A kinematic model for black hole X-ray power spectra

Abstract

view Abstract Citations (21) References (19) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Kinematic Model for Black Hole X-Ray Power Spectra Nowak, Michael A. Abstract The X-ray spectra of black hole candidates typically fall into one of three states: an 'off state,' characterized by low intensity and power-law spectrum; a 'high state,' characterized by little variability and a thermal-like spectrum peaking in the soft X-rays; and a 'low-state,' characterized by rapid X-ray variability and a spectrum with a power-law slope that extends to large X-ray energies. Recent observations of black hole candidates have revealed an additional 'very high state' characterized by rapid variability and a thermal-like spectrum with a hard tail. In this paper a simple kinematic model for the observed X-ray power spectra during the very high state of black hole candidates is presented. The model is based on viscous and thermal instabilities present in accretion disks. In this picture, the very high state is a transition phase between the high and low states that is characterized by a quasi-stable disk oscillating on the local instability timescales. The disk can be stabilized by a hot wind that in turn would feed a Compton cloud. The cloud would produce the hard tail in the observed X-ray spectra. The model is able to reproduce both the overall shape and the amplitude of the power spectral density and the observed frequency dependent lags between the hard and soft X-rays. In addition, the required energetics of a hot wind is consistent with the energy required to feed a Compton cloud. Specific comparisons between the model and data taken during the very high state of GX 339-4 are made. Publication: The Astrophysical Journal Pub Date: February 1994 DOI: 10.1086/173762 Bibcode: 1994ApJ...422..688N Keywords: Astronomical Models; Black Holes (Astronomy); Kinematics; Mathematical Models; Power Spectra; X Ray Astronomy; X Ray Spectra; X Ray Stars; Accretion Disks; Thermal Instability; Viscous Flow; Astrophysics; BLACK HOLE PHYSICS; X-RAYS: STARS full text sources ADS | data products SIMBAD (3)