2 Observations

 

 

Table 1: Spectroscopic log and radial velocity data ( $v_{\rm rad}$).

HJD	Phase	$v_{\rm rad}$	$\sigma_{\rm rad}$	Rotation	Tele-
(24+)	($^\circ$)	(kms-1)		cycle	scope
50391.770	90.4	-77.5	1.5	map 1	NSO
50392.661	103.3	-82.0	2.7	-	NSO
50393.748	119.0	-75.8	1.9	map 1	NSO
50394.781	133.9	-78.5	1.8	map 1	NSO
50395.602	145.7	-80.5	2.0	map 1	NSO
50396.648	160.8	-78.5	2.0	map 1	NSO
50398.713	190.4	-82.4	2.3	-	NSO
50400.629	218.2	-81.1	1.6	map 1	NSO
50401.630	232.6	-79.6	2.4	-	NSO
50404.641	276.1	-83.2	2.0	map 1	NSO
50405.617	290.1	-81.8	2.5	map 1	NSO
50406.623	304.7	-80.9	1.9	map 1	NSO
50408.624	333.5	-77.3	3.0	map 1	NSO
50409.617	347.8	-82.0	2.3	map 1	NSO
50411.618	16.7	-79.9	1.7	map 1	NSO
50412.611	31.0	-80.9	1.8	map 1	NSO
50413.609	45.4	-81.2	1.7	map 1	NSO
50415.610	74.3	-80.1	1.7	map 1	NSO
50416.623	88.9	-80.5	1.5	map 1	NSO
50417.710	104.4	-78.9	2.3	-	NSO
50418.683	118.6	-80.4	1.2	map 2	NSO
50419.597	131.8	-80.2	1.6	map 2	NSO
50420.607	146.4	-80.3	1.8	map 2	NSO
50421.690	162.0	-79.4	2.1	map 2	NSO
50422.602	175.1	-79.6	1.3	map 2	NSO
50423.609	189.7	-80.6	1.5	-	NSO
50424.701	205.4	-82.8	1.3	map 2	NSO
50425.674	219.4	-79.3	1.7	map 2	NSO
50426.693	234.1	-80.2	2.2	map 2	NSO
50429.661	276.9	-79.4	2.1	map 2	NSO
50430.682	291.7	-79.6	1.5	map 2	NSO
50431.569	304.5	-81.7	2.0	map 2	NSO
50432.603	319.4	-80.8	1.6	map 2	NSO
50433.593	333.7	-81.5	1.7	-	NSO
50434.599	348.2	-81.4	2.1	map 2	NSO
50436.645	17.6	-80.9	1.7	-	NSO
50438.592	45.7	-80.4	2.0	map 2	NSO
50440.618	75.0	-79.8	2.3	map 2	NSO
50441.604	89.3	-80.0	2.4	-	NSO
50445.594	146.9	-80.0	2.2	-	NSO
50446.595	161.3	-81.3	2.5	-	NSO
50450.682	220.0	-81.3	1.9	-	NSO
50457.625	320.4	-81.5	1.8	-	NSO
50821.638	170.3	-78.7	1.1	-	KPNO
50826.670	243.0	-80.0	1.0	-	KPNO
50828.628	271.4	-78.5	1.6	-	KPNO
50918.011	120.6	-79.0	1.0	-	KPNO
50921.003	163.4	-80.3	0.7	-	KPNO

Spectroscopic observations were obtained at the National Solar Observatory (NSO) with the McMath-Pierce main telescope using the stellar spectrograph from October 31, 1996 to January 8, 1997. The 800$\times$800-pixel TI CCD (TI-4 chip, 15$\mu$ pixels) allowed for a resolving power of $\approx$40000 and a useful wavelength range of about 45 Å around 6430 Å. Two additional spectra in the 6430-Å region plus one spectrum in the H$\gamma$ region, along with corresponding reference spectra, were obtained at Kitt Peak National Observatory (KPNO) with the coudé feed telescope in December 1997/January 1998. A very similar 800$\times$800 TI CCD (TI-5 chip, 15$\mu$ pixels) was used in combination with grating A, camera 5, and the long collimator. It allowed for a resolving power of 38000 and 22000 in the red and the blue-wavelength regions, respectively, with a useful wavelength range of between 50-80 Å. Two more spectra in the 6500-Å region included H$\alpha$ and were obtained with the same instrumental set-up at the coudé feed telescope in April 1998 but utilized the 3096$\times$1024 CCD (F3KB chip, 15$\mu$ pixels). The resolving power was 28000, and the useful wavelength range was 300 Å. Table 1 is a summary of the spectroscopic observations. Spectra taken after the second rotational cycle in early 1997 and spectra with signal-to-noise ratios below 100:1 are not used for Doppler imaging (these spectra are marked with a dash in Table 1).

All data were reduced using IRAF and included bias subtraction, flat fielding, cosmic-ray removal, and an optimal aperture extraction. The exposure level obtained with an integration time of 30 min corresponds to a signal-to-noise ratio of approximately 150:1. Usually twenty flat-field exposures with a Tungsten reference lamp were taken at the beginning of the night and again at the end of the night. These forty flat fields were co-added and used to remove the pixel-to-pixel variations in the stellar spectra. Spectra of bright radial-velocity standards were obtained several times throughout the night to ensure an accurate wavelength calibration. Radial velocities for the 1996/97 NSO data and the two KPNO spectra from JD 2450826 and JD 2450828 were derived from cross correlations with spectra of the IAU velocity standard $\alpha$Ari (K2III, $v_{\rm r} = -14.3$ kms^-1). The one spectrum from JD 2450821 was cross correlated with $\beta$Gem (K0III, $v_{\rm r} = 3.3$ kms^-1). 16Vir (K0.5III, $v_{\rm r} = 35.7$ kms^-1) was used for the remaining spectra.

The photometric data in this paper were obtained with the Amadeus 0.75-m automatic photoelectric telescope (APT), part of the University of Vienna twin APT at Washington Camp in southern Arizona (Strassmeier et al. 1997). The observations were made differentially with respect to HD218610 as the comparison star ( $V = 7\hbox{$.\!\!^{\rm m}$ }64$, $V-R_{\rm C} = 0\hbox{$.\!\!^{\rm m}$ }69$, $V-I_{\rm C} = 1\hbox{$.\!\!^{\rm m}$ }30$) and SAO91066 as the check star. The data cover the time interval JD 2450395-459 (54 data points, season 1996/97), JD 2450740-828 (80 data points, season 1997/98), and JD 2450960-998 (47 data points, season 1998/99). All photometry was transformed to match the Johnson-Cousins $V(RI)_{\rm C}$ system.