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We present the first systematic analysis of the X-ray variability of Sgr A∗ during the Chandra X-ray Observatory’s2012 Sgr A∗ X-ray Visionary Project. With 38 High Energy Transmission Grating Spectrometer observations an average of 7 days apart, this unprecedented campaign enables detailed study of the X-ray emission from supermassive black hole at high spatial, spectral and timing resolution. In 3 Ms of observations, we detect 39-ray flares from Sgr A∗, lasting from a few hundred seconds to approximately 8 ks, and ranging in 2–10 keV from ∼1034 erg s−1 to 2 × 1035 erg s−1. Despite tentative evidence for a gap in the distribution of flare count rates, there is no evidence for X-ray color differences between faint and bright flares. Our preliminary-ray flare luminosity distribution dN/dL is consistent with a power law with index −1. 9+0. 3 −0. 4; this is similar to estimates of Sgr A∗’s near-IR flux distribution. The observed flares contribute one-third of the total X-ray of Sgr A∗ during the campaign, and as much as 10% of the quiescent X-ray emission could be comprised weak, undetected flares, which may also contribute high-frequency variability. We argue that flares may be the source of X-ray emission from the inner accretion flow.
Neilsen et al. (Wed,) studied this question.