Astronomy and Astrophysics – Astrophysics – Cosmology and Extragalactic Astrophysics
Scientific paper
2011-12-19
Astronomy and Astrophysics
Astrophysics
Cosmology and Extragalactic Astrophysics
Accepted for publication in ApJ; 17 pages, 5 figures; Corresponding author: C. M. Hui
Scientific paper
VERITAS has been monitoring the very-high-energy (VHE; >100GeV) gamma-ray activity of the radio galaxy M87 since 2007. During 2008, flaring activity on a timescale of a few days was observed with a peak flux of (0.70 +- 0.16) X 10^{-11} cm^{-2} s^{-1} at energies above 350GeV. In 2010 April, VERITAS detected a flare from M87 with peak flux of (2.71 +- 0.68) X 10^{-11} cm^{-2} s^{-1} for E>350GeV. The source was observed for six consecutive nights during the flare, resulting in a total of 21 hr of good quality data. The most rapid flux variation occurred on the trailing edge of the flare with an exponential flux decay time of 0.90^{+0.22}_{-0.15} days. The shortest detected exponential rise time is three times as long, at 2.87^{+1.65}_{-0.99} days. The quality of the data sample is such that spectral analysis can be performed for three periods: rising flux, peak flux, and falling flux. The spectra obtained are consistent with power-law forms. The spectral index at the peak of the flare is equal to 2.19 +- 0.07. There is some indication that the spectrum is softer in the falling phase of the flare than the peak phase, with a confidence level corresponding to 3.6 standard deviations. We discuss the implications of these results for the acceleration and cooling rates of VHE electrons in M87 and the constraints they provide on the physical size of the emitting region.
Aliu Ester
Arlen Timothy
Aune Taylor
Beilicke Matthias
Benbow Wystan
No associations
LandOfFree
VERITAS Observations of day-scale flaring of M87 in 2010 April does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with VERITAS Observations of day-scale flaring of M87 in 2010 April, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and VERITAS Observations of day-scale flaring of M87 in 2010 April will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-54056