Torque-dependent orbital modulation of X-ray pulsar Cen X-3

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Hauptverfasser: Liao, Zhenxuan, Liu, Jiren
Format: Preprint
Veröffentlicht: 2024
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author Liao, Zhenxuan
Liu, Jiren
author_facet Liao, Zhenxuan
Liu, Jiren
contents Cen X-3 shows alternate spin-up/spin-down episodes lasting for tens of days. We study the orbital profiles and spectra of Cen X-3 during these spin-up/spin-down intervals, using long-term data monitored by Fermi/GBM, Swift/BAT and MAXI/GSC. In spin-up intervals, its orbital profile in 2-10 keV is symmetrically peaked around orbital phase 0.42, while in spin-down intervals of similar fluxes and similar magnitudes of spin change rate, its profile reaches a peak around orbital phase 0.22 and then declines gradually. Such a distinct orbital difference between spin-up and spin-down states of similar flux is hard to explain in the standard disk model and indicates that its torque reversals are related to processes on the orbital scale. The durations of continuous spin-up/spin-down trend (tens of days) also point to a superorbital variation. One possible scenario is the irradiation-driven warping disk instability, which may produce a flipped inner disk for tens of days.
format Preprint
id arxiv_https___arxiv_org_abs_2401_09197
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Torque-dependent orbital modulation of X-ray pulsar Cen X-3
Liao, Zhenxuan
Liu, Jiren
High Energy Astrophysical Phenomena
Cen X-3 shows alternate spin-up/spin-down episodes lasting for tens of days. We study the orbital profiles and spectra of Cen X-3 during these spin-up/spin-down intervals, using long-term data monitored by Fermi/GBM, Swift/BAT and MAXI/GSC. In spin-up intervals, its orbital profile in 2-10 keV is symmetrically peaked around orbital phase 0.42, while in spin-down intervals of similar fluxes and similar magnitudes of spin change rate, its profile reaches a peak around orbital phase 0.22 and then declines gradually. Such a distinct orbital difference between spin-up and spin-down states of similar flux is hard to explain in the standard disk model and indicates that its torque reversals are related to processes on the orbital scale. The durations of continuous spin-up/spin-down trend (tens of days) also point to a superorbital variation. One possible scenario is the irradiation-driven warping disk instability, which may produce a flipped inner disk for tens of days.
title Torque-dependent orbital modulation of X-ray pulsar Cen X-3
topic High Energy Astrophysical Phenomena
url https://arxiv.org/abs/2401.09197