Spectropolarimetric Study on Circumstellar Structure of Microquasar LS I +61deg 303

Abstract

We present optical linear spectropolarimetry of the microquasar LS I +61${}^{\circ }$ 303. The continuum emission is mildly polarized (up to 1.3 %) and shows almost no temporal change. We find a distinct change of polarization across the H$\alpha$ emission line, indicating the existence of polarization component intrinsic to the microquasar. We estimate the interstellar polarization (ISP) component from polarization of the H$\alpha$ line and derive the intrinsic polarization component. The wavelength dependence of the intrinsic component is well explained by Thomson scattering in equatorial disk of the Be-type mass donor. The position angle (PA) of the intrinsic polarization $\sim 25^{\circ }$ represents the rotational axis of the Be disk. This PA is nearly perpendicular to the PA of the radio jet found during quiescent phases. Assuming an orthogonal disk-jet geometry around the compact star, the rotational axis of the accretion disk is almost perpendicular to that of the Be disk. Moreover, according to the orbital parameters of the microquasar, the compact star is likely to get across the Be disk around their periastron passage. We discuss the peculiar circumstellar structure of this microquasar inferred from our observation and possible connection with its high-energy activities.

17pages, 7figures; accepted for Publications of the Astronomical Society of Japan

References in corpus (7)

• Variable Very High Energy Gamma-ray Emission from the Microquasar LS I +61 303
• Orbital Parameters of the Microquasar LSI +61 303
• XMM-Newton observations of PSr B1259-63 near the 2004 periastron passage
• 13 Years of Timing of PSR B1259-63
• LSI+61303 in the context of microquasars
• A microquasar shot out from its birth place
• Optical polarimetric observations of the microquasar LS 5039

Cited by in corpus (5)

• The Black Hole Candidate LSI+61303
• A Radio Pulsar Search of the Gamma-ray Binaries LS I +61 303 and LS 5039
• Orbital variability of the optical linear polarization of the $\gamma$-ray binary LS I +61 303 and new constraints on the orbital parameters
• Revisiting LS I +61 303 with VLBI astrometry
• Simultaneous long-term monitoring of LS I +61°303 by OVRO and Fermi-LAT