Superorbital modulation at GeV energies in the gamma-ray binary LS I +61 303

Abstract

We report the results from our analysis of 8 years of the data for the gamma-ray binary LS I +61 303, obtained with the Large Area Telescope onboard the Fermi Gamma-Ray Space Telescope. We find a significant dip around the binary's periastron in the superorbital light curves, and by fitting the light curves with a sinusoidal function, clear phase shifts are obtained. The superorbital modulation seen in the binary has been long known and different scenarios have been proposed. Based on our results, we suggest that the circumstellar disk around the Be companion of this binary has an elliptical shape and the major axis of the disk rotates at the superorbital period of 1667 days. As a result, the density of the ambient material around the compact star of the binary changes along the binary orbit over the superorbital period, causing the phase shifts in the modulation, and around periastron, the compact star probably enters the disk, causing the appearance of the dip. Numerical simulations may be conducted in order to study the detailed physical processes and verify our suggestion.

11 pages, 6 figures

References in corpus (14)

• Gamma-ray binaries: pulsars in disguise ?
• Accretion vs colliding wind models for the gamma-ray binary LS I +61 303: an assessment
• Periodic very high energy gamma-ray emission from LS I +61 303 observed with the MAGIC telescope
• Joint H-alpha and X-Ray Observations of Massive X-Ray Binaries. II. The Be X-ray Binary and Microquasar LS I +61 303
• Be discs in binary systems I. Coplanar orbits
• High-Energy emissions from the Pulsar/Be binary system PSR J2032+4127/MT91 213
• Superorbital modulation of X-ray emission from gamma-ray binary LSI +61 303
• Super-orbital variability of LS I +61°303 at TeV energies
• Origin of the long-term modulation of radio emission of LS I +61 303
• Optical spectroscopy of Be/gamma-ray binaries
• The Multi-wavelength Characteristics of the TeV Binary LS I +61${}^{\circ }$ 303
• Understanding the periodicities in radio and GeV emission from LS I+61303
• Orbital and superorbital variability of LS I +61 303 at low radio frequencies with GMRT and LOFAR
• Fermi Study of 5-300 GeV emission from the high-mass pulsar binary PSR B1259-63/LS 2883

Cited by in corpus (7)

• Advances in Understanding High-Mass X-ray Binaries with INTEGRAL and Future Directions
• Discovery of the Galactic High-Mass Gamma-ray Binary 4FGL J1405.1-6119
• Overview of non-transient gamma-ray binaries and prospects for the Cherenkov Telescope Array
• Evidence for periodic accretion-ejection in LSI+61303
• Modelling the correlated keV/TeV light curves of Be/gamma-ray binaries
• Simultaneous long-term monitoring of LS I +61°303 by OVRO and Fermi-LAT
• A precessing stellar disk model for superorbital modulations of the gamma-ray binary LS I+61${}^{\circ }$ 303