TY - JOUR
AU - D. Haggard
AU - Melania Nynka
AU - Brayden Mon
AU - Noelia Hernandez
AU - Michael Nowak
AU - Craig Heinke
AU - Joseph Neilsen
AU - Jason Dexter
AU - Chris Fragile
AU - Fred Baganoff
AU - Geoffrey Bower
AU - Lia Corrales
AU - Francesco Zelati
AU - Nathalie Degenaar
AU - Sera Markoff
AU - Mark Morris
AU - Gabriele Ponti
AU - Nanda Rea
AU - Jöern Wilms
AU - Farhad Yusef-Zadeh
AB - We analyze the two brightest Chandra X-ray flares detected from Sagittarius A*, with peak luminosities more than 600;and 245;greater than the quiescent X-ray emission. The brightest flare has a distinctive double-peaked morphology?it lasts 5.7 ks (?2 hr), with a rapid rise time of 1500 s and a decay time of 2500 s. The second flare lasts 3.4 ks, with rise and decay times of 1700 and 1400 s. These luminous flares are significantly harder than quiescence: the first has a power-law spectral index ?;=;2.06;;0.14 and the second has ?;=;2.03;;0.27, compared to ?;=;3.0;;0.2 for the quiescent accretion flow. These spectral indices (as well as the flare hardness ratios) are consistent with previously detected Sgr;A* flares, suggesting that bright and faint flares arise from similar physical processes. Leveraging the brightest flare?s long duration and high signal-to-noise, we search for intraflare variability and detect excess X-ray power at a frequency of ?;;3 mHz, but show that it is an instrumental artifact and not of astrophysical origin. We find no other evidence (at the 95% confidence level) for periodic or quasi-periodic variability in either flares? time series. We also search for nonperiodic excess power but do not find compelling evidence in the power spectrum. Bright flares like these remain our most promising avenue for identifying Sgr A*'s short timescale variability in the X-ray, which may probe the characteristic size scale for the X-ray emission region.
BT - The Astrophysical Journal
DA - 2019-12
DO - 10.3847/1538-4357/ab4a7f
IS - 2
N2 - We analyze the two brightest Chandra X-ray flares detected from Sagittarius A*, with peak luminosities more than 600;and 245;greater than the quiescent X-ray emission. The brightest flare has a distinctive double-peaked morphology?it lasts 5.7 ks (?2 hr), with a rapid rise time of 1500 s and a decay time of 2500 s. The second flare lasts 3.4 ks, with rise and decay times of 1700 and 1400 s. These luminous flares are significantly harder than quiescence: the first has a power-law spectral index ?;=;2.06;;0.14 and the second has ?;=;2.03;;0.27, compared to ?;=;3.0;;0.2 for the quiescent accretion flow. These spectral indices (as well as the flare hardness ratios) are consistent with previously detected Sgr;A* flares, suggesting that bright and faint flares arise from similar physical processes. Leveraging the brightest flare?s long duration and high signal-to-noise, we search for intraflare variability and detect excess X-ray power at a frequency of ?;;3 mHz, but show that it is an instrumental artifact and not of astrophysical origin. We find no other evidence (at the 95% confidence level) for periodic or quasi-periodic variability in either flares? time series. We also search for nonperiodic excess power but do not find compelling evidence in the power spectrum. Bright flares like these remain our most promising avenue for identifying Sgr A*'s short timescale variability in the X-ray, which may probe the characteristic size scale for the X-ray emission region.
PB - American Astronomical Society
PY - 2019
EP - 96
T2 - The Astrophysical Journal
TI - Chandra Spectral and Timing Analysis of Sgr A*'s Brightest X-Ray Flares
VL - 886
SN - 1538-4357
ER -