A study of stellar hydrogen lines and their relation to the Stark effect.

Abstract

view Abstract Citations (3) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A study of stellar hydrogen lines and their relation to the Stark effect. Elvey, C. T. ; Struve, O. Abstract We have examined the wings of the hydrogen lines ~n early type stars and have found them to be much more extensive than has heretofore been supposed. Spectrograms have been taken with Eastman Process plates to obtain high contrast, and with rather short exposures in order that the density of the continuous spectrum would fall within the range giving the largest deflections when the plate is analyzed with the microphotom- eter. Spectrograms taken with several instruments were compared in order to eliminate the selective absorptions in the glasses of the optical systems. A comparison of the spec- trograms of a Lyrae, a Cygni, 67 Ophiuchi, and 85 Herculis shows that in a Lyrae and ~perhaps ~n Herculis the red wing of HE, X 3970, overlaps the violet wing of H~, X 4102. The observations make it doi~btful that any of the continuo~ss spectrum between H~ and Hy is free from the wings of those lines. In a Cygni and in 67 Ophiuchi the overlapping is much less pronounced. These very extensive wings of the hydrogen lines indicate the influence of Stark effect. This is shown by comparing the hydrogen lines of 85 Herculis (dwarf), which have very extensive wings, with those of 67 Ophiuchi (giant), which have narrow wings. The total absorptions of Ho in these two stars differ greatly. This may in part be due, also, to Stark effect, but it is probable that another phenomenon is present which makes the total absorptions of the hydrogen lines larger in the dwarfs than in the giants. Two pairs of stars, the first a giant and the second a dwarf in each case, 7 Aurigae - 88y Pegasi and 50 a Cygni -24 y Orionis, selected according to total absorptions of the hydrogen lines and irrespective of the spectral type, show that the contours differ greatly. This is interpreted as being due to Stark effect. The overlapping of the wings of the hydrogen lines, possibly as far as Thy, adds a complication to the determination of the temperatures and color indices for the stars of classes A and B. An attempt ~as made to compute the influence of ionic fields upon the contour of a hydrogen line. For the purpose of the computation it was assumed that the undisturbed line has approximately the shape of Hy in 3o~ Leonis. The variation of the absorption coefficient in the line was determined as a function of optical depth, on the assumption that the pressures are as given in the work of E. A. Milne. For simplicity the absorption coefficient of the continuous spectrum, the concentration of absorbing atoms, and the temperature were taken as constant. The ratio of the absorption coefficients in the line 27 Publication: The Astrophysical Journal Pub Date: December 1930 DOI: 10.1086/143281 Bibcode: 1930ApJ....72..277E full text sources ADS |