Gravitationally distorted P Cygni profiles from outflows near compact objects

• Published in: Monthly notices of the Royal Astronomical Society Vol. 393; no. 4; pp. 1433 - 1448
• Main Author: Dorodnitsyn, A. V.
• Format: Journal Article
• Language: English; Russian
• Published: Oxford, UK Blackwell Publishing Ltd 11.03.2009; Wiley-Blackwell; Oxford University Press
• Subjects: Astronomy; galaxies: active; Gravity; line: formation; outflows; Plasma; radiation mechanisms: general; radiative transfer; Spectrum analysis; Stars & galaxies; stars: mass-loss; stars: winds; stars: winds, outflows; stars: mass-loss; line: formation; stars: winds, outflows; galaxies: active; radiation mechanisms: general; radiative transfer
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1111/j.1365-2966.2008.14171.x

We consider resonant absorption in a spectral line in the outflowing plasma within several tens of Schwarzschild radii from a compact object. We take into account both Doppler and gravitational shifting effects and reformulate the theory of P Cygni profiles in these new circumstances. It is found that a spectral line may have multiple absorption and emission components depending on how far the region of interaction is from the compact object and what the distribution of velocity and opacity is. Profiles of spectral lines produced near a neutron star or a black hole can be strongly distorted by Doppler blue- or redshifting and gravitational redshifting. These profiles may have both red- and blueshifted absorption troughs. The result should be contrasted with classical P Cygni profiles, which consist of redshifted emission and blueshifted absorption features. We suggest that this property of line profiles to have complicated narrow absorption and emission components in the presence of strong gravity may help researchers to study spectroscopically the innermost parts of an outflow.