1 Ocak 2022 Dergi makalesi Açık Erişim

Allak, S.; Akyuz, A.; Oralhan, I. Akkaya; Avdan, S.; Aksaker, N.; Vinokurov, A.; Soydugan, F.; Sonbas, E.; Dhuga, K. S.

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{
  "DOI": "10.1093/mnras/stab3693", 
  "abstract": "We present the results of a temporal and spectral analysis of the transient source ULX-4 in the galaxy M51. The data used were drawn from Chandra, XMM-Newton, and Swift-XRT archives, spanning the years 2000-2019.. The X-ray flux of the source is seen to vary by two orders of magnitudes within a month but a short-term variability was not observed over the time intervals of 100-2000 s in the 0.3-10 keV energy band. We find some evidence for the existence of bi-modality feature in the flux distribution of ULX-4. We identified two optical sources as possible counterparts within an error radius of 0.'' 18 at 95 per cent confidence level for ULX-4 based on the archival Hubble Space Telescope (HST)/ACS and HST/WFC3 data. Blackbody fits of the spectral energy distributions (SEDs) indicate the spectral type to be B-type stars. One of these counterparts exhibits a low-amplitude optical periodicity of 264 +/- 37 d in the F606W filter; if we assume this apparent periodicity is associated with the orbital motion of the donor, then it is more likely that the donor is a red supergiant satisfying the long periodicity and accretion via Roche lobe overflow. Consequently, the SED would then have to be interpreted as a superposition of emissions from a cold donor and a hot flow component, most likely from an accretion disc. If, on the other hand, the periodicity is superorbital in nature i.e. due to possible interactions of the compact object with a circumstellar disc, the donor could then be a Be/X star hosting a neutron star.", 
  "author": [
    {
      "family": "Allak", 
      "given": " S."
    }, 
    {
      "family": "Akyuz", 
      "given": " A."
    }, 
    {
      "family": "Oralhan", 
      "given": " I. Akkaya"
    }, 
    {
      "family": "Avdan", 
      "given": " S."
    }, 
    {
      "family": "Aksaker", 
      "given": " N."
    }, 
    {
      "family": "Vinokurov", 
      "given": " A."
    }, 
    {
      "family": "Soydugan", 
      "given": " F."
    }, 
    {
      "family": "Sonbas", 
      "given": " E."
    }, 
    {
      "family": "Dhuga", 
      "given": " K. S."
    }
  ], 
  "container_title": "MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY", 
  "id": "256679", 
  "issue": "3", 
  "issued": {
    "date-parts": [
      [
        2022, 
        1, 
        1
      ]
    ]
  }, 
  "page": "4355-4369", 
  "title": "The transient ultraluminous X-ray source, ULX-4, in M51", 
  "type": "article-journal", 
  "volume": "510"
}