Oops – HESS J1745–303
January 2008 HESS J1745-303 – a very faint source of very high energy gamma rays of about 0.2 x 0.1 degr. size, slightly south of the Galactic equator, was first mentioned in the 2nd…
The Starry TeV Sky
December 2007 Coming close to the end of the year it seems the appropriate time to use this column for a look at the sky at tera electron volt (TeV) energies, and in particular…
Probing Extragalactic Background Light with 1ES 0229+200
November 2007 Gamma traveling from extragalactic sources to Earth are attenuated by interactions with extragalactic background light (EBL), due to creation of electron-positron pairs in collisions between gamma rays and EBL photons. This attenuation…
Gamma Rays from the Distant BL Lac 1ES 0347-121
October 2007 The active galaxy 1ES 0347-121 was discovered as an X-ray source in the Einstein slew survey (Elvis et al. 1992) and was later classified as a BL Lac type object (Schachter et…
PKS 2155–304 – Photons from a Hotter Hell
September 2007 “Photons from a hotter hell” is the title of T. Weekes recent commentary in Nature, concerning the recent detection of giant outbursts of active galaxies observed in high-energy gamma rays. At the…
Confirming MGRO 1908+06
August 2007 Recently, the Milagro collaboration, operating a ground-based air shower detector based on the water Cherenkov technique, announced the detection of several new sources of very-high-energy gamma rays in the Galactic Plane (A.…
The Supernova Remnant RCW 86
July 2007 RCW 86 is a supernova remnant with a barrel-shaped shell, nicely visible in X-rays (top image), in the optical and in radio waves (Fig. 1). Concerning its age, two options are discussed…
PWN Abundance – HESS J1718–385
June 2007 Pulsar wind nebulae – PWNe – are amongst the most abundant sources of very high energy gamma rays in our Galaxy. Rotational energy of the neutron star is converted – by some…
HESS J1912+101 – Yet Another Pulsar Wind Nebula?
May 2007 The H.E.S.S. survey of the Galactic Plane (Aharonian et al. 2005, 2006) initially covered the range from –30 degr. to +30 degr. Galactic longitude. More recently, the survey region was extended to…
Gamma Rays from W28 – an Old Supernova Remnant and Molecular Clouds
April 2007 It is a long-held idea that supernova remnants are acceleration sites for nucleonic cosmic rays. Indeed supernova shells are clearly seen as sources of high energy gamma rays (SOM 2005/01, SOM 2005/03),…
