**3.2.3 Results**

168 Bio-Inspired Computational Algorithms and Their Applications

From our discussion on section 2, one can see that generating a synthetic spectrum is a Pproblem, as the result is obtained from a set of parameters, and no more computing is need. The generation time is obviously finite, and there are a number of very efficient software tools that do that. The only care to be taken is to assure that the artificial spectrum has the same wavelength resolution of the observed spectrum, in order to simplify the future

The above mentioned step 4, a methodology to optimize the artificial spectrum, is the trick point. If one wants to use GA so solve the abundances problem, it is necessary to invert the P-problem, that is, it is necessary to use the artificial spectrum generation tool as an external routine of a bigger and more complex algorithm. The algorithm used to this task is

Fig. 6. Main blocks of a GA code to fit multi-band spectra of T Tauri stars (adapted from

**3.2.2 Inverting the problem** 

comparison.

presented in figure 6.

Fig. 5. FEROS spectrum for star PDS054 (Rojas et al. 2008).

Hetem & Gregorio-Hetem 2009).

In this section we present the results of the GA method for three stars, whose highresolution spectra were obtained at *European Southern Observatory* (ESO) in La Silla, Chile, with the *Fibber Extended Range Optical Spectrograph* (FEROS) at the 1.52m telescope. The stellar parameters (effective temperature and gravity) were calculated by excitation and ionization equilibrium of iron absorption lines (Rojas et al. 2008). The atomic and molecular line data were mainly from the National Institute of Standards and Technology1 and the Kurucz site2. The solar atomic abundances are from Grevesse & Sauval (1998), and the hyperfine structure constants were taken from Dembczyński et al. (1979) and Luc & Gerstenkorn (1972). The atmosphere models where obtained from the Kurucz library. Specific atmosphere models were calculated through a GNU-Linux porting of the ATLAS9 program (Kurucz 1993).

The method performs a multi-range fitting of specific regions of the observed spectrum, looking for best fit. The demands and commands to SPECTRUM are only those for generating the specific regions of interest, but the χ2 comparing index is evaluated over all wavelength ranges. Figures 7 and 8 present the results for some stars on chosen lines.

The metallicities and abundances found for the stars are compatible with those previously obtained for this particular sample. These preliminary results, achieved by using the GA technique, indicate the efficiency of the method. In the future, we intend to use the method in a larger sample of T Tauri stars.
