XMM-Newton observation of a spectral state transition in the peculiar radio/X-ray/gamma-ray source LS I +61 303

Abstract

We report the results of XMM-Newton and BeppoSAX observations of the radio and X-ray emitting star LS I +61 303, likely associated with the gamma-ray source 2CG 135+01 and recently detected also at TeV energies. The data include a long XMM-Newton pointing carried out in January 2005, which provides the deepest look ever obtained for this object in the 0.3-12 keV range. During this observation the source flux decreased from a high level of 13E12 erg/cm2/s to 4E12 erg/cm2/s within 2-3 hours.This flux range is the same seen in shorter and less sensitive observations carried out in the past, but the new data show for the first time that transitions between the two levels can occur on short time scales. The flux decrease was accompanied by a significant softening of the spectrum, which is well described by a power law with photon index changing from 1.62+/-0.1 to 1.83+/-0.1. A correlation between hardness and intensity is also found when comparing different short observations spanning almost 10 years and covering various orbital phases.LS I +61 303 was detected in the 15-70 keV range with the PDS instrument in one of the BeppoSAX observations, providing evidence for variability also in the hard X-ray range. The X-ray spectra, discussed in the context of multiwavelength observations, place some interesting constraints on the properties and location of the high-energy emitting region.

arXiv commentRevised version, accepted for publication in A&A. Updated references, few typos corrected, minor changes following referee's suggestions

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• A compact pulsar wind nebula model of the gamma-ray loud binary LS I +61 303
• Multi-wavelength (radio, X-ray and gamma-ray) observations of the gamma-ray binary LS I +61 303
• Correlated X-ray and Very High Energy emission in the gamma-ray binary LS I +61 303
• Investigating the disc-jet coupling in accreting compact objects using the black hole candidate Swift J1753.5-0127
• Chandra Observations of the Gamma-ray Binary LSI+61303: Extended X-ray Structure?
• Long Term X-ray Monitoring Of The TeV Binary LS I +61 303 with RXTE
• Pulsar wind zone processes in LS 5039
• Multiwavelength Observations of LS I +61 303 with VERITAS, Swift and RXTE
• Non-thermal emission from secondary pairs in close TeV binary systems
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• Deep Chandra observations of TeV binaries I: LSI +61 303
• On the origin of correlated X-ray/VHE emission from LS I +61 303
• gamma-ray emission from LS I +61 303: The impact of basic system uncertainties
• Deep Chandra observations of TeV binaries II: LS 5039
• Swift/XRT monitoring of five orbital cycles of LSI +61 303
• The Black Hole Candidate LSI+61303
• Binaries with the eyes of CTA
• 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
• Intrinsic physical properties and Doppler boosting effects in LSI+61303
• Overview of non-transient gamma-ray binaries and prospects for the Cherenkov Telescope Array
• 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
• Theoretical overview on high-energy emission in microquasars
• Searches for periodic neutrino emission from binary systems with 22 and 40 strings of IceCube
• Modelling the correlated keV/TeV light curves of Be/gamma-ray binaries
• A precessing stellar disk model for superorbital modulations of the gamma-ray binary LS I+61${}^{\circ }$ 303
• Implications of the radio spectral index transition in LS I +61°303 for its INTEGRAL data analysis
• VHE Gamma-rays from Galactic X-ray Binary Systems
• 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
• Optical microflares in LS I +61 303 and the search for their multiwavelength counterpart
• LS I+61 303: microquasar or not microquasar?
• On the X-ray/TeV connection in Galactic jet sources
• Spectral lags of flaring events in $LSI+61^o$ 303 from RXTE Observations