COMMISSIONS 27 AND 42 OF THE IAU 
             INFORMATION BULLETIN ON VARIABLE STARS 
                          Number 3783 
 
                                           Konkoly Observatory 
                                           Budapest 
                                           2 October 1992 
 
                                           HU ISSN 0374 - 0676 
 
 
             Halpha SPECTROSCOPY OF NOVA CYGNI 1992 
 
 Nova Cygni 1992 was discovered by Collins (1992). Photometric 
observations by many observers indicate that the maximum brightness 
occurred at around February 22 with a visual magnitude of about 4.3, 
the brightest among the novae observed in the last 10 years. The 
light declined slowly and t_3 found to be about 47 days (Kidger 1992). 
The strong neon lines in IUE and optical spectra reveal that it is a 
new member of the "slow" ONeMg class of novae (Austin and Starrfield, 
1991) like QU Vul (Gehrz et al., 1985, Bergner et al., 1988). 
 
 In coordination with IUE; observation, two CCD Halpha spectra of 
Nova Cyg 1991 were obtained by us with the 2.16-m telescope at the 
Xinglong station of Beijing Observatory. A fiber-fed Cassegrain 
spectrograph was used together with a 576x384 CCD detector. The 
reciprocal dispersion of the. spectrum is 50 A/mm, corresponding to 
1.15 A per pixel. The two spectra were exposed on May 8.83 and 9.85 
UT, respectively. The Halpha lines on them show nearly the same 
structure. 


                          [FIGURE 1]

 Figure 1. CCD Halpha spectrum of Nova Cygni 1992 on 1992 May 8.83 UT.

 
 Figure 1 displays the spectrum on May 8.83 UT, with strong Halpha 
and apparently HeI 6678 A also in emission. The Halpha profile has a 
very complex structure with several peaks. Through multiple fitting 
six Gaussian profiles are found with five in emission and one in 
absorption as shown in Figure 2. The line identification of the 
Gaussian profiles as well as their radial velocities are listed in 
Table 1. 


                           [FIGURE 2]

      Figure 2. Multiple Gaussian fitting of the Halpha profile.

 
                     Table 1 
 
 lambda  Identification    Delta lambda    V_r 
  (A)                          (A)       (km/sec) 
 
6541.3   [NII] 6548.1 A       -6.8        -312 
6550.0   Halpha (?)          (-12.8)     (-58.5) 
6560.7   Halpha 6562.8 A      -2.1        -96 
6561.4   Halpha 6562.8 A      -1.4        -64 
6569.9   Halpha (?)          (+7.1)      (+325) 
6579.7   [NII] 6583.4 A       -3.7        -170 
 
 
 
 Two strong [NII] emission lines were observed be be blended with 
Halpha. Their radial velocities are found to be -312 and -170 km/s, 
respectively. 
 
 The large difference in the radial velocities could be caused by the 
emissions from distinct envelopes with different expansion velocities. 
The appearance of the forbidden [NII] lines confirms that the nova had 
already entered the nebular stage as reported by Austin and Starrfield 
(1992), as well as Rafanelli and Rosino (1992). It is interesting to 
notice that the nova experienced an obvious brightening by DeltaB approx. 
0.20 from May 2 to 9. (Hanzl et al., 1992, Dintinjana et al., 1992) 
and then resumed its decline in brightness but more slowly than 
before. 
 
 The two unidentified features at 6550.0 and 6569.9 A could both be 
shifted Halpha lines caused by the re-emission from the inner parts 
of a geometrically thick but optically thin dust disc. Their high 
radial velocities may be somehow connected with the spin of the disc, 
but the huge difference between them is an open question. 
 
 The Halpha emission profile exhibits no obvious P Cyg structure 
appear but there is a weak central absorption instead, which is 
typical for a star with expanding gas envelope. More Halpha spectra 
were obtained after this observation. Their careful analysis will 
help us to understand better the nature and evolution of Halpha 
emission during the outburst of Nova Cyg 1992. 

 
                          XIAOBIN ZHANG 
                          DISHENG ZHAI 
                          YULIAN GUO 
                          Beijing Observatory, Chinese Academy 
                            of Sciences 
                          Beijing, 100080 China 
 
 
 
 
References: 
 
Austin, S. J., and Starrfield, S. G., 1992, IAU Circ., No. 5522  [BIBCODE 1992IAUC.5522....2A ]
 
Bergner; Yu. K., Miroshnichenko, A. S., Yudin, R. V., Yutadov, N. 
  Yu., Dzakushem, K. G., Ilyin, V. V., Kuratov, R. S., and Mukanov, D. 
  S., 1988, Ap. Space Sci., 149, 63  [BIBCODE 1988Ap&SS.149...63B ]
 
Collins, P., 1992, IAU Circ., No. 5454  [BIBCODE 1992IAUC.5454....1C ]
 
Dintinjana, R., and Mikuz, H., 1992, IAU Circ., No. 5526 
 
Gehrz, R. D., Grasdalen, G. L., and Hackwell, J. A., 1985, Astrophys. 
  J., 298, L47  [BIBCODE 1985ApJ...298L..47G ]
 
Hanzl, D., Hrach, F., and Neureiterova, E., 1992, IAU Circ., No. 5520  [BIBCODE 1992IAUC.5520....2H ]
 
Hanzl, D., and Hrach, F., 1992, IAU Circ., No. 5537  [BIBCODE 1992IAUC.5537....1E ]
 
Kidger, M., 1992, IAU Circ., No. 5526  [BIBCODE 1992IAUC.5526....2H ]
 
Rafanelli, P., and Rosino, L., 1992, IAU Circ., No. 5525  [BIBCODE 1992IAUC.5525....1R ]