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We present the results of a preliminary study of a correction method applied to the Imaging Atmospheric Cherenkov Telescope images affected by clouds. The studied data are Monte Carlo simulations made with CORSIKA, imitating the very high energy events registered by the Large-Sized Telescopes, a type of telescope within the future Cherenkov Telescope Array. We implement the cloud correction method in the ctapipe/lstchain analysis framework. The correction is based on a simple geometrical model of the emission. We show the effect of the correction method on the image parameters and the stereo-reconstructed shower parameters., Comment: 7 pages, 4 figures, High Energy Astrophysics in Southern Africa 2022 - HEASA2022, 28 September - 1 October 2022, Brandfort, South Africa

Context. The presence of clouds during observations with Imaging Atmospheric Cherenkov Telescopes can strongly affect the performance of the instrument due to additional absorption of light and scattering of light beyond the field of view of the instrument. If not corrected for, the presence of clouds leads to increased systematic errors in the results. Aims. One approach to correct for the effects of clouds is to include clouds in Monte Carlo simulations to produce models for primary particle classification, energy and direction estimation. However, this method is challenging due to the dynamic nature of cloudy conditions and requires extensive computational resources. The second approach focuses on correcting the data itself for cloud effects, which allows the use of standard simulations. However, existing corrections often prioritise limiting systematic errors without optimising overall performance. By correcting the data already at the image level, it is possible to improve event reconstruction without the need for specialised simulations. Methods. We introduce a novel analysis method, based on a geometrical model that can correct the data already at the image level given a vertical transmission profile of a cloud. Using Monte Carlo simulations of an array of four Large-Sized Telescopes of the Cherenkov Telescope Array, we investigate the effect of the correction on the image parameters and the performance of the system. We compare the data correction at the camera level with the use of dedicated simulations for clouds with different transmissions and heights. Results. The proposed method efficiently corrects the extinction of light in clouds, eliminating the need for dedicated simulations. Evaluation using Monte Carlo simulations demonstrates improved gamma-ray event reconstruction and overall system performance., Comment: 15 pages, 11 figures, 2 tables, accepted for publication in A&A

The Cherenkov Telescope Array (CTA) will be the next generation ground-based very-high-energy gamma-ray observatory, constituted by tens of Imaging Atmospheric Cherenkov Telescopes at two sites once its construction and commissioning are finished. Like its predecessors, CTA relies on Instrument Response Functions (IRFs) to relate the observed and reconstructed properties to the true ones of the primary gamma-ray photons. IRFs are needed for the proper reconstruction of spectral and spatial information of the observed sources and are thus among the data products issued to the observatory users. They are derived from Monte Carlo simulations, depend on observation conditions like the telescope pointing direction or the atmospheric transparency and can evolve with time as hardware ages or is replaced. Producing a complete set of IRFs from simulations for every observation taken is a time-consuming task and not feasible when releasing data products on short timescales. Consequently, interpolation techniques on simulated IRFs are investigated to quickly estimate IRFs for specific observation conditions. However, as some of the IRFs constituents are given as probability distributions, specialized methods are needed. This contribution summarizes and compares the feasibility of multiple approaches to interpolate IRF components in the context of the pyirf python software package and IRFs simulated for the Large-Sized Telescope prototype (LST-1). We will also give an overview of the current functionalities implemented in pyirf., Comment: Presented at the 38th International Cosmic Ray Conference (ICRC 2023), 2023 (arXiv:2309.08219)

The Cherenkov Telescope Array (CTA) is the next-generation stereoscopic system of Imaging Atmospheric Cherenkov Telescopes (IACTs). In IACTs, the atmosphere is used as a calorimeter to measure the energy of extensive air showers induced by cosmic gamma rays, which brings along a series of constraints on the precision to which energy can be reconstructed. The presence of clouds during observations can severely affect Cherenkov light yield, contributing to the systematic uncertainty in energy scale calibration. To minimize these systematic uncertainties, a calibration of telescopes is of great importance. For this purpose, the influence of cloud transmission and altitude on CTA-N performance degradation was investigated using detailed Monte Carlo simulations for the case where no action is taken to correct for the effects of clouds. Variations of instrument response functions in the presence of clouds are presented. In the presence of clouds with low transmission ($\leq$ 80%) the energy resolution is aggravated by 30% at energies below 1 TeV, and by 10% at higher energies. For higher transmissions, the energy resolution is worse by less than 10% in the whole energy range. The angular resolution varies up to 10% depending both on the transmission and altitude of the cloud. The sensitivity of the array is most severely reduced at lower energies, even by 60% at 40 GeV, depending on the clouds' properties. A simple semi-analytical model of sensitivity degradation has been introduced to summarize the influence of clouds on sensitivity and provide useful scaling relations.

