HESS-II scope spots its first pulsar

Gamma ray source seen from ground for first time

Namibia's HESS-II telescope has shown off two-years' worth of software upgrades, identifying gamma rays at 30 GeV emanating from the Vela pulsar.

Vela is a well-known object, having been associated with the supernova remnant of the same name in 1968, and is visible in the radio, optical, X-ray and gamma spectra. HESS-II's achievement is that it's the first ground-based gamma ray detection of Vela.

It's also only the second ground-based gamma ray pulsar observation, the observatory says in this announcement.

HESS-II comprises a 28m telescope and four 12m telescopes, giving it the ability to spot energy sources down to the 30 GeV range, and the Vela pulsar represented a demonstration project. It's also the only telescope* that can use different sized antennae to detect Cherenkov radiation in sync, up to the TeV range.

The 28-metre telescope was added during the 2012 upgrade, and it saw “first light” in July 2012 with an observation of the high-luminosity J1640−465 supernova remnant.

That marked the start of the software development to implement what deputy director of the HESS collaboration and CNRS researcher at the Laboratoire Leprince-Ringuet Mathieu de Naurois called the “extremely complex algorithms” needed to detect the gamma rays from the ground.

HESS-II in Namibia. Image: Christian Föhr, MPIK

The period of the detected gamma rays, 89 milliseconds, matches what's known about the Vela pulsar. With HESS-II's operation confirmed, the facility will get to work investigating the pulsars at the centre of the Milky Way galaxy. ®

Bootnote: This sentence originally mis-described HESS-II as a "radio telescope". Thanks to the reader that pointed out the error. It's a Cherenkov radiation detector, which sees the flashes of light emitted when rays strike the atmosphere. ®