J/AJ/158/104ivo://CDS.VizieR/J/AJ/158/104doi:10.26093/cds/vizier.51580104CDSHu K.Chen K.Xiang F.-Y.Yu Y.-X.Zhao E.-G.2019-10-22T08:23:08Z2019-10-22T09:05:26ZCDS support team

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

cds-question@unistra.freclipsing-binary-starsinfrared-photometryvisible-astronomybroad-band-photometryDespite the discovery of LL Com, a Lyrae-type eclipsing binary system, approximately 60 yr ago, little has been found concerning its detailed photometry and orbital-period change until now. In this paper, we present the first multi-band charge-coupled-device photometric light curves, from which a significant luminosity reduction around the primary eclipse is revealed. Based on LAMOST data, we first determined LL Com's spectrum as F1V and then analyzed the light curves with the 2015 version of the Wilson-Devinney code. The fact that LL Com is a near-contact binary system with a semi-detached configuration, where the secondary component only fills its Roche lobe and the primary component fills more than 95% of its Roche lobe, is suggested through the photometric solution. In addition, according to archival photometry and previously published times of minima, a secular period increase at a rate of P=2.62x10^-7^ day/yr was found, which implies a continuous mass transfer from the secondary to the primary. Utilizing the photometric solution and the simulations of single-particle trajectories, we propose the existence of a cool spot on the surface of the primary component. This cool spot can be naturally produced by the impacts that occur during mass flow, and it also successfully interprets the luminosity reduction in the light curves. Finally, with the combination of thermal relaxation oscillation theory and the Roche-Lobe model, we conclude that LL Com is transitioning from the semi-detached to the detached phase.2019AJ....158..104Hhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/AJ/158/104CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/other/IBVS/5296 : Extrema of pulsating stars (Agerer+, 2002)J/other/IBVS/5438 : 162-nd list of minima of eclipsing binariesJ/AcA/54/207 : Ephemerids of eclipsing binaries (Kreiner, 2004)J/other/IBVS/5543 : 163-nd list of minima of eclipsing binariesJ/other/IBVS/5802 : Minima and maxima of 735 variables (Hubscher+, 2007)J/AJ/136/1067 : New beta Lyrae and Algol candidates in NSVSJ/other/IBVS/5918 : Minima and maxima of 452 variables (Hubscher+, 2010)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/AJ/158/104https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/AJ/158/104http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/AJ/158/104https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/AJ/158/104https://vizier.iucaa.in/viz-bin/votable?-source=J/AJ/158/104http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/AJ/158/104GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapInfraredOpticaldefaultJ/AJ/158/104/table2BVR bands photometric data for the eclipsing binary LL ComrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintHJD-BHeliocentric Julian Date of B band observationdtime.epochdoublePhase-B[0.001/0.999] Corresponding phase for HJD of B bandtime.phasefloatDBmag[-0.672/-0.078] Differential B band magnitudemagphot.mag;em.opt.B;arith.difffloate_DBmag[0.002/0.01] Photometric error in DBmagmagstat.error;phot.magfloatHJD-VHeliocentric Julian Date of V band observationdtime.epochdoublePhase-V[0/0.998] Corresponding phase for HJD of V bandtime.phasefloatDVmag[-0.604/-0.049] Differential V band magnitudemagphot.mag;em.opt.V;arith.difffloate_DVmag[0.002/0.007] Photometric error in DVmagmagstat.error;phot.magfloatHJD-R? Heliocentric Julian Date of R band observationdtime.epochdoublenullablePhase-R[0.001/0.999]? Corresponding phase for HJD of R bandtime.phasefloatnullableDRmag[-0.574/-0.043]? Differential R band magnitudemagphot.mag;em.opt.R;arith.difffloatnullablee_DRmag[0.002/0.006]? Photometric error in DRmagmagstat.error;phot.magfloatnullableJ/AJ/158/104/table4Times of light minimum of LL ComrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintHJD-MinHeliocentric Julian Date of light-minimum timedtime.epochdoublee_HJD-Min[0.0001/0.0047]? Corresponding error for HJD-Mindstat.errorfloatnullableTypeType of light minimum (I=Primary; II=Secondary)meta.notecharMeth[pg ccd] Method of observation (1)meta.code;obscharRef[1/44] Reference (2)meta.ref;pos.frameint