Detection of very high energy radiation from HESS J1908+063 confirms the Milagro unidentified source MGRO J1908+06

Abstract

Aims: Detection of a γ-ray source above 300 GeV is reported, confirming the unidentified source MGRO J1908+06, discovered by the Milagro collaboration at a median energy of 20 TeV.

Methods: The source was observed during 27 h as part of the extension of the HESS Galactic plane survey to longitudes >30°.

Results: HESS J1908+063 is detected at a significance level of 10.9σ with an integral flux above 1 TeV of (3.76 ± 0.29stat± 0.75sys)×10-12 ph cm-2 s-1, and a spectral photon index Γ = 2.10±0.07stat± 0.2sys. The positions and fluxes of HESS J1908+063 and MGRO J1908+06 are in good agreement. Possible counterparts at other wavelengths and the origin of the γ-ray emission are discussed. The nearby unidentified GeV source, GRO J1908+0556 (GeV) which also remains unidentified and the new Fermi pulsar 0FGL J1907.5+0617, may be connected to the TeV source.

Astronomy & Astrophysics 499, 723-728 (2009)
ArXiv pre-print

Auxiliary informations

Spectrum

Data points for Figure 3

Mean energy Flux Flux Error
[TeV] [/TeV cm^2 s]
0.38 3.22e-11 1.17e-11
0.60 1.18e-11 2.35e-12
0.94 4.99e-12 7.64e-13
1.50 1.75e-12 3.07e-13
2.36 8.78e-13 1.22e-13
3.73 2.35e-13 5.89e-14
5.90 5.45e-14 2.25e-14
9.33 3.08e-14 9.33e-15
14.75 1.37e-14 4.06e-15

Remarks: Statistical errors only. Systematic error on energy scale estimated to 20%. See paper for details.

FITS images

Figure 1 Excess Map (sigma=0.5)
Figure 2 Excess Map (sigma=0.11)

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