Search

We report on the observation of the region around supernova remnant G65.1+0.6 with the stand-alone MAGIC-I telescope. This region hosts the two bright GeV gamma-ray sources 1FGL J1954.3+2836 and 1FGL J1958.6+2845. They are identified as GeV pulsars and both have a possible counterpart detected at about 35 TeV by the Milagro observatory. MAGIC collected 25.5 hr of good quality data and found no significant emission in the range around 1 TeV. We therefore report differential flux upper limits, assuming the emission to be point-like ([?] 0.deg1) or within a radius of 0.deg3. In the point-like scenario, the flux limits around 1 TeV are at the level of 3% and 2% of the Crab Nebula flux for the two sources, respectively. This implies that the Milagro emission is either extended over a much larger area than our point-spread function or it must be peaked at energies beyond 1 TeV, resulting in a photon index harder than 2.2 in the TeV band.

Cygnus X-3 is a microquasar consisting of an accreting compact object orbiting around a Wolf-Rayet star. It has been detected at radio frequencies and up to high-energy g rays (above 100 MeV). However, many models also predict a very high energy (VHE) emission (above hundreds of GeV) when the source displays relativistic persistent jets or transient ejections. Therefore, detecting such emission would improve the understanding of the jet physics. The imaging atmospheric Cherenkov telescope MAGIC observed Cygnus X-3 for about 70 hr between 2006 March and 2009 August in different X-ray/radio spectral states and also during a period of enhanced g-ray emission. MAGIC found no evidence for a VHE signal from the direction of the microquasar. An upper limit to the integral flux for energies higher than 250 GeV has been set to 2.2 x 10-12 photons cm-2 s-1 (95% confidence level). This is the best limit so far to the VHE emission from this source. The non-detection of a VHE signal during the period of activity in the high-energy band sheds light on the location of the possible VHE radiation favoring the emission from the innermost region of the jets, where absorption is significant. The current and future generations of Cherenkov telescopes may detect a signal under precise spectral conditions.

The Perseus galaxy cluster was observed by the MAGIC Cherenkov telescope for a total effective time of 24.4 hr during 2008 November and December. The resulting upper limits on the g-ray emission above 100 GeV are in the range of 4.6-7.5 x 10-12 cm-2 s-1 for spectral indices from -1.5 to -2.5, thereby constraining the emission produced by cosmic rays, dark matter annihilations, and the central radio galaxy NGC 1275. Results are compatible with cosmological cluster simulations for the cosmic-ray-induced g-ray emission, constraining the average cosmic ray-to-thermal pressure to <4% for the cluster core region (<8% for the entire cluster). Using simplified assumptions adopted in earlier work (a power-law spectrum with an index of -2.1, constant cosmic ray-to-thermal pressure for the peripheral cluster regions while accounting for the adiabatic contraction during the cooling flow formation), we would limit the ratio of cosmic ray-to-thermal energy to E CR/E th < 3%. Improving the sensitivity of this observation by a factor of about 7 will enable us to scrutinize the hadronic model for the Perseus radio mini-halo: a non-detection of g-ray emission at this level implies cosmic ray fluxes that are too small to produce enough electrons through hadronic interactions with the ambient gas protons to explain the observed synchrotron emission. The upper limit also translates into a level of g-ray emission from possible annihilations of the cluster dark matter (the dominant mass component) that is consistent with boost factors of [?]104 for the typically expected dark matter annihilation-induced emission. Finally, the upper limits obtained for the g-ray emission of the central radio galaxy NGC 1275 are consistent with the recent detection by the Fermi-LAT satellite. Due to the extremely large Doppler factors required for the jet, a one-zone synchrotron self-Compton model is implausible in this case. We reproduce the observed spectral energy density by using the structured jet (spine-layer) model which has previously been adopted to explain the high-energy emission of radio galaxies.

The MAGIC collaboration has searched for high-energy gamma-ray emission of some of the most promising pulsar candidates above an energy threshold of 50 GeV, an energy not reachable up to now by other ground-based instruments. Neither pulsed nor steady gamma-ray emission has been observed at energies of 100 GeV from the classical radio pulsars PSR J0205+6449 and PSR J2229+6114 (and their nebulae 3C58 and Boomerang, respectively) and the millisecond pulsar PSR J0218+4232. Here, we present the flux upper limits for these sources and discuss their implications in the context of current model predictions.

