Show simple item record

dc.contributor.authorAbdel-Rahman, I. H. Abelen
dc.date.accessioned2019-02-15T14:17:33Z
dc.date.available2019-02-15T14:17:33Z
dc.date.issued1940
dc.identifier.urihttp://hdl.handle.net/1842/33614
dc.description.abstracten
dc.description.abstractPART I: EMISSION LINES IN EARLY TYPE SPECTRA - GENERAL SURVEY The present state of the study of emission line stars of early spectral types is briefly reviewed, mainly from the observational point of view. PART II: THE BE- VARIABLE SPECTRUM OF O PERSEI Radial velocities of central hydrogen absorption lines were measured on 23 quartz -prism spectrograms, covering the star's period of variation. The new observations agree well with the period given by Dustheimer, but it is probable that the decrease in the velocity range is real. The secondary variation is discussed. It is likely that the extent of this variation increases for lines of shorter wave -length. The observations are compared with Schiefer's results. The variation of the number of Balmer lines with sharp central cores is examined. It is shown that this variation is not likely to occur in the same atmosphere, and therefore the binary hypothesis seems necessary. PART III: LINE INTENSITITES IN SOME BE- STARS Line intensities in seven plates of `. Per., covering about 30 days of the star' s period were measured. A clear correlation is found between emission line intensity and the colour of the star as given by Roach. The widths of emission lines in some Be -stars are compared with the value computed from Curtiss' formula. The possibility of measuring the hydrogen-decrement in Be -stars is discussed and the previous observations criticised. Equivalent widths of helium and hydrogen lines in K Cas. and B Ceph. are also given. H a is definitely variable in K Cas., while HB is apparently constant. The most probable turbulent velocity is obtained for the two stars. PART IV: TOTAL INTENSITIES OF A TRIPLET OF SiIII IN STELLAR SPECTRA Total intensities of the three Si III lines, 4552, 4567 and 4574 were measured on 81 plates of 32 -early type stars. Deviations from the square roots of the multiplet intensities are small, but nevertheless real. Previous measures are included in a discussion of the differences between high and low luminosity stars and between wide and narrow line stars. The formation of the lines, mainly through damping, is examined. A definite discrepancy is observed between observation and theory. This discrepancy may be removed by assuming a negative turbulence velocity in the atmosphere, an incipient emission filling the lines, or a damping constant more than 440 times the classical value. This last assumption may be nearest the truth.en
dc.publisherThe University of Edinburghen
dc.relation.ispartofAnnexe Thesis Digitisation Project 2019 Block 22en
dc.relation.isreferencedbyen
dc.titleStudy of stars of early spectral type: with special reference to emission line spectraen
dc.typeThesis or Dissertationen
dc.type.qualificationlevelDoctoralen
dc.type.qualificationnamePhD Doctor of Philosophyen


Files in this item

This item appears in the following Collection(s)

Show simple item record