Radio Spectral Index Analysis and Classes of Ejection in LS I +61 303

Details Radio Spectral Index Analysis and Classes of Ejection in LS I +61 303 Radio Spectral Index Analysis and Classes of Ejection in LS I +61 303

2009-08-18

arxiv.org/abs/0908.2600v1

Astrophysical Journal 702 (2009) 1179-1189

Astronomy and Astrophysics

Astrophysics

High Energy Astrophysical Phenomena

27 pages, 7 figures, accepted for publication in ApJ

Scientific paper

LS I +61303 is a gamma-ray binary with periodic radio outbursts coincident with the orbital period of P=26.5 d. The origin of the radio emission is unclear,it could be due either to a jet, as in microquasars, or to the shock boundary between the Be star and a possible pulsar wind. We here analyze the radio spectral index over 6.7 yr from Green Bank Interferometer data at 2.2 GHz and 8.3 GHz. We find two new characteristics in the radio emission. The first characteristic is that the periodic outbursts indeed consist of two consecutive outbursts; the first outburst is optically thick, whereas the second outburst is optically thin. The spectrum of LS I +61 303 is well reproduced by the shock-in-jet model commonly used in the context of microquasars and AGNs: the optically thin spectrum is due to shocks caused by relativistic plasma ("transient jet") traveling through a pre-existing much slower steady flow ("steady jet"). This steady flow is responsible for the preceding optically thick spectrum. The second characteristic we find is that the observed spectral evolution, from optically thick to optically thin emission, occurs twice during the orbital period. We observed this occurrence at the orbital phase of the main 26.5 d outburst and also at an earlier phase, shifted by $\Delta \Phi \sim$ 0.3 (i.e almost 8 days before). We show that this result qualitatively and quantitatively agrees with the two-peak accretion/ejection model proposed in the past for LS I +61303. We conclude that the radio emission in LS I +61303 originates from a jet and suggest that the variable TeV emission comes from the usual Compton losses expected as an important by-product in the shock-in-jet theory.

Affiliated with

Also associated with

No associations

Rating

Radio Spectral Index Analysis and Classes of Ejection in LS I +61 303 does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Radio Spectral Index Analysis and Classes of Ejection in LS I +61 303, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Radio Spectral Index Analysis and Classes of Ejection in LS I +61 303 will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-8981