We present results of the multiwavelength campaign on the TeV blazar Mkn 501 performed in 2006 July, including MAGIC for the very-high-energy (VHE) g-ray band and Suzaku for the X-ray band. A VHE g-ray signal was clearly detected with an average flux above 200 GeV of [?]20% of the Crab Nebula flux, which indicates a low state of source activity in this energy range. No significant variability has been found during the campaign. The VHE g-ray spectrum can be described by a simple power law from 80 GeV to 2 TeV with a photon index of 2.8 +- 0.1, which corresponds to one of the steepest photon indices observed in this energy range so far for this object. The X-ray spectrum covers a wide range from 0.6 to 40 keV, and is well described by a broken power law, with photon indices of 2.257 +- 0.004 and 2.420 +- 0.012 below and above the break energy of 3.24+0.13 -0.12 keV. No apparent high-energy cut-off is seen above the break energy. Although an increase of the flux of about 50% is observed in the X-ray band within the observation, the data indicate a consistently low state of activity for this source. Time-resolved spectra show an evidence for spectral hardening with a flux level. A homogeneous one-zone synchrotron self-Compton (SSC) model can adequately describe the spectral energy distribution (SED) from the X-ray to the VHE g-ray bands with a magnetic field intensity B = 0.313 G and a Doppler beaming factor d = 20, which are similar to the values in the past multiwavelength campaigns in high states. Based on our SSC parameters derived for the low state, we are able to reproduce the SED of the high state by just changing the Lorentz factor of the electrons corresponding to the break energy in the primary electron spectrum. This suggests that the variation of the injected electron population in the jet is responsible for the observed low-high state variation of the SED.

We report on the results of two coordinated multiwavelength campaigns that focused on the blazar Markarian 421 during its 2006 and 2008 outbursts. These campaigns obtained UV and X-ray data using the XMM-Newton satellite, while the gamma-ray data were obtained utilizing three imaging atmospheric Cerenkov telescopes, the Whipple 10 m telescope and VERITAS, both based in Arizona, as well as the MAGIC telescope, based on La Palma in the Canary Islands. The coordinated effort between the gamma-ray groups allowed for truly simultaneous data in UV/X-ray/gamma-ray wavelengths during a significant portion of the XMM-Newton observations. This simultaneous coverage allowed for a reliable search for correlations between UV, X-ray, and gamma-ray variability over the course of the observations. Investigations of spectral hysteresis and modeling of the spectral energy distributions are also presented.

Based on MAGIC observations from 2007 June to July, we have obtained an integral upper limit to the VHE energy emission of the globular cluster M13 of F(E>200 GeV) < 5.1 x 10-12 cm-2 s-1, and differential upper limits for E > 140 GeV. Those limits allow us to constrain the population of millisecond pulsars within M13 and to test models for acceleration of leptons inside their magnetospheres and surrounding. We conclude that in M13 either millisecond pulsars are fewer than expected or they accelerate leptons less efficiently than predicted.

We present the result of the observation of the ultrafaint dwarf galaxy Willman 1 performed with the 17 m MAGIC telescope during 15.5 hr between March and May 2008. No significant g-ray emission was found. We derived upper limits of the order of 10-12 ph cm-2 s-1 on the integral flux above 100 GeV, which we compare with predictions from several of the established neutralino benchmark models in the mSUGRA parameter space. The neutralino annihilation spectra are defined after including the recently quantified contribution of internal bremsstrahlung from the virtual sparticles that mediate the annihilation. Flux boost factors of three orders of magnitude are required even in the most optimistic scenario to match our upper limits. However, uncertainties in the dark matter intrinsic and extrinsic properties (e.g., presence of substructures, Sommerfeld effect) may significantly reduce this gap.

The MAGIC collaboration has recently reported the discovery of g-ray emission from the binary system LS I +61deg303 in the TeV energy region. Here we present new observational results on this source in the energy range between 300 GeV and 3 TeV. In total, 112 hr of data were taken between 2006 September and December covering four orbital cycles of this object. This large amount of data allowed us to produce an integral flux light curve covering for the first time all orbital phases of LS I +61deg303. In addition, we also obtained a differential energy spectrum for two orbital phase bins covering the phase range 0.5 < ph < 0.6 and 0.6 < ph < 0.7. The photon index in the two phase bins is consistent within the errors with an average index G = 2.6 +- 0.2stat +- 0.2sys. LS I +61deg303 was found to be variable at TeV energies on timescales of days. These new MAGIC measurements allowed us to search for intranight variability of the very high energy emission; however, no evidence for flux variability on timescales down to 30 min was found. To test for possible periodic structures in the light curve, we apply the formalism developed by Lomb and Scargle to the LS I +61deg303 data taken in 2005 and 2006. We found the LS I +61deg303 data set to be periodic with a period of (26.8 +- 0.2) days (with a post-trial chance probability of 10-7), close to the orbital period.

