Spectral libraries of late-type stars are a very powerful tool for the study of the chromospheric activity by application of the spectral subtraction technique (see Montes et al. 1995a,b,c; and references therein). Furthermore, these libraries are also very useful in many areas of astrophysics such as the stellar spectral classification, modelling stellar atmospheres, stellar abundances, calibration of temperatures, spectral synthesis applied to composite systems, and spectral synthesis of the stellar population of galaxies.
While for many of this purposes, obtaining as large a spectral range as
possible was the main priority,
for the chromospheric activity studies, which are centered in
specific spectral features, it is much more important to increase the
spectral resolution.
However, previously published stellar libraries are of poor spectral
resolution (between 45 and 1.25 ) and the only attempt to improve the
spectral resolution is our
library of high and mid-resolution spectra in the
Ca II H & K, H
, H
,
Na I D1, D2, and He I D3
line regions of F, G, K and M field stars
(Montes et al. 1997a, hereafter Paper I)
with resolutions that range between 3 and 0.2 .
However, even more higher resolutions are needed when we are interested in very detailed studies of chromospheric activity such as the analysis of the difference features present in the chromospheric emission line profiles, the study of chromospherically active binaries aimed to determine from which component of the binary belong the emission lines (see Montes et al. 1997b), or the analysis of the time variations and line asymmetries that occur during a stellar flare (see Montes et al. 1998b).
On the other hand, the simultaneous observations of different lines, that are formed at different height in the chromosphere (from the region of temperature minimum to the higher chromosphere), are of special interest for stellar activity studies since they provide very useful information about this stellar region. Ideally, simultaneous observations should be performed at all wavelengths in order to develop a coherent 3-D atmosphere model (see the multiwavelength optical observations of chromospherically active binary systems by Montes et al. 1997b, 1998a). So, to carry out these purposes applying the spectral subtraction technique, to as many lines as possible, a spectral library with a good spectral resolution and a good spectral coverage is needed.
The spectral library that we present in this paper is an extension
of our previous one (Paper I)
to higher spectral resolution covering a large spectral range.
The library consist of echelle spectra
of a sample of F, G, K and M field dwarf stars
covering the spectral range from 4800 to 10600 and
with spectral resolution ranging from 0.19 to 0.09 .
These spectra include some of
the spectral lines most widely used as
optical and near-infrared indicators of chromospheric activity
such as:
Na I D1, D2, and Mg I b triplet
(formed in the upper photosphere and lower chromosphere),
Ca II IRT lines (lower chromosphere),
H, H (middle chromosphere), and
He I D3 (upper chromosphere),
as well as a large number of
photospheric lines which can also be affected by chromospheric activity.
Furthermore, the spectra also include a lot of lines of interest to
spectral classification and calibration of temperatures purposes,
as well as other lines normally used for the application
of the Doppler imaging technique.
In Sect. 2 we report the details of our observations and data reduction. The library is presented in Sect. 3 with comments on the behaviour of some interesting spectral lines.