Research on Very-high energy astrophysics with Cherenkov telescopes

Tuorla observatory is a member of Major Atmospheric Gamma-ray Imaging Cherenkov Telescopes (MAGIC) as well as Cherenkov Telescope Array (CTA) collaborations. MAGIC experiment is located in the Roque de los Muchachos European North Observatory (2200m a.s.l.) on the Canary island of La Palma. The system of two MAGIC telescopes, each of 17m in diameter, is currently measuring very high energy (VHE) gamma-rays from cosmic sources in the energy range 25 GeV-50 TeV. The neutral gamma rays penetrate into Earth’s atmosphere and produce avalanches of secondary particles that emit Cherenkov light. MAGIC is studying gamma-rays from galactic and extragalactic sources by recording and analyzing stereoscopic pictures of these Cherenkov flashes. Tuorla group is responsible for the optical monitoring support of VHE sources such as blazars which are among the main targets for MAGIC (see the project site for recent lightcuves). E.Lindfors is currently coordinating activity of the MAGIC AGN group.

CTA is a multinational, world-wide project to build a new generation ground-based gamma-ray instrument in the energy range extending from some tens of GeV to above 100 TeV. It is proposed as an open observatory and will consist of two arrays of IACTs, a first array at the Northern Hemisphere with emphasis on the study of extragalactic objects at the lowest possible energies, and a second array at the Southern Hemisphere, which is to cover the full energy range and concentrate on galactic sources. CTA intends to improve the flux sensitivity of the current generation of IACTs such as MAGIC, HESS, and VERITAS by an order of magnitude.

Figure 1: The radio image of the central part of the radio galaxy IC 310. MAGIC has observed extraordinary short variations in the gamma-ray flux from this object at 5 min timescale, which is four times smaller than the light-crossing time of the event horizon of the supermassive black hole which is the engine behind this activity. The data can be explained only of the gamma-ray emission happens in an extremely narrow region located near the event horizon of the black hole and permeated by strong electromagnetic fields.

Selected publications:

Working groups

X-ray binaries

Description of the group activity.
Group meetings take place on Wednesdays (first and third of each month), 15.00 in the coffee room.

Stellar explosions

Description of the group activity.
Group meetings take place on Mondays, 15.00 in the coffee room.

AGNs and Very High Energy Astrophysics

Description of the group activity.
Group meetings take place on Wednesday (second and fourth of each month), 15.00 in the coffee room.