J/A+A/682/A151ivo://CDS.VizieR/J/A+A/682/A151doi:10.26093/cds/vizier.36820151CDSSacchi A.Esposito P.de Martino D.Soria R.Israel G.L.Sander A.A.C.,Sidoli L.Buckley D.A.H.Monageng I.M.Tiengo A.Arca Sedda M.,Pinto C.Di Stefano R.Imbrogno M.Carleo A.Rivolta G.2024-11-06T20:06:56Z2024-02-14T07:58:17ZCDS support team

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

cds-question@unistra.frgalaxiesx-ray-sourcesvisible-astronomyspectroscopyWe investigate the nature of CXOU J005440.5-374320 (J0054), a peculiar bright (~4x10^39^erg/s) and soft X-ray transient in the spiral galaxy NGC300 with a six-hour periodic flux modulation that was detected in a 2014 Chandra observation. Subsequent observations with Chandra and XMM-Newton, as well as a large observational campaign of NGC300 and its sources performed with the Swift Neil Gehrels Observatory, showed that this source exhibits recurrent flaring activity: four other outbursts were detected across 8 years of monitoring. Using data from the Swift/UVOT archive and from the XMM-Newton/OM and Gaia catalogues, we determined that the source is likely associated with a bright blue optical/ultraviolet counterpart. This prompted us to perform followup observations with the Southern African Large Telescope in December 2019. With the multi-wavelength information at hand, we discuss several possibilities for the nature of J0054. Although none is able to account for the full range of the observed peculiar features, we found that the two most promising scenarios are a stellar-mass compact object in a binary system with a Wolf-Rayet star companion, or the recurrent tidal stripping of a stellar object trapped in a system with an intermediate-mass (1000M_{sun}_) black hole.2024A&A...682A.151Shttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/682/A151CatalogResearchIsServedByTAP VizieR generic servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/682/A151https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/682/A151http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/682/A151https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/682/A151https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/682/A151http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/682/A151GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapX-rayOpticaldefaultJ/A+A/682/A151/spectrumSALT spectrum of CXOU J005440.5-374320recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintlambdaWavelength0.1nmem.wldoubleCountsCountsctphot.count;em.X-raydouble