Astron. Astrophys. Suppl. Ser. 135, 187-195
O. Bendinelli 1 - D. Bonaccini 2 - S. Falsini 1 - G. Parmeggiani 3
Send offprint request: O. Bendinelli
1 - Dipartimento di Astronomia, Universitá di
Bologna, Via Zamboni 33, 40050 Bologna, Italy
e-mails: bendinelli@bo.astro.it, falsini@bo.astro.it
2 -
European Southern Observatory,
Karl-Schwarzschild-Str. 2, D-85746 Garching bei
Muenchen, Germany
e-mail: dbonacci@eso.org
3 -
Osservatorio Astronomico di Bologna,
Via Zamboni 33, 40050 Bologna, Italy
e-mail: parmeggiani@bo.astro.it
Received December 15, 1997; accepted October 2, 1998
We present a fast and robust ad-hoc method to analyze a set of
short exposure images of a close binary star taken by the adaptive optics
system of the ESO 3.6 m telescope. At first each image is fitted, assuming
as a radially symmetrical approximation of its "instantaneous'' PSF, the
superposition of a central Gaussian and of a Moffat torus. Owing
to the coral variability and asymmetry of the PSF the fit gives a poor
estimate of the component's luminosity ratio; nevertheless it reproduces
satisfactorily the global structure of the PSF and above all gives
the accurate sub-pixel positions
of the two stars. This allows to obtain, by the shift-and-add procedure,
the mean set image from which the final parameters
of the two stars and the mean PSF during the observing run are derived.
The results from a set of AO images of the close binary
system Canis Maioris
are consistent with those previously obtained by one of us using the
iterative blind deconvolution. Extensive simulations give evidence that
the magnitude difference and the separation of the components can be
estimated within about 0.05 mag and 0
005 respectively when
the secondary star image
does not overlap a bright artifact of the AO system.
Key words: stars: Canis Majoris -- instrumentation -- adaptive
optics; techniques: image processing
Copyright The European Southern Observatory (ESO)