2381/38987
J. Neilsen
J.
Neilsen
M. A. Nowak
M. A.
Nowak
C. Gammie
C.
Gammie
J. Dexter
J.
Dexter
S. Markoff
S.
Markoff
D. Haggard
D.
Haggard
S. Nayakshin
S.
Nayakshin
Q. D. Wang
Q. D.
Wang
N. Grosso
N.
Grosso
D. Porquet
D.
Porquet
J. A. Tomsick
J. A.
Tomsick
N. Degenaar
N.
Degenaar
P. C. Fragile
P. C.
Fragile
J. C. Houck
J. C.
Houck
R. Wijnands
R.
Wijnands
J. M. Miller
J. M.
Miller
F. K. Baganoff
F. K.
Baganoff
A CHANDRA/HETGS CENSUS OF X-RAY VARIABILITY FROM Sgr A* DURING 2012
University of Leicester
2016
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 11:41:05
Journal contribution
https://figshare.le.ac.uk/articles/journal_contribution/A_CHANDRA_HETGS_CENSUS_OF_X-RAY_VARIABILITY_FROM_Sgr_A_DURING_2012/10140872
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.