Hydrogen line and continuum emission in young stellar objects. I - Excitation model

Abstract

view Abstract Citations (14) References (33) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Hydrogen Line and Continuum Emission in Young Stellar Objects. I. Excitation Model Kwan, John ; Alonso-Costa, Jose L. Abstract Two mechanisms that populate the n = 2 level of hydrogen after the Lyman continuum is depleted are identified. They are ionization of N I from its excited states, followed by charge-exchange between N II and H I, and Ly-beta line wing absorption. Both processes involve absorption of the sub-Lyman continuum between 11 and 13.6 eV. With population in level n = 2 thus maintained, the strong Brackett line fluxes observed are then produced as a result of Balmer photoionization. The magnitude of the sub-Lyman continuum dictates the fraction of Balmer continuum that will be absorbed. Numerical calculations for four young stellar objects with luminosity ranging from 10 to 10,000 solar are performed, and it is concluded that this two-step process of sub-Lyman continuum absorption followed by Balmer photoionization can account for the great majority of observed Brackett line fluxes. The location and mass of the emitting as as determined from the Brackett line fluxes are reported. The Br-alpha luminosity is calculated as a function of the mass loss rate. Publication: The Astrophysical Journal Pub Date: July 1988 DOI: 10.1086/166519 Bibcode: 1988ApJ...330..870K Keywords: Early Stars; Pre-Main Sequence Stars; Stellar Radiation; Balmer Series; Continuous Radiation; Cooling; Heating; Hydrogen; Lyman Spectra; Photoionization; Radiative Transfer; Spectral Energy Distribution; Stellar Models; Astrophysics; ATOMIC PROCESSES; RADIATION MECHANISMS; STARS: PRE--MAIN-SEQUENCE full text sources ADS | Related Materials (2) Part 2: 1989ApJ...338..403A Part 3: 1990ApJ...356..662A