Disc precession to explain the superorbital modulation of LMC X-4: results from the Swift monitoring campaign - Archive ouverte HAL
Article Dans Une Revue Monthly Notices of the Royal Astronomical Society Année : 2022

Disc precession to explain the superorbital modulation of LMC X-4: results from the Swift monitoring campaign

Elena Ambrosi
  • Fonction : Auteur
Antonino d'Aì
  • Fonction : Auteur
Melania del Santo
  • Fonction : Auteur
Alberto Segreto
  • Fonction : Auteur
Carlo Ferrigno
  • Fonction : Auteur
Giancarlo Cusumano
  • Fonction : Auteur

Résumé

We studied the spectral changes of the high-mass X-ray binary system LMC X-4 to understand the origin and mechanisms beyond its superorbital modulation (30.4 d). To this aim, we obtained a monitoring campaign with Swift/XRT (0.3–10 keV) and complemented these data with the years-long Swift/BAT survey data (15–60 keV). We found a self-consistent, physically motivated, description of the broad-band X-ray spectrum using a Swift/XRT and a NuSTAR observation at the epoch of maximum flux. We decomposed the spectrum into the sum of a bulk + thermal Comptonization, a disc reflection component, and a soft contribution from a standard Shakura–Sunyaev accretion disc. We applied this model to 20 phase-selected Swift spectra along the superorbital period. We found a phase-dependent flux ratio of the different components, whereas the absorption column does not vary significantly. The disc emission is decoupled with respect to the hard flux. We interpret this as a geometrical effect in which the inner parts of the disc are tilted with respect to the obscuring outer regions.
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Dates et versions

hal-03594301 , version 1 (08-04-2023)

Identifiants

Citer

Elena Ambrosi, Antonino d'Aì, Melania del Santo, Alberto Segreto, Carlo Ferrigno, et al.. Disc precession to explain the superorbital modulation of LMC X-4: results from the Swift monitoring campaign. Monthly Notices of the Royal Astronomical Society, 2022, 512 (3), pp.3422-3435. ⟨10.1093/mnras/stac450⟩. ⟨hal-03594301⟩
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