2. Observations and data reduction
The observations were collected with the 4.2m William Herschel Telescope (WHT) at the Observatorio del Roque de los Muchachos on the island of La Palma, Canary Islands, on two nights, viz. 4 and 5 August 1993. The telescope was equipped with the Utrecht Echelle Spectrograph (UES, Unger et al. 1993) which, in combination with a 1242 1152 pixel EEV CCD detector yielded spectra at a resolving power of =49 000 (FWHM) over the wavelength region 4500-7150 Å. Because of the placing of the detector with respect to the echellogramme, wavelength coverage was incomplete. Spectral gaps of about 19% occured at the red end of the range, decreasing to the blue, where complete coverage was achieved from 4500 Å. Exposure times were typically 200s, with a dead time of 100s due to chip readout, making an effective cycle time of 5min. A log of the data will be found in Table 1.
Table 1. Log of the spectroscopic observations of BD+ taken with the WHT/UES 4-5 August 1993. The start and end times of continuous sequences of spectra are recorded. The series were interrupted in order to take thorium-argon arc lamp exposures or correct autoguide errors. These gaps were normally not larger than 3min. Phases () have all been referred to the first exposure of the object and were calculated using the period of 10.17hr (J94)
Spectra were flat fielded and bias corrected, wavelength calibrated and extracted from the echellogrammes using standard routines within the astronomical computing environment IRAF (Tody et al. 1986) on the STARLINK (Bromage 1984) computers at Armagh Observatory.
© European Southern Observatory (ESO) 1999
Online publication: December 4, 1998