J/ApJ/894/19ivo://CDS.VizieR/J/ApJ/894/19doi:10.26093/cds/vizier.18940019CDSReding J.S.Hermes J.J.Vanderbosch Z.Dennihy E.Kaiser B.C.,Mace C.B.Dunlap B.H.Clemens J.C.2021-12-03T12:38:57Z2021-10-18T10:18:18ZCDS support team

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

cds-question@unistra.frwhite-dwarf-starsvisible-astronomyspectroscopyWe report the discovery of short-period photometric variability and modulated Zeeman-split hydrogen emission in SDSSJ125230.93-023417.72 (EPIC 228939929), a variable white dwarf star observed at long cadence in K2 Campaign 10. The behavior is associated with a magnetic (B=5.0MG) spot on the stellar surface, making the 317.278s period a direct measurement of the stellar rotation rate. This object is therefore the fastest-rotating, apparently isolated (without a stellar companion) white dwarf yet discovered and the second found to exhibit chromospheric Balmer emission after GD 356, in which the emission has been attributed to a unipolar inductor mechanism driven by a possible rocky planet. We explore the properties and behavior of this object, and consider whether its evolution may hold implications for white dwarf mergers and their remnants.2020ApJ...894...19Rhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/894/19CatalogResearchIsServedByTAP VizieR generic servicerelated-toII/328 : AllWISE Data Release (Cutri+ 2013)V/147 : The SDSS Photometric Catalogue, Release 12 (Alam+, 2015)II/335 : Revised catalog of GALEX UV sources (GUVcat_AIS GR6+7) (Bianchi+ 2017)IV/34 : K2 Ecliptic Plane Input Catalog (EPIC) (Huber+, 2017)I/345 : Gaia DR2 (Gaia Collaboration, 2018)J/ApJS/133/413 : BVRIJHK photometry of cool white dwarfs (Bergeron+, 2001)J/AJ/132/1221 : VJHK and SDSS photometry of DA white dwarfs (Holberg+, 2006)J/MNRAS/417/1210 : DA-white dwarfs from SDSS and UKIDSS (Girven+, 2011)J/ApJ/730/128 : Spectroscopy of DA WD from the SDSS-DR4 (Tremblay+, 2011)J/ApJS/201/19 : Hawaii Infrared Parallax Program. I. (Dupuy+, 2012)J/ApJ/833/96 : Hawaii infrared plx prog. II. Ultracool dwarfs (Liu+, 2016)J/ApJS/232/23 : 27 pulsating DA WDs follow-up observations (Hermes+, 2017)J/MNRAS/482/4570 : Gaia DR2 white dwarf candidates (Gentile Fusillo+, 2019)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/894/19https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/894/19http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/894/19https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/894/19https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/894/19http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/894/19GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticaldefaultJ/ApJ/894/19/fig3Flux-calibrated and phase-binned SOAR spectra of SDSS J125230.93-023417.7recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintlambda[3725.9/7079.5] Wavelength; in Angstrom units0.1nmem.wldoubleFlux15[1.6e-16/9.1e-16] Flux at 15 degree phase (1)cW.m**-2.nm**-1phot.fluxdoubleFlux87[1.5e-16/8.8e-16] Flux at 87 degree phase (1)cW.m**-2.nm**-1phot.fluxdoubleFlux159[1.5e-16/8.1e-16] Flux at 159 degree phase (1)cW.m**-2.nm**-1phot.fluxdoubleFlux231[1.5e-16/8.7e-16] Flux at 231 degree phase (1)cW.m**-2.nm**-1phot.fluxdoubleFlux303[1.6e-16/8.8e-16] Flux at 303 degree phase (1)cW.m**-2.nm**-1phot.fluxdouble