Simultaneous X‐Ray and Radio Monitoring of the Unusual Binary LS I +61o303: Measurements of the Light Curve and High‐Energy Spectrum

Harrison, F.; Ray, Paul S.; Leahy, D. A.; Waltman, E. B.; Pooley, G. G.

doi:10.1086/308157

Cited by 89 publications

(141 citation statements)

References 19 publications

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“…2 that the computed radio flux is not particularly high during periastron, although it strongly increases later on, as it is observed (see Ray et al 1997 for example). The computed X-ray luminosity is the highest around phase 0.5, like for TeV radiation, and is similar to what is observed in both energy bands (Harrison et al 2000 andAlbert et al 2006, respectively). There is a clear peak for computed GeV emission at periastron passage, as observed, and at phase 0.5 our model predicts just a smooth bump, with flux levels between those found in Radio and X-ray data at periastron and phase 0.5 are available from the literature and shown.…”

Section: Discussionsupporting

confidence: 83%

The radio to TeV orbital variability of the microquasar LS I +61 303

Bosch‐Ramon¹,

Paredes²,

Romero³

et al. 2006

A&A

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Context. The microquasar LS I +61 303 has recently been detected at TeV energies by the Cherenkov telescope MAGIC, presenting variability on timescales similar to its orbital period. This system has been intensively observed at different wavelengths during the last three decades, showing a very complex behavior along the orbit. Aims. We aim to explain, using a leptonic model in the accretion scenario, the observed orbital variability and spectrum from radio to TeV energies of LS I +61 303. Methods. We apply a leptonic model based on accretion of matter from the slow inhomogeneous equatorial wind of the primary star, assuming particle injection proportional to the accretion rate. The relativistic electron energy distribution within the binary system is computed taking into account convective/adiabatic and radiative losses. The spectral energy distribution (SED) has been calculated accounting for synchrotron and (Thomson/Klein Nishina -KN-) inverse Compton (IC) processes and the photon-photon absorption in the ambient photon fields. The angle dependence of the photon-photon and IC cross sections has been considered in the calculations. Results. We reproduce the main features of the observed light curves from LS I +61 303 at radio, X-rays, high-energy (HE), and very high-energy (VHE) gamma-rays, and the whole spectral energy distribution. Conclusions. Our model is able to explain the radio to TeV orbital variability taking into account that radiation along the orbit is strongly affected by the variable accretion rate, the magnetic field strength, and by the ambient photon field via dominant IC losses and photon-photon absorption at periastron.

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Section: Discussionsupporting

confidence: 83%

The radio to TeV orbital variability of the microquasar LS I +61 303

Bosch‐Ramon¹,

Paredes²,

Romero³

et al. 2006

A&A

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“…Previous multi-wavelength campaigns undertaken with different instruments (Taylor et al 1996;Harrison et al 2000) indicate that the X-ray emission peak tends to precede the radio outburst by a few days. However, the exact phase of the X-ray maximum was difficult to estimate because of the poor sampling of the orbit of LS I +61 • 303.…”

Section: Ls I +61mentioning

confidence: 97%

Swift/XRT monitoring of five orbital cycles of LS I +61° 303

Esposito

Caraveo

Luca

et al. 2007

A&A

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Context. LS I +61• 303 is one of the most interesting high-mass X-ray binaries owing to its spatially resolved radio emission and its TeV emission, generally attributed to non-thermal particles in an accretion-powered relativistic jet or in the termination shock of the relativistic wind of a young pulsar. Also, the nature of the compact object is still debated. Only LS 5039 and PSR B1259−63 (which hosts a non-accreting millisecond pulsar) have similar characteristics. Aims. We study the X-ray emission from LS I +61 • 303 covering both short-term and orbital variability. We also investigate the source spectral properties in the soft X-ray (0.3-10 keV) energy range. Methods. Twenty-five snapshot observations of LS I +61 • 303 were collected in 2006 with the XRT instrument on-board the Swift satellite over a period of four months, corresponding to about five orbital cycles. Since individual data sets have too few counts for a meaningful spectral analysis, we extracted a cumulative spectrum. Results. The count rate folded at the orbital phase shows a clear modulation pattern at the 26.5 days period and suggests that the X-ray peak occurs around phase 0.65. Moreover, the X-ray emission appears to be variable on a timescale of ∼1 ks. The cumulative spectrum is well described by an absorbed power-law model, with hydrogen column density N H = (5.7 ± 0.3) × 10 21 cm −2 and photon index Γ = 1.78 ± 0.05. No accretion disk signatures, such as an iron line, are found in the spectrum.

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“…This object has also been proposed to be associated with the γ-ray source 2CG 135+01 (=3EG J0241+6103) (Gregory & Taylor 1978, Kniffen et al 1997. Although the broadband 1 keV-100 MeV spectrum of LS I +61 303 remains uncertain, because OSSE and COMP- TEL observations were likely dominated by the quasar QSO 0241+622 emission, the EGRET angular resolution is high enough to exclude this quasar as the source of the high-energy γ-ray emission (Harrison et al 2000). BATSE marginally detected the source, the quasar also being excluded as the origin of this emission (see Table I).…”

Section: Ls I +61 303 / 3eg J0241+6103mentioning

confidence: 99%