J/ApJ/961/168ivo://CDS.VizieR/J/ApJ/961/168CDSKyer R.Albrecht S.Williams B.F.Hinton K.Binder B.Lazzarini M.,Garofali K.Lehmer B.Eracleous M.Plucinsky P.P.Antoniou V.2026-05-27T08:39:12Z2026-05-27T09:27:28ZCDS support team

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

cds-question@unistra.frx-ray-binary-starstransient-sourcesgalaxiesWe present a new five-epoch Chandra X-ray Observatory monitoring survey of the nearby spiral galaxy M33 which probes X-ray variability with time sampling between two weeks and four months. We characterize the X-ray variability of 55 bright point sources outside of the nucleus, many of which are expected to be high-mass X-ray binaries (HMXBs). We detect eight new candidate transients not detected in previous X-ray catalogs of M33 and discuss their possible nature. The final catalog includes 26 known HMXB candidates identified in the literature. We extend the baseline of the X-ray light curves up to 21yr by including archival X-ray observations of these sources. We compare the detection and nondetection epochs of the sources to suites of simulated source duty cycles and infer that most of our detected sources have duty cycles >30%. We find only four sources whose detection patterns are consistent with having duty cycles below 30%. This large fraction of sources with high duty cycles is unexpected for a population of HMXBs; thus more frequent X-ray monitoring will likely reveal many more low duty cycle HMXBs in M33.2024ApJ...961..168Khttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/961/168CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/ApJS/89/85 : Blue and red supergiants in M33 (Ivanov+ 1993)J/ApJ/609/735 : M31 Chandra X-ray sources (Williams+, 2004)J/ApJS/161/271 : The X-ray binary population in M33. I (Grimm+, 2005)J/A+A/451/835 : X-ray sources in M31/M33 (Hatzidimitriou+, 2006)J/A+A/448/1247 : XMM-Newton survey of M33 (Misanovic+, 2006)J/ApJ/643/356 : Transient X-ray sources in M31 (Williams+, 2006)J/A+A/469/807 : Catalogue of Galactic low-mass X-ray binaries (Liu+, 2007)J/AJ/134/2474 : Ha emission-line stars in 7 dwarfs galaxies (Massey+, 2007)J/ApJS/174/366 : Chandra ACIS survey of M33 (ChaSeM33) (Plucinsky+, 2008)J/ApJS/187/495 : SNRs in M33 from optical and X-ray (Long+, 2010)J/ApJS/192/6 : A GALEX UV imaging survey of nearby galaxies (Lee+, 2011)J/ApJ/733/123 : The Wolf-Rayet content of M33 (NGC 598) (Neugent+, 2011)J/ApJS/193/31 : M33 Chandra ACIS survey: final catalog (Tullmann+, 2011)J/MNRAS/419/2095 : HMXBs in nearby galaxies (Mineo+, 2012)J/other/Sci/337.444 : RV curves of Galactic massive O stars (Sana+, 2012)J/ApJ/764/41 : X-ray binary evolution across cosmic time (Fragos+, 2013)J/ApJ/776/L31 : Energy feedback from XRB from z=0 to z=19.92 (Fragos+, 2013)J/ApJ/774/136 : X-ray observations of SINGS galaxies (Tzanavaris+, 2013)J/AJ/150/94 : Chandra Local Volume Survey. I. (Binder+, 2015)J/MNRAS/449/4048 : The H{alpha} rotation curve of M33 (Kam+, 2015)J/ApJS/218/9 : Deep XMM-Newton survey of M33 (Williams+, 2015)J/A+A/586/A81 : High-mass X-ray binaries in the SMC (Haberl+, 2016)J/ApJS/222/15 : WATCHDOG: all-sky database of Gal. BHXBs (Tetarenko+, 2016)J/ApJ/836/50 : Chandra observations of IC 10 (Laycock+, 2017)J/MNRAS/473/4937 : AllWISE ctp to ROSAT/2RXS & XMMSLEW2 cat. (Salvato+, 2018)J/ApJ/887/20 : Deep Chandra survey of the SMC. III. HMXBs (Antoniou+, 2019)J/ApJS/243/3 : Chandra observations of SINGS galaxies (Lehmer+, 2019)J/MNRAS/501/2790 : The Swift Bulge Survey. 