The classification of nova spectra.

Abstract

view Abstract Citations (1) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The classification of nova spectra. McLaughlin, Dean B. Abstract A proposed decimal subdivision of class Q is based on the presence and relative strengths of four systems of absorption lines and associated emissions, and upon the changing composition of the emission spectrum in the later stages. The absorption and emission systems are: (I) the pre-maximum spectrum; (2) the principal spectrum (resembling that of a supergiant star); (3) the "diffuse enhanced" spectrum (strong hydrogen and enhanced metallic lines); (4) the Orion spectrum (He I, N II and 0 II). A fifth set is a survival of the Orion system, the dark lines of N III and the hazy "4640' emission band. After that, the principal emission spectrum changes to the "nebular" type with the emergence of the EO III~ lines. Finally, as these fade, the star itself is revealed, with a continuous spectrum and usually weak narrow emissions. Class Qo is the early pre-maximum spectrum of weak absorption lines, sometimes accompanied by hazy emission. Class Q I is the stronger absorption spectrum at maximum light. Class ,Q2 is the strong "principal" absorption spectrum with bright bands of hydrogen, Fe ii, etc., which dominates just after maximum. Class Q3 is the stage in which, besides the principal spectrum, the very strong "diffuse enhanced" absorption system of hydrogen and ionized metals is present. Class Q4 is a mixed "diffuse enhanced" and Orion spectrum. Class Q5 is the Orion stage. Absorptions of He I, N ii and 0 Ii are present, with wide hazy emissions of N II. Class Q6 is characterized by the hazy band at 4640A and by strong N III absorption (the "4640" stage). Class Q7 still has the "4640" band, but emissions of EO III~ are appearing. All absorption lines have disappeared. Class Q8 has the EO III~ emissions as strong as those of hydrogen, and the hazy "4640" band is gone. Class Q9 is the fully developed nebular spectrum, with EO III~ considerably stronger than hydrogen. Class Q9.5 begins to show the continuous spectrum of the star, with narrow bright lines of hydrogen and He II, while the nebular lines have weakened. The remaining sta~r, after the nebular lines have disappeared, resembles the Wolf-Rayet type and may be designated Q(W). The best-known peculiarities are: (i) strong ENe III~ as in Nova Persei; (2) strong EFe II~ in Nova Herculis; (3) strong EO I~ as in Nova Herculis; (4) weak EO IJ and EO IIIJ as in Nova Pictoris; (5) coronal emissions, as in RS Ophiuchi. Observatory, University of Michigan, Ann Arbor, Mich. Publication: The Astronomical Journal Pub Date: July 1946 DOI: 10.1086/105904 Bibcode: 1946AJ.....52...46M full text sources ADS |