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Astron. Astrophys. 325, 1253-1258 (1997)

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Photometry with a periodic grid *

I. A new method to derive angular diameters and brightness distribution

D. Hestroffer 1, 2 and F. Mignard 3

1 Present address: Astrophysics Division, ESTEC, Postbus 299, 2200 AG Noordwijk, The Netherlands
2 Bureau Des Longitudes, URA CNRS 707, 77 Avenue Denfert Rochereau, F-75014 Paris, France
3 Observatoire de la Côte d'Azur, Dept. CERGA, UMR CNRS 6527, Av. N. Copernic, F-06130 Grasse, France

Received 20 February 1997 / Accepted 15 April 1997

Abstract

The interest of observations of point sources with a periodic grid has been recognized for long in astrometry because of the direct relation existing between the position in the sky and the phase of the modulated signal. We investigate in this paper a complementary aspect by showing how observations of an extended stellar or planetary object carried out with a periodic grid may also yield valuable information on its size and on the light distribution over its surface. Several categories of objects may benefit from this kind of observation depending on the modulation period, the telescope focal length, and the signal-to-noise ratio that can be achieved. We discuss the overall principles of this method and derive an analytical formulation for the `modulation function' defined in the text. An application based on Hipparcos observations of the largest minor planet (1) Ceres is provided as an illustration of the method.

Key words: photometry – scattering – minor planets, asteroids – stars: fundamental parameters of

* Based on data from the Hipparcos astrometry satellite.

Send offprint requests to: D. Hestroffer, dhestrof@estec.esa.nl

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© European Southern Observatory (ESO) 1997

Online publication: April 28, 1998

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