A Jet-ADAF model for Sgr A*

By F. Yuan, S. Markoff, Heino Falcke. 2001

217 citations recorded by the source corpus.

The recent Chandra observation of the radio source at the center of our Galaxy, Sgr A * , puts new constraints on its theoretical models. The spectrum is very soft, and the source is rapidly variable. We consider different models to explain the observations. We find that the features of the X-ray spectrum can be marginally explained with an advection-dominated accretion flow (ADAF) model while it does not well fit the radio spectrum. An ADAF with strong winds (ADIOS) model is not favored if we assume that the wind does not radiate. Alternatively, we propose a coupled jet plus accretion disk model to explain the observations for Sgr A * . The accretion flow is described as an ADAF fed by Bondi-Hoyle accretion of hot plasma in the Galactic Center region. A small fraction of the accretion flow is ejected near the black hole, forming a jet after passing through a shock. As a result, the electron temperature increases to ~$2 \times 10^{11}~{\rm K}$, which is about 10 times higher than the highest temperature attained in the ADAF. The model is self-consistent since the main jet parameters are determined by the underlying accretion disk at the inner edge. The emergent spectrum of Sgr A * is the sum of the emission from jet and underlying ADAF. The very strong Comptonization of synchrotron emission from the jet can dominate the bremsstrahlung from the ADAF, therefore, a very short variability timescale is expected and the predicted X-ray slope and the radio spectrum is in very good agreement with the observations.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/47c5abccb617dbf28fb997aca3173b2599a69c12

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Citations in the corpus

Polarimetry of near-infrared flares from Sagittarius A* (2006, background): “Such a jet could be responsible especially for the emission at FIR/mm-wavelengths (Yuan et al. 2002).”
GIANT GAMMA-RAY BUBBLES FROM FERMI-LAT: ACTIVE GALACTIC NUCLEUS ACTIVITY OR BIPOLAR GALACTIC WIND? (2010, background): “Both radiative inefficient accretion flow (RIAF) models and outflow-dominated models have been invented (Falcke & Markoff 2000; Blandford & Begelman 1999; Yuan et al. 2002).”
Hot Accretion Flows Around Black Holes (2014, methodology): “…disk may be present at larger radii, as indicated by a “big red bump” in their spectra (Lasota et al. 1996a, Quataert et al. 1999, Gammie et al. 1999, Yuan et al. 2002b, Chiang & Blaes 2003, Ptak et al. 2004, Yuan & Narayan 2004, Nemmen et al. 2006, Wu et al. 2007, Yu et al. 2011).21 As further…”
SINFONI in the Galactic Center: Young Stars and Infrared Flares in the Central Light-Month (2005, background): “Our observed slope is in good agreement with the synchrotron models of Yuan et al. (2002, 2003, 2004) and Liu et al. (2004).”
Nuclear Activity in Nearby Galaxies (2008, methodology): “For example, Yuan et al. (2002) successfully fitted the multiwavelength data of NGC 4258 with effectively a jet-only model.”
An Accretion-Jet Model for Black Hole Binaries: Interpreting the Spectral and Timing Features of XTE J1118+480 (2004, background): “In previous work we have discussed this possibility also for two other sources, Sgr A* and NGC 4258 (Yuan, Markoff, & Falcke 2002; Yuan et al. 2002).”
General relativistic magnetohydrodynamical simulations of the jet in M 87 (2015, background): “The high temperature ratio in the disk was postulated in the early advection-dominated accretionflow models by Narayan et al. (1995), and the potential difference in Tp/Te between jet and disk was later suggested by Yuan et al. (2002).”
EVIDENCE FOR LOW BLACK HOLE SPIN AND PHYSICALLY MOTIVATED ACCRETION MODELS FROM MILLIMETER-VLBI OBSERVATIONS OF SAGITTARIUS A* (2010, methodology): “It is presently unclear how this emission is produced, evidenced by the variety of models that have been proposed (e.g., Narayan et al. 1998; Blandford & Begelman 1999; Falcke & Markoff 2000; Yuan et al. 2002, 2003; Loeb & Waxman 2007).”
First Sagittarius A* Event Horizon Telescope Results. V. Testing Astrophysical Models of the Galactic Center Black Hole (2022, background): “The broad range of values is due to the differences in regions of radio emission in the theoretical models that are considered (ADAFs: Narayan et al. 1998; Yuan et al. 2003; jet models: Falcke et al. 1993; Falcke & Markoff 2000; ADAF+jet models: Yuan et al. 2002).”
The structure of the nuclear stellar cluster of the Milky Way (2006, background): “Also, there a theoretical and observational arguments that favour the presence of a jet in Sgr A* (e.g., Melia & Falcke 2001; Markoff et al. 2001; Yuan et al. 2002; Bower et al. 2004).”
Very high-energy gamma rays from the direction of Sagittarius A* (2004, methodology): “…to be offset from the GC by 0.21◦, excluding Sgr A∗ at 99.9% C.L. Models for the wide-band spectra of Sgr A∗ include Advection Dominated Accretion Flow (ADAF) models (Narayan et al. 1998; Yuan et al. 2003), possibly combined with a jet extracting energy from the accretion disk (Yuan et al. 2002).”