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Authors: 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.
First Published: 14-Aug-2013
Publisher: American Astronomical Society, IOP Publishing
Citation: Astrophysical Journal, 774:42 (14pp), 2013 September 1
Abstract: 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.
DOI Link: 10.1088/0004-637X/774/1/42
ISSN: 0004-637X
eISSN: 1538-4357
Version: Publisher Version
Status: Peer-reviewed
Type: Journal Article
Rights: Creative Commons “Attribution Non-Commercial No Derivatives” licence CC BY-NC-ND, further details of which can be found via the following link: Archived with reference to SHERPA/RoMEO and publisher website.
Appears in Collections:Published Articles, Dept. of Physics and Astronomy

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