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Astron. Astrophys. 345, 137-148 (1999)

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2. Observations and data reduction

2.1. Photoelectric photometry

Most of our photoelectric observations of AW UMa were carried out at the Skalnaté Pleso (SP) and Stará Lesná (SL) observatories of the Astronomical Institute of the Slovak Academy of Sciences. In both cases a single-channel pulse-counting photoelectric photometer installed in the Cassegrain focus of the 0.6 m reflector was used. The integration time was chosen between 6 s and 10 s according to the observational conditions.

Further photoelectric observations were obtained using a two-beam multi-mode photoelectric photometer mounted on the 1.22 m Cassegrain reflector at the Kryonerion Astronomical Station (KAS) of the National Observatory of Athens, Greece.

All SP and SL observations were obtained in the U,B,V passbands except in March 1992, when only the V passband was used. The KAS observations were obtained in the B and V passbands. The stars HD 99832 (V = 7.20, B-V = 0.47, U-B = -0.03) and SAO 62580 (V = 9.47, B-V = 0.73, U-B = -0.24) were used as a comparison and check star respectively. All the observations were corrected for atmospheric extinction and transformed to the standard UBV system. The list of photometric observations is given in Table 1. The KAS observations were used only for determination of the times of minima.


Table 1. The journal of photometric observations of AW UMa. Times of observations (middles of the observing runs) are given in JD-2 400 000. Phases were calculated using the ephemerides (2) and (3)

The total number of the SP and SL individual observations exceeded 3000 in each passband. Individual observations of AW UMa are plotted in the phase diagram (Fig. 1) constructed according to ephemerides (2) and (3).

[FIGURE] Fig. 1. Photoelectric UBV light-curves of AW UMa

2.2. Optical spectroscopy

Optical spectroscopy in the blue part of the spectrum (360-500 nm) was performed by using the 2 m telescope at the Ondejov Observatory of the Astronomical Institute of the Academy of Sciences of the Czech Republic from February 29, 1992 to April 7, 1992. Spectra with a reciprocal dispersion 1.75 nm mm-1 were taken by using a spectrograph mounted at the Coudé focus on Kodak IIaO plates hypersensitized in hydrogen. All spectra were measured with the five-channel microphotometer of the Ondejov Observatory using the reduction software SPEFO (Horn et al., 1996). The same software package was employed for the reduction of the raw data and analysis of the spectral lines. The spectroscopic observations of AW UMa are listed in Table 2.


Table 2. The list of spectroscopic observations of AW UMa at the Ondejov and Toledo observatories. The times of the middles of the exposures are given in JD-2 400 000. The corresponding phases were calculated using the ephemerides (2) and (3). Exposure times are in minutes

At the time of observations of AW UMa two spectra of the standard star 59 Dra (HD180777) were taken. The radial velocity (henceforth RV) measured from the Doppler profiles of hydrogen lines was (-3.8[FORMULA]2.2) km s-1 in perfect agreement with the standard velocity -4.0 km s-1 given by Duflot et al. (1995). Therefore no zero-point correction was applied to the measured RVs.

Two further spectra were taken with the 1 m telescope of the University of Toledo, U.S.A., on March 3, 1995 and March 1, 1996. The spectra were projected by the high dispersion echelle spectrograph on a 1200x800 CCD chip cooled by liquid nitrogen. The chip was sensitized in the blue part of the spectrum. The spectra comprised nine echelle orders from 547 to 673 nm and were reduced by Dr. K. Gordon. These two spectroscopic observations are listed at the end of Table 2.

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© European Southern Observatory (ESO) 1999

Online publication: April 12, 1999