2 Observations and data analysis

Spectra of the newly detected Be stars were obtained on four nights during January - February 1997, using the Universal Astronomical Grating Spectrograph (UAGS) at the Cassegrain focus and also using the Echelle spectrograph at the Coudé focus of the 1 m reflector of VBO, with a CCD system. Iron-Argon or Iron-Neon and Thorium-Argon source spectra were used for wavelength calibration for UAGS and Echelle spectrograph, respectively. Dome flat-field frames were obtained to remove the pixel to pixel quantum efficiency variations. The reciprocal dispersions of UAGS and Echelle spectrograph are 19.6 Å mm^-1 at H$_\alpha$ (0.45 Å pixel^-1) and 7.4 Å mm^-1 at H$_\alpha$ (0.14 Å pixel^-1), respectively. The spectra were analyzed using IRAF software package installed on the SUN SPARC CLASSIC

Workstation. The following steps were followed for the reductions:

i)

Trimming of the bias, the flat-field and the star spectrum CCD frames.

ii)

Bias subtraction from the flat-field and the star spectrum CCD frames.

iii)

Normalization of the flat-field frame and the division of the star spectrum frame by the normalized flat-field frame.

iv)

Extraction of different orders of star and the comparison spectra.

v)

Wavelength calibration of the stellar spectra using the coefficients of a high order polynomial fit to the comparison spectra.

vi)

Normalization of the stellar spectra.

vii)

Measurements of different parameters (equivalent width, full width at half intensity maximum by fitting a Gaussian profile, intensities of emission and absorption components, peak-separations, etc.) of stellar absorption and emission profiles.

The error in wavelength calibration for Coudé and Cassegrain spectra was around 0.05 Å to 0.10 Å respectively. To reduce the error in normalization we normalized each spectrum, at least, three to four times and finally these spectra were averaged. Around 2% of the local continuum is estimated to be the error in normalization. The instrumental broadening was computed by measuring the FWHM of the narrowest line of the comparison spectral lines and this value of the FWHM was taken as the instrumental broadening of the spectrograph. The values of instrumental broadening for the UAGS and the Echelle spectrographs are 0.5 Å and 0.2 Å respectively, at H$_\alpha$. These values were used to correct for instrumental broadening of the measured FWHM values of Be stars. Using the expression of $\sigma$(EW), given in Ghosh (1988) and Ghosh et al. (1990), the errors in equivalent width measurements were computed.

  

Figure 1: Coudé Echelle H$_\alpha$ profiles of two known Be stars, HR 1037 and HR 2244. Sharp lines present throughout the spectra are H2O telluric absorption features

  

Figure 2: a) Same as Fig. 1, but for two new Be stars, HR 1544 and HR 4552. b) Same as Fig. 1, but for the new Be star, HR 1544 and the B type star HR 2155 of similar spectral type and rotational velocity as that of HR 1544. For comparison, the H$_\alpha$ profiles of these two stars are plotted one over the other and the subtracted spectrum (the H$_\alpha$ profile of HR 1544 minus the H$_\alpha$profile HR 2155) is presented on the top that shows the presence of emission in the H$_\alpha$ profile of HR 1544. c) Same as Fig. 1, but for the Cassegrain spectra of five new Be stars, HR 1056, HR 2191, HR 2300, HR 3134, and HR 3878