2 Observations and data reduction

High-resolution spectroscopic observations of $\delta$ Sco were obtained at the 1m telescope of Ritter Observatory (Toledo, OH, USA) between 2000 August 5 and 2001 February 20, at the 2.6m Shajn telescope of the Crimean Astrophysical Observatory (CAO, Ukraine) between 2000 July 29 and 2000 August 21, and at 1.52m telescope at the ESO (La Silla, Chile) on 2000 October 23. Low-resolution spectroscopic observations were performed with the 1.3m telescope of the Skinakas Observatory (Crete, Greece) on 2000 July 19-22 and with the 1.52m G. D. Cassini telescope at the Loiano Observatory (BOL, Italy) 2000 July 26 and 29. We also found two archived, previously unpublished, spectra. One was obtained at Ritter on 1994 May 18 in almost the same spectral region and with the same equipment as in 2000. The other one was obtained at the 1.9m telescope of the South African Astronomical Observatory on 1998 April 16 with the GIRAFFE fiber-fed échelle spectrograph, which gives a resolving power $R \simeq$ 39000 in the range 5200-10400 Å.

At Ritter we used a fiber-fed échelle spectrograph with a Wright Instruments Ltd. CCD camera. The spectra consisted of 9 non-overlapping $\sim$70 Å orders in the range 5285-6597 Å with $R \simeq$ 26000. The Ritter data were reduced with IRAF. In total 24 spectra were obtained; the exposure time for each spectrum was 20 min. Most of the spectra have a signal-to-noise ratio $(S/N) \ge 100$. The following lines were detected: He I 5876, Si II 6347 & 6371 Å, H$\alpha$ (emission), and Na I D_1,2 5889 & 5895 Å (absorption).

At CAO the Coude spectrograph with a GEC CCD-detector ( $576\times380$ pixel array) was used. All observations were obtained in the second order of a diffraction grating with a reciprocal dispersion of 3 Åmm^-1, which corresponds to $R \sim 40\,000$. A typical exposure time for each spectrum was 4-10 min, giving a $S/N \ge200$. A region of 31 Å around the H$\alpha$ (5 spectra) and He I 6678 Å line (4 spectra) was covered in all cases. Data reduction was done with the SPE code developed by S. G. Sergeev at CAO.

At ESO the Fiber-fed Extended Range Optical Spectrograph (FEROS) and a thinned back-illuminated EEV detector with $2048\times 4096$ 15-$\mu$m pixels were used. The spectrum was obtained in the range 3700-9000 Å with $R \simeq 48\,000$ and a $S/N \simeq 120$ near H$\alpha$; the exposure time was 3 min. The spectrum was reduced with the FEROS data reduction package under MIDAS.

At Skinakas the telescope was equipped with a 2000$\times$800 ISA SITe chip CCD, a 1301 line mm^-1 grating, and an 80 $\mu$m width slit, giving a dispersion of 1 Å pixel^-1 ($R \simeq$ 3000). The range 5500-7550 Å was observed on July 19-20, while the range 3750-5750 Å was observed on July 21-22. Ten spectra with exposure times from 1 to 5 s were obtained.

At BOL the telescope was equipped with the Bologna Faint Object Spectrograph and Camera (BFOSC) and several gratings ($R \simeq$ 1000-2000 in the range 5400-8100 Å). On July 29 the #9 grism in échelle mode was used with the grism #10 as cross-disperser, which gives $R \simeq$ 6000 in the region 3692-8046 Å. Both the Skinakas and BOL spectra were reduced using the Starlink supported FIGARO package (Shortridge et al. 1997).

The log of our observations is presented in Table 2. Due to the northern location of all the observing sites, the star was observed at large airmasses, and strong telluric water vapour lines appear in the spectra. Because of the high resolution of our data, most of these lines are unblended. They were removed by interpolation between unaffected spectral regions, which were used for construction of the normalized line profiles.

 

 

Table 2: Summary of spectroscopic observations of $\delta$ Sco in 2000-2001.

Date	HJD	Obs.	Sp.region	n
2000	2451000+		Å
07/19	745.264	Ski	5500-7550	2
07/20	746.302	Ski	5500-7550	3
07/21	747.323	Ski	3750-5750	2
07/22	748.302	Ski	3750-5750	3
07/25	751.313	BOL	5400-8100	3
07/28	754.286	CAO	H$\alpha$	1
07/29	755.320	BOL	3692-8046	1
08/04	761.575	Rit	5290-6600	1
08/07	764.246	CAO	H$\alpha$	1
08/07	764.568	Rit	5290-6600	1
08/09	766.239	CAO	He I 6678	1
08/09	766.258	CAO	H$\alpha$	1
08/10	767.592	Rit	5290-6600	1
08/12	769.246	CAO	He I 6678	1
08/12	769.269	CAO	H$\alpha$	1
08/13	770.207	CAO	He I 6678	1
08/20	777.225	CAO	H$\alpha$	1
08/20	777.233	CAO	He I 6678	1
08/20	777.546	Rit	5290-6600	1
08/24	781.577	Rit	5290-6600	1
08/30	787.566	Rit	5290-6600	2
08/31	788.548	Rit	5290-6600	2
09/04	792.538	Rit	5290-6600	1
09/06	794.541	Rit	5290-6600	1
09/12	800.527	Rit	5290-6600	1
09/13	801.525	Rit	5290-6600	1
09/16	804.532	Rit	5290-6600	1
09/17	805.524	Rit	5290-6600	1
09/18	806.508	Rit	5290-6600	1
09/19	807.506	Rit	5290-6600	1
09/21	809.506	Rit	5290-6600	1
09/26	814.494	Rit	5290-6600	1
09/27	815.502	Rit	5290-6600	1
09/28	816.503	Rit	5290-6600	1
10/03	821.497	Rit	5290-6600	1
10/23	841.493	ESO	3700-9000	1
02/10$^{\rm a}$	951.948	Rit	5290-6600	1
02/20$^{\rm a}$	961.904	Rit	5290-6600	1
02/27$^{\rm a}$	968.978	Rit	5290-6600	1
03/09$^{\rm a}$	978.944	Rit	5290-6600	1

The spectral range in Col. 4 expressed either in Å or by the spectral line in its centre.
Multiple spectra obtained during the same date (Col. 5) were co-added.
$^{\rm a}$ The spectrum was obtained in 2001.