2 Observations

  

Table 2: Program stars and journal of observations. See text (Sect. 2) for detailed column description

 

Table 2: continued

The observations have been carried out with the Echelle spectrograph mounted at the Cassegrain focus of the 1.82 m telescope operated by Astronomical Osservatories of Padova and Asiago on top of Mt. Ekar, Asiago (Italy). The detector has been a Thomson THX31156 CCD 1024 $\times$ 1024 pixels, 19 $\mu$m each. A 3 mm thick OG455 filter was used to suppress the cross-disperser II order. Great care was put in maintaining constant the dispersion and resolution over the whole observing campaign. The observations have been completed in 12 months (Dec. 1997 - Dec. 1998), which contributed to the homogeneity of the spectra included in this atlas. Reduction of the spectra has been performed in a standard way with the IRAF package running on PCs under the Linux operative system.

The program stars have been selected mainly from the Yamashita et al. (1977) atlas of the MKK classification system (identified by YNN in the 7$^{\rm th}$column of Table 2). If a given spectral type was not covered by YNN or the YNN star was too south and/or too faint, suitable targets were selected from other compilations of spectral standard stars. In the latter case, intercomparison of the spectral classifications given in the various catalogues and atlases generally show agreement at a level of $\pm$1 spectral subclass and $\pm$1 luminosity class (which is fully acceptable because the aim of this paper is not to reclassify the program stars but to investigate the classification potential of high resolution spectra in the near-IR). The 131 selected target stars are listed in Table 2, which columns give the following content:
Column 1. HD number.
Column 2. HIP number from the Hipparcos Catalogue.
Column 3. V magnitude from the Hipparcos Catalogue.
Columns 4-5. RA and DEC from the Hipparcos Catalogue expressed on the International Celestial Reference System (ICRS; for the few program stars not in the Hipparcos Catalogue, the V, RA and DEC. values come from the SIMBAD database).
Column 6. Spectral type.
Column 7. Source for the spectral type: YNN = Yamashita, Nariai $\&$ Norimoto (1977); w = Walborn (1973); g = Garcia (1989); l = Lang (1992); gg = Gray $\&$ Garrison (1989a,b); kmn = Keenan $\&$ McNeil (1989); j = Jaschek (1978); bsc = The Bright Star Catalogue, Hoffleit et al. (1991).
Column 8. [Fe/H] from Cayrel de Strobel et al. (1997); * from Taylor (1994).
Column 9. Projected rotational velocities from Uesugi & Fukuda (1982), in km s^-1.
Column 10. cv: coarse variability from the Hipparcos Catalogue: 1 $\leq$ 0.06 mag; 2 = 0.06-0.6 mag; 3 $\geq$ 0.6 mag.
Column 11. var: variability type from the Hipparcos Catalogue: C = constant or not detected as variable; D = a duplicity-induced variability; M = possible micro-variable (amplitude less than 0.03 mag); P = periodic variable; U = unsolved variable; $\alpha$ = $\alpha$ Cygni type; EB = eclipsing binary of $\beta$ Lyrae type; SPB = slowly pulsating B star; $\gamma$ = $\gamma$ Cassiopeiae type; $\delta$ = $\delta$ Scuti type; EA = eclipsing binary of Algol type; RS = RS Canum Venaticurum type; BY = BY Draconis type; L, LC = slow irregular pulsating star; I, IS = irregular eruptive star; SR, SRB, SRC = semi-regular pulsating star; ell = rotating ellipsoidal.
Column 12. SB: spectroscopic binaries from Batten et al. (1989) catalogue; SB1 and SB2: single and double spectrum spectroscopic binary, respectively (for none of the three SB2 binaries the companion is expected to significally affect the spectral appearance of the primary over the $\lambda\lambda$ 8500-8750 Å range here investigated. Details on the three SB2 are given by Abhyankar 1958; Morrison & Conti 1978; Wright 1970).
Column 13. Total exposure time (seconds) accumulated over separated observations.
Column 14. S/N ratio for the continuum at 8570 Å.
Column 15. Atlases which include the same star (cf. Table 1): m = Montes $\&$ Martin (1998); a = Andrillat et al. (1995); s = Serote Roos et al. (1996); k = Kiehling (1987); d = Danks $\&$ Dennefeld (1994); t = Torres-Dodgen $\&$ Weaver (1993); w = Weaver $\&$ Torres-Dodgen (1995).

All spectra are electronically available as continuum normalized ASCII files (from CDS at http://cdsweb.u-strasbg.fr/Abstract.html or from the personal web-page at http://ulisse.pd.astro.it/Astro/Atlases/), with a heliocentric corrected wavelength scale. The normalization to unity of Echelle spectra quite rarely is a trouble-free exercise, particularly when the wings of stark-broadened lines span a large fraction of an Echelle order (like in fast rotating early type stars). Continuum normalization was however necessary both to prepare the figures for the atlas and to overcome the largely variable shape of the Echelle order response (which depends on several factors: stellar color temperature, instrumental blaze-function, star's placing on the slit, uneven opacity of the CCD-dewar entrance window caused by condensing humidity, etc.). How difficult is the normalization of the continuum in hot stars can be easily guessed by considering a normal O star. In this case, the hydrogen Paschen 14 (at $\lambda$ 8598 Å, e.g. right at the center of the explored interval) has a peak absorption of just 1.5% the adjacent continuum in not-rotating stars, and therefore less than 1% in normally rotating stars. In the case of the O7 V star HD 217086 in Fig. 28 (which has a rotational speed $V\sin i=315$ km s^-1, cf. Table 2) the peak absorption in Paschen 14 reaches just $\sim$0.1% of the adjacent continuum. At such a level, to distinguish what is the profile of a stellar line and what instead is due to the instrumental blaze function is essentially impossible.