Observation of VHE γ-rays from Cassiopeia A with the MAGIC telescope

Abstract

Aims. We searched for very high energy (VHE) γ-ray emission from the supernova remnant Cassiopeia A Methods. The shell-type supernova remnant Cassiopeia A was observed with the 17 m MAGIC telescope between July 2006 and January 2007 for a total time of 47 h. Results. The source was detected above an energy of 250 GeV with a significance of 5.2σ and a photon flux above 1 TeV of (7.3 ± 0.7 stat ± 2.2 sys ) × 10 −13 cm −2 s −1 . The photon spectrum is compatible with a power law dN/dE ∝ E −Γ with a photon index Γ = 2.3 ± 0.2 stat ± 0.2 sys . The source is point-like within the angular resolution of the telescope.

SPITZERSPECTRAL MAPPING OF SUPERNOVA REMNANT CASSIOPEIA A

“…Supernova remnant Cassiopeia A (Cas A) is both nearby (3.4 kpc) and very young (∼330 yr; Fesen et al 2006), giving it a bright, richly detailed ejecta structure which has led to intensive study at many wavelengths, from gamma rays to radio (Rudnick 2002;Albert et al 2007). Spectroscopy of distant light echoes from the original blast indicates that Cas A was the type IIb core collapse of a ∼ 15 M main-sequence star , which models indicate are highly stratified, having lost a significant portion of the original outer layers of hydrogen and helium prior to collapse in stellar winds (Woosley et al 1987).…”

Prospects for Cherenkov Telescope Array Observations of the Young Supernova Remnant RX J1713.7−3946

“…So far, VHE gamma-ray observations have revealed the existence of high-energy particles at the shock of young SNRs (e.g., Enomoto et al 2002;Aharonian et al 2004Aharonian et al , 2005Aharonian et al , 2006Aharonian et al , 2007aAharonian et al , 2007bAharonian et al , 2009Katagiri et al 2005;Albert et al 2007;Acero et al 2010;Abramowski et al 2011;Acciari et al 2011;see also Ferrand & Safi-Harb 2012). Although the gamma rays are suggested to originate from either leptonic (low-energy photons upscattered by high-energy electrons) or hadronic (π 0 -decay photons generated by accelerated protons colliding with surrounding gas) processes, it is generally a nontrivial task to distinguish these processes despite abundant multiwavelength studies.…”

Nuclear de-excitation line spectrum of Cassiopeia A

“…Faint X-ray filaments outside of the shell mark the location of the forward shock where nonthermal X-ray synchroton radiation is produced by shock-accelerated electrons (Gotthelf et al 2001;Vink & Laming 2003). Detected by HEGRA (Aharonian et al 2001), MAGIC (Albert et al 2007) and VERITAS (Humensky 2008), Cas A was the first SNR verified in TeV gamma rays. Recent observations with Fermi-LAT in the GeV range do not rule out either a leptonic or a hadronic emission scenario: a combination of nonthermal bremsstrahlung and inverse-Compton emission on the one hand as well as neutral pion decays on the other hand could be responsible for the measured spectrum (Abdo et al 2010).…”