Variability of hot supergiant IRAS 19336-0400 in the early phase of planetary nebula ionization |
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Authors: | V. P. Arkhipova M. A. Burlak V. F. Esipov N. P. Ikonnikova G. V. Komissarova |
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Affiliation: | 1.Sternberg Astronomical Institute,Moscow,Russia |
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Abstract: | We present photoelectric and spectral observations of a hot candidate proto-planetary nebula—early B-type supergiant with emission lines in spectrum—IRAS 19336-0400. The light and color curves display fast irregular brightness variations with maximum amplitudes (Delta V = 0_ cdot ^m 30), (Delta B = 0_ cdot ^m 35), (Delta U = 0_ cdot ^m 40) and color-brightness correlations. By the variability characteristics IRAS 19336-0400 appears similar to other hot proto-planetary nebulae. Based on low-resolution spectra in the range λ4000–7500 Å we have derived absolute intensities of the emission lines Hα, Hβ, Hγ, [S II], [N II], physical conditions in gaseous nebula: n e = 104 cm?3, T e = 7000 ± 1000 K. The emission line Hα, Hβ equivalent widths are found to be considerably variable and related to light changes. By UBV-photometry and spectroscopy the color excess has been estimated: E B-V = 0.50–0.54. Joint photometric and spectral data analysis allows us to assume that the star variability is caused by stellar wind variations. |
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