Spectral analysis in orbital/superorbital phase space and hints of superorbital variability in the hard X-rays of LS I +61 303

Abstract

We present INTEGRAL spectral analysis in the orbital/superorbital phase space of LS I +61 303. A hard X-ray spectrum with no cutoff is observed at all orbital/superorbital phases. The hard X-ray index is found to be uncorrelated with the radio index (non-simultaneously) measured at the same orbital and superorbital phases. In particular, the absence of an X-ray spectrum softening during the periods of negative radio index does not favor a simple interpretation of the radio index variations in terms of changes of state in a microquasar. We uncover hints for the superorbital variability in the hard X-ray flux, in phase with the superorbital modulation in soft X-rays. An orbital phase drift of radio peak flux and index along the superorbital period is observed in the radio data. We explore its influence on a previously reported double peak structure of radio orbital lightcurve, posing it as a plausible explanation.

13 pages, 4 figures, 1 table; accepted to ApJ Letters

References in corpus (4)

• INTEGRAL and XMM-Newton observations of LSI +61 303
• Chandra Observations of the Gamma-ray Binary LSI+61303: Extended X-ray Structure?
• Superorbital modulation of X-ray emission from gamma-ray binary LSI +61 303
• Long-term periodicity in LSI+61303 as beat frequency between orbital and precessional rate

Cited by in corpus (12)

• Advances in Understanding High-Mass X-ray Binaries with INTEGRAL and Future Directions
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• Overview of non-transient gamma-ray binaries and prospects for the Cherenkov Telescope Array
• GeV detection of HESS J0632+057
• Study of orbital and superorbital variability of LSI +61 303 with X-ray data
• Orbital variability of the optical linear polarization of the $\gamma$-ray binary LS I +61 303 and new constraints on the orbital parameters
• The GeV emission of PSR B1259-63 during its last three periastron passages observed by Fermi-LAT
• Radio QPO in the $\gamma$-ray-loud X-ray binary LS I +61${}^{\circ }$303
• A Precessing Jet Scenario for the Multi-Wavelength Long-Term Modulation of LS I +61${}^{\circ }$303
• Temporal features of LS I +61${}^{\circ }$303 in hard X-rays from the Swift/BAT survey data
• Achromatic rapid flares in hard X-rays in the $\gamma$-ray binary LS I +61-303
• X-Ray spectral evolution of PSR~J2032+4127 during the 2017 periastron passage