J/A+A/644/A135ivo://CDS.VizieR/J/A+A/644/A135doi:10.26093/cds/vizier.36440135CDSSiwak M.Ogloza W.Krzesinski J.2021-03-29T12:24:22Z2020-12-11T07:41:50ZCDS support team

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

cds-question@unistra.frvariable-starsinfrared-photometryvisible-astronomybroad-band-photometrysloan-photometryspectroscopyWe investigate small-scale light variations in V646 Pup occurring in the timescales of days, weeks and years. To check if this variability is similar to that observed in FU Ori. We observed V646 Pup on six occasions at the SAAO and CTIO during 2013-2018 in Johnson and Sloan filters, typically with 1 d cadence maintained for 2-4 weeks. We also utilise the public-domain 1512 day long ASAS-SN light curve and TESS photometry obtained in 2019 during 24.1 days with 30 min cadence. New SAAO low-resolution spectra help to update major disc parameters, while the archival high-resolution Keck spectra are used to search for temporal changes in the disc rotational profiles. The ground-based observations confirm the constantly decreasing brightness of V646 Pup at the rate of 0.018mag per year. Precise i-band sensitive TESS data show that the little 0.005-0.01mag light variations imposed on this general trend do consist of a few independent wave trains of apparently time-coherent nature. Assuming that this is typical situation, from analysis of colour-magnitude diagrams obtained on earlier epochs we preliminarily inferred that the bulk of observed light changes could be owing to rotation of disc photosphere inhomogeneities, arising between 10-12 solar radii from the star. It is not excluded that these inhomogeneities could also manifest themselves in rotational profiles of the disc, as obtained from the high-resolution spectra. Assuming Keplerian rotation of these inhomogeneities, we preliminarily determine the stellar mass at 0.7-0.9 solar masses. At least during certain weeks V646 Pup shows time-coherent light variability pattern(s) that could be explained by rotation of an inhomogeneous disc photosphere. These preliminary results are similar to those better established for FU Ori, what suggests a common driving mechanism(s).2020A&A...644A.135Shttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/644/A135CatalogResearchIsServedByTAP VizieR generic servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/644/A135https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/644/A135http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/644/A135https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/644/A135https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/644/A135http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/644/A135GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticalInfrareddefaultJ/A+A/644/A135/tablea1SAAO Johnson-Cousins VRcIc standardised light curves (nightly averages, Fig.1a)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintDateHelocentric Julian Datedtime.epochdoublemagStandard magnitudemagphot.magfloate_magrms error of std. magnitudemagstat.error;phot.magfloatFilter[VRcIc BVI] Filter name (1)meta.id;instr.filtercharJ/A+A/644/A135/tablea2CTIO Sloan-i differential magnitudes (nightly averages, Fig.1b)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintDateHelocentric Julian Datedtime.epochdoubledmagDifferential magnitudemagphot.mag;arith.difffloate_dmagrms error of differential magnitudemagstat.error;phot.magfloatFilter[gri] Filter namemeta.id;instr.filtercharJ/A+A/644/A135/tablea3CTIO Sloan-gi differential magnitudes (nightly averages, Fig.1c)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintDateHelocentric Julian Datedtime.epochdoubledmagDifferential magnitudemagphot.mag;arith.difffloate_dmagrms error of differential magnitudemagstat.error;phot.magfloatFilter[gri] Filter namemeta.id;instr.filtercharJ/A+A/644/A135/tablea4SAAO Johnson BVI standardised light curves (nightly averages, Fig.1d)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintDateHelocentric Julian Datedtime.epochdoublemagStandard magnitudemagphot.magfloate_magrms error of std. magnitudemagstat.error;phot.magfloatFilter[VRcIc BVI] Filter name (1)meta.id;instr.filtercharJ/A+A/644/A135/tablea5SAAO Sloan-gri differential magnitudes (nightly averages, Fig.1e)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintDateHelocentric Julian Datedtime.epochdoubledmagDifferential magnitudemagphot.mag;arith.difffloate_dmagrms error of differential magnitudemagstat.error;phot.magfloatFilter[gri] Filter namemeta.id;instr.filtercharJ/A+A/644/A135/tablea6SAAO Sloan-gri differential magnitudes (nightly averages, Fig.1f)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintDateHelocentric Julian Datedtime.epochdoubledmagDifferential magnitudemagphot.mag;arith.difffloate_dmagrms error of differential magnitudemagstat.error;phot.magfloatFilter[gri] Filter namemeta.id;instr.filtercharJ/A+A/644/A135/tablea7Reprocessed TESS data (Fig.2c)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintDateBarrycentric TESS Julian Datedtime.epochdoubleFluxFlux normalised to unity at mean brightnessphot.flux;arith.ratiodoubleJ/A+A/644/A135/spectrumSpectrum obtained in Mar 12, 2017, calibrated to absolute flux [cgs] units by means of LTT 3864 spectrophotometric standardrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintlambdaWavelength in Angstroms0.1nmem.wlfloatFluxFlux calibrated to cgs units (erg/cm^2^/s/{AA})10mW.m**-2.nm**-1meta.unit;phot.fluxdouble