Page 8 - UNAM Forum ED2-2021

Front-row view reveals exceptional cosmic explosion
...continued from pg 8
with energies well beyond the currently being built in the Chilean The University of Namibia
burn-off limit. Instead, current Andes and on the Canary Island (UNAM) is a member of the
theories assume that in a gamma- of La Palma look promising,” says H.E.S.S. collaboration since its
ray burst, fast electrons collide H.E.S.S. spokesman Stefan Wagner inception. Currently, there are 7
with synchrotron photons and from Landessternwarte Heidelberg. staff members, 4 with PhDs and
thereby boost them to gamma- “The general abundance of 3 working towards it, and 2 MSc
ray energies in a process dubbed gamma-ray bursts leads us to and Honours students conducting
synchrotron self-Compton. expect that regular detections their research in the context of
in the very-high-energy band will H.E.S.S and gamma-ray astronomy
But the observations of GRB become rather common, helping in the Faculty of Agriculture,
190829A’s afterglow now show us to fully understand their physics.” Engineering and Natural Sciences,
that both components, X-ray and spearheaded by the Department
gamma-ray, faded in sync. Also, More than 230 scientists from 41 of Physics, Chemistry and Material
the gamma-ray spectrum clearly institutes in 15 countries (Namibia, Science at UNAM. In the course of
matched an extrapolation of the South Africa, Germany, France, this year, these were supplemented
X-ray spectrum. Together, these the UK, Ireland, Italy, Austria, by two postdoctoral fellows,
results are a strong indication the Netherlands, Poland, supported by a grant from the
that X-rays and very-high-energy Sweden, Armenia, Japan, China, UK Global Challenges Research
gamma rays in this afterglow were and Australia), comprising Fund together with the University
produced by the same mechanism. the international H.E.S.S. of Oxford. The support for
“It is rather unexpected to observe collaboration, contributed to observations by the Namibian local
such remarkably similar spectral this research. H.E.S.S. is a system crew and UNAM students were
and temporal characteristics in of five Imaging Atmospheric pivotal to H.E.S.S. being able to
the X-ray and very-high energy Cherenkov Telescopes that continue observations throughout
gamma-ray energy bands, if investigates cosmic gamma rays. the pandemic.
the emission in these two energy The name H.E.S.S. stands for High
ranges had different origins,” says Energy Stereoscopic System, and
co-author Dmitry Khangulyan from is also intended to pay homage Reference:
Rikkyo University in Tokyo. This poses to Victor Franz Hess, who received Revealing x-ray and gamma-ray
a challenge for the synchrotron the Nobel Prize in Physics in temporal and spectral similarities in
self-Compton origin of the very- 1936 for his discovery of cosmic the GRB 190829A afterglow; H.E.S.S.
high-energy gamma-ray emission. radiation. H.E.S.S. is located in collaboration; Science, 2021; DOI:
Namibia, near the Gamsberg 10.1126/science.abe8560
The far-reaching implication of Mountain, an area well known
this possibility highlights the need for its excellent optical quality. Open access pre-print: http://arxiv.
for further studies of very-high Four H.E.S.S. telescopes went into org/abs/2106.02510
energy GRB afterglow emission. operation in 2002/2003, the much
GRB 190829A is only the fourth larger fifth telescope – H.E.S.S. II Science contacts:
gamma-ray burst detected from – is operational since July 2012, – Dr Sylvia Zhu, DESY, sylvia.zhu@
the ground. However, the earlier extending the energy coverage desy.de
detected explosions occurred towards lower energies and – Dr Andrew Taylor, DESY, +49 152
much farther away in the cosmos further improving sensitivity. In 5943 1749, andrew.taylor@desy.de
and their afterglow could only be 2015-2016, the cameras of the first – Dr Stefan Ohm, head of the
observed for a few hours each four H.E.S.S. telescopes were fully H.E.S.S. group at DESY, +49 176 5550
and not to energies above 1 tera- refurbished using state of the art 6543, stefan.ohm@desy.de
electronvolts (TeV). “Looking to electronics and in particular the
the future, the prospects for the NECTAr readout chip designed Media contact:
detection of gamma-ray bursts by for the next big experiment in the – Dr Michael Backes, head of the
next-generation instruments like the field, the Cherenkov Telescope H.E.S.S. group at UNAM, +264 81
Cherenkov Telescope Array that is Array (CTA). 361 8228, mbackes@unam.na

8 Official Newsletter