DETECTING FLARING STRUCTURES IN SAGITTARIUS A* WITH HIGH-FREQUENCY VLBI

By Sheperd S. Doeleman, Vincent L. Fish, A. Broderick, Abraham Loeb, A. Rogers. 2008

134 citations recorded by the source corpus.

The super-massive black hole candidate, Sagittarius A*, exhibits variability from radio to X-ray wavelengths on timescales that correspond to <10 Schwarzschild radii. We survey the potential of millimeter wavelength very long baseline interferometry (VLBI) to detect and constrain time-variable structures that could give rise to such variations, focusing on a model in which an orbiting hot spot is embedded in an accretion disk. Nonimaging algorithms are developed that use interferometric closure quantities to test for periodicity, and applied to an ensemble of hot spot models that sample a range of parameter space. We find that structural periodicity in a wide range of cases can be detected on most potential VLBI arrays using modern VLBI instrumentation. Future enhancements of millimeter/submillimeter VLBI arrays including phased-array processors to aggregate VLBI station collecting area, increased bandwidth recording, and addition of new VLBI sites all significantly aid periodicity detection. The methods described herein can be applied to other models of Sagittarius A*, including jet outflows and magnetohydrodynamic accretion simulations.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/7033118b536fc07c66b79b3e4813b2ba189bdcef

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Citations in the corpus

1.3 mm WAVELENGTH VLBI OF SAGITTARIUS A*: DETECTION OF TIME-VARIABLE EMISSION ON EVENT HORIZON SCALES (2010, methodology): “If small-scale variable structures are present, 1.3 mm VLBI can sensitively monitor the changing morphology of Sgr A* using non-imaging techniques with time resolutions of tens of seconds (Doeleman et al. 2009; Fish et al. 2009b).”
THE SUBMILLIMETER BUMP IN Sgr A* FROM RELATIVISTIC MHD SIMULATIONS (2010, methodology): “In addition, the short coherence time of the atmosphere and varying signal/noise between telescopes in the arrays may prevent proper calibration of the visibilities (Doeleman et al. 2009).”
A coordinate-independent characterization of a black hole shadow (2015, background): “…black holes, the observation of the black hole shadow and of the deformations resulting in the case of nonzero spin, is also expected to help determine many of the black hole properties (see e.g. Chandrasekhar 1998; Falcke & Markoff 2013; Takahashi 2004; Falcke et al. 2000; Doeleman et al. 2009).”
EVIDENCE FOR LOW BLACK HOLE SPIN AND PHYSICALLY MOTIVATED ACCRETION MODELS FROM MILLIMETER-VLBI OBSERVATIONS OF SAGITTARIUS A* (2010, background): “TheEvent Horizon Telescopeis a mm and sub-mm wavelength VLBI network whose goal is to observe, image, and time resolve structures near th black hole event horizon (Doeleman et al. 2009a).”
Magnetic field strength and spectral distribution of six parsec-scale active galactic nuclei jets (2009, unknown): “This is out of the range of current VLBI but could be probed with future sub-mm VLBI arrays (e.g. Doeleman et al. 2009).”
PHOTON RINGS AROUND KERR AND KERR-LIKE BLACK HOLES (2013, methodology): “The supermassive black holes at the centers of the Milky Way and M87 are the prime targets for highresolution very-long baseline interferometric (VLBI) observations with the Event Horizon Telescope (EHT), a planned global array of (sub)millimeter telescopes (Doeleman et al. 2009a,b; Fish et al. 2009”
TESTING THE NO-HAIR THEOREM WITH OBSERVATIONS IN THE ELECTROMAGNETIC SPECTRUM. IV. RELATIVISTICALLY BROADENED IRON LINES (2012, background): “Recently, we explored the prospects of imaging this ring using very-long baseline interferometric observations with the Event Horizon Telescope (Johannsen et al. 2012a), a planned global array of (sub-)mm telescopes (Doeleman et al. 2009a,b; Fish et al. 2009).”
TESTING THE NO-HAIR THEOREM WITH OBSERVATIONS IN THE ELECTROMAGNETIC SPECTRUM. II. BLACK HOLE IMAGES (2010, methodology): “If this time variability is produced by a highly coherent, orbiting inhomogeneity in the accretion flow, it may allow measuring the properties of the compact object via nonimaging techniques (Doeleman et al. 2009).”