Recent Results from the MAGIC Telescopes

MAGIC (Major Atmospheric Gamma-ray Imaging Cherenkov Telescope) is a system of two 17 meters Cherenkov telescopes, sensitive to very high energy (VHE; $> 10^{11}$ eV) gamma radiation above an energy threshold of 50 GeV. The first telescope was built in 2004 and operated for five years in stand-alone mode. A second MAGIC telescope (MAGIC-II), at a distance of 85 meters from the first one, started taking data in July 2009. Together they integrate the MAGIC stereoscopic system. Stereoscopic observations have improved the MAGIC sensitivity and its performance in terms of spectral and angular resolution, especially at low energies. We report on the status of the telescope system and highlight selected recent results from observations of galactic and extragalactic gamma-ray sources. The variety of sources discussed includes pulsars, galactic binary systems, clusters of galaxies, radio galaxies, quasars, BL Lacertae objects and more.Comment: Proceedings of the 13th ICATPP Conference on Astroparticle, Particle, Space Physics and Detectors for Physics Application

Gamma-rays from pulsar wind nebulae in starburst galaxies

Recently, gamma-ray emission at TeV energies has been detected from the starburst galaxies NGC253 (Acero et al., 2009) and M82 (Acciari et al., 2009. It has been claimed that pion production due to cosmic rays accelerated in supernova remnants interacting with the interstellar gas is responsible for the observed gamma rays. Here, we show that the gamma-ray pulsar wind nebulae left behind by the supernovae contribute to the TeV luminosity in a major way. A single pulsar wind nebula produces about ten times the total luminosity of the Sun at energies above 1 TeV during a lifetime of 10^5 years. A large number of 3x10^4 pulsar wind nebulae expected in a typical starburst galaxy at a distance of 4 Mpc can readily produce the observed TeV gamma rays.Comment: 5 pages, 2 figures, accepted for publication in Astropart. Phy

A search for VHE counterparts of Galactic Fermi bright sources and MeV to TeV spectral characterization

Very high-energy (VHE; E>100 GeV) gamma-rays have been detected from a wide range of astronomical objects, such as pulsar wind nebulae (PWNe), supernova remnants (SNRs), giant molecular clouds, gamma-ray binaries, the Galactic Center, active galactic nuclei (AGN), radio galaxies, starburst galaxies, and possibly star-forming regions as well. At lower energies, observations using the Large Area Telescope (LAT) onboard Fermi provide a rich set of data which can be used to study the behavior of cosmic accelerators in the MeV to TeV energy bands. In particular, the improved angular resolution of current telescopes in both bands compared to previous instruments significantly reduces source confusion and facilitates the identification of associated counterparts at lower energies. In this paper, a comprehensive search for VHE gamma-ray sources which are spatially coincident with Galactic Fermi/LAT bright sources is performed, and the available MeV to TeV spectra of coincident sources are compared. It is found that bright LAT GeV sources are correlated with TeV sources, in contrast to previous studies using EGRET data. Moreover, a single spectral component seems unable to describe the MeV to TeV spectra of many coincident GeV/TeV sources. It has been suggested that gamma-ray pulsars may be accompanied by VHE gamma-ray emitting nebulae, a hypothesis that can be tested with VHE observations of these pulsars.Comment: Astronomy and Astrophysics, in press, 17 pages, 12 figures, 5 table

No X-Ray Excess from the HESS J1741-302 Region except a New Intermediate Polar Candidate

With the Suzaku satellite, we observed an unidentified TeV gamma-ray source HESS J1741$-$302 and its surroundings. No diffuse or point-like X-ray sources are detected from the bright southern emission peak of HESS J1741$-$302. From its neighborhood, we found a new intermediate polar candidate at the position of (\alpha, \delta)_{\rm J2000.0} = (\timeform{17h40m35.6s}, \timeform{-30D14m16s}), which is designated as Suzaku J174035.6$-$301416. The spectrum of Suzaku J174035.6$-$301416 exhibits emission lines at the energy of 6.4, 6.7 and 7.0 keV, which can be assigned as the K$\alpha$ lines from neutral, He-like and H-like iron, respectively. A coherent pulsation is found at a period of 432.1 $\pm$ 0.1 s. The pulse profile is quasi-sinusoidal in the hard X-ray band (4$-$8 keV), but is more complicated in the soft X-ray band (1$-$3 keV). The moderate period of pulsation, the energy flux, and the presence of the iron K$\alpha$ lines indicate that Suzaku J174035.6$-$301416 is likely an intermediate polar, a subclass of magnetized white dwarf binaries (cataclysmic variables). Based on these discoveries, we give some implications on the origin of GCDX and brief comments on HESS J1741$-$302 and PSR B1737$-$30.Comment: Accepted by PAS