Astronomy and Astrophysics – Astrophysics – Instrumentation and Methods for Astrophysics
Scientific paper
2011-06-23
Astronomy and Astrophysics
Astrophysics
Instrumentation and Methods for Astrophysics
23 pages, 13 figures
Scientific paper
This paper considers the problem of accurate measurement of circular polarization in imaging spectral-line VLBI observations in the lambda=7 mm and lambda=3 mm wavelength bands. This capability is especially valuable for the full observational study of compact, polarized SiO maser components in the near-circumstellar environment of late-type, evolved stars. Circular VLBI polarimetry provides important constraints on SiO maser astrophysics, including the theory of polarized maser emission transport, and on the strength and distribution of the stellar magnetic field and its dynamical role in this critical circumstellar region. We perform an analysis here of the data model containing the instrumental factors that limit the accuracy of circular polarization measurements in such observations, and present a corresponding data reduction algorithm for their correction. The algorithm is an enhancement of existing spectral line VLBI polarimetry methods using autocorrelation data for calibration, but with innovations in bandpass determination, autocorrelation polarization self-calibration, and general optimizations for the case of low SNR, as applicable at these wavelengths. We present an example data reduction at $\lambda=7$ mm and derive an estimate of the predicted accuracy of the method of m_c < 0.5% or better at lambda=7 mm and m_c < 0.5-1% or better at lambda=3 mm. Both the strengths and weaknesses of the proposed algorithm are discussed, along with suggestions for future work.
Kemball Athol J.
Richter L. L.
No associations
LandOfFree
Circular polarization measurement in millimeter-wavelength spectral-line VLBI observations 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 Circular polarization measurement in millimeter-wavelength spectral-line VLBI observations, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Circular polarization measurement in millimeter-wavelength spectral-line VLBI observations will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-393389