The Spectrum Analysis of the Hot Carbon Star, R Coronae Borealis

Abstract

view Abstract Citations (37) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Spectrum Analysis of the Hot Carbon Star, R Coronae Borealis Berman, Louis Abstract A detailed investigation of the spectrum of the irregular variable R Coronae Borealis, in the region XX 4300-4900 was undertaken for the purpose of studying the physical conditions of its atmosphere. The wave-lengths of approximately 6~o lines were measured on the Lick three-prism spectrograms and the corresponding elements identified. Only 2 per cent of the lines belong to the non-metals. The average radial velocity of the system is + 25.1 km/sec. and is slightly variable at the time of maximum light (6.o mag.). A calibration-curve, based upon the theoretical intensity ratios of supermultiplets, connects the observed line intensities and the absolute numbers of atoms engaged in their production. The chemical composition of the atmosphere is found to be 69 per cent carbon, 27 per cent hydrogen, less than 0.3 per cent nitrogen, and 4 per cent metals. (chiefly magnesium and iron). (The theoretical abundance of the carbon molecule, C2, whose appearance is feebly indicated by the Swan spectrum, is 0.00003 per cent.) With these compositions and the value of the general atomic absorption coefficient derived from wave-mechanics, the computed optical depth of the photospheric level is o.oo6. This improbably small value may result from the incomplete state of the theory at the present time and from the neglect of molecular opacity arising from dissociation. The Russell-Adams analysis, used to determine the absolute temperature, does not reveal any marked deviation from thermodynamic equilibrium up to an excitation po- tential of io volts. The energy distribution of the continuous spectrum leads to a higher color temperature in the red than in the blue, but the difference may arise from the diffi- culty of drawing the true continuous background, owing to the peculiarity of the spec- trum. The color temperature in the blue is found to be over 10000 higher than the effective temperature. Finally, the physical parameters that define the state of the atmosphere are pre- sented: spectral class, cF7p; effective temperature, 53000 K; color temperature, 6700° K (XX 3500-4500), 77000 K (XX 4500-6500); electron pressure at base of reversing layer, 8.3XIo7 atm., mean total pressure, 9.3X io~ atm.; level of ionization, 9.6 volts; surface gravity, 2.7X 102 cm/sec.2; mean molecular weight, io chemical units; velocity of turbulence, io km/sec.; number of neutral atoms above i sq. cm of surface, 4.4X 1Q21, corresponding number of ionized atoms, 2.3 X 1020, corresponding total number of all particles, 4.9X 1021. 36 Publication: The Astrophysical Journal Pub Date: June 1935 DOI: 10.1086/143644 Bibcode: 1935ApJ....81..369B full text sources ADS |