FIT{\it spec}: a new algorithm for the automated fit of synthetic stellar spectra for OB stars

Abstract: In this paper we describe the FIT\textit{spec} code, a data mining tool for the automatic fitting of synthetic stellar spectra. The program uses a database of 27\,000 {\sc cmfgen} models of stellar atmospheres arranged in a six-dimensional (6D) space, where each dimension corresponds to one model parameter. From these models a library of 2\,835\,000 synthetic spectra were generated covering the ultraviolet, optical, and infrared region of the electromagnetic spectrum. Using FIT\textit{spec} we adjust the effective temperature and the surface gravity. From the 6D array we also get the luminosity, the metallicity, and three parameters for the stellar wind: the terminal velocity ($v_\infty$), the $\beta$ exponent of the velocity law, and the clumping filling factor ($F_{\rm cl}$). Finally, the projected rotational velocity ($v\cdot\sin i$) can be obtained from the library of stellar spectra. Validation of the algorithm was performed by analyzing the spectra of a sample of eight O-type stars taken from the {\sc iacob} spectroscopic survey of Northern Galactic OB stars. The spectral lines used for the adjustment of the analyzed stars are reproduced with good accuracy. In particular, the effective temperatures calculated with the FIT\textit{spec} are in good agreement with those derived from spectral type and other calibrations for the same stars. The stellar luminosities and projected rotational velocities are also in good agreement with previous quantitative spectroscopic analyses in the literature. An important advantage of FIT\textit{spec} over traditional codes is that the time required for spectral analyses is reduced from months to a few hours.