VLBI for Gravity Probe B. VII. the evolution of the radio structure of im Pegasi

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DOIResolve DOI: http://doi.org/10.1088/0067-0049/201/1/7
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TypeArticle
Journal titleAstrophysical Journal, Supplement Series
ISSN0067-0049
Volume201
Issue1
Article number7
AbstractWe present measurements of the total radio flux density as well as very long baseline interferometry images of the star, IM Pegasi, which was used as the guide star for the NASA/Stanford relativity mission Gravity ProbeB. We obtained flux densities and images from 35 sessions of observations at 8.4GHz (λ = 3.6cm) between 1997 January and 2005 July. The observations were accurately phase-referenced to several extragalactic reference sources, and we present the images in a star-centered frame, aligned by the position of the star as derived from our fits to its orbital motion, parallax, and proper motion. Both the flux density and the morphology of IM Peg are variable. For most sessions, the emission region has a single-peaked structure, but 25% of the time, we observed a two-peaked (and on one occasion perhaps a three-peaked) structure. On average, the emission region is elongated by 1.4 ± 0.4mas (FWHM), with the average direction of elongation being close to that of the sky projection of the orbit normal. The average length of the emission region is approximately equal to the diameter of the primary star. No significant correlation with the orbital phase is found for either the flux density or the direction of elongation, and no preference for any particular longitude on the star is shown by the emission region. © 2012. The American Astronomical Society. All rights reserved..
Publication date
LanguageEnglish
AffiliationNational Research Council Canada (NRC-CNRC); NRC Herzberg Institute of Astrophysics (HIA-IHA)
Peer reviewedYes
NPARC number21269380
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Record identifier04cc790c-e5a7-44dd-a0b8-f9414343a071
Record created2013-12-12
Record modified2016-05-09
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