2 Observations

 

 

Table 1: Journal of spectroscopic observations

Date (UT)	Hel. JD	Instrument	dispersion	range (Å)	$\Delta t$
2000	(2451000+)		element		(day)
May 3/4	668.867	1.88-m	1800 l/mm	5080-5290	-0.6
	668.875	1.88-m	1800 l/mm	6500-6700	-0.6
May 5/6	670.884	1.88-m	1800 l/mm	6500-6700	+1.3
May 8/9	673.741	1.88-m	1800 l/mm	5080-5290	+4.2
	673.755	1.88-m	1800 l/mm	6500-6700	+4.2
May 10/11	675.860	1.88-m	1800 l/mm	5080-5290	+6
	675.876	1.88-m	1800 l/mm	6500-6700	+6
May 15/16	680.818	1.88-m	600 l/mm	3860-4490	+11
	680.837	1.88-m	1800 l/mm	6500-6700	+11
May 25/26	690.644	1.88-m	1800 l/mm	6500-6700	+21
	690.867	1.88-m	1800 l/mm	5800-6000	+21
May 26/27	691.452	0.6-m Schmidt	5$^\circ$ prism	4200-8900	+22
May 27/28	692.453	0.6-m Schmidt	5$^\circ$ prism	4200-8900	+23
May 28/29	693.472	0.6-m Schmidt	5$^\circ$ prism	4200-8900	+24
May 29/30	694.415	0.6-m Schmidt	5$^\circ$ prism	4200-8900	+25
May 30/31	695.419	0.6-m Schmidt	5$^\circ$ prism	4200-8900	+26
June 6/7	702.711-702.839	1.88-m	1800 l/mm	6500-6700	+33
	(8 spectra)
June 21/22	717.802	1.88-m	1800 l/mm	6500-6700	+48
June 26/27	722.765	1.88-m	1800 l/mm	6500-6700	+53

The presented data were acquired on 14 nights at two observatories in May and June, 2000. Medium resolution ( $\lambda/\Delta\lambda\approx7000$-$10\,000$) spectroscopic observations were carried out on 9 nights with the Cassegrain-spectrograph attached to the 1.88-m telescope of the David Dunlap Observatory (Richmond Hill, Canada). The detector was a Thomson $1024 \times 1024$CCD chip (with a 6 e^- readout noise). The slit width was 306$\mu$ corresponding to 1 $.\!\!^{\prime\prime}$8 on the sky. Typical observing circumstances at DDO are far from being photometric which is reflected, for instance, in the usual seeing values ( $2{-}3\hbox{$^{\prime\prime}$ }$). That is why we did not attempt to flux calibrate the data. All spectra presented throughout the paper were continuum normalized, though it was a quite difficult task in certain cases. Further observational details are given in Table 1.

The DDO spectra were reduced with standard IRAF tasks. Nightly master biases were created by forming a median of the individual bias frames. The bias subtraction was followed by flat-fielding with a similar nightly master flat-field from five to seven individual flat-field images. The aperture extraction and wavelength calibration was done with the task doslit. The wavelength scale was determined in each case with two FeAr spectral lamp exposures obtained immediately before and after every stellar exposure. The comparison spectral lines were identified with the web-based Iron-Argon Spectral Atlas by Willmarth & Cheselka. The integration times ranged between 200-1200 s, depending on the actual brightness, wavelength range and resolving power. As well as the nova, we observed HD 177724 (rapidly rotating A-type star) to identify telluric lines. This turned out to be crucial when distinguishing sharp absorption features in the late high-resolution H$\alpha$ profiles. The continuum normalization was made by fitting low-order Chebyshev-functions (with the IRAF task contin) to those parts of the individual spectra which were not or only slighty affected by the broad line profiles.

Low-resolution objective prism spectra were obtained on five nights in May, 2000 at Piszkésteto Station of the Konkoly Observatory with the 60/90/180 cm Schmidt-telescope. The detector was a Photometrics AT200 CCD camera (1536$\times$1024 pixels, KAF-1600 chip with UV-coating). The objective prism has a refracting angle of 5$^\circ$ giving an image scale of 580 Å/mm at H$\gamma$. In the case of objective prism spectroscopy, the resolving power is grossly affected by the seeing that smooths the detected image along and perpendicular to the dispersion. The resolution ( $\lambda/\Delta\lambda$) was estimated from the width of the spectral images (typically $\sim$3 pixels) and the actual Å/pixel image scale which strongly depends on the wavelength range. The resulting resolution values are 290 and 110 for the blue and red end of the spectra, respectively. Although the unfiltered observations covered the whole optical region between 3800 and 9000 Å, the useful spectral coverage was a slightly narrower (4200-8900 Å). The full journal of observations is presented in Table 1.

The spectral extraction of the objective prism frames was done with routines developed by the first author. Briefly, an automatic detection of the spectral images is performed, which results in the location of the spectra perpendicular and along the dispersion. For the wavelength calibration two comparison-star spectra were used, where unambiguous spectral features provide good calibrator data (hydrogen Balmer-series in an A-type star, molecular bands in a M-type star). The common features (strong atmospheric lines at 7200 Å, 7600 Å and 8170 Å) helped adjust the spectra to the same wavelength scale. The residual scatter of calibrating spectral lines is typically about 1 pixel, corresponding to 5-20 Å depending on the spectral region. The next step was a relative flux-calibration by dividing the extracted spectra with the spectral response function of the instrument (determined from the observed and absolute flux distribution of Vega taken from Gray 1992). However, this calibration may suffer from large systematic errors as Vega was observed at a significantly different air-mass with the shortest exposure time available (1 msec). Since neither the observing conditions were extremely good (strong variations of the seeing), nor could the possible shutter effects be included in the reduction, we normalized the low-resolution spectra to the continuum. In this way we have lost the possible hints of a red continuum (due to the cooler secondary star) but the most important spectral features could be well identified.