J/MNRAS/483/2941ivo://CDS.VizieR/J/MNRAS/483/2941doi:10.26093/cds/vizier.74832941CDSWilson D.J.Gansicke B.T.Koester D.Toloza O.Holberg J.B.,Preval S.P.Barstow M.A.Belardi C.Burleigh M.R.Casewell S.L.,Cauley P.W.Chote P.Farihi J.Hollands M.A.Long K.S.Redfield S.2024-08-19T20:15:47Z2022-08-11T09:25:11ZCDS support team

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

cds-question@unistra.frvariable-starswhite-dwarf-starsspectroscopyultraviolet-astronomyvisible-astronomyWe present new Hubble Space Telescope (HST) ultraviolet and ground-based optical observations of the hot, metal-rich white dwarf GD 394. Extreme-ultraviolet (EUV) observations in 1992-1996 revealed a 1.15d periodicity with a 25 per cent amplitude, hypothesized to be due to metals in a surface accretion spot. We obtained phase resolved HST/Space Telescope Imaging Spectrograph high resolution far-ultraviolet spectra of GD 394 that sample the entire period, along with a large body of supplementary data. We find no evidence for an accretion spot, with the flux, accretion rate, and radial velocity of GD 394 constant over the observed time-scales at ultraviolet and optical wavelengths. We speculate that the spot may have no longer been present when our observations were obtained, or that the EUV variability is being caused by an otherwise undetected evaporating planet. The atmospheric parameters obtained from separate fits to optical and ultraviolet spectra are inconsistent, as is found for multiple hot white dwarfs. We also detect non-photospheric, high ionisation absorption lines of multiple volatile elements, which could be evidence for a hot plasma cocoon surrounding the white dwarf.2019MNRAS.483.2941Whttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/MNRAS/483/2941CatalogResearchIsServedByTAP VizieR generic servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/MNRAS/483/2941https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/MNRAS/483/2941http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/MNRAS/483/2941https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/MNRAS/483/2941https://vizier.iucaa.in/viz-bin/votable?-source=J/MNRAS/483/2941http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/MNRAS/483/2941GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapUVOpticaldefaultJ/MNRAS/483/2941/tablea1Summary of the spectroscopic observations of GD 394recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintDateDate of observationtime.epochnullableInstTelescope and instrument used for the observationinstr.setupcharTimeTime of observationtime.epochnullableExpTimeTotal exposure timestime.duration;obs.exposureintPhase? Phase positions relative to the start of the first observation (1)src.orbitalfloatnullableWvlrangeWavelenght range (in {AA})0.1nminstr.bandwidthcharJ/MNRAS/483/2941/tableb1Observed photospheric metal absorption lines detected in the FUSE, STIS, and HIRES spectrarecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintInstInstrument used for the spectra (FUSE, STIS or HIRES)instr.setupcharLineDetected metal absorption linesmeta.id;spect.linecharf_Line[?*] Flag on Line (1)meta.codecharRestwvlRest wavelength of the detected line (2)0.1nmem.wldoubleObswvl? Observed wavelenght of the detected line0.1nmem.wldoublenullableDeltav? Velocity variationkm/sphys.veloc;arith.difffloatnullablee_Deltav? Error on Deltavkm/sstat.errorfloatnullableEW? Equivalent width measured according to the prescriptions found in Vollmann & Eversberg (2006AN....327..862V)0.0001nmspect.line.eqWidthfloatnullablee_EW? Error on EW0.0001nmstat.error;spect.line.eqWidthfloatnullableJ/MNRAS/483/2941/tableb2High-ionization absorption lines suspected to be circumstellar detected in the FUSE and STIS spectrarecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintInstInstrument used for the spectra (FUSE or STIS)instr.setupcharLineDetected metal absorption linesmeta.id;spect.linecharf_Line[*] Flag on Line (1)meta.codecharRestwvlRest wavelength of the detected line0.1nmem.wldoubleObswvl? Observed wavelenght of the detected line0.1nmem.wlfloatnullableDeltav? Velocity variationkm/sphys.veloc;arith.difffloatnullablee_Deltav? Error on Deltavkm/sstat.errorfloatnullableEW? Equivalent width measured according to the prescriptions found in Vollmann & Eversberg (2006AN....327..862V)0.0001nmspect.line.eqWidthfloatnullablee_EW? Error on EW0.0001nmstat.error;spect.line.eqWidthfloatnullableJ/MNRAS/483/2941/tableb3ISM absorption lines detected in the FUSE, STIS, and HIRES spectrarecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintInstInstrument used for the spectra (FUSE, STIS or HIRES)instr.setupcharLineDetected metal absorption linesmeta.id;spect.linecharRestwvlRest wavelength of the detected line (1)0.1nmem.wldoubleObswvlObserved wavelenght of the detected line0.1nmem.wlfloatDeltav? Velocity variationkm/sphys.veloc;arith.difffloatnullablee_Deltav? Error on Deltavkm/sstat.errorfloatnullableEWEquivalent width measured according to the prescriptions found in Vollmann & Eversberg (2006AN....327..862V)0.0001nmspect.line.eqWidthfloate_EWError on EW0.0001nmstat.error;spect.line.eqWidthfloatu_Line[?] Uncertainty flag on Linemeta.code.error;spect.linechar