H.E.S.S. observations of the Carina nebula and its enigmatic colliding wind binary Eta Carinae


الملخص بالإنكليزية

The massive binary system Eta Carinae and the surrounding HII complex, the Carina Nebula, are potential particle acceleration sites from which very-high-energy (VHE; E > 100 GeV) gamma-ray emission could be expected. This paper presents data collected during VHE gamma-ray observations with the H.E.S.S. telescope array from 2004 to 2010, which cover a full orbit of Eta Carinae. In the 33.1-hour data set no hint of significant gamma-ray emission from Eta Carinae has been found and an upper limit on the gamma-ray flux of 7.7 x 10-13 ph cm-2 s-1 (99% confidence level) is derived above the energy threshold of 470 GeV. Together with the detection of high-energy (HE; 0.1 GeV > E > 100 GeV) gamma-ray emission by the Fermi-LAT up to 100 GeV, and assuming a continuation of the average HE spectral index into the VHE domain, these results imply a cut-off in the gamma-ray spectrum between the HE and VHE gamma-ray range. This could be caused either by a cut-off in the accelerated particle distribution or by severe gamma-gamma absorption losses in the wind collision region. Furthermore, the search for extended gamma-ray emission from the Carina Nebula resulted in an upper limit on the gamma-ray flux of 4.2 x 10-12 ph cm-2 s-1 (99% confidence level). The derived upper limit of ~23 on the cosmic-ray enhancement factor is compared with results found for the old-age mixed-morphology supernova remnant W 28.

تحميل البحث