Astron. Astrophys. 347, 212-224 (1999)

2. Observations

The spectroscopic observations in this paper were obtained at the Kitt Peak National Observatory (KPNO) and at the National Solar Observatory (NSO). The KPNO observations were made with the coudé feed telescope in May 1990 (dataset "May 1990" in Table 1) and in April 1997 (dataset "April 1997"). In 1990, the 800800 TI-3 CCD (15µ pixels) was used with grating A, camera 5, and the long collimator yielding R=24,000 and an effective wavelength resolution of 0.27 Å at Å. In 1997, the slightly more efficient TI-5 CCD was used with the same grating and camera A but with a narrower slit yielding R=33,000 and a wavelength resolution of 0.20 Å. The NSO observations were part of the synoptic night-time program at the McMath-Pierce telescope during the years 1988 and 1989. Again, a similar 800800 TI CCD (TI-4 chip, 15 µ pixels) was used in conjunction with the Milton-Roy grating # 1 to give R=42,000 and an effective wavelength resolution of 0.15 Å. The signal-to-noise ratio is always around 200:1. Table 1 is a summary of the spectroscopic observations (HJD is the heliocentric Julian date, phase is the rotational phase according to Eqs. (1-4) and denotes the integration time). Based on previous observations, we felt that the total elapsed time for one image should not exceed approximately 20 days or equivalently six stellar rotations. Consequently, our data were grouped into five sets of 8, 22, 20, 5, and 11 days in length as indicated in Table 1.

Table 1. Spectroscopic observations

All spectroscopic data were reduced with IRAF and included averaged bias subtraction, flat fielding and optimal aperture extraction. Frequent wavelength comparison spectra were obtained throughout the night to guarantee an accurate calibration. The TI CCDs are free of fringing to much below the noise level of our stellar spectra. A representative spectrum of HD 199178 centered at the Ca I 6439-Å line is shown in Fig. 1a.

Fig. 1a-d. A comparison of observed and synthesized spectra in the Ca I 6439-Å line region. a  A spectrum of HD 199178 (thick line) compared with the reference stars CrB (G5III-IV; dashed line) and Boo (K1.5III; dotted line). A broadened synthetic Ca I profile, computed from a =5500/=2.5 model atmosphere and our revised 's, is shown as a thick dotted line while the unaltered and unbroadened spectrum is shown as a thin full line. b  A spectrum of the Sun (thick line) and two fits with Kurucz's (1991) solar model with (thin full line) and without (dotted line) modified transition probabilities. c  The observed spectrum of CrB (thick line) and two fits with solar abundances (dotted line) and adjusted elemental abundances (thin full line), respectively. d  A spectrum of  Boo = Arcturus (thick line) and the fit with revised abundances (thin line).

The new photometric data for April 1997 was obtained with one of the University of Vienna automatic photoelectric telescopes (Amadeus APT; see Strassmeier et al. 1997) at Fairborn Observatory in southern Arizona. The observations were made differentially with respect to SAO 50313 (V = 6:m 636, Jetsu et al. 1999b; I = 5:m 592, Strassmeier et al. 1999) and filters were selected to match the standard Cousins V(RI)_C system. The 1988-1990 BV photometry from the Phoenix-10 APT was published by Jetsu et al. (1990b), and again analysed in Jetsu et al. (1999b). Additional UBVRI photometry for 1990 was taken from Heckert & Stewart (1992).

© European Southern Observatory (ESO) 1999

Online publication: June 18, 1999
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