The Marly spectrograph was installed at the Newtonian focus of the 1.2m telescope. A detailed study of Marly optical characteristics is in Lemaître et al. (1990). Let us recall that the radius of curvature of the camera mirror was 420mm and the aperture ratio in the direction perpendicular to the dispersion was f/2.8. The spectra covered 24mm in the direction of dispersion. The dispersion was 80Åmm-1 with the 600Lmm-1 grating, allowing to observe a magnitude B = 9 in about 30min. The central wavelength was 4260Å with an usable range of 1200Å. The slit width was 50m (14 on the sky and 30m on the plate). The slit height was 250m (70 on the sky and 500m on the plate). The emulsion of plates was IIaO. Six spectra were taken on each plate. An iron spectrum was made before and after each exposure for wavelength calibration. The focus of the camera was tested before each run. The use of an exposuremeter allowed very even plate density levels and therefore homogeneous expositions whatever the spectral type. Spectra were digitalized on the Fentomix device, specially built in OHP for this programme. Until the end, the use of plates was dictated to keep a precision consistent with Hipparcos data. During the observation range (1983-1995), an adapted CCD (more than 2000 pixels of maximum size 15) was not available, allowing adequate resolution and wavelength range. A minimum of 3 spectra per star was obtained. The rule was to separate the two first by at least 8 days and the third by at least 10 months, allowing to detect possible variability. To avoid the influence of the instrumental flexions, stars were observed near the meridian (hour). This instrumentation allowed a range of magnitude B=6.5 to 9 with observation times from about 3 to 30mn. Some brighter reference stars were observed using a neutral filter. A possible influence of this neutral filter on the radial velocity was tested as other parameters (see Sect. 2.3). A cross correlation method was adopted for the obtention of the radial velocities.
The reduction program took into account both spectral classifications, visual and automatic, selecting an optimum grid of templates. For Am stars, the Hydrogen type has been adopted, corresponding to the effective temperature of the star. The three radial velocities corresponding to the three best correlation index were kept for further discussion. At each step the consistency of the data was checked and as a result 4% spectra have been discarded.
The correlation process gave a relative radial velocity but several parameters had to be determined: generally an IAU standard was observed every night to obtain the zero-point of each run. The radial velocity was a linear function of the radial velocity itself and depended of a colour effect as a linear function of the of the template. To determine all these parameters a model has been built inside Gaussfit task (Jefferys et al. 1988), a system for least squares and robust estimation by an iterative process.
Gaussfit was running into three steps:
- In the first step the parameters A, B and Cn were computed with the IAU standard and some early-type stars with good radial velocity. These stars are given in Table 2 with their adopted published radial velocity. For IAU stars, the Coravel homogeneous velocities given by Mayor (1997) were adopted, taking into account the duplicity information from Mazeh et al. (1996).
The mean radial velocities have been derived for each star as well as its standard error .
The radial velocities of the reference stars were taken from the WEB (Duflot et al. 1995b), Barbier-Brossat & Figon (1997), Nordström et al. (1997), Liu et al. (1991), Morse et al. (1991), Mayor (1989), Prévot (1990) and also from measurements made on 1.5m OHP telescope with the Coude spectrograph and later the Aurelie spectrometer not published yet. Very wide binaries (Halbwachs 1986) were used when the second component was observed with Coravel. If this late-type component did not show a variable velocity, its value of radial velocity was adopted for the primary. All these selected radial velocities have a standard deviation kms-1. For Coravel velocities (Mayor 1989 and Prévot 1990) the ratio external vs. internal errors was considered. Moreover, when the difference of the velocities (Marly minus published value) was greater than 8kms-1, the star was rejected. The duplicity flags of Hipparcos were taken into account and Hipparcos binaries have been rejected except those undetectable for us in any way.
This method allowed to test the influence of parameters such as the meteorological conditions (turbulence and transparency), the exposure time or the observing people, entailing some rejected spectra.
The external error was computed on the mean radial velocity for each star:
the standard deviation equals , the maximum of its distribution being at 5.3kms-1 corresponding to an external error equal to 3.1kms-1 for 3 observations and 2.7 for 4. In the beginning some stars with negative declination were included. For them could be greater.
