J/ApJ/859/145ivo://CDS.VizieR/J/ApJ/859/145doi:10.26093/cds/vizier.18590145CDSOtani T.Oswalt T.D.Lynas-Gray A.E.Kilkenny D.Koen C.Amaral M.,Jordan R.2020-01-31T15:34:44Z2019-06-27T10:00:59ZCDS support team

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

cds-question@unistra.frspectroscopic-binary-starsvisible-astronomybroad-band-photometryAmong the competing evolution theories for subdwarf-B (sdB) stars is the binary evolution scenario. EC 20117-4014 (=V4640 Sgr) is a spectroscopic binary system consisting of a pulsating sdB star and a late F main-sequence companion; however, the period and the orbit semimajor axes have not been precisely determined. This paper presents orbital characteristics of the EC 20117-4014 binary system using 20 years of photometric data. Periodic observed minus calculated (O-C) variations were detected in the two highest-amplitude pulsations identified in the EC 20117-4014 power spectrum, indicating the binary system's precise orbital period (P=792.3d) and the light-travel-time amplitude (A=468.9s). This binary shows no significant orbital eccentricity, and the upper limit of the eccentricity is 0.025 (using 3{sigma} as an upper limit). This upper limit of the eccentricity is the lowest among all wide sdB binaries with known orbital parameters. This analysis indicated that the sdB is likely to have lost its hydrogen envelope through stable Roche lobe overflow, thus supporting hypotheses for the origin of sdB stars. In addition to those results, the underlying pulsation period change obtained from the photometric data was dP/dt=5.4(+/-0.7)x10^-14^d.d^-1^, which shows that the sdB is just before the end of the core helium-burning phase.2018ApJ...859..145Ohttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/859/145CatalogResearchIsServedByTAP VizieR generic servicerelated-toVI/65 : Evolutionary models of evolved stars (Dorman+ 1993)J/ApJ/419/596 : Pop I UV radiation models (Dorman+, 1993)J/MNRAS/287/867 : Edinburgh-Cape Blue Object Survey. Zone 1. (Kilkenny+ 1997)J/A+A/513/A6 : NOT survey of subdwarf B stars (Ostensen+, 2010)J/MNRAS/427/2180 : GALEX survey subdwarf atmospheric parameters (Nemeth+, 2012)J/A+A/576/A44 : Hot subdwarf binaries from MUCHFUSS (Kupfer+, 2015)J/MNRAS/459/4343 : Edinburgh-Cape Blue Object Survey (Kilkenny+, 2016)J/ApJ/832/183 : Bin. stellar evolution data for Kepler syst. (Kostov+, 2016)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/859/145https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/859/145http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/859/145https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/859/145https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/859/145http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/859/145GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticaldefaultJ/ApJ/859/145/table2Observation log for EC 20117-4014recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintDateUT date of observationtime.epoch;obsnullableStart[4869.4/12191.7] Start of run; BJD-2445000)dtime.epochdoubleLength[0.8/9.3] Observation lengthhtime.intervalfloatObsObservatory ("SAAO" --75 occurrences-- or "SARA-CT" --14 occurrences)meta.id;instr.obstycharRef[1/4]? Publications using the data (1)meta.bibintnullableJ/ApJ/859/145/table4O-C data points for F1 (7.29mHz) and F2 (7.04mHz) pulsation modes before removing the second order polynomial fitrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTime[4869.4/12191.9] Mid-observing time; BJD-2445000dtime.epochdoubleO-C(F1)[-467/470] O-C value of F1sstat.value;stat.fit.omcfloate_O-C(F1)[1.9/14.2] Uncertainty in F1sstat.errorfloatO-C(F2)[-467/472]? O-C values of F2sstat.value;stat.fit.omcfloatnullablee_O-C(F2)[4.9/18.5]? Uncertainty in F2sstat.errorfloatnullable