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Results of modeling the spectra of two supernovae SN 2008D and SN 2006aj related to the X-ray flash XRF 080109 and gamma-ray burst GRB / XRF 060218, respectively, are studied. The spectra were obtained with the 6-meter BTA telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences in 6.48 and 27.61 days after the explosion of SN 2008D, and in 2.55 and 3.55 days after the explosion of SN 2006aj. The spectra were interpreted in the Sobolev approximation with the SYNOW code. An assumption about the presence of envelopes around the progenitor stars is confirmed by an agreement between the velocities of lines interpreted as hydrogen and helium, and the empiric power-law velocity drop with time for the envelopes of classic core-collapse supernovae. Detection of a P Cyg profile of the H-beta line in the spectra of optical afterglows of GRBs can be a determinative argument in favor of this hypothesis.

WOS: 000262332800003 The spectra of the supernova SN2006aj identified with the X-ray. ash (XRF) and gammaray burst XRF/GRB 060218/SN2006aj taken with the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences are found to exhibit features, which can be interpreted as hydrogen lines. Such features indicate the existence of a stellar-wind envelope around the massive star the progenitor of the gamma-ray burst. The results of our modeling of two early spectra taken with the 6-m telescope 2.55 and 3.55 days after the explosion of the type-Ic supernova SN2006aj (z=0.0331) are reported. The spectra are modeled in the Sobolev approximation using SYNOW code [1, 2]. The spectra of the optical afterglow of the X-ray. ash XRF/GRB 060218 are found to exhibit spectral features, which can be interpreted as: (1) the P Cyg-profile of the H alpha line for the velocity of 33000 km/s-a broad and small deformation of the continuum in the wavelength interval 5600-6600 A for the first epoch (2.55 days) and (2) a part of the P Cyg-profile of the Ha line in absorption blueshifted by 24000 km/s-a broad spectral feature with a minimum at 6100 A (rest wavelength) for the second epoch (3.55 days). Given earlier observations made with the 6-m telescope and the spectra taken with other telescopes (ESO Lick, ESO VLT and NOT) prior to February 23, 2006, it can be concluded that we are observing the evolution of optical spectra of the type Ic massive supernova SN2006aj during its transition from the short phase with the "shock breakout" into the external layers of the stellar-wind envelope to the spectra of the phase of rising supernova luminosity, which corresponds to radiative heating. We are the first to observe the signs of hydrogen in the spectra of a gamma-ray afterglow. Observatory of the Russian Academy of SciencesRussian Academy of Sciences; Spanish research programs [ESP200507714-C03-03, AYA2004-s] We are grateful to David Branch and other authors of SYNOW code for their consultations on running the code at the Special Astrophysical Observatory of the Russian Academy of Sciences and its practical use. We are also grateful to E. L. Chentsov and S.N. Fabrika for reading the first version of the text and constructive criticism. This paper was supported in part by the Spanish research programs ESP200507714- C03-03 and AYA2004-s.