Sct stars form the second most numerous group of pulsators
in the Galaxy after the pulsating white dwarfs. They are located in the lower
part of the instability strip and have spectral types A-F and a range of
luminosities that extends from the Main Sequence to two magnitudes above it.
These stars are characterized by having periods shorter
than 
, amplitudes ranging from some thousandths of magnitude to
some tenths and complicated light curves that can
vary with time (Rodríguez et al. 1994). Some 
Sct
stars are known to be in binary systems. The pulsation behaviour ranges from
single-mode radial or multimode radial to mixed radial/non-radial
oscillations. Pulsation does not seem to be related to age since 
Scuti
stars are found in clusters as young as 
yr. and in older disk
population groups such as 
Pup (Eggen 1971).
Although in the past those stars with large amplitudes
were called dwarf Cepheids (Smith 1955),
AI Vel (Bessel 1969) and RRs stars (Kukarkin et al. 1969),
nowadays it is widely accepted that in their physical characteristics
they resemble the low amplitude
Sct stars (e.g. McNamara & Feltz 1978; Breger
1980). Whilst most 
Scutis belong to Population I there is a
small group that belong to Population II. They are called SX Phe
stars or variable blue stragglers (Eggen & Iben 1989;
Nemec & Mateo 1990). In this work, those Population I stars with
amplitudes greater than 
will be simply referred to as large
amplitude 
Scuti stars.
In the last years most work on 
Sct stars has been
devoted to the identification
of pulsational modes from photometric observations (see, for instance, the series
of papers by Poretti et al. (1992 and references therein) and
Rodríguez et al. 1993a, b).
Relatively little spectroscopic analysis has been done,
even though the 
Sct stars, especially the low amplitude ones, are
bright objects.
The goal of this paper is to derive, using spectroscopical techniques,
accurate values of the
effective temperature and rotational velocities of the sample of 
Sct
and non-variable
stars given in Tables 1 and 2 and to relate
them with the pulsational parameters, period and amplitude. In particular
we are interested in looking at differences between large and small
amplitude pulsators. The cut-off amplitude below which a star may be
considered small amplitude and above which it may be considered large
amplitude is somewhat arbitrary. Breger (1979) presented a
frequency-amplitude histogram and based on this we adopt a value of
for the cut-off. In a second
paper a detailed abundance analysis of iron, calcium and oxygen will be
presented for the same sample of stars.
Table 2: Program non-variable stars. The identification, V magnitude and
spectral type were obtained from Centre de Données Stellaires (CDS)
using SIMBAD. The last column indicates the telescope where the observation
was made (2.1 means 2.1 meters telescope at McDonald Observatory)
