J/A+A/706/A175ivo://CDS.VizieR/J/A+A/706/A175CDSDu Y.-J.Wang P.-J.Ducci L.Ji L.Kong L.-D.Bu Q.-C.Mehrotra C.,Santangelo A.2026-03-02T06:25:50Z2026-02-09T08:08:15ZCDS support team

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

cds-question@unistra.frpulsarsaccretiongamma-ray-astronomyWe investigated the long-term evolution of the cyclotron line energy, as well as the relationship between cyclotron line energy and luminosity in the high-mass X-ray binary Vela X-1, based on archival Swift/BAT monitoring from 2005 to 2024 and pulse-to-pulse analysis of nine NuSTAR observations from 2012 to 2024. Our results provide the first confirmation that the long-term decay of the harmonic line energy (E_cyc_,H) in Vela X-1 has ended. We further report the first detection of a transient increase in E_cyc_,H between 2020 and 2023, which suggests a sudden and significant change in the magnetic field configuration or accretion geometry. In addition, E_cyc_,H shows slightly lower values at low luminosities and tends to flatten at higher luminosities, in the range of (0.13-1.21)x10^37^erg/s. The fundamental line energy (E_cyc_,F) exhibits no significant variation with time or luminosity, remaining stable at approximately 25keV.2026A&A...706A.175Dhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/706/A175CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/A+A/377/925 : Radial velocity curves of Vela X-1 (Barziv+, 2001)J/A+A/395/129 : Cyclotron lines in Vela X-1 (Kreykenbohm+, 2002)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/706/A175https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/706/A175http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/706/A175https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/706/A175https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/706/A175http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/706/A175GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapGamma-rayRadiodefaultJ/A+A/706/A175/tablea1Best-fitting parameters of Vela X-1 from Swift/BAT monitoringrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTimeModified Julian Date interval of each spectrum (MJD)time.epochchartauCompCompton optical depthphys.absorption.opticalDepthfloatkTCompComptonizing plasma temperaturekeVphys.temperaturefloate_kTCompLower error on kTCompkeVstat.errorfloatE_kTCompUpper error on kTCompkeVstat.error;stat.maxfloate_tauCompLower error on tauCompstat.errorfloatE_tauCompUpper error on tauCompstat.error;stat.maxfloatEcyclHCentroid energy of the harmonic CRSFphys.energyfloate_EcyclHLower error on EcyclHstat.errorfloatE_EcyclHUpper error on EcyclHstat.error;stat.maxfloatsigmaHWidth of the harmonic CRSFkeVspect.line.widthfloate_sigmaHLower error on sigmaHkeVstat.errorfloatE_sigmaHUpper error on sigmaHkeVstat.error;stat.maxfloatDepthHLine depth of the harmonic CRSFkeVphys.absorption.opticalDepthfloate_DepthHLower error on DepthHkeVstat.errorfloatE_DepthHUpper error on DepthHkeVstat.error;stat.maxfloatJ/A+A/706/A175/tablea2NuSTAR phase-averaged spectra (eight observations)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintParamName of parameter as defined in the paper (G1)meta.id;stat.paramObsID1Value for ObsID = 10002007001stat.fit.paramObsID2Value for ObsID = 30002007002stat.fit.paramObsID3Value for ObsID = 30002007003stat.fit.paramObsID4Value for ObsID = 90402339002stat.fit.paramObsID5Value for ObsID = 30501003002stat.fit.paramObsID6Value for ObsID = 90602328002stat.fit.paramObsID7Value for ObsID = 90602328004stat.fit.paramObsID8Value for ObsID = 90602328006stat.fit.paramJ/A+A/706/A175/tablea3Pulse-to-pulse spectra for ObsID 10002007001recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintParamSpectral parameter names (G1)meta.note6769-9636Best-fit values for 6769-9636 [ct/pulse] amplitude rangestat.fit.param9636-13580Best-fit values for 9636-13580 [ct/pulse] amplitude rangestat.fit.param1358-16240Best-fit values for 1358-16240 [ct/pulste] amplitude rangestat.fit.param1624-27083Best-fit values for 1624-27083 [ct/pulste] amplitude rangestat.fit.paramJ/A+A/706/A175/tablea4Pulse-to-pulse spectra for ObsID 30002007003recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintParamSpectral parameter names (G1)meta.note304-2108Best-fit values for 304-2108 [ct/pulse] amplitude rangestat.fit.param2108-2557Best-fit values for 2108-2557 [ct/pulse] amplitude rangestat.fit.param2557-3422Best-fit values for 2557-3422 [ct/pulste] amplitude rangestat.fit.param3422-6340Best-fit values for 3422-6340 [ct/pulste] amplitude rangestat.fit.paramJ/A+A/706/A175/tablea5Pulse-to-pulse spectra for ObsID 305010030026693-8728Best-fit values for 6693-8728 [ct/pulste] amplitude rangestat.fit.param8728-18521Best-fit values for 8728-18521 [ct/pulste] amplitude rangestat.fit.paramrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintParamSpectral parameter names (G1)meta.note3113-5287Best-fit values for 3113-5287 [ct/pulse] amplitude rangestat.fit.param5287-6693Best-fit values for 5287-6693 [ct/pulse] amplitude rangestat.fit.paramJ/A+A/706/A175/tablea6Pulse-to-pulse spectra for ObsID 90402339002recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintParamSpectral parameter names (G1)meta.note372-2639Best-fit values for 372-2639 [ct/pulse] amplitude rangestat.fit.param2639-3581Best-fit values for 2639-3581 [ct/pulse] amplitude rangestat.fit.param3581-4382Best-fit values for 3581-4382 [ct/pulste] amplitude rangestat.fit.param4382-14043Best-fit values for 4382-14043 [ct/pulste] amplitude rangestat.fit.paramJ/A+A/706/A175/tablea7Pulse-to-pulse spectra for ObsID 91002349002recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintParamSpectral parameter names (G1)meta.note246-3098Best-fit values for 246-3098 [ct/pulse] amplitude rangestat.fit.param3098-5884Best-fit values for 3098-5884 [ct/pulse] amplitude rangestat.fit.param5884-12359Best-fit values for 5884-1235 [ct/pulste] amplitude rangestat.fit.param