1st X-ray results (Bahramian+, 2021)J/ApJ/906/120 : X-Ray binary population in M31 (Lazzarini+, 2021)J/ApJ/907/17 : HMXB-dominant galaxy sample and properties (Lehmer+, 2021)J/ApJS/253/53 : PHATTER. I. HST obs. of stars in M33 (Williams+, 2021)J/ApJ/938/81 : PHATTER. IV. Star cluster catalog (Johnson+, 2022)J/MNRAS/517/2990 : ~1000 RC sources in M33 with the VLA (Tabatabaei+, 2022)J/A+A/677/A186 : UltraCompCAT catalog (Armas Padilla+, 2023)J/ApJ/952/114 : HMXBs in M33 with Chandra & HST obs. (Lazzarini+, 2023)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/961/168https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/961/168http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/961/168https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/961/168https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/961/168http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/961/168GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/961/168/table3 (Final source catalog)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/961/168/table3?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/961/168/table3?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/961/168/table3?GETtext/xml+votable180.050000true23.2990138930.645306940.0055555555555555566/2154-2155https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/961/168?format=asciiX-raydefaultJ/ApJ/961/168/table3Final source catalogrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameSource J2000 position-based namemeta.id;meta.maincharprimaryRAJ2000[23.29/23.72] Right Ascension (J2000)degpos.eq.ra;meta.mainDEJ2000[30.45/30.93] Declination (J2000)degpos.eq.dec;meta.mainPosErr[0.5/2.71] Positional error (1)arcsecstat.error;posfloatTheta[2.2/13.8] Average off-axis angle of source on detectorarcmininstr.offsetfloatNobs[1/10] Number of observationsmeta.numberintMatchArchival Matches (2)meta.id;meta.datasetcharT11Tullmann+ 2011, J/ApJS/193/31 Final Catalog designations (3)meta.id.crosscharDet[0.5/1]? Source detected in single pixel size wavdetect (4)meta.codefloatnullableM06Display data from Misanovic+ 2006, J/A+A/448/1247 within 7"meta.ref.urlintnullableW15Display data from Williams+ 2015, J/ApJS/218/9 within 8"meta.ref.urlintnullableJ/ApJ/961/168/table4Final catalog source likelihood and count ratesNameSource J2000 position-based namemeta.id;meta.maincharprimaryrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintObsIDChandra Observation identifier (1)meta.id;obs.param;obscharExp[4808/49748]? Exposure or Total exposure time (1)stime.expofloatnullablePNS1[0/1]? Catalog source likelihood, 0.35-8.0keVstat.likelihoodfloatnullablePNS2[0/1]? Catalog source likelihood, 0.35-1.1keVstat.likelihoodfloatnullablePNS3[0/1]? Catalog source likelihood, 1.1-2.6keVstat.likelihoodfloatnullablePNS4[0/1]? Catalog source likelihood, 2.6-8.0keVstat.likelihoodfloatnullablel_CR1Limit flag on CR1 (2)meta.code.errorcharCR1[-0.4/696]? Count rate, 0.35-8.0keV0.001count.s**-1phot.count;em.X-raydoublenullablee_CR1[0.05/10]? Lower uncertainty on CR10.001count.s**-1stat.error;phot.count;em.X-raydoublenullableE_CR1[0.08/10]? Upper uncertainty on CR10.001count.s**-1stat.error;phot.count;em.X-raydoublenullablel_CR2Limit flag on CR2 (2)meta.code.errorcharCR2[0.02/36]? Count rate, 0.35-1.1keV0.001count.s**-1phot.count;em.X-ray.softfloatnullablee_CR2[0.03/3]? Lower uncertainty on CR20.001count.s**-1stat.error;phot.count;em.X-ray.softfloatnullableE_CR2[0.05/3]? Upper uncertainty on CR20.001count.s**-1stat.error;phot.count;em.X-ray.softfloatnullablel_CR3Limit flag on CR3 (2)meta.code.errorcharCR3[0.04/408]? Count rate, 1.1-2.6keV0.001count.s**-1phot.count;em.X-rayfloatnullablee_CR3[0.03/9]? Lower uncertainty on CR30.001count.s**-1stat.error;phot.count;em.X-rayfloatnullableE_CR3[0.07/9]? Upper uncertainty on CR30.001count.s**-1stat.error;phot.count;em.X-rayfloatnullablel_CR4Limit flag on CR4 (2)meta.code.errorcharCR4[0.04/268]? Count rate, 2.6-8.0keV0.001count.s**-1phot.count;em.X-ray.mediumfloatnullablee_CR4[0.03/7]? Lower uncertainty on CR40.001count.s**-1stat.error;phot.count;em.X-ray.mediumfloatnullableE_CR4[0.07/8]? Upper uncertainty on CR40.001count.s**-1stat.error;phot.count;em.X-ray.mediumfloatnullable