Astronomy and Astrophysics – Astronomy
Scientific paper
May 1998
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998astl...24..365a&link_type=abstract
Astronomy Letters, Volume 24, Issue 3, May 1998, pp.365-371; Pis'ma v Astronomicheskii Zhurnal, Vol. 24, p. 431
Astronomy and Astrophysics
Astronomy
5
Scientific paper
The UBV observations of FG Sge in 1992-1997, which were corrected for the contribution of the companion and the nebula, are presented. The brightness distribution over the planetary nebula He 1-5 was measured in the H alpha line. A ring structure of the nebula was detected. A total of five R CrB-type minima have been observed in FG Sge since 1992, with the deepest minimum being in 1996. The star exhibited a dramatic bluing on the descent to some minima. In 1997, pulsations with a period of ~115 days were observed in the bright state. The epochs of pulsation minima and profound R CrB-type dimmings were found to fit the same photometric elements. Low-resolution spectroscopic observations of the star show that the intensity of the Swan bands varies with pulsation phase. In the summer of 1996 the Na I lines in its spectrum were in emission. In the classification of carbon stars, the spectral type of FG Sge in 1996-1997 is estimated to be C1,1-C1,2, and, accordingly, its temperature is 4600-4800 K.
Arkhipova V. P.
Esipov Valentine F.
Sokol G. V.
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