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

Bosch‐Ramon, V.; Paredes, J. M.; Romero, Gustavo E.; Ribó, M.

doi:10.1051/0004-6361:20065830

Cited by 70 publications

(98 citation statements)

References 33 publications

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“…As shown by several authors for the eccentric orbit of LS I +61303, two peaks result: one peak corresponds to the periastron passage because of the highest density; the second peak occurs in the phase interval (toward apastron) where the reduced velocity of the compact object compensates for the decrease in density (Taylor et al 1992;Marti & Paredes 1995;Bosch-Ramon et al 2006;Romero et al 2007). At each accretion peak, matter is assumed to be ejected outward in two jets perpendicular to the accretion disk plane as for microquasars, but for the two ejections different energetic losses for the particles occur.…”

Section: Introductionmentioning

confidence: 92%

Long-term OVRO monitoring of LS I +61°303: confirmation of the two close periodicities

Massi

Jaron

Hovatta

2015

A&A

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Context. The gamma-ray binary LS I +61 • 303 shows multiple periodicities. The timing analysis of 6.7 yr of GBI radio data and of 6 yr of Fermi-LAT GeV gamma-ray data both have found two close periodicities P 1,GBI = 26.49 ± 0.07 d, P 2,GBI = 26.92 ± 0.07 d and P 1,γ = 26.48 ± 0.08 d, P 2,γ = 26.99 ± 0.08 d. Aims. The system LS I +61 • 303 is the object of several continuous monitoring programs at low and high energies. The frequency difference between ν 1 and ν 2 of only 0.0006 d −1 requires long-term monitoring because the frequency resolution in timing analysis is related to the inverse of the overall time interval. The Owens Valley Radio Observatory (OVRO) 40 m telescope has been monitoring the source at 15 GHz for five years and overlaps with Fermi-LAT monitoring. The aim of this work is to establish whether the two frequencies are also resolved in the OVRO monitoring. Methods. We analysed OVRO data with the Lomb-Scargle method. We also updated the timing analysis of Fermi-LAT observations. Results. The periodograms of OVRO data confirm the two periodicities P 1,OVRO = 26.5 ± 0.1 d and P 2,OVRO = 26.9 ± 0.1 d. Conclusions. The three independent measurements of P 1 and P 2 with GBI, OVRO, and Fermi-LAT observations confirm that the periodicities are permanent features of the system LS I +61 • 303. The similar behaviours of the emission at high (GeV) and low (radio) energy when the compact object in LS I +61 • 303 is toward apastron suggest that the emission is caused by the same periodically (P 1 ) ejected population of electrons in a precessing (P 2 ) jet.

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Section: Introductionmentioning

confidence: 92%

Long-term OVRO monitoring of LS I +61°303: confirmation of the two close periodicities

Massi

Jaron

Hovatta

2015

A&A

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“…The hypothesis that the compact object in LS I +61 • 303, which accretes material from the Be wind, undergoes a periodical (P 1 ) increase in the accretion rateṀ at a particular orbital phase along an eccentric orbit has been suggested and developed by several authors (Taylor et al 1992;Marti & Paredes 1995;Bosch-Ramon et al 2006;Romero et al 2007). Recently, the presence of P 1 and P 2 have been confirmed as stable features in more recent Fermi-LAT and OVRO monitorings of the GeV gamma-ray emission (Jaron & Massi 2014) and of the radio emission , respectively.…”

