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Astron. Astrophys. 329, 606-612 (1998)

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2. Observations and data reduction

All the images and the spectra were taken at La Silla with different ESO telescopes. Table 1 gives the complete journal of observations. The upper part of Table 1 lists the images, while the lower part reports the spectroscopic observations.


Table 1. The journal of the observations. The upper part of the Table lists the photometric data, while the spectroscopic observations are reported in the lower part

We have globally obtained 128 images (53 in the B, 41 in the V and 34 in the R Johnson bands) and 19 spectra (with slit widths varying from 1" to 2", giving a resolution between 2.0 and 9.6 Å/pixel) over a period of nearly one year (from January 15, 1991 to January 1, 1992). However most observations are concentrated within the first three months after the outburst. Standard bias and flat field corrections were performed on each frame.

Images were reduced with DAOPHOT II (Stetson 1987) and ALLSTAR inside MIDAS. The nova has been calibrated in B and V magnitudes by using the field stars 1, 2 and 3 (Bailyn 1992). We have measured the R magnitudes of these three stars through Mark A and T Phe Landolt fields (Landolt 1992), and obtained [FORMULA], [FORMULA] and [FORMULA], respectively. Table 2 reports the B, V and R magnitudes of the object, together with the ([FORMULA]) and ([FORMULA]) color indexes. The typical photometric error for each measurement is of the order of [FORMULA] 0.05 mag in the B band and [FORMULA] 0.03 mag in both V and R.


Table 2. B, V and R magnitudes, along with the ([FORMULA]) and ([FORMULA]) colors, of GU Mus. The typical error is [FORMULA] 0.05 mag for the B values and [FORMULA] 0.03 mag for V and R. When more than one measurement in the same band was available during the same night, the mean value has been reported. The magnitudes are referred to the mean Heliocentric Julian Day (HJD) of the observations

The reduction of the spectroscopic material was carried out with IRAF. He-Ar lamps were used for the wavelength calibration, and the standards Feige 56, EG 76, L970-30, LTT 3218, Hiltner 600, CD-32, Wolf 485A and EG 274 for the flux calibration. We corrected the spectra for interstellar reddening with the prescription of Cardelli et al. (1989), and using [FORMULA] as derived by Della Valle et al. (1991).

Finally, the observation times have been corrected to heliocentric times of mid-exposure.

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© European Southern Observatory (ESO) 1998

Online publication: December 8, 1997