Imaging bright-spots in the accretion flow near the black hole horizon of Sgr A*

By A. Broderick, Abraham Loeb Institute for Theory, Computation, Harvard University. 2005

166 citations recorded by the source corpus.

Images from the vicinity of the black hole horizon at the Galactic centre (Sgr A*) could be obtained in the near future with a Very Large Baseline Array of submillimetre telescopes. The recently observed short-term infrared and X-ray variability of the emission from Sgr A* implies that the accretion flow near the black hole is clumpy or unsteady. We calculate the appearance of a compact emission region (bright-spot) in a circular orbit around a spinning black hole as a function of orbital radius and orientation. We find that the mass and spin of the black hole can be extracted from their generic signatures on the spot image as well as on the light curves of its observed flux and polarization. The strong field distortion remains notable even when the spot image is smoothed over the expected ∼20-μ as resolution of the future submillimetre observations.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/b96ee71845deb32f32de488e4ca6d28e09b43f7b

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Citations in the corpus

Detection of orbital motions near the last stable circular orbit of the massive black hole SgrA* (2018, methodology): “Figure B.2 shows models of hot spots on circular orbits in the Schwarzschild metric (angular momentum parameter a = 0) obtained with ray tracing methods of the geodesics, including secondary, tertiary, and quaternary images (Hamaus et al. 2009, see also Broderick & Loeb 2005, 2006; Vincent et al. 20”
TESTING THE NO-HAIR THEOREM WITH OBSERVATIONS IN THE ELECTROMAGNETIC SPECTRUM. II. BLACK HOLE IMAGES (2010, background): “Unless an orbiting density inhomogeneity (a “hot spot”) can be securely identified and imaged throughout its orbit (e.g., Broderick & Loeb 2005), time-averaged overall images of black-hole accretion disks may appear a priori not well suited for testing the no-hair theorem.”
General relativistic magnetohydrodynamic simulations of the jet formation and large-scale propagation from black hole accretion systems (2006, methodology): “…will include a realistic equation of state; photodisintegration of nuclei; general relativistic ray-tracing neutrino transport (similar to, e.g., Broderick & Loeb 2005); neutrino cooling (similar to, e.g., Kohri et al. 2005); general relativistic accounting for the neutrino annihilation;…”
A public code for general relativistic, polarised radiative transfer around spinning black holes (2016, methodology): “…transport (Connors & Stark 1977; Connors, Stark & Piran 1980), and has been applied to ⋆ E-mail: jdexter@mpe.mpg.de the polarised radiative transfer of synchrotron radiation from thick accretion discs, e.g. in order to model the Galactic center black hole Sgr A* (Broderick & Loeb 2005, 2006).”
RADIATIVE MODELS OF SGR A* FROM GRMHD SIMULATIONS (2009, background): “Other workers have modeled the VLBI and submillimeter emission (Broderick & Loeb 2005, 2006a, 2006b; Huang et al. 2007; Miyoshi et al. 2008; Broderick et al. 2009; Yuan et al. 2009) assuming a stationary RIAF or time-dependent general relativis- tic MHD models (Dexter et al. 2009) and computing…”
DETECTING FLARING STRUCTURES IN SAGITTARIUS A* WITH HIGH-FREQUENCY VLBI (2008, background): “Claims of periodicity in some NIR flares (Genzel et al. 2003; Bélanger et al. 2006) suggest that at least a subset of these flares could arise from orbiting hot spots (Broderick & Loeb 2005; Melia et al. 2001).”
A geometric distance measurement to the Galactic center black hole with 0.3% uncertainty (2019, background): “They occur very close to the innermost stable circular orbit, and orbital motion of a few 10 µas has been proposed since their discovery (Genzel et al. 2003; Broderick & Loeb 2005; Hamaus et al. 2009).”
IPOLE - semi-analytic scheme for relativistic polarized radiative transport (2017, background): “This form of the polarized transport equation is equivalent to that used in Broderick & Blandford (2004).”
Magnetic Reconnection and Hot Spot Formation in Black Hole Accretion Disks (2020, background): “Dissipation of magnetic energy through the process of magnetic reconnection in thin current layers is conjectured as the main mechanism producing the energetic electrons powering flares and hot spots (Broderick & Loeb 2005, 2006; Younsi & Wu 2015; Ball et al. 2016; Gutirrez et al. 2019).”
Calculating black hole shadows: Review of analytical studies (2021, background): “Falcke, The Supermassive Black Hole at the Galactic Center, Annual Review of Astronomy and Astrophysics 39 (2001) 309 [17] A.”
Imaging optically-thin hotspots near the black hole horizon of Sgr A* at radio and near-infrared wavelengths (2005, methodology): “However, as mentioned in Broderick & Loeb (2005), and alluded to above, the most significant discriminator is likely to be the event time-scale.”
THE EVENT HORIZON OF SAGITTARIUS A* (2009, background): “Due to its mass and proximity, Sgr A* has the largest angular size of any known black hole and offers the best prospects for direct imaging of its silhouette (Falcke et al. 2000; Broderick & Loeb 2005, 2006a, 2006b).”