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The 1960 Minimum of R Coronae Borealis.

1963; IOP Publishing; Volume: 138; Linguagem: Inglês

10.1086/147647

1538-4357

Cecilia Payne-Gaposchkin,

Astronomy and Astrophysical Research

view Abstract Citations (85) References (23) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The 1960 Minimum of R Coronae Borealis. Payne-Gaposchkin, Cecilia Abstract The spectrum of R Coronae Borealis at maximum is that of a supergiant carbon star of spectral class equivalent to F7. As the star drops to minimum, veiling of the absorption spectrum is followed by the appearance of a very rich, bright4ined spectrum with relatively sharp lines, which fades exponentially, and also by the appearance of several strong, broad, bright lines, which persist with little change for some time and later fade abruptly. The average conditions in the layers that produce the rich, bright-lined spectrum correspond to 0 = 1.02, log P = -2.0, somewhat lower in temperature than the photosphere and at much lower electron pressure. The broad, bright-lined spectrum shows the H and K lines, the D lines, and a line at 3889 A which is ascribed to He I. The changes during the minimum are ascribed to a slow contraction of the envelope, leading to increased density and the deposition of carbon black, which is responsible for the large changes in brightness and for the reddening of the star's light. The rich, bright-lined spectrum is neither obscured nor reddened and is ascribed to an expanding chromosphere that fades progressively. The broad, bright-lined spectrum is ascribed to material which is ejected with high velocity in connection with the initial contraction of the envelope and is collisionally excited when it interacts with a circumstellar cloud. The other cool stars of R Coronae class behave in a similar manner, and their rate of variation is shown to be related to their photospheric temperatures. Publication: The Astrophysical Journal Pub Date: August 1963 DOI: 10.1086/147647 Bibcode: 1963ApJ...138..320P full text sources ADS | data products SIMBAD (5)