J/ApJ/831/89ivo://CDS.VizieR/J/ApJ/831/89doi:10.26093/cds/vizier.18310089CDSStrader J.Li K.-L.Chomiuk L.Heinke C.O.Udalski A.Peacock M.,Shishkovsky L.Tremou E.2017-06-13T11:08:58Z2017-02-27T13:03:54ZCDS support team

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

cds-question@unistra.frx-ray-binary-starsinfrared-photometryvisible-astronomybroad-band-photometrygamma-ray-astronomyWe report the discovery of an eclipsing low-mass X-ray binary at the center of the 3FGL error ellipse of the unassociated Fermi/Large Area Telescope {gamma}-ray source 3FGL J0427.9-6704. Photometry from OGLE and the SMARTS 1.3m telescope and spectroscopy from the SOAR telescope have allowed us to classify the system as an eclipsing low-mass X-ray binary (P=8.8hr) with a main-sequence donor and a neutron-star accretor. Broad double-peaked H and He emission lines suggest the ongoing presence of an accretion disk. Remarkably, the system shows separate sets of absorption lines associated with the accretion disk and the secondary, and we use their radial velocities to find evidence for a massive (~1.8-1.9M_{sun}_) neutron-star primary. In addition to a total X-ray eclipse with a duration of ~2200s observed with NuSTAR, the X-ray light curve also shows properties similar to those observed among known transitional millisecond pulsars: short-term variability, a hard power-law spectrum ({Gamma}~1.7), and a comparable 0.5-10keV luminosity (~2.4x10^33^erg/s). We find tentative evidence for a partial (~60%) {gamma}-ray eclipse at the same phase as the X-ray eclipse, suggesting the {gamma}-ray emission may not be confined to the immediate region of the compact object. The favorable inclination of this binary is promising for future efforts to determine the origin of {gamma}-rays among accreting neutron stars.2016ApJ...831...89Shttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/831/89CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/ApJ/820/8 : 3FGL sources statistical classifications (Saz Parkinson+, 2016)J/ApJS/218/23 : Fermi LAT third source catalog (3FGL) (Acero+, 2015)J/ApJS/209/9 : Unidentified gamma-ray sources. IV. X-ray (Paggi+, 2013)J/ApJS/208/17 : 2nd Fermi LAT cat. of gamma-ray pulsars (2PC) (Abdo+, 2013)J/ApJS/207/19 : Hard X-ray survey from Swift-BAT 2004-2010 (Baumgartner+, 2013)J/AcA/63/1 : OGLE-IV Magellanic Bridge Data supernovae (Kozlowski+, 2013)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/831/89https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/831/89http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/831/89https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/831/89https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/831/89http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/831/89GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticalInfraredGamma-raydefaultJ/ApJ/831/89/table1OGLE and SMARTS photometry of 3FGL J0427.9-6704recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintBJDBarycentric Julian Date (TDB) of observationdtime.epochdoublemag[15.5/20.3] Photometric Vega magnitude in Bandmagphot.magfloate_mag[0.004/0.4] Uncertainty in magmagstat.error;phot.magfloatBand[BVIH] Photometric band used in the observationinstr.setup;obschar