J/ApJ/660/1428ivo://CDS.VizieR/J/ApJ/660/1428doi:10.26093/cds/vizier.16601428CDSKaplan D.L.Van Kerkwijk M.H.Anderson J.2018-01-30T07:17:50Z2009-04-19T21:17:56ZCDS support team

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

cds-question@unistra.frx-ray-sourcesastrometryWe have used a set of dedicated astrometric data from the Hubble Space Telescope to measure the parallax and proper motion of the nearby neutron star RX J0720.4-3125. At each of eight epochs over 2 years, we used the High Resolution Camera of the Advanced Camera for Surveys to measure the position of the B=26.6 target to a precision of ~2mas (~0.07pix) relative to 22 other stars. From these data we measure a parallax of plx=2.8+/-0.9mas (for a distance of 360^+170^_-90_pc) and a proper motion of mu=107.8+/-1.2mas/yr. Exhaustive testing of every stage of our analysis suggests that it is robust, with a maximum systematic uncertainty on the parallax of 0.4mas. The distance is compatible with earlier estimates made from scaling the optical emission of RX J0720.4-3125 relative to the even closer neutron star RX J1856.5-3754. The distance and proper motion imply a transverse velocity of 180^+90^_-40_km/s, comparable to velocities observed for radio pulsars. The speed and direction suggest an origin for RX J0720.4-3125 in the Trumpler 10 OB association ~0.7Myr ago, with a possible range of 0.5-1.0Myr given by the uncertainty in the distance.2007ApJ...660.1428Khttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/660/1428CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/660/1428https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/660/1428http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/660/1428https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/660/1428https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/660/1428http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/660/1428GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/660/1428/table4 (*Astrometry of reference sources)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/660/1428/table4?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/660/1428/table4?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/660/1428/table4?GETtext/xml+votable180.050000true110.1040083-31.43057860.0055555555555555566/39825https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/660/1428?format=asciiX-raydefaultJ/ApJ/660/1428/table4*Astrometry of reference sourcesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintIDObject identifier (G1)meta.id;meta.maincharprimaryo_ID[1/8] Number of epochs for which a source could be measuredmeta.numberintmagInstrumental magnitude (2)magphot.magfloatDRAOffset in right ascension (3)arcsecpos.eq.ra;arith.diffdoublee_DRArms uncertainty on DRA10masstat.errorintDDEOffset in declination (3)arcsecpos.eq.dec;arith.diffdoublee_DDErms uncertainty on DDE10masstat.errorintpmRAProper motion along RA (4)mas/yrpos.pm;pos.eq.rafloate_pmRArms uncertainty on pmRAmas/yrstat.error;pos.pm;pos.eq.rafloatpmDEProper motion along DE (4)mas/yrpos.pm;pos.eq.decfloate_pmDErms uncertainty on pmDEmas/yrstat.error;pos.pm;pos.eq.decfloatRchi2Reduced {chi}^2^ (5)stat.fit.chi2float_RAComputed Right Ascension for Equinox: J2000degpos.eq.ra;meta.main_DEComputed Declination for Equinox: J2000degpos.eq.dec;meta.mainJ/ApJ/660/1428/table7ePSF position measurements for all exposuresrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintIDObject identifier (G1)meta.id;meta.maincharExpExposure identifier (hrcNN)meta.id;obs.exposurecharDXpixDistortion-corrected X positionpixpos.cartesian.x;instr.detdoublee_DXpixUncertainty in Xpixpixstat.errordoubleDYpixDistortion-corrected Y positionpixpos.cartesian.y;instr.detdoublee_DYpixUncertainty in Ypixpixstat.errordoubleNumNumber of bad pixel and distance to nearest bad one (1)meta.numberfloatRchi2Reduced {chi}^2^ of the ePSF fitstat.fit.chi2doubleXpixMeasured X position on chippixpos.cartesian.x;instr.detdoublee_XpixUncertainty in Xpixpixstat.error;pos.cartesian.xdoubleYpixMeasured Y position on chippixpos.cartesian.y;instr.detdoublee_YpixUncertainty in Ypixpixstat.error;pos.cartesian.ydoubleAmpAmplitude of effective PSF (ePSF)src.var.amplitudedoublee_AmpUncertainty in Ampstat.errorfloatSkySky levelinstr.skyLevelfloate_SkyUncertainty in Sky (0 = fixed sky value)stat.errorfloatJ/ApJ/660/1428/table9Merged positions for each epochrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintIDObject identifier (G1)meta.id;meta.maincharExpExposure identifier (hrcN)meta.id;obs.exposurecharDXpixDistortion-corrected X positionpixpos.cartesian.x;instr.detdoublee_DXpixUncertainty in D-Xpixpixstat.errordoubleDYpixDistortion-corrected Y positionpixpos.cartesian.y;instr.detdoublee_DYpixUncertainty in D-Ypixpixstat.errordoubleNumNumber of measurements (2x number of exposures)meta.numberintRchi2Reduced {chi}^2^ (={chi}^2^/(Num-6))stat.fit.chi2float