation techniques, which will be presented in a second paper.2024A&A...690A..36Shttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/690/A36CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/690/A36https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/690/A36http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/690/A36https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/690/A36https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/690/A36http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/690/A36GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/690/A36/list (Information on spectrum file)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/690/A36/list?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/690/A36/list?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/690/A36/list?GETtext/xml+votable180.050000true256.2432173.078670.0055555555555555566/11760https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/690/A36?format=asciiOpticaldefaultJ/A+A/690/A36/allfreRaw (unfiltered) list of all prewhitened frequencies in 4 data sets available for TIC 441725813g3period? Period corresponding to the frequency in g3 (3)stime.period;em.freqdoublenullablee_g3period? Period corresponding to the frequency in g3 errorsstat.errorfloatnullableg4period? Period corresponding to the frequency in g4 (4)stime.period;em.freqdoublenullablee_g4period? Period corresponding to the frequency in g4 errorsstat.errorfloatnullableg2S/N? S/N corresponding to the frequency in g2stat.snrfloatnullableg3S/N? S/N corresponding to the frequency in g3stat.snrfloatnullableg4S/N? S/N corresponding to the frequency in g4stat.snrfloatnullableg4freq? Effective frequency extracted from dataset g4 (4)uHzem.freqdoublenullablee_g4freq? Effective frequency extracted from dataset g4 erroruHzstat.errorfloatnullableg1period? Period corresponding to the frequency in g1 (1)stime.period;em.freqdoublenullablee_g1period? Period corresponding to the frequency in g1 errorsstat.errorfloatnullableg2period? Period corresponding to the frequency in g2 (2)stime.period;em.freqdoublenullablee_g2period? Period corresponding to the frequency in g2 errorsstat.errorfloatnullableg1S/N? S/N corresponding to the frequency in g1stat.snrfloatnullablerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintFreqFrequency IDmeta.id;meta.maincharg1freq? Effective frequency extracted from dataset g1 (1)uHzem.freqdoublenullablee_g1freq? Effective frequency extracted from dataset g1 erroruHzstat.errorfloatnullableg2freq? Effective frequency extracted from dataset g2 (2)uHzem.freqdoublenullablee_g2freq? Effective frequency extracted from dataset g2 erroruHzstat.errorfloatnullableg3freq? Effective frequency extracted from dataset g3 (3)uHzem.freqdoublenullablee_g3freq? Effective frequency extracted from dataset g3 erroruHzstat.errorfloatnullableJ/A+A/690/A36/listInformation on spectrum filedWaveWavelength resolution0.1nmspect.resolutiondoublesizeSize of FITS fileKibytephys.size;meta.fitsintFileNameName of FITS file, in subdirectory fitsmeta.id;meta.fitscharTitleTitle of the FITS filemeta.title;meta.fitscharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRAJ2000Right Ascension of center (J2000)degpos.eq.ra;meta.mainDEJ2000Declination of center (J2000)degpos.eq.dec;meta.mainNxNumber of pixels along X-axismeta.numberintBWaveUpper value of wavelength interval0.1nmem.wlintspShow the spectrummeta.ref.urlcharObs.dateObservation datetime.epoch;obsnullablebWaveLower value of wavelength interval0.1nmem.wlint