next previous
Up: H observations of Be


2 Observations

Observations of the 44 Be stars presented here, were carried out between April 1998 and January 2000 on the 1.2 m. Cassegrain telescope of the Mount Abu Infrared Observatory, India. All the observations were made using a fibre linked astronomical grating spectrograph (FLAGS), recently made operational (Banerjee et al. 1999). The spectrograph has a Czerny Turner configuration with f/10optics of 1.5 m focal length. It is mounted on a bench and light from the f/13 Cassegrain focal plane of the telescope is fed into it by means of an optical fibre (fibre type FIP 320385415, manufactured by Polymicro Technologies, U.S.A.). The dispersing element is a 2400 lines/mm Jobin Yvon holographic grating used in first order. It gives a reciprocal dispersion of 0.135 Å pixel at the detector and a spectral coverage of about 25 Å per CCD frame. The resolving power of the spectrograph, constrained primarily by the 320 micron diameter of the core of the optical fibre, is approximately 13000 at the H$\alpha$ wavelength. We have used a CCD with a Kodak KAF 1600 grade 1 chip as the detector. The main limitation of the detector is that it is only thermo-electrically cooled and does not generally permit cooling below $-15\;^\circ$C. Incidentally, we are trying to acquire a liquid nitrogen cooled CCD for the spectrograph with which we plan to continue the Be star programme.

All our spectra have been obtained at $-15\;^\circ$C. Consequently the dark count level has been just sufficient to given moderate S/N ratios in our spectra vis-a-vis those obtained by some other observers like for example Hanuschik et al. (1996). Nevertheless, our data compares reasonably well with earlier studies of Dachs et al. (1986), and Andrillat & Fehrenbach (1982), and should supplement the existing data base of emission line profiles of Be stars, especially in regards to their temporal variation. Indeed, even at its present performance level, FLAGS does provide adequate resolving power and S/N ratio to detect fine structures like wine-bottle inflections in the profiles. As pointed out by Hanuschik (1996), these structures become apparent only when high resolution and S/N profiles are available (Hanuschik 1986, 1987; Hanuschik et al. 1988; Doazan et al. 1991; Slettebak et al. 1992; Dachs et al. 1992).

 

 
Table 1:
HR No. Name HD No. mv Epoch
         
193 Omi Cas 4180 4.54 23.12.98
264 Gamma Cas 5394 2.47 23.12.98
264 Gamma Cas 5394 2.47 29.11.99
335 Phi And 5394 4.25 22.12.98
496 Phi Per 10516 4.07 30.1.00
1087 Psi Per 22192 4.23 22.12.98
1165 Eta Tau 23630 2.87 30.11.99
1180 28 Tau 23862 5.09 30.11.99
1273 48 Per 25940 4.04 23.12.98
1508 56 Eri 30076 5.9 16.3.99
1622 11 Cam 32343 5.08 15.3.99
1660 105 Tau 32991 5.89 15.3.99
1789 25 Psi Ori 35439 4.95 30.1.00
1858 120 Tau 36576 5.69 14.4.99
1910 Zet Tau 37202 3 16.3.99
1934 Ome Ori 37490 4.57 22.12.98
1956 Alpha Col 37795 2.64 13.4.99
2284 FR CMa 44458 5.64 19.2.99
2343 Nu Gem 45542 4.15 12.4.99
2356 Beta MonA 45725 4.6 28.11.98
2358 Beta MonC 45727 5.6 28.11.98
2492 10 CMa 48917 5.2 23.12.98
2538 13 K Cma 50013 3.96 15.3.99
2749 28 Ome Cma 56139 3.85 20.2.99
2787   57150 4.69 14.4.99
2817   58050 6.41 26.11.98
2825   58343 5.33 20.2.99
2845 3 Beta CMi 58715 2.9 12.4.99
3135   65875 6.51 23.12.98
3237 MX Pup 68980 4.78 13.4.99
3858   83953 4.77 19.2.99
3946   86612 6.21 14.4.99
4621 Del Cen 105435 2.6 14.4.99
4696 5 Crv 107348 5.21 14.4.99
4787 5 KDra 109387 3.87 19.2.99
5193 Mu Cen 120324 3.04 21.2.99
5440 Eta Cen 127972 2.31 21.2.99
5778 4 The Crb 138749 4.14 12.4.99
5941 48 Lib 142983 4.88 15.3.99
6118 Chi Oph 148184 4.42 28.4.98
6118 Chi Oph 148184 4.42 15.3.99
6510 Alpha Ara 158427 2.95 13.4.99
6712 66 Oph 164284 4.64 12.4.99
7106 10 Beta Lyr 174638 3.45 12.4.99
7763 34 P Cyg 193237 4.81 30.11.99
8773 4 Beta Psc 217891 4.53 27.11.98


The details of the observations are presented in Table 1. The table gives the HR number, the star name, the HD number, the magnitude mvand the epoch of observation for all the stars that have been studied. Each of the spectra was obtained with an integration time of 10 min. Calibration of the wavelength scale on the detector was done using the identified lines of the solar spectrum (Kurucz et al. 1984). The rest wavelength of the laboratory H$\alpha$ line was determined by using a hydrogen spectral lamp. The hydrogen lamp calibration frames were taken regularly before, in between and after the object frames to keep a check on the instrument performance and the position of the H$\alpha$ rest wavelength.


next previous
Up: H observations of Be

Copyright The European Southern Observatory (ESO)