Section: Beat Between P 1 and Pmentioning

confidence: 99%

Origin of the long-term modulation of radio emission of LS I +61°303

Massi

Torricelli‐Ciamponi

2016

A&A

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Context. One of the most unusual aspects of the X-ray binary LS I +61 • 303 is that at each orbit (P 1 = 26.4960 ± 0.0028 d) one radio outburst occurs whose amplitude is modulated with P long , a long-term period of more than 4 yr. It is still not clear whether the compact object of the system or the companion Be star is responsible for the long-term modulation. Aims. We study here the stability of P long . Such a stability is expected if P long is due to periodic (P 2 ) Doppler boosting of periodic (P 1 ) ejections from the accreting compact object of the system. On the contrary it is not expected if P long is related to variations in the mass loss of the companion Be star. Methods. We built a database of 36.8 yr of radio observations of LS I +61 • 303 covering more than 8 long-term cycles. We performed timing and correlation analysis. We also compared the results of the analyses with the theoretical predictions for a synchrotron emitting precessing (P 2 ) jet periodically (P 1 ) refilled with relativistic electrons.Results. In addition to the two dominant features at P 1 and P 2 , the timing analysis gives a feature at P long = 1628 ± 48 days. The determined value of P long agrees with the beat of the two dominant features, i.e. P beat = 1/(ν 1 − ν 2 ) = 1626 ± 68 d. Lomb-Scargle results of radio data and model data compare very well. The correlation coefficient of the radio data oscillates at multiples of P beat , as does the correlation coefficient of the model data. Conclusions. Cycles in varying Be stars change in length and disappear after 2-3 cycles following the well-studied case of the binary system ζ Tau. On the contrary, in LS I +61 • 303 the long-term period is quite stable and repeats itself over the available 8 cycles. The long-term modulation in LS I +61 • 303 accurately reflects the beat of periodical Doppler boosting (induced by precession) with the periodicity of the ejecta. The peak of the long-term modulation occurs at the coincidence of the maximum number of ejected particles with the maximum Doppler boosting of their emission; this coincidence occurs every 1 ν 1 −ν 2 and creates the long-term modulation observed in LS I +61 • 303.

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“…The stellar wind material can have a temperature ∼10 4 K close to the star, adding a photon field component that effectively absorbs γ-rays with TeV energies (Bosch-Ramon et al 2006b;Orellana & Romero 2006), though here we do not consider such a contribution. The pairs created by absorption can boost lower-energy photons to very high energy via Inverse Compton scattering, and the absorption of these new γ-rays leads to pair creation, so electromagnetic cascades are developed.…”

Section: Photospheric Opacity: Inverse Compton Cascadesmentioning

confidence: 99%

Very high energy γ-ray emission from X-ray transients during major outbursts

Orellana

Romero

Pellizza

et al. 2007

A&A

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Context. Some high mass X-ray binaries (HMXB) have been recently confirmed as γ-ray sources by ground based Cherenkov telescopes. In this work, we discuss the γ-ray emission from X-ray transient sources formed by a Be star and a highly magnetized neutron star. This kind of systems can produce variable hadronic γ-ray emission through the mechanism proposed by Cheng and Ruderman, where a proton beam accelerated in the pulsar magnetosphere impacts the transient accretion disk. We choose as case of study the best known system of this class: A0535+26. Aims. We aim at making quantitative predictions about the very high-energy radiation generated in Be-X ray binary systems with strongly magnetized neutron stars. Methods. We study the gamma-ray emission generated during a major X-ray outburst of a HMXB adopting for the model the parameters of A0535+26. The emerging photon signal from the disk is determined by the grammage of the disk that modulates the optical depth. The electromagnetic cascades initiated by photons absorbed in the disk are explored, making use of the so-called "Approximation A" to solve the cascade equations. Very high energy photons induce Inverse Compton cascades in the photon field of the massive star. We implemented Monte Carlo simulations of these cascades, in order to estimate the characteristics of the resulting spectrum. Results. TeV emission should be detectable by Cherenkov telescopes during a major X-ray outburst of a binary formed by a Be star and a highly magnetized neutron star. The γ-ray light curve is found to evolve in anti-correlation with the X-ray signal.

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

Cited by 70 publications

References 33 publications

Long-term OVRO monitoring of LS I +61°303: confirmation of the two close periodicities

Long-term OVRO monitoring of LS I +61°303: confirmation of the two close periodicities

Origin of the long-term modulation of radio emission of LS I +61°303

Very high energy γ-ray emission from X-ray transients during major outbursts

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