We present the results of the first multiwavelength observing campaign on the high-mass X-ray binary LS I +61 303, comprising observations at the TeV regime with the MAGIC telescope, along with X-ray observations with Chandra, and radio interferometric observations with the MERLIN, EVN, and VLBA arrays, in 2006 October and November. From our MERLIN observations, we can exclude the existence of large-scale (~100 mas) persistent radio jets. Our 5.0 GHz VLBA observations display morphological similarities to previous 8.4 GHz VLBA observations carried out at the same orbital phase, suggesting a high level of periodicity and stability in the processes behind the radio emission. This makes it unlikely that variability of the radio emission is due to the interaction of an outflow with variable wind clumps. If the radio emission is produced by a milliarcsecond scale jet, it should also show a stable, periodic behavior. It is then difficult to reconcile the absence of a large-scale jet (~100 mas) in our observations with the evidence of a persistent relativistic jet reported previously. We find a possible hint of temporal correlation between the X-ray and TeV emissions and evidence for radio/TeV noncorrelation, which points to the existence of one population of particles producing the radio emission and a different one producing the X-ray and TeV emissions. Finally, we present a quasi-simultaneous energy spectrum including radio, X-ray, and TeV bands.

All but three (M87, BL Lac, and 3C 279) extragalactic sources detected so far at very high energy g-rays belong to the class of high-frequency-peaked BL Lac objects. This suggested to us a systematic scan of candidate sources with the MAGIC telescope, based on the Donato et al. compilation of X-ray blazars. The observations took place from 2004 December to 2006 March and cover northern sky sources visible under small zenith distances zd < 30deg at culmination, constraining the declination to -2deg to +58deg. The sensitivity of the search was planned for detecting X-ray-bright [ 2\ \mu \mathrm{Jy}\,"/> F(1 keV) > 2 m Jy ] sources emitting at least the same energy flux at 200 GeV as at 1 keV. To avoid strong g-ray attenuation close to the energy threshold, source redshift was constrained to z < 0.3. Of the 14 sources observed, 1ES 1218+304 (for the first time at VHE) and 1ES 2344+514 (strong detection in a low flux state) were detected in addition to the known bright TeV blazars Mrk 421 and Mrk 501. A marginal excess of 3.5 s from the position of 1ES 1011+496 was observed and then confirmed as a VHE g-ray source by a second MAGIC observation triggered by a high optical state. For the remaining sources, we present 99% c.l. upper limits on the integral flux [?]200 GeV. We characterize the HBL sample (including all HBLs detected at VHE so far) by looking for correlations between their multifrequency spectral indices determined from simultaneous optical, archival X-ray, and radio luminosities, finding that VHE-emitting HBLs do not seem to constitute a unique subclass. The HBLs' absorption-corrected g-ray luminosities at 200 GeV are generally not higher than their X-ray luminosities at 1 keV.

We present the results from a multiwavelength campaign on the TeV blazar 1ES 1959+650, performed in 2006 May. Data from the optical, UV, soft- and hard-X-ray, and very high energy (VHE) gamma-ray ( 100"/> E > 100 GeV) bands were obtained with the Suzaku and Swift satellites, the MAGIC telescope, and other ground-based facilities. The source spectral energy distribution (SED), derived from Suzaku and MAGIC observations at the end of 2006 May, shows the usual double hump shape, with the synchrotron peak at a higher flux level than the Compton peak. With respect to historical values, during our campaign the source exhibited a relatively high state in X-rays and optical, while in the VHE band it was at one of the lowest level so far recorded. We also monitored the source for flux spectral variability on a time window of 10 days in the optical-UV and X-ray bands and 7 days in the VHE band. The source varies more in the X-ray than in the optical band, with the 2-10 keV X-ray flux varying by a factor of ~2. The synchrotron peak is located in the X-ray band and moves to higher energies as the source gets brighter, with the X-ray fluxes above it varying more rapidly than the X-ray fluxes at lower energies. The variability behavior observed in the X-ray band cannot be produced by emitting regions varying independently and suggests instead some sort of "standing shock" scenario. The overall SED is well represented by a homogeneous one-zone synchrotron inverse Compton emission model, from which we derive physical parameters that are typical of high-energy peaked blazars.

