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Paper: VSOP and Stellar Sources - The Case of LS I +61°303
Volume: 402, Approaching Micro-Arcsecond Resolution with VSOP-2: Astrophysics and Technologies
Page: 408
Authors: Dougherty, S.
Abstract: Space-VLBI observations of stellar sources represent a challenge since there are few sources with sufficiently high brightness temperature for detection on space-ground baselines. X-ray binaries (XRB) are among the few types of stellar radio sources that can be detected. Observations of the unusual X-ray and γ-ray binary system LS I +61° 303 obtained with the HALCA satellite and a 20-element ground array are described. The data in this 48-hour experiment represent some of the best quality VLBI observations of LS I +61° 303. No fringes were detected on HALCA baselines. 10-minute snapshot images were produced from the global ground array data and reveal an expansion velocity of 800 km s−1. Some of these image data reveal hints of more extended emission but high-SNR closure phase data do not support relativistic outflow in the plane-of-the-sky in LS I +61° 303. The largest closure phase rates are consistent with an outflow of ∼ 1000 km s−1 as deduced from the image data. The closure phases also show no evidence of structure variation on size scales greater than ∼ 10 mas. A number of issues related to VSOP2 observations of stellar radio sources are raised.
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