Model atmosphere analysis of two new early–type O4 dwarfs stars

We present a synthetic spectra study of two new galactic early-type O4 dwarf stars(ALS 19618 and BD+50886) with high signal-to-noise ratio, typically S/N ∼ 300, medium-rosalution R ∼ 2500 optical spectra of O4 dwarfs stars from Galactic O-Stars Spectroscopic Survey (GOSSS), The main stellar parameters (Teff, surface gravity, rotational velocity) have been established using non-LTE, line-blanketed, atmospheric models calculated by TLUSTY204 and SYNSPEC49.