Spectroscopy and photometry of the protoplanetary nebula candidate StH alpha 62=IRAS 07171+1823статья
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Дата последнего поиска статьи во внешних источниках: 7 февраля 2018 г.
Аннотация:We present the results of spectroscopic and photometric observations for the B star StH alpha 62 with an IR excess, a post-AGB candidate identified with the IR source IRAS 07171+1823. High-resolution spectroscopy has allowed the lambda 4330-7340 angstrom spectrum of the star to be identified: it contains absorption lines of an early B star and emission lines of a gaseous shell. The residual line intensities have been measured. The heliocentric radial velocities measured from absorption lines of the star and emission lines of the shell are (V-r) = +45 +/- 1 and +52 +/- 1 km s(-1), respectively. The line-of-sight velocities of gas-dust clouds determined from the interstellar Na I lines are 12 and 33 km s(-1). The He I lambda 5876 angstrom line exhibits a P Cyg profile, which is indicative of an ongoing mass loss by the star. The expansion velocity of the outer shell estimated from forbidden lines is 12-13 km s(-1). Quantitative classification gives the spectral type B0.51 for the star. The parameters of the gaseous shell have been determined: N-e = 3.1 x 10(3) cm(-3) and T-e similar to 21000 K. Over 4 years of its observations, the star showed rapid irregular light variations with the amplitudes Delta V = Delta 0.(m)2. Delta B =0.(m)2, and Delta U = 0.(m)3 and no color-magnitude correlation. We estimate the total extinction for the star from our photometric observations as A(V) = 0.(m)4. Near-IR observations have revealed dust radiation with a temperature of similar to 1300 K. We estimate the distance to StH alpha 62 to be r = 5.2 +/- 1.2 kpc by assuming that the star is a low-mass (M = 0.55 +/- 0.05 M-circle dot) protoplanetary nebula.