Astronomy and Astrophysics – Astrophysics
Scientific paper
Nov 1977
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1977a%26a....61..459c&link_type=abstract
Astronomy and Astrophysics, vol. 61, no. 4, Nov. 1977, p. 459-467. Research supported by the Consiglio Nazionale delle Ricerche
Astronomy and Astrophysics
Astrophysics
32
Planetary Nebulae, Stellar Spectrophotometry, Variable Stars, Light Curve, O Stars, Spectrum Analysis, Stellar Evolution, Stellar Spectra
Scientific paper
Previously obtained plates and photographic photometry of the eruptive variable HM Sge are analyzed. A light curve of the star is plotted, and its spectrum is shown to indicate a gaseous envelope in a fairly high state of excitation. Emission features observed over the ionization-potential ranges from 7 to 12 eV, 13 to 16 eV, 23 to 27 eV, 34 to 41 eV, and 47 to 55 eV are described. Intensities are deduced for the main emission lines, and it is found that the overall appearance of the line spectrum resembles that of a planetary nebula of very high density and medium excitation class. A heliocentric radial velocity of +12 (+ or - 7) km/s is computed, HM Sge is tentatively identified as a peculiar variable of the V1016 Cyg type, and it is suggested that this object be included in the group of BQ / / stars. Some morphological features of HM Sge and several compact planetary nebulae are compared, and a possible evolutionary sequence is considered for the star. It is concluded that the observed outburst of HM Sge was caused by the degradation of UV energy into optical emission as well as by the excitation of low metastable levels of many ions.
Ciatti F.
Mammano Augusto
Vittone A. A.
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