Deep Chandra observations of TeV binaries I: LSI +61 303

Abstract

We report on a 95ks Chandra observation of the TeV emitting High Mass X-ray Binary LSI +61 303, using the ACIS-S camera in Continuos Clocking mode to search for a possible X-ray pulsar in this system. The observation was performed while the compact object was passing from phase 0.94 to 0.98 in its orbit around the Be companion star (hence close to the apastron passage). We did not find any periodic or quasi-periodic signal (at this orbital phase) in a frequency range of 0.005-175 Hz. We derived an average pulsed fraction 3 sigma upper limit for the presence of a periodic signal of ~10% (although this limit is strongly dependent on the frequency and the energy band), the deepest limit ever reached for this object. Furthermore, the source appears highly variable in flux and spectrum even in this very small orbital phase range, in particular we detect two flares, lasting thousands of seconds, with a very hard X-ray spectrum with respect to the average source spectral distribution. The X-ray pulsed fraction limits we derived are lower than the pulsed fraction of any isolated rotational-powered pulsar, in particular having a TeV counterpart. In this scenario most of the X-ray emission of LSI +61 303 should necessarily come from the interwind or inner-pulsar wind zone shock rather than from the magnetosphere of the putative pulsar. Furthermore, we did not find evidence for the previously suggested extended X-ray emission (abridged).

9 pages, 6 figures, MNRAS in press

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• Long-term monitoring of the high-energy gamma-ray emission from LS I +61° 303 and LS 5039
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• On the binary nature of the gamma-ray sources AGL J2241+4454 (=MWC 656) and HESS J0632+057 (=MWC 148)
• Large-scale flow dynamics and radiation in pulsar gamma-ray binaries
• Unveiling the super-orbital modulation of LS I +61 303 in X-rays
• On the origin of correlated X-ray/VHE emission from LS I +61 303
• Deep Chandra observations of TeV binaries II: LS 5039
• Super-orbital variability of LS I +61°303 at TeV energies
• Possible changes of state and relevant timescales for a neutron star in LS I +61°303
• Variability in the orbital profiles of the X-ray emission of the gamma-ray binary LS I +61 303
• Long-term X-ray monitoring of LS I +61 303: analysis of spectral variability and flares
• Binaries with the eyes of CTA
• GeV detection of HESS J0632+057
• Extended X-ray emission in the vicinity of the microquasar LS 5039: pulsar wind nebula?
• Long-term monitoring of LS I+61303 with INTEGRAL
• Study of orbital and superorbital variability of LSI +61 303 with X-ray data
• The TeV binary HESS J0632+057 in the low and high X-ray state
• The missing GeV γ-ray binary: Searching for HESS J0632+057 with Fermi-LAT
• Search for radio pulsations in LS I +61 303
• H-alpha Emission Variability in the gamma-ray Binary LS I +61 303
• Multiwavelength Observations of The TeV Binary LS I +61 303 with VERITAS, Fermi-LAT and Swift-XRT During a TeV Outburst
• Chandra Imaging of Gamma-Ray Binaries
• NuSTAR Hard X-ray Observation of the Gamma-ray Binary Candidate HESS J1832-093
• Achromatic rapid flares in hard X-rays in the $\gamma$-ray binary LS I +61-303
• Rapid X-ray variability of the gamma-ray binary LS I+61 303