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  1. OA@INAF
  2. PRODOTTI RICERCA INAF
  3. 1 CONTRIBUTI IN RIVISTE (Journal articles)
  4. 1.01 Articoli in rivista
Please use this identifier to cite or link to this item: http://hdl.handle.net/20.500.12386/29399
Title: Chandra Spectral and Timing Analysis of Sgr A*'s Brightest X-Ray Flares
Authors: Haggard, Daryl
Nynka, Melania
Mon, Brayden
de la Cruz Hernandez, Noelia
Nowak, Michael
Heinke, Craig
Neilsen, Joseph
Dexter, Jason
Fragile, P. Chris
Baganoff, Fred
Bower, Geoffrey C.
Corrales, Lia R.
Coti Zelati, Francesco
Degenaar, Nathalie
Markoff, Sera
Morris, Mark R.
PONTI, GABRIELE 
Rea, Nanda
Wilms, Jöern
Yusef-Zadeh, Farhad
Issue Date: 2019
Journal: THE ASTROPHYSICAL JOURNAL 
Number: 886
Issue: 2
First Page: 96
Abstract: 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 Γ = 2.06 ± 0.14 and the second has Γ = 2.03 ± 0.27, compared to Γ = 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 ν ≈ 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.
URI: http://hdl.handle.net/20.500.12386/29399
URL: https://iopscience.iop.org/article/10.3847/1538-4357/ab4a7f
ISSN: 0004-637X
DOI: 10.3847/1538-4357/ab4a7f
Bibcode ADS: 2019ApJ...886...96H
Fulltext: open
Appears in Collections:1.01 Articoli in rivista

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