The Spectrum of R Coronae Borealis at the 1948-1949 Minimum.
1949; IOP Publishing; Volume: 110; Linguagem: Inglês
10.1086/145193
ISSN1538-4357
Autores Tópico(s)Solar and Space Plasma Dynamics
Resumoview Abstract Citations (62) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Spectrum of R Coronae Borealis at the 1948-1949 Minimum. Herbig, George H. Abstract The spectrum of R Coronae Borealis was observed at the McDonald Observatory on the descent to the 1948-1949 minimum and for some time after it had reached minimum brightness. No change was noted in the spectrum until the star had fallen to magnitude 10.0, when emission cores appeared in the H and K lines. As the variable continued to fade, these emission lines strengthened, and others appeared. In addi- tion, a curious "veiling" of the absorption spectrum was observed. Near minimum light, the strongest emission lines were the D lines of Na i, followed by H and K of Ca ii, and a line near X 3888 which may be due to Hei. Most of the other emission lines were due to Sc U, Tiu, Sr ii, and Ca i, but XX 3726-3729 of [On] was also present. There was no sign of hydrogen emission, and Fe ii appeared oniy weakly. The fact that lines of low excitation were strong indicated that a low excitation temperature was at least partly responsible for the character of the emission spectrum. No marked change was seen in the C I or C2 ab- sorption features as the star faded. Likewise, no change in radial velocity was observed during the first 4.8 mag. of the descent to minimum, the oniy period for which spectrograms of adequate dispersion were available. The emission lines showed an apparently constant shortward displacement of about 12 km/sec with respect to the absorption spectrum. Spectrophotometry of the H and K emission lines showed that their relative intensities (with respect to the underlying continuum) increased during the star's fall to minimum but that the absolute intensities seemed to pass through a maximum when the star was at about magnitude 11. The reality of this decrease at fainter magnitudes, however, depends crucially on the as- sumption of constant color temperature during the variations. O'Keefe's proposed explanation for the variations of R CrB, in terms of an obscuring cloud thrown off by the star, is discussed only briefly. The lack of marked reddening of the variable at minimum requires, if the O'Keefe picture is correct, that the effective temperature of the obscuring cloud be less than 14000 or 1500° Publication: The Astrophysical Journal Pub Date: September 1949 DOI: 10.1086/145193 Bibcode: 1949ApJ...110..143H full text sources ADS |
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