Rikus Grobler | Oct 18, 2017 | 0
Velan pulsar sends galactic Morse
The gamma rays from a pulsar in the Vela constellation signalled the perfect premiere for the so-called HESS telescope near the Gamsberg in the Khomas Hochland. The pulsed radiation from Vela is the first to be measured in the southern sky and is only the second pulsar ever from which gamma rays have been detected by a ground-based telescope.
This exciting astronomic observation was recently made by the staff and students from the Department of Physics at the University of Namibia who are involved in this project.
The 28-metre Cherenkov telescope uses a High Energy Spectroscopic System (H.E.S.S.), giving it its popular name of a HESS telescope. The first pulsar readings proved the efficiency of HESS for inter-stellar observations from terrestrial telescopes.
Head of Physics at UNAM, Dr Riaan Steenkamp said H.E.S.S. II is a system of reflecting telescopes of different sizes which detect cosmic gammarays in sync. “It is run by an international collaboration of 31 institutions in 11 countries, including institutions from South Africa and the University of Namibia. Since the upgrade of the H.E.S.S. experiment in 2012, H.E.S.S. II with its fifth and larger Cherenkov telescope CT5 is the first Cherenkov telescope system with telescopes of different sizes detecting cosmic TeV gamma rays in sync. The 28-metre CT5 is placed in the centre of the four 12-metre telescopes that are operational for more than 10 years. It extends the energy range of the array to lower energies and allows for the detection of cosmic particle accelerators down to 30 GeV.”
The project scientists developed a tailor-made reconstruction analysis for these low-energy gamma rays. With this, the scientists were able to detect a pulsed, repeating gamma-ray signal in the energy range of 30 GeV and attribute it to the Vela pulsar. This opens the door to new observation possibilities of the inner Galaxy. The first results were presented at a conference on 23 June 2014 by Christian Stegmann, speaker of the H.E.S.S. collaboration.
Besides intensive efforts in the construction and calibration of CT5, two years of dedicated software development determined this success. “For the reconstruction of the data from CT5, we elaborated a highly sensitive analysis based on extremely complex statistical algorithms. This allows us to detect gamma radiation of only 30 GeV from ground level,” explain H.E.S.S. scientists. “Since we are able to survey a projected area of 10 hectares in the atmosphere, we have a considerably higher yield of gamma rays than for example satellite experiments like Fermi LAT.” From some sources, it is possible to spot up to one gamma per second – a record” said Dr Steenkamp.
“The whole Milky Way is full of pulsars and from Namibia we can exactly see into its centre. The H.E.S.S. data shows that, with Cherenkov telescopes, we will still discover quite a number of mysteries in the universe” he added. The H.E.S.S. telescopes are operated by an international collaboration including the University of Namibia and more than 30 institutions in 11 countries: Germany, France, United Kingdom, Namibia, South Africa, Ireland, Armenia, Poland, Australia, Austria and Sweden.