Forbidden and permitted emission lines of singly ionized iron as a diagnostic in the investigation of stellar emission-line spectra

Abstract

view Abstract Citations (63) References (30) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Forbidden and permitted emission lines of singly ionized iron as a diagnostic in the investigation of stellar emission-line spectra. Viotti, R. Abstract We present a diagnostic approach to the problem of the origin of the [Fe ii] and Fe ii emission lines in the extended atmospheres of hot stars. The rates of excitation and de-excitation of Fe + levels by electron impact, spontaneous decay, and photoexcitation are studied. Radiative recombination of doubly ionized iron is also considered in an approximate form. It is found that there are three typical conditions (radiative, collisional, and nebular) of excitation of Fe +, characterized by the predominance of different excitation processes. The two relevant parameters which describe the physical conditions in the envelopes of hot stars are NeTe -112 and the dilution factor W. We then introduce a two-parameter diagram [W, NeTe -112], and discuss the position in this diagram of Be stars, novae, composite-spectrum variables, and other peculiar stars. We also compute the [Fe ii]/Fe ii intensity ratio for two particular lines as a function of NeTe - 112and W and compare it with observations. We find that in Car the Fe ii emission lines are most probably excited by radiative recombination. Subject headings: atomic processes - stars: circumstellar shells - stars: emission-line Publication: The Astrophysical Journal Pub Date: February 1976 DOI: 10.1086/154171 Bibcode: 1976ApJ...204..293V Keywords: Emission Spectra; Hot Stars; Iron; Stellar Envelopes; Stellar Spectra; Atomic Excitations; Electron Impact; Forbidden Transitions; Radiative Recombination; Stellar Atmospheres; Astrophysics full text sources ADS | data products SIMBAD (18)