Blazars, active galactic nuclei whose jet axis is pointed towards the observer, constitute the most numerous class of extragalactic very high energy (VHE, E > 100, GeV) gamma-ray emitters. The MAGIC experiment, a system of two Imaging Atmospheric Che
renkov Telescopes located in the Canary Island of La Palma (Northern hemisphere), with an energy threshold of 50 GeV, is a well suited experiment for observations of such objects. Here we present the discovery of the BL Lac 1ES 1727+502 (z = 0.055) as VHE source. This object was identified as a promising TeV candidate based on archival data and the observation that lead to this detection was not triggered by any high state alert in other wavebands. The MAGIC observations are complemented by other observations are lower frequencies: optical data from the KVA telescope, UV, optical and X-ray archival data taken with the instruments on board the Swift satellite and high energy (HE, 300 MeV < E < 100 GeV) data from the textit{Fermi}-LAT instrument. We studied the spectral energy distribution of 1ES 1727+502 and interpreted it with a one-zone synchrotron self-Compton model with parameters that are typical for this class of sources.
We present results of multi-wavelength (MWL) observations of the high-frequency-peaked BL Lacertae (HBL) object 1ES 0806+524 (z=0.138). Triggered by a high optical state, very high energy (VHE; E > 100 GeV) observations were carried out with the MAGI
C stereoscopic system from January to March 2011. During the observations a relatively short VHE gamma-ray flare was detected that lasted no longer than one night. To complement the VHE observations, simultaneous MWL data were collected in high energy gamma-rays using the textit{Fermi Large Area Telescope (HE, 300 MeV - 100 GeV), in the X-ray and UV band with the textit{Swift} satellite, in the optical R--band through observations with the KVA telescope and in the radio band using the OVRO telescope. This constitutes the first time that such a broad band coverage has been obtained for this source. We study the source properties through the characterization of the spectral energy distribution (SED) and its evolution through two different VHE flux states. The SED can be modeled with a simple one-zone SSC model, resulting in parameters that are comparable to those obtained for other HBLs.
In 2006 the stand-alone MAGIC-I telescope discovered very high energy gamma-ray emission from 3C279. Additional observations were triggered when the source entered an exceptionally bright optical state in January 2007 and the Fermi space telescope me
asured a bright GeV gamma-ray flare in December 2008 until April 2009. While the complete January 2007 dataset does not show a significant signal, a short flare (of one day duration) has been detected on January 16th with a significance of 5.4 sigma (trial-corrected). The flux corresponds to F(> 150 GeV) = (3.8 pm 0.8)cdot 10-11 ph cm-2 s-1. The December 2008 - April 2009 observations did not detect the source. We collected quasi-simultaneous data at optical and X-ray frequencies and for 2009 also gamma-ray data from Fermi, which we use to determine the spectral energy distributions and the light curves. The hard gamma-ray spectrum is a challenge for standard one-zone models, which are based on relativistic electrons in a jet scattering broad line region photons. We study additionally a two zone model and a lepto-hadronic model, which fit the observed spectral energy distribution more satisfactorily.
MAGIC, a stereoscopic cherenkov telescope array, sensitive to gamma-rays between 50 GeV and several tens of TeV, is ideally suited to observe promising Fermi LAT sources with a hard gamma-ray spectrum. Here we discuss the discovery of very high energ
y gamma-ray (VHE, E > 100 GeV) emission from the Fermi LAT sources 1FGL J2001.1+4351 and B3-2247+381 with MAGIC. 1FGL J2001.1+4351, recently identified as MG4 J200112+4352 (Bassani et al. 2010), is most likely a high peaked BL Lacertae object. The red shift of this source is still unknown, though the identification of the optical host galaxy suggests z < 0.2. MAGIC observations indicate short term variability, since the source showed a strong emission of 20% of the Crab Nebula flux above 90 GeV during the 16th of July 2010 and none of the other observation nights yielded a detection. B3-2247+381 is classified as a BL Lac object at z = 0.1187 (Veron-Cetty & Veron catalogue of known AGN). In July 2010 it showed increased optical activity in the Tuorla blazar monitoring program, which subsequently activated target of opportunity observations by MAGIC. Within 18 hours of observation time extended over 13 days between September and October 2010, a strong signal was found above an energy threshold of 150 GeV. The flux (4% of the Crab Nebula) is consistent with being constant over the entire observation campaign. We compute the light curves, model the spectral energy distributions of these new very high energy gamma-ray emitters and discuss the physical properties of the VHE gamma-ray emission region.
