Long-term variability of the optical spectra of NGC 4151 - II. Evolution of the broad Hα and Hβ emission-line profiles

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Table 5:

Yearly-averaged and period-averaged variations in the integral Balmer decrement (BD) and continuum fluxes.
Year	F(H $\alpha$ )/F(H $\beta$ $)\pm \sigma$		F(5100 $)\pm \sigma$ ^a
1996	3.65	0.51	11.18	1.55
1997	3.39	0.36	7.62	1.03
1998	3.58	0.35	6.08	1.19
1999	4.49	0.74	5.12	1.62
2000	5.01	0.62	2.75	1.33
2001	5.43	1.07	1.87	0.47
2002	3.67	0.44	3.59	0.29
2003	3.16	0.27	4.84	0.58
2004	3.70	0.29	2.44	0.57
2005	3.96	0.54	1.99	0.18
2006	3.58	0.36	2.60	0.80
mean (1996-1998):	3.54	0.13	8.29	2.62
mean 1999(Jan.-Apr.):	4.21	0.59	5.89	0.56
1999 (Dec.):	5.33		2.78	0.12
mean (2000-2001):	5.22	0.30	2.31	0.62
mean (2002-2006):	3.61	0.29	3.09	1.14

^a In units of $10^{-14} \;\rm erg ~ cm^{-2}~s^{-1}~\AA^{-1}$ .
Columns: 1 - year or yearly-intervals; 2 - F(H $\alpha$ )/F(H $\beta$ ), H $\alpha$ and H $\beta$ flux ratio or integrated Balmer Decrement (BD); 3 - $\sigma$ (F(H $\alpha$ )/F(H $\beta$ )), the estimated F(H $\alpha$ )/F(H $\beta$ ) error; 4 - F(5100), continuum flux at $\lambda 5100~\AA$ ; 5 - $\sigma$ , estimated continuum flux error. The last four lines provide the mean BD, mean continuum flux, and their estimated errors in year-periods.

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