On Search and Detection of Hard X-Ray Emission from Orion-Like Complexes Produced by a Flux of Subrelativistic Nuclei

Abstract

We analyze the origin of the Orion γ-rays discovered by the COMPTEL telescope and possibilities to search Orion-like sources with X-ray telescopes. We have shown that if these γ-rays are produced by a flux of carbon and oxygen subrelativistic nuclei (as it is usually assumed) then we expect a flux of continuous and line X-ray emission. We showed that in addition to the bremsstrahlung and inverse bremsstrahlung radiation a significant part of the continuous X-ray flux is generated by radiative capture of background electrons. The calculations showed also that the 6.4 keV iron line is the most prominent in the Orion X-ray spectrum, if the nuclei fill the whole volume of the Orion complex. The line flux is estimated by Lx ∼ 4 · 1040 ph s−1. Since the region of the emission is expected to be extended (the total area is about 100 square degrees) the intensity of the line near Earth is 4.6 · 10−3 ph cm−2 s−1 sr−1. This value is below the 3σ level of the ASCA telescope. Therefore, a search of distant (point-like) Orion-like candidates with X-ray telescopes seems to be more perspective. As an example, we analyze the flux of the 6.4 keV iron line observed with ASCA in the direction of the galactic center. If this line is emitted by an Orion-like object in the center of the Galaxy then we expect that there is a powerful source of subrelativistic cosmic rays with energies ≤ 25 MeV n−1 as well as γ-rays in the range 3 to 7 MeV. Their luminosities are Ln ∼ 4 · 1043 n s−1 and Lγ ∼ 1041 ph s−1, respectively.