Helium abundance in ejecta from CP Lacertae and V446 Herculis

Abstract

view Abstract Citations (24) References (55) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Helium abundance in ejecta from CP Lacertae and V446 Herculis. Ferland, G. J. Abstract Published emission-line intensities are used in this paper to measure the helium abundances in ejecta from the novae CP Lacertae and V446 Herculis. Recombination lines of hydrogen and helium indicate the helium abundance directly if corrections for unseen stages of ionization and recombination-line self-absorption are unimportant. These corrections are minimized by considering only spectra obtained during the late nebular phase of the outburst, when models show that ionization corrections are small and when self-absorption affects only certain lines. The physical conditions in the gas need not be accurately measured since ratios of recombination lines are only slightly affected by the density-temperature structure of the ejecta. Ejecta from the fast nova CP Lac (1936) have a nearly cosmic helium abundance (He/H = 0.11 + 0.02), but ejecta from V446 Her (1960) are enhanced (He/H = 0.19 + 0.03). Previous studies have found high (He/H = 0.2) abundances of helium in ejecta from HR Del, V544 Her, RR Pic, and RR Tel. Three novae are now known to have nearly cosmic helium abundances (CP Lac, V1500 Cyg, and DQ Her). No evidence for extreme overabundances of helium (He/H > 0.3) is found. The range in helium abundances in nova ejecta is similar to the range in planetary nebulae, but the sample of novae seems to be more clustered toward higher helium abundances. Cosmic or nearly cosmic helium abundances are probably an indication that the majority of the matter ejected in the nova outburst originated in the cool companion rather than in the white dwarf. There is no tight correlation between helium abundances and other properties of the nova outburst, but high helium abundances tend to occur in slower novae. Subject headings: stars: abundances - stars: individual - stars: novae Publication: The Astrophysical Journal Pub Date: August 1979 DOI: 10.1086/157243 Bibcode: 1979ApJ...231..781F Keywords: Abundance; Helium; Novae; Stellar Mass Ejection; Balmer Series; Chemical Composition; Emission Spectra; Hydrogen Recombinations; Photoionization; Self Absorption; Astrophysics; Helium:Novae; Nova V446 Herculis; Nova Herculis 1960; Nova Lacertae 1936 full text sources ADS | data products SIMBAD (9)