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3 Data reduction and analysis

Preliminary data reduction of the CCD frames, including dark subtraction and flat fielding, were done using the PMIS software, supplied by the CCD manufacturer. The spectra were then exported into IRAF and the physical parameters of the line profiles, such as equivalent widths, V/R ratios, half widths etc. were computed from it. A five point moving average or boxcar smoothing was done for all the spectra to reduce the noise, except in the case of HR 5778 where the spectrum was rather noisy and smoothing did not really help. The final spectra of the 44 Be stars are presented in Figs. 1-8.

Listed in Table 2 are the computed emission line parameters for the Be stars. The columns in sequential order give the HR number, the projected rotational velocity of the star vsini in km s-1, the equivalent width W in Angströms, the peak to continuum ratio ${I_{\rm p}}/{I_{\rm c}}$, the half width (i.e. full width at half maximum) l in Angströms, the full width at zero maximum E' in Angströms, the V/Rratio and the separation of the V and R components $\Delta v$ in Angströms. For maintaining uniformity, we have adopted the same definitions for these terms as laid down in the paper of Andrillat (1983, refer Fig. 1), except that, following Dachs (1981), we have used a negative sign for the equivalent width when lines are in emission, and a positive sign in absorption. In some cases either the Vor the R component does not form a sharp peak, but a rather extended flat/sloping region. In such cases the centre of the region has been taken for calculating the intensity of the component and measuring $\Delta v$. Such stars are marked with an asterisk in the V/Rcolumn. The majority of the mv (Table 1) and vsini values have been taken from an electronic version of the Bright Star Catalogue (Hoffleit & Warren 1991), but we have also referred in some cases to Dachs (1986). It may also be noted that HR 264 (Gamma Cas) and HR 6118 (Chi Oph) are repeated twice in Tables 1 and 2 since their spectra were taken at two different epochs.

We have not given the errors in the values of the above parameters for each specific star as we feel it would suffice to give only a typical range of them. The parameters which suffer most from the errors are the equivalent width W and the total width E'. In the former, the errors mainly arise when the continuum is not too well defined due to inadequate S/N. In the case of E', on the other hand, they arise when the lines are so broad that they seem to marginally extend beyond the 25 Å spectral coverage of the CCD. Using several independent measurements on IRAF, we estimate the errors in E' and W to be in the range of 5 to 10 percent. The other parameters are better defined and have errors in the range of 1 to 4 percent. As expected, smaller the S/N ratio, larger the errors.

 

 
Table 2:
HR No. $v{\rm sin}i$ Eq. Width ${I_{\rm p}}/{I_{\rm c}}$ Half Width Full Width V/R $\Delta v$
  (km s-1) W(Å)   l(Å) $E{^{\prime}}$(Å)   (Å)
               
193 260 -29.5 6.36 5.27 13.11    
264 300 -22.47 4.12 6.07 21.33    
264 300 -26.72 4.63 6.62 23.41 1.25* 2.116
335 71 -4 2.12 3.20 6.86    
496 450 -21.88 3.03 10.69 24.63 1.01 4.11
1087 369 -39 6.11 7.40 22.28 0.98 2.86
1165 215 -8.62 2.71 5.08 12.73 1.02 1.543
1180 329 -60.93 10.48 6.03 15.31 0.92* 1.214
1273 217 -28.04 6.74 4.44 15.17    
1508 240 -24.7 4.49 6.44 20.13 0.97 1.37
1622 131 -19.92 5.80 3.69 3.94 0.72* 1.3
1660 220 -26.93 6.29 4.67 14.38    
1789 316 -15.6 2.71 9.60 17.92 1.00 5.64
1858 271 -25.73 4.57 7.83 16.12 1.02 2.29
1910 310 -20.64 3.06 9.80 22.35    
1934 194 -4.07 1.33 9.64 15.71 0.96 5.54
1956 176 -10.36 2.79 5.43 12.35 1.00 1.77
2284 265 -34.6 5.08 7.72 19.01 0.98* 1.85
2343 219 -3.64 1.73 7.76 15.86 0.86 4.07
2356 346 -24.08 3.65 9.15 19.66 1.00 3.2
2358 331 -21.1 3.78 7.30 19.28 1.32* 2.93
2492 200 -18.88 3.56 6.36 18.83 0.98 1.506
2538 199 -15.42 3.19 6.47 22.25 0.94 1.95
2749 120 -18.6 6.75 3.06 9.23    
2787 220 -28.45 5.46 5.83 12.54 1.12 2.11
2817 140 -27.88 6.38 5.12 10.81    
2825 33 -11.73 6.45 2.18 6.44    
2845 276 -6.56 1.97 6.57 13.99 1.00 2.956
3135 148 -46.53 10.13 4.19 4.41    
3237 156 -43.7 11.73 3.42 13.46    
3858 332 -19.7 2.95 9.18 20.76 1.00 2.85
3946 220 -35.03 6.53 5.65 13.66 1.02 1.355
4621 181 -35.46 6.89 5.16 17.66    
4696 -7.3 2.11 6.77 13.07 0.94 3.04  
4787 249 -8.2 2.07 7.11 16.34 1.01 2.977
5193 175 -8.75 2.89 5.12 10.28 1.03 1.77
5440 333 -0.59 1.41 13.27 22.71 0.93 7.12
5778 393 2.79 0.76 10.88 22.93    
5941 393 -17.28 3.95 7.65 22.26 0.65 5.119
6118 134 -35.63 10.58 13.09 15.86    
6118 134 -37.63 10.72 13.15 17.64 1.72* 1.4
6510 298 -19.2 3.26 8.32 18.71 1.06 2.83
6712 221 -35.53 5.97 6.97 14.88 0.99 2.07
7106 -28.36 4.80 5.80 21.95 0.58 5.802  
7763 75 -51.52 13.83 4.03 11.48 0.02 4.44
8773 128 -21.8 8.24 2.93 11.06    



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