J/ApJ/917/69ivo://CDS.VizieR/J/ApJ/917/69doi:10.26093/cds/vizier.19170069CDSStrader J.Swihart S.J.Urquhart R.Chomiuk L.Aydi E.Bahramian A.,Kawash A.Sokolovsky K.V.Tremou E.Udalski A.2023-02-22T08:31:20Z2023-02-17T12:59:38ZCDS support team

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

cds-question@unistra.frpulsarsgamma-ray-astronomyx-ray-binary-starsvisible-astronomyspectroscopyphotometryWe report the discovery of a new low-mass X-ray binary near the center of the unassociated Fermi GeV {gamma}-ray source 4FGL J0540.0-7552. The source shows the persistent presence of an optical accretion disk and exhibits extreme X-ray and optical variability. It also has an X-ray spectrum well-fit by a hard power law with {Gamma}=1.8 and a high ratio of X-ray to {gamma}-ray flux. Together, these properties are consistent with the classification of the binary as a transitional millisecond pulsar (tMSP) in the subluminous disk state. Uniquely among the candidate tMSPs, 4FGL J0540.0-7552 shows consistent optical, X-ray, and {gamma}-ray evidence for having undergone a state change, becoming substantially brighter in the optical and X-rays and fainter in GeV {gamma}-rays sometime in mid-2013. In its current subluminous disk state, and like one other candidate tMSP in the Galactic field, 4FGL J0540.0-7552 appears to always be in an X-ray "flare mode", indicating that this could be common phenomenology for tMSPs.2021ApJ...917...69Shttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/917/69CatalogResearchIsServedByTAP VizieR generic servicerelated-toB/swift : Swift Master Catalog (HEASARC, 2004-)B/xmm : XMM-Newton Obs. Log (XMM-Newton Science Operation Center, 2012)I/352 : Distances to 1.47 billion stars in Gaia EDR3 (Bailer-Jones+, 2021)I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)J/MNRAS/360/974 : Proper motions of pulsars (Hobbs+, 2005)J/ApJS/199/31 : Fermi LAT second source catalog (2FGL) (Nolan+, 2012)J/ApJS/208/17 : 2nd Fermi LAT cat. of gamma-ray pulsars (2PC) (Abdo+, 2013)J/ApJ/788/48 : X-ray through NIR photometry of NGC 2617 (Shappee+, 2014)J/A+A/588/A103 : 2nd ROSAT all-sky survey (2RXS) sources (Boller+, 2016)J/MNRAS/458/3341 : 42 ms pulsars high-precision timing (Desvignes+, 2016)J/ApJ/831/89 : Eclipsing LMXB in 3FGL J0427.9-6704 (Strader+, 2016)J/ApJ/838/139 : Radio obs. of 3FGL unassociated sources (Schinzel+, 2017)J/ApJS/237/28 : WISE catalog of periodic variable stars (Chen+, 2018)J/ApJ/866/83 : Opt/NIR obs. of 1FGLJ1417.7-4407 (Swihart+, 2018)J/ApJ/872/42 : Opt. sp. of redback ms pulsar binaries (Strader+, 2019)J/ApJS/247/33 : Fermi LAT fourth source catalog (4FGL) (Abdollahi+, 2020)J/ApJ/901/57 : MAVERIC survey: X-ray sources in GCs (Bahramian+, 2020)J/ApJ/904/49 : 4FGLJ0407.7-5702 opt. sp. & light curve (Miller+, 2020)J/MNRAS/501/1116 : GAIA pulsars and where to find them (Antoniadis, 2021)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/917/69https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/917/69http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/917/69https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/917/69https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/917/69http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/917/69GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tap1.9867573869263685e-19 3.916500758235022e-19Gamma-rayX-rayOpticalRadiodefaultJ/ApJ/917/69/table1SOAR/Goodman photometry of J0540B (Gaia DR3 4648562676357022208)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintBMJD[59227/59233.3] Barycentric Modified Julian Date (BJD-2400000.5) on the TDB system (Eastman+ 2010PASP..122..935E)dtime.epochdoubleGmag[19.29/21.11] SOAR/Goodman G band (calibrated to Gaia G) magnitudemagphot.mag;em.optfloate_Gmag[0.007/0.04] Uncertainty in Gmagmagstat.error;phot.magfloat