HESS observations of the Carina nebula and its enigmatic colliding wind binary Eta Carinae
2012 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 424, no 1, 128-135 p.Article in journal (Refereed) Published
The massive binary system Eta Carinae and the surrounding H ii complex, the Carina nebula, are potential particle acceleration sites from which very high energy (VHE; E= 100 GeV) ?-ray emission could be expected. This paper presents data collected during VHE ?-ray observations with the HESS telescope array from 2004 to 2010, which cover a full orbit of Eta Carinae. In the 33.1-h data set no hint of significant ?-ray emission from Eta Carinae has been found and an upper limit on the ?-ray flux of (99 per cent confidence level) is derived above the energy threshold of 470 GeV. Together with the detection of high energy (HE; 0.1 =E= 100 GeV) ?-ray emission by the Fermi Large Area Telescope 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 ?-ray spectrum between the HE and VHE ?-ray range. This could be caused either by a cut-off in the accelerated particle distribution or by severe ?? absorption losses in the wind collision region. Furthermore, the search for extended ?-ray emission from the Carina nebula resulted in an upper limit on the ?-ray flux of (99 per cent 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 W28.
Place, publisher, year, edition, pages
2012. Vol. 424, no 1, 128-135 p.
acceleration of particles, radiation mechanisms: non-thermal, ISM: individual objects: Carina nebula, ISM: individual objects: Eta Carina, open clusters and associations: general, X-rays: binaries
Astronomy, Astrophysics and Cosmology
IdentifiersURN: urn:nbn:se:su:diva-80423DOI: 10.1111/j.1365-2966.2012.21180.xISI: 000306140600012OAI: oai:DiVA.org:su-80423DiVA: diva2:556195