Superorbital Phase Evolution and a Soft-Hard X-ray Phase Shift in LMC X-4
Fuente:
arXiv
Guardado en:
| Autor principal: | |
|---|---|
| Formato: | Preprint |
| Publicado: |
2026
|
| Materias: | |
| Acceso en línea: | |
| Etiquetas: |
Agregar Etiqueta
Sin Etiquetas, Sea el primero en etiquetar este registro!
|
| _version_ | 1866917274544242688 |
|---|---|
| author | Chou, Yi |
| author_facet | Chou, Yi |
| contents | The superorbital period of LMC X-4 is among the most stable known in Roche-lobe overflow, high-mass X-ray binaries. We analyzed 33 years of monitoring data from the Compton Gamma Ray Observatory Burst and Transient Source Experiment (CGRO BATSE), the Rossi X-ray Timing Explorer All-Sky Monitor (RXTE ASM), the Neil Gehrels Swift Burst Alert Telescope (Swift BAT), the Monitor of All-sky X-ray Image Gas Slit Camera (MAXI GSC), and the Fermi Gamma-ray Burst Monitor (Fermi GBM). The measured phases show a smooth long-term trend with superposed systematic fluctuations. Fits with cubic, quartic, and sinusoidal models indicate that the quartic and sinusoidal forms provide significantly better descriptions, with the sinusoidal model yielding an $8900^{+210}_{-230}$-day modulation. Such a long timescale is unlikely to arise from orbital motion around a tertiary companion. The fluctuations resemble stochastic, glitch-like events on several-hundred-day timescales. Their rms period variation exceeds that of the smooth trend, yet the total rms period variation over 33 years remains only 0.55\%, demonstrating the exceptional stability of the superorbital period. During MJD 57000-60461, we detect a phase offset of 0.044$\pm$0.010 cycles between the soft and hard X-ray bands. This offset can be reproduced by including a higher-harmonic term in the azimuthal disk model, allowing a transition from antisymmetric to asymmetric structure. A contemporaneous decline in the hard X-ray flux suggests a partial obscuration of the emission region, similar to the anomalous low state in Her X-1. This evolving-disk scenario may also explain the superorbital phase shift previously reported in Her X-1. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2602_13491 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Superorbital Phase Evolution and a Soft-Hard X-ray Phase Shift in LMC X-4 Chou, Yi High Energy Astrophysical Phenomena The superorbital period of LMC X-4 is among the most stable known in Roche-lobe overflow, high-mass X-ray binaries. We analyzed 33 years of monitoring data from the Compton Gamma Ray Observatory Burst and Transient Source Experiment (CGRO BATSE), the Rossi X-ray Timing Explorer All-Sky Monitor (RXTE ASM), the Neil Gehrels Swift Burst Alert Telescope (Swift BAT), the Monitor of All-sky X-ray Image Gas Slit Camera (MAXI GSC), and the Fermi Gamma-ray Burst Monitor (Fermi GBM). The measured phases show a smooth long-term trend with superposed systematic fluctuations. Fits with cubic, quartic, and sinusoidal models indicate that the quartic and sinusoidal forms provide significantly better descriptions, with the sinusoidal model yielding an $8900^{+210}_{-230}$-day modulation. Such a long timescale is unlikely to arise from orbital motion around a tertiary companion. The fluctuations resemble stochastic, glitch-like events on several-hundred-day timescales. Their rms period variation exceeds that of the smooth trend, yet the total rms period variation over 33 years remains only 0.55\%, demonstrating the exceptional stability of the superorbital period. During MJD 57000-60461, we detect a phase offset of 0.044$\pm$0.010 cycles between the soft and hard X-ray bands. This offset can be reproduced by including a higher-harmonic term in the azimuthal disk model, allowing a transition from antisymmetric to asymmetric structure. A contemporaneous decline in the hard X-ray flux suggests a partial obscuration of the emission region, similar to the anomalous low state in Her X-1. This evolving-disk scenario may also explain the superorbital phase shift previously reported in Her X-1. |
| title | Superorbital Phase Evolution and a Soft-Hard X-ray Phase Shift in LMC X-4 |
| topic | High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2602.13491 |