Using the test, the variability of the radial velocities was estimated with a confidence level of probability of .The histogram of the probability shows its distribution. The peak at is relative to the detected variable radial velocities.
In Table 4 the duplicity flags of Hipparcos were added. This Catalogue (ESA, 1997) gives several flags about suspected or confirmed double or multiple systems from photometry and/or astrometric solution. Lindegren (1997) gives the conditions of detection which are different from the spectroscopic binaries in terms of the separation of components, their magnitude difference and the orbital period. Table 4 gives some indications about the number of components found by Hipparcos, the adopted solution, the quality of the solution, the separation and the difference of Hipparcos magnitude when computed or given in CCDM (Dommanget & Nys 1994). Moreover an astrometric orbit in CCDM is indicated by O. Details about these parameters are given in the Hipparcos Catalogue Vol. 1, Sect. 1.4. These double stars can be physical or optical: certain physical when orbital solution (noted "O" in Table 4), probable physical when acceleration solution "G" and physical or optical when resolved system "C" or stochastic solution "X". These flags have two interests: they complete our results for their utilisation and they will be useful to observe these stars again with an another resolution.
Some stars belong to MSC, the catalogue of physical multiple stars of Tokovinin (1997): HD 1658, 4161, 24909, 37438, 58946, 67159, 67501, 102509, 130188, 170073, 172044 and 222326.
As a result from the Table 4, 23% radial velocities are found variables, 13% stars are doubles or suspected by Hipparcos and 3% are commons.
To test the luminosity class, the absolute magnitude MV* was computed (Crifo 1997) taking into account the Hipparcos trigonometric parallax (if it is > 0.1mas), the V magnitude and the interstellar absorption. This absorption was estimated by when this excess was known, or by 0.7magkpc-1. The error on MV* was estimated taking into account the relative error on the parallax .The used reference HR-diagram was picked in Luri (1998) whose first results are given in Gómez et al. (1997). For each spectral class and each luminosity class, Luri (1998) gave the mean (B-V)0, the mean absolute magnitude and the standard deviation around the mean value. For each star, MV* was compared with the absolute magnitude given by its spectral type in the HR-diagram. For 88% stars, they were consistent at one level. When they were significantly different taking into account and , the HIP and HD numbers are given in Table 6 with the visual spectral type, the luminosity class found from MV* in the HR-diagram and a possible code explained below.
Some remarks have to be made.
- The luminosity class was determined from MV* taking into account the assumption of a reliable spectral sub-class. This was justified by the verified consistency between the visual spectral type and the best correlation index obtained in Sect. 2.2. Nevertheless the distinction between a normal A giant and an Am was sometimes difficult. An other error origin could be a bad estimation of the interstellar absorption AV. When the value of (B-V)0, computed using AV was not consistent with the spectral type, a code is given in the Table 6 (available in electronic form only; see footnote to title page): "1" if AV seemed overestimated and "2" if underestimated. This possible correction on MV* was taken into account. A third error origin could be due to a binary star. When the Hipparcos Catalogue gives a binary with a separation lower than and magnitude difference lower than 2mag, the code "3" is given in Table 6. The code "4" agrees with a variable velocity or a suspected binary by Hipparcos.
- For some stars, the value of the parallax was of the order of its error and brought an error on MV*=2mag. When > 2mag, the code is "5" the absolute magnitude giving the indication of supergiant generally.
- The place of Ap and Am stars in the HR-diagram showing a mean standard deviation 0.75 (Gómez et al. 1998) and the luminosity classes V, IV and III being close in this part of HR-diagram, these classes were considered as normal. It was found 40 Ap not belonging to the general catalog of Ap and Am stars (Renson et al. 1991) and 139 Am not belonging to the fourth catalogue of Am stars with KNO (Hauck 1992). These new classifications have to be confirmed.
- Generally the classes V and IV were not separated because they are very close in the range B5-F5 and the probable precision on the luminosity classes did not justify this distinction.
- On the other hand the height of the spectra did not allow to distinguish the class VI as Hipparcos data displayed some of them. In the Table 6 the adopted classes were:
and VI if
being the absolute magnitude of the class V.
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