The nearby dwarf spheroidal galaxy Draco, with its high mass to light ratio, is one of the most auspicious targets for indirect dark matter (DM) searches. Annihilation of hypothetical DM particles can result in high-energy g-rays, e.g., from neutralino annihilation in the supersymmetric framework. A search for a possible DM signal originating from Draco was performed with the MAGIC telescope during 2007. Analysis of the data results in a flux upper limit (2 s) of 1.1 x 10[?]11 photons cm[?]2 s[?]1 for photon energies above 140 GeV, assuming a pointlike source. A comparison with predictions from supersymmetric models is also given. While our results do not constrain the mSUGRA phase parameter space, a very high flux enhancement can be ruled out.

We report about very high energy (VHE) g-ray observations of the Crab Nebula with the MAGIC telescope. The g-ray flux from the nebula was measured between 60 GeV and 9 TeV. The energy spectrum can be described by a curved power law dF/dE = f0(E/300 GeV)[a+blog10(E/300 GeV)] $dF/dE = f₀(E/300 GeV) ^{[ a + b&mathrm;{&log;}₁₀(E/300 GeV) ] }$ with a flux normalization f0 of (6.0 +- 0.2stat) x 10[?]10 cm[?]2 s[?]1 TeV[?]1, a = [?] 2.31 +- 0.06stat, and b = [?] 0.26 +- 0.07stat. The peak in the spectral energy distribution is estimated at 77 +- 35 GeV. Within the observation time and the experimental resolution of the telescope, the g-ray emission is steady and pointlike. The emission's center of gravity coincides with the position of the pulsar. Pulsed g-ray emission from the pulsar could not be detected. We constrain the cutoff energy of the pulsed spectrum to be less than 27 GeV, assuming that the differential energy spectrum has an exponential cutoff. For a superexponential shape, the cutoff energy can be as high as 60 GeV.

The blazar Mrk 501 was observed at energies above 0.10 TeV with the MAGIC Telescope from 2005 May through July. The high sensitivity of the instrument enabled the determination of the flux and spectrum of the source on a night-by-night basis. Throughout our observational campaign, the flux from Mrk 501 was found to vary by an order of magnitude. Intranight flux variability with flux-doubling times down to 2 minutes was observed during the two most active nights, namely, June 30 and July 9. These are the fastest flux variations ever observed in Mrk 501. The ~20 minute long flare of July 9 showed an indication of a 4 +- 1 minute time delay between the peaks of F(<0.25 TeV) and F(>1.2 TeV), which may indicate a progressive acceleration of electrons in the emitting plasma blob. The flux variability was quantified for several energy ranges and found to increase with the energy of the g-ray photons. The spectra hardened significantly with increasing flux, and during the two most active nights, a spectral peak was clearly detected at 0.43 +- 0.06 and 0.25 +- 0.07 TeV, respectively, for June 30 and July 9. There is no evidence of such a spectral feature for the other nights at energies down to 0.10 TeV, thus suggesting that the spectral peak is correlated with the source luminosity. These observed characteristics could be accommodated in a synchrotron self-Compton framework in which the increase in g-ray flux is produced by a freshly injected (high energy) electron population.

We report on very high energy g-ray observations with the MAGIC Telescope of the pulsar PSR B1951+32 and its associated nebula, CTB 80. Our data constrain the cutoff energy of the pulsar to be less than 32 GeV, assuming the pulsed g-ray emission to be exponentially cut off. In the case that the cutoff follows a superexponential behavior, the cutoff energy can be as high as ~60 GeV. The upper limit on the flux of pulsed g-ray emission above 75 GeV is 4.3 x 10-11 photons cm-2 s-1, and the upper limit on the flux of steady emission above 140 GeV is 1.5 x 10-11 photons cm-2 s-1. We discuss our results in the framework of recent model predictions and other studies.

