EXPLORING THE DARK ACCELERATOR HESS J1745-303 WITH THEFERMILARGE AREA TELESCOPE

Abstract

We present a detailed analysis of the γ -ray emission from HESS J1745-303 with the data obtained by the Fermi Gamma-ray Space Telescope in its first ∼29 month observation. The source can clearly be detected at the levels of ∼18σ and ∼6σ in 1-20 GeV and 10-20 GeV, respectively. We do not find any evidence of the variability seen in the results obtained by the Compton Gamma-ray Observatory.

Observing two dark accelerators around the Galactic Centre withFermiLarge Area Telescope

“…The γ−ray emission of this source can be detected at a significance of ∼ 22σ in 0.65-25 GeV. In comparison with the Figure 2 in Hui et al (2011), we can now resolve the feature much better. It is now clear that most of the MeV-GeV emission of HESS J1745-303 is originated from Region A.…”

“…Fig. 3 in Hui et al 2011). However, the spatial resolution of the results reported in our previous work did not allow one to discriminate whether the GeV emission is from which spatial component(s) of HESS J1745-303 (cf.…”

“…2 in Hui et al 2011). If such spectrally connected GeV-TeV emission can be confirmed to be originated from Region A, together with the X-ray reflection and molecular cloud onsite, this can shed light on the cosmic ray density and/or the past activities of the Galactic centre (see discussion in Hui et al 2011, Dogiel et al 2015. This provides us with the motivation to revisit this target with the LAT data with a much longer time span and improved calibrations.…”

“…One of the most interesting dark accelerators is HESS J1745-303 (Aharonian et al 2008;Bamba et al 2009: Hui et al 2011. It was firstly discovered by the H.E.S.S.…”

“…Using the first 29 months of data obtained by Fermi LAT, we have detected and examined the GeV emission from HESS J1745-303 (Hui et al 2011). We found that a simple power law is sufficient to describe the GeV spectrum with a photon index of ∼ 2.6.…”