Diagnosing the Black Hole Accretion Physics of Sgr A*: Spitzer/Chandra Observations
Abstract
The Galactic center offers the closest opportunity for studying accretion onto a supermassive black hole. The fluctuating source, Sgr A*, is detected across the electromagnetic spectrum and its flux may originate in either the accretion flow or a jet, or both. Disentangling the power source and emission mechanisms of the flares is a central challenge to our understanding of the Sgr A* accretion flow. Recent general relativistic magneto-hydrodynamic (GRMHD) models indicate that variability can be produced by a tilted inner disk, gravitational lensing of bright spots in the disk by the hole, or particle acceleration in reconnection events. These models produce different flare characteristics, and better characterization of flares may enable us to distinguish between strong and weakly magnetized disks. Following our successful Spitzer observations of the variability of Sgr A* in 2013 and 2014, we have undertaken a program of simultaneous IRAC (4.5 micron) and Chandra (2-10 keV) observations to (1) probe the accretion physics of Sgr A* on event-horizon scales and (2) detect any effect of the object G2 on Sgr A*. In addition, several ground-based observatories participated in the campaigns, at wavelengths including radio, sub-mm, and the near-infrared. We will present initial Spitzer/Chandra results from the two 24-hour epochs in 2016 July. Only such long-duration, continuous, multi-wavelength observations can achieve a comprehensive view of the dominant emission process(es) and quantify the physical properties near the event horizon.
- Publication:
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American Astronomical Society Meeting Abstracts #229
- Pub Date:
- January 2017
- Bibcode:
- 2017AAS...22910703H