During its first data cycle, between 2005 and the beginning of 2006, the fast repositioning system of the MAGIC telescope allowed the observation of nine different gamma-ray bursts as possible sources of very high energy g-rays. These observations were triggered by alerts from Swift, HETE-2, and INTEGRAL; they started as quickly as possible after the alerts and lasted for several minutes, with an energy threshold varying between 80 and 200 GeV, depending on the zenith angle of the burst. No evidence for gamma signals was found, and upper limits for the flux were derived for all events using the standard analysis chain of MAGIC. For the bursts with measured redshifts, the upper limits are compatible with a power-law extrapolation, when the intrinsic fluxes are evaluated taking into account the attenuation due to the scattering in the metagalactic radiation field.

The MAGIC telescope took data of very high energy g-ray emission from the blazar Markarian 421 (Mrk 421) between 2004 November and 2005 April. We present a combined analysis of data samples recorded under different observational conditions, down to g-ray energies of 100 GeV. The flux was found to vary between 0.5 and 2 crab (integrated above 200 GeV), considered a low state when compared to known data. Although the flux varied day by day, no short-term variability was observed, although there is some indication that not all nights show an equally quiescent state. The results at higher energies were found to be consistent with previous observations. A clear correlation is observed between g-ray and X-ray fluxes, whereas no significant correlation between g-ray and optical data is seen. The spectral energy distribution between 100 GeV and 3 TeV shows a clear deviation from a power law, more clearly and at lower flux than previous observations at higher energies. The deviation persists after correcting for the effect of attenuation by the extragalactic background light, and most likely is source-inherent. There is a rather clear indication of an inverse Compton peak around 100 GeV. The spectral energy distribution of Mrk 421 can be fitted by a one-zone synchrotron self-Compton model, suggesting once again a leptonic origin of the very high energy g-ray emission from this blazar.

The MAGIC collaboration has observed very high energy gamma-ray emission from the AGN 1ES 2344+514. A gamma-ray signal corresponding to an 11 s excess and an integral flux of (2.38 +- 0.30stat +- 0.70syst) x 10-11 cm-2 s-1 above 200 GeV has been obtained from 23.1 hr of data taking between 2005 August 3 and 2006 January 1. The data confirm the previously detected gamma-ray emission from this object during a flare seen by the Whipple collaboration in 1995 and the evidence (below 5 s significance level) from long-term observations conducted by the Whipple and HEGRA groups. The MAGIC observations show a relatively steep differential photon spectrum that can be described by a power law with a photon index of a = -2.95 +- 0.12stat +- 0.2syst between 140 GeV and 5.4 TeV. The observations reveal a low-flux state, about 6 times below the 1995 flare seen by Whipple and comparable with the previous Whipple and HEGRA long-term measurements. During the MAGIC observations no significant time variability was observed.

Using the Major Atmospheric Gamma Imaging Cerenkov Telescope (MAGIC), we have observed the nearest ultraluminous infrared galaxy, Arp 220, for about 15 hr. No significant signal was detected within the dedicated amount of observation time. The first upper limits to the very high energy g-ray flux of Arp 220 are herein reported and compared with theoretical expectations.

The MAGIC Cerenkov telescope has observed very high energy (VHE) g-ray emission from the active galactic nucleus 1ES 1959+650 during 6 hr in 2004 September and October. The observations were carried out alternating with observations of the Crab Nebula, whose data were used as a reference source for optimizing g -ray/hadron separation and for flux comparison. The data analysis shows VHE g-ray emission of 1ES 1959+650 with ~8 s significance, at a time of low activity in both optical and X-ray wavelengths. An integral flux above ~180 GeV of about 20% that of the Crab Nebula was obtained. The light curve, sampled over 7 days, shows no significant variations. The differential energy spectrum between 180 GeV and 2 TeV can be fitted with a power-law of index -2.72 +- 0.14. The spectrum is consistent with the slightly steeper spectrum seen by HEGRA at higher energies, also during periods of low X-ray activity.

Between 2004 and 2009, a sample of 28 X-ray selected high- and intermediate-frequency peaked blazars with an X-ray flux larger than 2 uJy at 1 keV in the redshift range from 0.018 to 0.361 was observed with the MAGIC telescope at energies above 100 GeV. Seven among them were detected and the results of these observations are discussed elsewhere. Here we concentrate on the remaining 21 blazars which were not detected during this observation campaign and present the 3s (99.7%) confidence upper limits on their flux. The individual flux upper limits lie between 1.6% and 13.6% of the integral flux from the Crab Nebula. Applying a stacking method to the sample of non-detections with a total of 394.1 hr exposure time, we find evidence for an excess with a cumulative significance of 4.9 standard deviations. It is not dominated by individual objects or flares, but increases linearly with the observation time as for a constant source with an integral flux level of [?]1.5% of that observed from the Crab Nebula above 150 GeV.

