A Method for Internal Calibration of Optical Interferometer
Data and Application to the Circumstellar Envelope of
 Cas
Christopher Tycner,1
Arsen R. Hajian,2
D. Mozurkewich,3
J.T. Armstrong,3
J.A. Benson,4
G.C. Gilbreath,3
D.J. Hutter,4
T.A. Pauls,3 and
John B. Lester5
1
Department of Astronomy and Astrophysics,
University of Toronto, 60 St. George Street, Toronto, ON M5S 3H8, Canada
2United States Naval Observatory, 3450 Massachusetts
Avenue NW, Washington, DC 20392-5420
3Remote Sensing Division, Naval Research Laboratory, Code 7210,
Washington, DC 20375
4U.S. Naval Observatory, Flagstaff Station, P.O. Box 1149,
Flagstaff, AZ 86002-1149
5Department of Astronomy, University of Toronto
at Mississauga, 3359 Mississauga Road North, Mississauga, ON L5L 1C6,
Canada
We present a technique for calibrating optical long-baseline
interferometric observations in which both the calibration corrections
and the source characteristics are obtained from the observations of a
program star. This calibration can only be applied to certain classes
of objects, such as emission-line sources or binary systems, in which
the parameters describing the characteristics of the source are
orthogonal to the calibration parameters. The technique is applied to
observations of
 Cassiopeiae, obtained on four
different nights with the Navy Prototype Optical Interferometer, and
utilizes measurements obtained simultaneously in many spectral
channels covering a wide spectral range, of which only two channels
contain a strong signal due to the circumstellar envelope in the
H emission line.
The calibrated observations in
H
show a clearly resolved circumstellar structure. The best-fit
ellipsoidal Gaussian model fitted to our observations has an ensemble
average parameters of 3.67±0.09 mas for the angular size of the
major axis, 0.79±0.03 for the axial ratio, and
32°±5° for the position angle, all in good
agreement with values reported by previous investigations.
2003 AJ, 125, 3378
Preprints from
tycner@astro.utoronto.ca
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