A precessing stellar disk model for superorbital modulations of the gamma-ray binary LS I+61$^{\circ}$ 303
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| Format: | Preprint |
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2024
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| author | Chen, A. M. Takata, J. Yu, Y. W. |
| author_facet | Chen, A. M. Takata, J. Yu, Y. W. |
| contents | Gamma-ray binary LS I+61$^{\circ}$ 303 consists of a neutron star orbiting around a Be star with a period of $P_{\rm orb}\simeq26.5\ {\rm d}$. Apart from orbital modulations, the binary shows long-term flux variations with a superorbital period of $P_{\rm sup}\simeq4.6\ {\rm yrs}$ as seen in nearly all wavelengths. The origin of this superorbital modulation is still not well understood. Under the pulsar wind-stellar outflow interaction scenario, we propose that the superorbital modulations of LS I+61$^{\circ}$ 303 could be caused by the precession of the Be disk. Assuming X-rays arise from synchrotron radiation of the intrabinary shock, we develop an analytical model to calculate expected flux modulations over the orbital and superorbital phases. The asymmetric two-peak profiles in orbital light curves and sinusoidal-like long-term modulations are reproduced under the precessing disk scenario. The observed orbital phase drifting of the X-ray peak and our fitting of long-term X-ray data indicate that the neutron star is likely orbiting around the star with a small eccentricity and periastron phase around $Φ_{\rm p}\sim0.6$. We compare the Corbet diagrams of LS I+61$^{\circ}$ 303 with other Be/X-ray binaries and the linear correlation in the $P_{\rm sup}-P_{\rm orb}$ diagram suggests that the precession of the Be disk in LS I+61$^{\circ}$ 303 is induced by the tidal torque of its neutron star companion. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2409_04818 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | A precessing stellar disk model for superorbital modulations of the gamma-ray binary LS I+61$^{\circ}$ 303 Chen, A. M. Takata, J. Yu, Y. W. High Energy Astrophysical Phenomena Gamma-ray binary LS I+61$^{\circ}$ 303 consists of a neutron star orbiting around a Be star with a period of $P_{\rm orb}\simeq26.5\ {\rm d}$. Apart from orbital modulations, the binary shows long-term flux variations with a superorbital period of $P_{\rm sup}\simeq4.6\ {\rm yrs}$ as seen in nearly all wavelengths. The origin of this superorbital modulation is still not well understood. Under the pulsar wind-stellar outflow interaction scenario, we propose that the superorbital modulations of LS I+61$^{\circ}$ 303 could be caused by the precession of the Be disk. Assuming X-rays arise from synchrotron radiation of the intrabinary shock, we develop an analytical model to calculate expected flux modulations over the orbital and superorbital phases. The asymmetric two-peak profiles in orbital light curves and sinusoidal-like long-term modulations are reproduced under the precessing disk scenario. The observed orbital phase drifting of the X-ray peak and our fitting of long-term X-ray data indicate that the neutron star is likely orbiting around the star with a small eccentricity and periastron phase around $Φ_{\rm p}\sim0.6$. We compare the Corbet diagrams of LS I+61$^{\circ}$ 303 with other Be/X-ray binaries and the linear correlation in the $P_{\rm sup}-P_{\rm orb}$ diagram suggests that the precession of the Be disk in LS I+61$^{\circ}$ 303 is induced by the tidal torque of its neutron star companion. |
| title | A precessing stellar disk model for superorbital modulations of the gamma-ray binary LS I+61$^{\circ}$ 303 |
| topic | High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2409.04818 |