Neilsen, J. Nowak, M. A. Gammie, C. Dexter, J. Markoff, S. Haggard, D. Nayakshin, S. Wang, Q. D. Grosso, N. Porquet, D. Tomsick, J. A. Degenaar, N. Fragile, P. C. Houck, J. C. Wijnands, R. Miller, J. M. Baganoff, F. K. A CHANDRA/HETGS CENSUS OF X-RAY VARIABILITY FROM Sgr A* DURING 2012 We present the first systematic analysis of the X-ray variability of Sgr A∗ during the Chandra X-ray Observatory’s 2012 Sgr A∗ X-ray Visionary Project. With 38 High Energy Transmission Grating Spectrometer observations spaced an average of 7 days apart, this unprecedented campaign enables detailed study of the X-ray emission from this supermassive black hole at high spatial, spectral and timing resolution. In 3 Ms of observations, we detect 39 X-ray flares from Sgr A∗, lasting from a few hundred seconds to approximately 8 ks, and ranging in 2–10 keV luminosity from ∼1034 erg s−1 to 2 × 1035 erg s−1. Despite tentative evidence for a gap in the distribution of flare peak count rates, there is no evidence for X-ray color differences between faint and bright flares. Our preliminary X-ray flare luminosity distribution dN/dL is consistent with a power law with index −1.9+0.3 −0.4; this is similar to some estimates of Sgr A∗’s near-IR flux distribution. The observed flares contribute one-third of the total X-ray output of Sgr A∗ during the campaign, and as much as 10% of the quiescent X-ray emission could be comprised of weak, undetected flares, which may also contribute high-frequency variability. We argue that flares may be the only source of X-ray emission from the inner accretion flow. Science & Technology;Physical Sciences;Astronomy & Astrophysics;ASTRONOMY & ASTROPHYSICS;accretion, accretion disks;black hole physics;radiation mechanisms: non-thermal;SUPERMASSIVE BLACK-HOLE;SOFT GAMMA-RAY;SAGITTARIUS-A;GALACTIC-CENTER;FUNDAMENTAL PLANE;XMM-NEWTON;FREQUENCY-DISTRIBUTIONS;GRMHD SIMULATIONS;MOLECULAR CLOUDS;FLARE STATISTICS 2016-12-16
    https://figshare.le.ac.uk/articles/journal_contribution/A_CHANDRA_HETGS_CENSUS_OF_X-RAY_VARIABILITY_FROM_Sgr_A_DURING_2012/10140872