Timing analysis of Swift J0243.6+6124 with NICER and Fermi/GBM during the decay phase of the 2017–2018 outburst

Serim M., DÖNMEZ Ç. K., Serim D., Ducci L., BAYKAL A., Santangelo A.

Monthly Notices of the Royal Astronomical Society, cilt.522, sa.4, ss.6115-6122, 2023 (SCI-Expanded, Scopus) identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 522 Sayı: 4
  • Basım Tarihi: 2023
  • Doi Numarası: 10.1093/mnras/stad1407
  • Dergi Adı: Monthly Notices of the Royal Astronomical Society
  • Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Academic Search Premier, Aerospace Database, Applied Science & Technology Source, Communication Abstracts, Compendex, INSPEC, Metadex, zbMATH, DIALNET, Civil Engineering Abstracts
  • Sayfa Sayıları: ss.6115-6122
  • Anahtar Kelimeler: accretion, accretion discs, methods: data analysis, pulsars: individual: Swift J0243.6+6124
  • TED Üniversitesi Adresli: Hayır

Özet

We present a timing and noise analysis of the Be/X-ray binary system Swift J0243.6+6124 during its 2017–2018 super-Eddington outburst using NICER/XTI observations. We apply a synthetic pulse timing analysis to enrich the Fermi/GBM spin frequency history of the source with the new measurements from NICER/XTI. We show that the pulse profiles switch from double-peaked to single-peaked when the X-ray luminosity drops below ∼7 × 1036 erg s−1. We suggest that this transitional luminosity is associated with the transition from a pencil beam pattern to a hybrid beam pattern when the Coulomb interactions become ineffective to decelerate the accretion flow, which implies a dipolar magnetic field strength of ∼5 × 1012 G. We also obtained the power density spectra (PDS) of the spin frequency derivative fluctuations. The red noise component of the PDS is found to be steeper (ω−3.36) than the other transient accreting sources. We find significantly high noise strength estimates above the super-Eddington luminosity levels, which may arise from the torque fluctuations due to interactions with the quadrupole fields at such levels.