A&A 369, 552-553 (2001)
DOI: 10.1051/0004-6361:20010078

Research Note

Nice Observatory CCD measurements of visual double stars (3rd series)

M. Salaman1,2 - G. Morlet1,3 - R. Gili1,4


1 - Observatoire de la Côte d'Azur, Département Fresnel, BP 229, 06304 Nice Cedex, France
2 - 284 route des Choseaux, 74320 Sevrier, France
3 - 25 Bld. Arago, 75013 Paris, France
4 - 161 Av. Ste Marguerite, Clos Ste Marguerite, 06210 Nice, France

Received 15 November 2000 / Accepted 19 December 2000

Abstract
We present the measurements of 58 visual double stars made in 1999 and 2000 with the 50 cm refractor of the Nice Observatory and attached CCD camera, using an algorithm based on the adjustment of a tridimensional mathematical surface (Table 1). 2 new binaries discovered by Hipparcos were measured.

Key words: astrometry - stars: binaries: visual


1 Introduction

We present the results of measurements of binaries made at the Nice Observatory, including pairs rarely measured since their discovery and also double stars measured or discovered by the Hipparcos satellite.

2 Image acquisition

We used a Hi-SIS22 CCD camera mounted on the 50 cm refractor (Gili & Couteau 1997).

The camera consists of a $768 \times 512$ square pixel detector, of side 9 $\mu$m. Its field on the sky is 0.12 $^{\prime\prime}$. The theoretical resolving power of the instrument (1.22 $\lambda$/D) is 0.33 $^{\prime\prime}$ (at 0.68 $\mu$m, the highest sensitivity of CCD sensors). Images were acquired with a focal length of 15.349 m using a Barlow $2\times$ lens (see Salaman et al. 1999, 2000). The focal length was checked on wide pairs measured by the Hipparcos satellite.

The program of acquisition was QMIPS32 (Buil C. et al. 1997, QuickMips32 V. 1.8). For each binary, 10 to 15 images were recorded with integration times ranging from 0.02 to 1 s.

During our two missions, in 1999 from July 9th to 20th and in 2000 from May 3rd to 16th, the images of 58 binaries were acquired.

3 Reduction method and results

The acquired images are visually sorted, by eliminating those showing important distortions. The selected images are composited (shift and add) using MIPS software (Buil C. et al. 1993, Mips V. 1.02). We verify that the FWHM does not exceed a maximum of 1.2 $^{\prime\prime}$. To measure composite images, we used a custom image reduction program (Salaman et al. 1999), which calculates the position angle, angular separation and magnitude difference. In the case where the composite image does not show two components obviously separated, it is treated by the wavelet method (Wavelet function of the QMIPS32 program), which analyses the spatial frequencies of the image. The selective extraction of the higher frequencies allows separation of the components.


  Table 1: Measurements of visual double stars (this table is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/369/552)


 
Table 2: Comparison, for the orbital binaries, between our observations (O) and values calculated (C) from the Fifth Catalog of Orbits of USNO, update 20 Nov. 2000
\begin{table} \par \includegraphics[width=16cm,clip]{table2.eps}\end{table}

Acknowledgements
We would like to thank J.-C. Valtier, Head of the Fresnel Department, who welcomed us at the Observatory. We also wish to thank D. Bonneau, J. Dommanget and P. Couteau, scientific advisers of the Binary Commission of the SAF, for their help. We are grateful to Laurence Morlet for translating this paper.

References

 
Copyright ESO 2001