J/ApJ/896/124ivo://CDS.VizieR/J/ApJ/896/124doi:10.26093/cds/vizier.18960124CDSSugizaki M.Oeda M.Kawai N.Mihara T.Makishima K.Nakajima M.2021-12-03T13:33:27Z2021-11-30T07:30:31ZCDS support team

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

cds-question@unistra.frpulsarsx-ray-binary-starsx-ray-sourcesThis paper reports on the X-ray emission evolution of the ultraluminous Galactic X-ray pulsar Swift J0243.6+6124 during the giant outburst from 2017 October to 2018 January as observed by the MAXI GSC all-sky survey. The 2-30keV light curve and the energy spectra confirm the source luminosity LX assuming an isotropic emission reached 2.5x10^39^erg/s, 10 times higher than the Eddington limit for a 1.4M_{sun}_ neutron star. When the source was luminous with L_X_>~0.9x10^38^erg/s, it generally exhibited a negative correlation on a hardness-intensity diagram. However, two hardness ratios, a soft color (=4-10keV/2-4keV) and a hard color (=10-20keV/4-10keV), showed somewhat different behavior across a characteristic luminosity of L_c_~5x10^38^erg/s. The soft color changed more than the hard color when L_X_<L_c_, whereas the opposite was observed above Lc. The spectral change above Lc was represented by a broad enhanced feature at ~6keV on top of the canonical cutoff power-law continuum. The pulse profiles, derived daily, made the transition from a single-peak to a double-peak as the source brightened across Lc. These spectral and pulse-shape properties can be interpreted by a scenario in which the accretion columns on the neutron-star surface, producing the Comptonized X-ray emission, gradually became taller as LX increases. The broad 6keV enhancement could be a result of cyclotron-resonance absorption at ~10keV, corresponding to a surface magnetic field B_s_~1.1x10^12^G. The spin-frequency derivatives calculated with the Fermi GBM data showed a smooth positive correlation with LX up to the outburst peak, and its linear coefficient is comparable to those of typical Be binary pulsars whose B_s_ are (1-8)x10^12^G. These results suggest that the B_s_ of Swift J0243.6+6124 is a few times 10^12^G.2020ApJ...896..124Shttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/896/124CatalogResearchIsServedByTAP VizieR generic servicerelated-toB/vsx : AAVSO International Variable Star Index VSX (Watson+, 2006-2014)I/347 : Distances to 1.33 billion stars in Gaia DR2 (Bailer-Jones+, 2018)I/345 : Gaia DR2 (Gaia Collaboration, 2018)VIII/76 : Leiden/Argentine/Bonn (LAB) Survey of Galactic HI (Kalberla+ 2005)J/ApJS/238/32 : 3rd MAXI/GSC X-ray cat at high Galactic lat. (Kawamuro+, 2018)J/A+A/645/A18 : SVOM-ECLAIRs known X-ray sources catalogue (Dagoneau+, 2021)J/A+A/645/L8 : Plx & proper motions of OB stars from Gaia EDR3 (Xu+, 2021)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/896/124https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/896/124http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/896/124https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/896/124https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/896/124http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/896/124GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapX-rayRadiodefaultJ/ApJ/896/124/fig1X-ray light curves and hardness ratios of Swift J0243.6+6124 observed by the MAXI GSCrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintMJD[58001.5/58393.5] Modified Julian Datedtime.epochfloatF2-4keV[-0.22/14.4] Photon flux 2-4keV bandcount.cm**-2.s**-1phot.flux;em.X-ray.softdoublee_F2-4keV[0.007/0.61] F2-4keV uncertaintycount.cm**-2.s**-1stat.errordoubleF4-10keV[-0.4/13.8] Photon flux 4-10keV bandcount.cm**-2.s**-1phot.flux;em.X-ray.mediumdoublee_F4-10keV[0.007/0.4] F4-10keV uncertaintycount.cm**-2.s**-1stat.errordoubleF10-20keV[-0.4/4.2] Photon flux 10-20keV bandcount.cm**-2.s**-1phot.flux;em.X-ray.harddoublee_F10-20keV[0.01/0.4] F10-20keV uncertaintycount.cm**-2.s**-1stat.errordoublesCol[-26/154] 4-10keV/2-4keV hardness ratiophot.flux;arith.ratiodoublee_sCol[0.01/80158] SCol uncertaintystat.errordoublehCol[-49.7/16.4] 10-20keV/4-10keV hardness ratiophot.flux;arith.ratiodoublee_hCol[0.006/474] HCol uncertaintystat.errordoubleFlag[0/1] Data quality flag 1=good (246 occurrences), 0=degradedmeta.code.errorint