Spectrum of the Iron Star XX Ophiuchi

Abstract

view Abstract Citations (6) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Spectrum of the Iron Star XX Ophiuchi Merrill, Paul W. Abstract The light-variation is of the R Coronae type. The light-curve since 1919, as deter- mined at Harvard, is shown in Fig. i. The spectrum is of class Bep. Between 1921 and 1931 it passed through a remarkable cycle of variation. At the beginning and end pf this period it was marked by emission lines of H and Fe ii, but in 1925 wide, displaced absorption lines appeared, among which lines of Ti ii were prominent. Estimated intensities of bright and dark lines of H, Fe ii, and Ti ii are in Table II. The behavior of lines of Cr ii, Sc ii, Mg ii, Al iii, and He i is described. The bright metallic lines (Fe ii, [Fe n], Ti ii, Cr ii, Sc ii, Mg ii, and Al in) give displacements which agree within observational errors, but the mean displacement of H lines is algebraically greater by about 3° km/sec. Widths of dark lines were about 6 A 111 1925, but decreased thereafter. The relative displacements of dark components with respect to the bright lines are shown in Tables V and VI. On plate C ~ the narrow dark components do not adjoin the bright lines but are displaced toward the violet. Discussion-At the beginning and end of the period of observation certain lines were strongest, particuhrly H em and Fe ii em, while in 1925 the following were strong- est: H abs, Fe ii abs, Ti em and abs, Cr em and abs, Sc em and abs. The behavior of a close pair of Fe ii lines suggests that the absorbing stratum overlay that in which the emission occurred. The positions of the bright lines are nearly independent of the in- tensities and positions of the dark lines. The great change in spectrum during a period of constant brightness is puzzling. Comparing this star with novae, we may use Haim's expanding-shell hypothesis to explain some of the differences between them by a difference in the relative radii of shell and stellar surface Publication: The Astrophysical Journal Pub Date: March 1932 DOI: 10.1086/143363 Bibcode: 1932ApJ....75..133M full text sources ADS | Related Materials (1) Reprint: 1932CMWCI.444....1M