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Astron. Astrophys. 322, 511-522 (1997)

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3. New observations

3.1. Spectroscopic data

All spectroscopic observations were obtained at Kitt Peak National Observatory (KPNO) with the coudé feed telescope during March 4-18, 1994 and again in January 10-24, 1996. In 1994 a 800 [FORMULA] 800 TI CCD (TI-5 chip, 15µ pixels) was used with grating A, camera 5, and the long collimator, resulting in a two-pixel resolution of [FORMULA] 0.20 Å ([FORMULA] = 35,000) and this data is used for Doppler imaging. In 1996 we applied the new 3k [FORMULA] 1k Ford CCD (F3KB chip, 15µ pixels) that enables a much larger wavelength region but at a somewhat lower resolution of 0.27 Å . These spectra are being used to determine fluxes for the chromospheric-activity indicators (see Sect. 5). All spectra taken in March 1994 have signal-to-noise ratios of at least 150-200:1 while the January 1996 spectra are well in excess of 200:1. Table 1 is a log of the spectroscopic observations.


Table 1. Spectroscopic-observations log and radial velocities

3.2. Photometric data

The new photometric data in this paper were obtained during every clear night between February and July 1996 with the Vienna-T6 automatic photoelectric telescope (dubbed "Wolfgang") on Mt. Hopkins, Arizona and were taken in and transformed to the Strömgren b and y system. This data set is plotted in Fig. 1a together with the Vienna-T7-"Amadeus" Johnson- [FORMULA] data from the same period using a shift between Strömgren y and Johnson V of -0.0110 mag, as determined from the Check-minus-Comparison data. The Amadeus-APT data from late-1992 through mid-1996 were already included in the study of 23 spotted variables by Strassmeier et al. (1997), along with UBV data gathered with the Catania APT in Italy, [FORMULA] data from Konkoly Observatory in Hungary, and previously unpublished BV observations from Vienna Observatory by Schnell (1996) from 1984 through 1988. From the 1994 data we extracted the simultaneous and contemporaneous photometry that is used to constrain the Doppler images from March 1994 (see Sect. 6).

[FIGURE] Fig. 1. Differential Julian-date light and color curves and periodograms of IN Comae between February and July 1996. Panel a shows our new Strömgren y and Johnson V data - the latter shifted by -0.0110 mag -, panel b shows the differential [FORMULA] color, and panel c the check minus comparison values in y. The resulting window function and the periodogram for the data in panel a are shown in panel d and panel e, respectively. The periodogram in panel f is a separate Fourier analysis of the prewhitened data with the strongest frequency ([FORMULA] ; i.e. 5.913 days) subtracted. Note that only the one-day aliases remain.

The new by data are average values from three sequences of Ck-sky-C-V-C-V-C-V-C-sky-Ck readings, each with 30 sec integration time. Altogether we collected 331 by points during five consecutive months with a nightly average external uncertainty of 0.004 mag. The T7-Amadeus data as well as the new observations in this paper were made differentially with respect to HD 112299 as the comparison star ([FORMULA] mag, [FORMULA], [FORMULA], [FORMULA], [FORMULA] mag) and HD 112706 as the check star ([FORMULA] mag, [FORMULA], [FORMULA], [FORMULA], [FORMULA] mag). Their respective Johnson-Cousins colors were derived from absolute UBV observations with the Catania APT and [FORMULA] observations of K. Oláh at Konkoly Observatory (see Strassmeier et al. 1997).

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© European Southern Observatory (ESO) 1997

Online publication: June 5, 1998