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Spectroscopy and photometry of the protoplanetary nebula candidate stHα62 = IRAS 07171+1823
We present the results of spectroscopic and photometric observations forthe B star StHα62 with an IR excess, a post-AGB candidateidentified with the IR source IRAS 07171+1823. High-resolutionspectroscopy has allowed the λ4330 7340 Å spectrum of thestar to be identified: it contains absorption lines of an early B starand emission lines of a gaseous shell. The residual line intensitieshave been measured. The heliocentric radial velocities measured fromabsorption lines of the star and emission lines of the shell are 〈Vr 〉 = +45 ± 1 and +52 ± 1 km s-1, respectively. Theline-of-sight velocities of gas-dust clouds determined from theinterstellar Na I lines are 12 and 33 km s-1. The He I λ5876Å line exhibits a P Cyg profile, which is indicative of an ongoingmass loss by the star. The expansion velocity of the outer shellestimated from forbidden lines is 12 13 km s-1. Quantitativeclassification gives the spectral type B0.51 for the star. Theparameters of the gaseous shell have been determined: N e = 3.1 ×103 cm-3 and T e 21 000 K. Over 4 years of its observations, thestar showed rapid irregular light variations with the amplitudesΔV = &$0(m) .2; , ΔB = &0(m) .2; , and ΔU = &0(m) .3; and no color-magnitude correlation. We estimate the total extinctionfor the star from our photometric observations as A v = &0(m) .4$; . Near-IR observations have revealed dust radiation with a temperatureof 1300 K. We estimate the distance to StHα62 to be r = 5.2± 1.2 kpc by assuming that the star is a low-mass (M = 0.55± 0.05 M ȯ) protoplanetary nebula.
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