Observations in the H
and
Na I D1, D2, He I D3 line regions
have been obtained during
three nights (1995 September 13-15) with
the Isaac Newton Telescope (INT) at the
Observatorio del Roque de Los Muchachos (La Palma, Spain) using the
Intermediate Dispersion Spectrograph (IDS) with grating H1800V, camera 500
and a 
pixel TEK3 CCD as detector.
The reciprocal dispersion achieved is
0.24 Å/pixel
which yields a spectral resolution of 0.48 Å and a useful wavelength
range of 250 Å centered at 6563 Å (H)
and 5876 Å (HeI D3) respectively.
The spectra have been extracted using the standard reduction procedures in the IRAF package (bias subtraction, flat-field division, and optimal extraction of the spectra). The wavelength calibration was obtained by taking spectra of a Cu-Ar lamp. Finally, the spectra have been normalized by a polynomial fit to the observed continuum.
In Table 1 (click here) we give the observing log.
For each star we list
the date, UT, orbital phase (
) and signal to noise ratio (S/N)
obtained for each observation in both spectral regions.
Where appropriate, we also give the reference
of our previous observation of these
systems in the H and Ca II H & K lines.
In Table 2 (click here) we show the HD number, name and the adopted stellar parameters (from CABS or the references given in the table) for the 18 chromospherically active binary systems selected.
We have obtained the chromospheric contribution in
H Na I D1, D2, and He I D3 lines using
the spectral subtraction technique described in
detail by Montes et al. (1995a,c).
The synthesized spectra were constructed using artificially rotationally broadened, radial-velocity shifted, and weighted spectra of inactive stars chosen to match the spectral types and luminosity classes of both components of the active system under consideration. The reference stars used have been observed in this campaign and previous observational seasons with similar spectral resolution (see the spectral library of Montes et al. 1997).
In some case, the difference spectrum obtained appears noisier than
expected from the observation S/N ratio (
300) due to
small differences in spectral type between active and reference star, or to
non appropriate evaluation of the rotational broadening
and/or of the Doppler shift.
In addition, in some spectra telluric lines also appear in the difference
spectrum.
This noise in the the difference spectrum
have been evaluated as the mean standard deviation (
)
in the regions outside the chromospheric features.
We have obtained values of in the range 0.01-0.03 which
could be important in low active star but in the more active stars
the errors in the excess H EW are small.
We have considered as a clear detection of excess emission or absorption
in H, Na I D1, D2, and He I D3 only
when these features in the difference spectrum are
larger than 3 .
Table 3 (click here) gives the H line parameters, measured in the
observed and subtracted spectra of the sample.
Column (2) of this Table gives the orbital phase ()
for each spectrum,
and in Col. (3), H and C mean emission belonging to hot and
cool component respectively, and T means that at these phases
the spectral features cannot be deblended.
Column (4) gives the contributions for the hot and cool component
to the total continuum (
and 
).
Column (5) describes the observed H profile, i.e. if the
line is in absorption (A) in emission (E) or totally filled by
emission (F).
Columns (6), (7), (8) give the following parameters
measured in the observed spectrum:
the full width at half maximum (
);
the residual intensity, 
; and the H core flux, F(1.7 Å),
measured as the residual area below the central 1.7 Å passband.
The last four Columns give he following parameters
measured in the subtracted spectrum:
the full width at half maximum
), the peak emission intensity (I),
the excess H emission equivalent width (EW( H)), and
absolute fluxes at the stellar surface log
(H) obtained
with the calibration of Pasquini & Pallavicini (1991) as a function of
(V-R), very similar values of (H) are obtained
using the more recently calibration of Hall (1996) as a function of
(V-R) and (B-V).
For a more detailed description of the parameters given in this table
see our previous study of the excess H emission in active binaries
(Montes et al. 1995a).
In Table 4 (click here) we list the parameters (I, FWHM, EW)
of the broad and narrow components used in the two Gaussian components fit
to the H subtracted emission profile, which we have performed in the
stars that present broad wings. See the comments for each individual star in
Sect. 3 and the interpretation of these components given in Sect. 4.
Figure 1: H, Na I D1, D2, and He I D3
spectra of BD Cet
Figure 2: H, Na I D1, D2, and He I D3
spectra of AY Cet