J/ApJ/879/112ivo://CDS.VizieR/J/ApJ/879/112doi:10.26093/cds/vizier.18790112CDSJin R.Kong A.K.H.2021-09-10T09:08:33Z2021-01-18T15:02:00ZCDS support team

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

cds-question@unistra.frgalaxiesx-ray-sourcessupernovaex-ray-binary-starsvisible-astronomyX-ray point sources in galaxies are dominated by X-ray binaries (XRBs) that are variables or transients, and whether their variability would alter the X-ray luminosity functions (XLFs) is still in debate. Here we report on NGC 7331 as an example to test this with seven Chandra observations. Their detection limit is 7x10^37^erg/s in the energy range 0.3-8.0keV by assuming a power-law (PL) spectral model with a photon index of 1.7. We detected 55 X-ray sources. Thirteen of them are variables, of which three are transients, and some of the sources possess a bimodal feature in their luminosity-hardness ratio, which is often observed among XRBs. Nine more ultraluminous X-ray sources are found in comparison with previous studies and eight are likely to be low-mass or high-mass XRBs. Twenty-one optical counterpart candidates are found based on the Hubble Space Telescope images, but we cannot rule out the possibility of positional coincidence. The spectral analysis of SN 2014C shows a trend of increasing soft photons and decreasing hydrogen column densities as its outer shell expands. We fit the seven incompleteness-corrected XLFs to both a PL and a PL with an exponential cut-off (PLC) model using the Bayesian method, which is used for the first time in XLF fitting. The hierarchical PLC model can describe the XLF of NGC 7331 best with a slope of ~0.5 and a luminosity cut-off around 8x10^38^erg/s. This study proves that multi-epoch observations decrease the deviation due to the variable luminous sources in XLFs.2019ApJ...879..112Jhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/879/112CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toB/chandra : The Chandra Archive Log (CXC, 1999-2014)B/hst : HST Archived Exposures Catalog (STScI, 2007)VIII/10 : Bell Laboratories H I Profiles (Stark+ 1992)VIII/28 : Bell Laboratories H I Survey (Stark+ 1992)J/ApJS/79/77 : Bell Lab. H I Survey - High Velocity Clouds (Stark+ 1992)J/A+AS/131/317 : NGC 7331 HII regions catalogue (Petit 1998)J/AJ/122/2810 : Chandra Deep Field North Survey. V. (Brandt+, 2001)J/ApJ/577/738 : M31 Chandra X-ray point sources (Kong+, 2002)J/ApJ/589/225 : Chandra X-ray sources toward Galactic Center (Muno+, 2003)J/ApJ/599/218 : Chandra LMXB in NGC 4365 and NGC 4382 (Sivakoff+, 2003)J/ApJS/144/213 : Chandra X-ray observations of M81 (Swartz+, 2003)J/ApJ/602/231 : Chandra X-ray point sources in nearby gal. (Colbert+, 2004)J/ApJS/161/271 : The X-ray binary population in M33. I (Grimm+, 2005)J/ApJS/173/572 : GALEX/Spitzer photometry in NGC 7331 (Thilker+, 2007)J/AJ/136/2782 : Star formation efficiency in nearby galaxies (Leroy+, 2008)J/ApJ/735/26 : Chandra observations of M81 (Sell+, 2011)J/ApJ/741/49 : ULX candidates in nearby galaxies (Swartz+, 2011)J/ApJ/836/50 : Chandra observations of IC 10 (Laycock+, 2017)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/879/112https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/879/112http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/879/112https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/879/112https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/879/112http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/879/112GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/879/112/table2 (Chandra source properties)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/879/112/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/879/112/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/879/112/table2?GETtext/xml+votable180.050000true339.2264833334.440888890.0055555555555555566/13522https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/879/112?format=asciiX-rayOpticaldefaultJ/ApJ/879/112/table2Chandra source propertiesClassClass (5)meta.code.classcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSeq[1/55] Source numbermeta.id;meta.mainintRAJ2000[22] Hour of Right Ascension (J2000)pos.eq.ra;meta.mainDEJ2000[34] Degree of Declination (J2000)pos.eq.dec;meta.mainNcts[9/1437] Net counts (1)ctphot.count;em.X-rayintCR[0.04/5.2] Count rate (2)0.01count.s**-1phot.count;em.X-rayfloate_CR[0.02/0.3] Lower uncertainty in CR (2)0.01count.s**-1stat.errorfloatE_CR[0.02/0.3] Upper uncertainty in CR (2)0.01count.s**-1stat.error;stat.maxfloatFlux[0.4/63] Flux; 10^-14^erg/s/cm^2^ (3)1e-14mW.m**-2phot.flux;em.X-rayfloate_Flux[0.1/2.8] Lower uncertainty in Flux1e-14mW.m**-2stat.error;phot.fluxfloatE_Flux[0.2/3] Upper uncertainty in Flux1e-14mW.m**-2stat.error;stat.maxfloatLx[1e+38/1.7e+40] X-ray luminosity; erg/s (4)1e-07Wphys.luminosity;em.X-raydouble