The very high energy (VHE; E > 100 GeV) blazar Markarian 501 (Mrk 501) has a well-studied history of extreme spectral variability and is an excellent laboratory for studying the physical processes within the jets of active galactic nuclei. However, there are few detailed multiwavelength studies of Mrk 501 during its quiescent state, due to its low luminosity. A short-term multiwavelength study of Mrk 501 was coordinated in 2009 March, focusing around a multi-day observation with the Suzaku X-ray satellite and including g-ray data from VERITAS, MAGIC, and the Fermi Gamma-ray Space Telescope with the goal of providing a well-sampled multiwavelength baseline measurement of Mrk 501 in the quiescent state. The results of these quiescent-state observations are compared to the historically extreme outburst of 1997 April 16, with the goal of examining variability of the spectral energy distribution (SED) between the two states. The derived broadband SED shows the characteristic double-peaked profile. We find that the X-ray peak shifts by over two orders of magnitude in photon energy between the two flux states while the VHE peak varies little. The limited shift in the VHE peak can be explained by the transition to the Klein-Nishina (KN) regime. Synchrotron self-Compton models are matched to the data and the implied KN effects are explored.

We report on the g-ray activity of the blazar Mrk 501 during the first 480 days of Fermi operation. We find that the average Large Area Telescope (LAT) g-ray spectrum of Mrk 501 can be well described by a single power-law function with a photon index of 1.78 +- 0.03. While we observe relatively mild flux variations with the Fermi-LAT (within less than a factor of two), we detect remarkable spectral variability where the hardest observed spectral index within the LAT energy range is 1.52 +- 0.14, and the softest one is 2.51 +- 0.20. These unexpected spectral changes do not correlate with the measured flux variations above 0.3 GeV. In this paper, we also present the first results from the 4.5 month long multifrequency campaign (2009 March 15--August 1) on Mrk 501, which included the Very Long Baseline Array (VLBA), Swift, RXTE, MAGIC, and VERITAS, the F-GAMMA, GASP-WEBT, and other collaborations and instruments which provided excellent temporal and energy coverage of the source throughout the entire campaign. The extensive radio to TeV data set from this campaign provides us with the most detailed spectral energy distribution yet collected for this source during its relatively low activity. The average spectral energy distribution of Mrk 501 is well described by the standard one-zone synchrotron self-Compton (SSC) model. In the framework of this model, we find that the dominant emission region is characterized by a size [?]0.1 pc (comparable within a factor of few to the size of the partially resolved VLBA core at 15-43 GHz), and that the total jet power ([?]1044 erg s-1) constitutes only a small fraction ([?]10-3) of the Eddington luminosity. The energy distribution of the freshly accelerated radiating electrons required to fit the time-averaged data has a broken power-law form in the energy range 0.3 GeV-10 TeV, with spectral indices 2.2 and 2.7 below and above the break energy of 20 GeV. We argue that such a form is consistent with a scenario in which the bulk of the energy dissipation within the dominant emission zone of Mrk 501 is due to relativistic, proton-mediated shocks. We find that the ultrarelativistic electrons and mildly relativistic protons within the blazar zone, if comparable in number, are in approximate energy equipartition, with their energy dominating the jet magnetic field energy by about two orders of magnitude.

We report new observations of the intermediate-frequency peaked BL Lacertae object 3C 66A with the MAGIC telescopes. The data sample we use were taken in 2009 December and 2010 January, and comprises 2.3 hr of good quality data in stereoscopic mode. In this period, we find a significant signal from the direction of the blazar 3C 66A. The new MAGIC stereoscopic system is shown to play an essential role for the separation between 3C 66A and the nearby radio galaxy 3C 66B, which is at a distance of only 6'. The derived integral flux above 100 GeV is 8.3% of the Crab Nebula flux and the energy spectrum is reproduced by a power law of photon index 3.64 +- 0.39stat +- 0.25sys. Within errors, this is compatible with the one derived by VERITAS in 2009. From the spectra corrected for absorption by the extragalactic background light, we only find small differences between the four models that we applied, and constrain the redshift of the blazar to z < 0.68.