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Astron. Astrophys. 350, 485-490 (1999)

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2. The observations

During the night of 7 June 1996 (UT), HD 76534 was observed in service time, employing the UCLES spectrograph mounted on the 3.9 m Anglo-Australian Telescope. The observational set-up included the 31 grooves/mm echelle and a 1024[FORMULA]1024 Tektronix CCD detector. The resulting spectrum contains 44 orders covering the spectral coverage of 4650 to 7240 Å, including both H[FORMULA] and H[FORMULA]. The observing strategy was fairly straightforward, we aimed to obtain spectra every few minutes, and employed different exposure times in order to compromise between time-resolution and signal-to-noise. Within a time span of two hours, we obtained 30 spectra with signal-to-noise ratios (SNR) in the H[FORMULA] setting ranging from [FORMULA] 60 in the shortest (60 s) exposures to [FORMULA] 140 in the longest (240 s) exposures. The observing conditions were not ideal, so the total count-rates and SNR are slightly variable.

Data reduction was performed in IRAF (Tody, 1993), and included the procedures of bias-subtraction, flatfielding and wavelength calibration. An observation of a Th-Ar arc lamp was used to provide the wavelength calibration of each spectrum. The resulting spectral resolution was determined to be [FORMULA] 10 km s-1 from Gaussian fits through telluric absorption lines.

In total 30 spectra with different exposure times were taken. The summed total spectrum, with a total exposure time of 4500 s has a SNR of [FORMULA]200 in the H[FORMULA] order and [FORMULA]300 in the H[FORMULA] order. The log of the observations and the SNR in the H[FORMULA] order are provided in Table 1.


Table 1. Log of the observations

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© European Southern Observatory (ESO) 1999

Online publication: October 4, 1999