We investigate the detectability of starburst signatures in the nuclear spectrum of Seyfert 2 galaxies by constructing spectral models in the wavelength range \lambda \lambda 3500–4100Å , combining the spectrum of a bulge population ( of age \approx 10 Gyr ) with that of younger stellar populations , spanning ages from \approx 3 Myr to 1 Gyr .
The major constraints in the analysis are : ( i ) the continuum ratio 3660Å/4020Å , which efficiently discriminates between models combining a bulge spectrum with a stellar population younger than \approx 50 Myr and those with older stellar populations ; ( ii ) the presence of the Balmer lines H8 , H9 and H10 in absorption , which are unambiguous signatures of stellar populations with ages in the range 10 Myr–1 Gyr for the relevant metallicities .
Their detectability depends both on the age of the young component and on its contribution to the total flux relative to that of the bulge .

We also construct models combining the bulge template with a power-law ( PL ) continuum , which is observed in some Seyfert 2 ’ s in polarized light , contributing with typically 10–40 % of the flux at \lambda 4020Å .
We conclude that such continuum can not be distinguished from that of a very young stellar population ( age \leq 10 Myr ) , contributing with less than \approx 0.02 % of the mass of the bulge .

The models are compared with nuclear spectra — corresponding to a radius of 200–300 pc at the galaxy — of 20 Seyfert 2 galaxies , in which we specifically look for the signatures above of young to intermediate age stellar populations .
We find them in ten galaxies , thus 50 % of the sample .
But only in six cases ( 30 % of the sample ) they can be attributed to young stars ( age < 500 Myr ) : Mrk 1210 , ESO 362-G8 , NGC 5135 , NGC 5643 , NGC 7130 and NGC 7582 .
In the remaining four cases , the signatures are due to intermediate age stars ( \approx 1 Gyr ) .

We find a tendency for the young stars to be found more frequently among the late type Seyfert ’ s .
This tendency is supported by a comparison between the equivalent widths ( W ) of absorption lines of the nuclear spectra of the Seyfert 2 ’ s with those of normal galaxies of the same Hubble type : for the late-type ( Sb or later ) , the W values of the Seyfert ’ s are within the observed range of the normal galaxies , while the W values are lower than those of the normal galaxies for 7 out of the 11 early-type galaxies ( S0 and Sa ) .