J/ApJ/851/31ivo://CDS.VizieR/J/ApJ/851/31doi:10.26093/cds/vizier.18510031CDSSwihart S.J.Strader J.Johnson T.J.Cheung C.C.Sand D.Chomiuk L.,Wasserman A.Larsen S.Brodie J.P.Simonian G.V.Tremou E.,Shishkovsky L.Reichart D.E.Haislip J.2018-10-22T13:11:26Z2018-09-10T10:29:17ZCDS support team

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

cds-question@unistra.frgamma-ray-astronomyspectroscopic-binary-starsinfrared-photometryvisible-astronomybroad-band-photometryradial-velocityspectroscopyWe present optical photometric and spectroscopic observations of the likely stellar counterpart to the unassociated Fermi Large Area Telescope (LAT) {gamma}-ray source 2FGL J0846.0+2820, selected for study based on positional coincidences of optical variables with unassociated LAT sources. Using optical spectroscopy from the SOAR telescope, we have identified a late-G giant in an eccentric (e=0.06) 8.133-day orbit with an invisible primary. Modeling the spectroscopy and photometry together led us to infer a heavy neutron star primary of ~2M_{sun}_ and a partially stripped giant secondary of ~0.8M_{sun}_. H{alpha} emission is observed in some of the spectra, perhaps consistent with the presence of a faint accretion disk. We find that the {gamma}-ray flux of 2FGL J0846.0+2820 dropped substantially in mid-2009, accompanied by an increased variation in the optical brightness, and since then, it has not been detected by Fermi. The long period and giant secondary are reminiscent of the {gamma}-ray bright binary 1FGL J1417.7-4407, which hosts a millisecond pulsar (MSP) apparently in the final stages of the pulsar recycling process. The discovery of 2FGL J0846.0+2820 suggests the identification of a new subclass of MSP binaries that are the likely progenitors of typical field MSPs.2017ApJ...851...31Shttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/851/31CatalogResearchIsServedByTAP VizieR generic servicerelated-toB/vsx : AAVSO International Variable Star Index VSX (Watson+, 2006-2014)II/183 : UBVRI Photometric Standards (Landolt 1992)I/284 : The USNO-B1.0 Catalog (Monet+ 2003)II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)V/139 : The SDSS Photometric Catalog, Release 9 (Adelman-McCarthy+, 2012)J/A+AS/146/407 : Symbiotic stars catalogue (Belczynski+, 2000)J/ApJS/188/405 : Fermi-LAT first source catalog (1FGL) (Abdo+, 2010)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/ApJS/213/9 : Catalina Surveys periodic variable stars (Drake+, 2014)J/ApJS/218/23 : Fermi LAT third source catalog (3FGL) (Acero+, 2015)J/ApJ/831/89 : Eclipsing LMXB at the center of 3FGL J0427.9-6704 (Strader+,https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/851/31https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/851/31http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/851/31https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/851/31https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/851/31http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/851/31GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapGamma-rayInfraredOpticaldefaultJ/ApJ/851/31/table1PROMPT photometry of 2FGL J0846.0+2820recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintJD[7057.6/7181.5] Julian Date, JD-2450000dtime.epochdoubleBandObservational band (B, V or R)meta.code;instr.filtercharmag[6.3/17.4] Apparent magnitude in Bandmagphot.magfloate_mag[0.01/3] The 1{sigma} error in magmagstat.error;phot.magfloatJ/ApJ/851/31/table2Barycentric radial velocities of J0846recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintBJDBarycentric Julian Datedtime.epochdoublef_BJD[a] a: from the Keck/HIRES spectrummeta.codecharRV[-12.4/97] Barycentric radial velocitykm/sphys.veloc;pos.barycenterfloate_RV[0.9/3.4] RV uncertaintykm/sstat.errorfloat