Journal
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Volume 473, Issue 1, Pages 306-316Publisher
OXFORD UNIV PRESS
DOI: 10.1093/mnras/stx2408
Keywords
accretion, accretion discs; methods: data analysis; Galaxy: centre; X-rays: individual (Sgr A*)
Categories
Funding
- 100 Talents program of Chinese Academy of Sciences
- NASA via the SAO/CXC grant [G06-17024X]
- STFC [ST/N000811/1] Funding Source: UKRI
- Science and Technology Facilities Council [ST/N000811/1] Funding Source: researchfish
Ask authors/readers for more resources
The routinely flaring events from Sgr A* trace dynamic, high-energy processes in the immediate vicinity of the supermassive black hole. We statistically study temporal and spectral properties, as well as fluence and duration distributions, of the flares detected by the Chandra X-ray Observatory from 1999 to 2012. The detection incompleteness and bias are carefully accounted for in determining these distributions. We find that the fluence distribution can be well characterized by a power law with a slope of 1.73(-0.19)(+ 0.20), while the durations (tau in seconds) by a lognormal function with a mean log(tau) = 3.39(-0.24)(+0.27) and an intrinsic dispersion sigma = 0.28(-0.06)(+0.08). No significant correlation between the fluence and duration is detected. The apparent positive correlation, as reported previously, is mainly due to the detection bias (i.e. weak flares can be detected only when their durations are short). These results indicate that the simple self-organized criticality model has difficulties in explaining these flares. We further find that bright flares usually have asymmetric light curves with no statistically evident difference/preference between the rising and decaying phases in terms of their spectral/timing properties. Our spectral analysis shows that although a power-law model with a photon index of 2.0 +/- 0.4 gives a satisfactory fit to the joint spectra of strong and weak flares, there is weak evidence for a softer spectrum of weaker flares. This work demonstrates the potential to use statistical properties of X-ray flares to probe their trigger and emission mechanisms, as well as the radiation propagation around the black hole.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available