The Cherenkov Telescope Array (CTA) is the future ground-based observatory for gamma-ray astronomy at very high energies. The atmosphere is an integral part of every Cherenkov telescope. Different atmospheric conditions, such as clouds, can reduce the fraction of Cherenkov photons produced in air showers that reach ground-based telescopes, which may affect the performance. Decreased sensitivity of the telescopes may lead to misconstructed energies and spectra. This study presents the impact of various atmospheric conditions on CTA performance. The atmospheric transmission in a cloudy atmosphere in the wavelength range from 203 nm to 1000 nm was simulated for different cloud bases and different optical depths using the MODerate resolution atmospheric TRANsmission (MODTRAN) code. MODTRAN output files were used as inputs for generic Monte Carlo simulations. The analysis was performed using the MAGIC Analysis and Reconstruction Software (MARS) adapted for CTA. As expected, the effects of clouds are most evident at low energies, near the energy threshold. Even in the presence of dense clouds, high-energy gamma rays may still trigger the telescopes if the first interaction occurs lower in the atmosphere, below the cloud base. A method to analyze very high-energy data obtained in the presence of clouds is presented. The systematic uncertainties of the method are evaluated. These studies help to gain more precise knowledge about the CTA response to cloudy conditions and give insights on how to proceed with data obtained in such conditions. This may prove crucial for alert-based observations and time-critical studies of transient phenomena.

Large fraction of studies of active galactic nuclei objects is based on performing follow-up observations using high-sensitivity instruments of high flux states observed by monitoring instruments (the so-called Target of Opportunity, ToO). Due to transient nature of such enhanced states it is essential to quickly evaluate if such a ToO event should be followed. We use a machine learning method to assess the possibility to predict the evolution of high flux states in gamma-ray band observed with Fermi-LAT in context of following such alerts with current and future Cherenkov telescopes. We probe flux and Test Statistic predictions using different training schemes and sample selections. We conclude that a partial prediction of the flux over a time scale of one day with an accuracy of ~35% is possible. The method provides accurate predictions of the raising/falling emission trend with 60 - 75% probability, however deeper investigations shows that this is likely based on typical properties of the source, rather than on the result of most recent measurements., Comment: 12 pages, 10 figures, 4 tables, accepted for publication in Astroparticle Physics

We observed the gravitationally lensed blazar JVAS B0218+357 with the KVN and VERA Array (KaVA) at 22, 43, and 86 GHz. The source has recently been identified as an active gamma-ray source up to GeV/TeV energy bands, rendering a unique target for studying relativistic jets through gravitational lensing. Here we report the first robust VLBI detection and imaging of the lensed images up to 86 GHz. The detected mas-scale/parsec-scale morphology of the individual lensed images (A and B) is consistent with that previously seen at 22 and 15 GHz, showing the core-jet morphology with the jet direction being the same as at the low frequencies. The radio spectral energy distributions of the lensed images become steeper at higher frequencies, indicating that the innermost jet regions become optically thin to synchrotron emission. Our findings confirm that the absorption effects due to the intervening lensing galaxy become negligible at millimeter wavelengths. These results indicate that high-frequency VLBI observations are a powerful tool to better recover the intrinsic properties of lensed active galactic nucleus jets, which therefore allow us to study the interplay between the low- and high-energy emission., Comment: 11pages, 7 pages, 4 tables, accepted for publication in ApJ

At the 36 th ICRC during 11 parallel Gamma-Ray Indirect sessions in total about 70 talks were presented. A few of the plenary highlight talks as well concerned mostly indirect observations of gamma rays. In addition about 140 posters on this topic have been shown in poster sessions. This rapport tries to summarize the results presented in those contributions., Comment: 22 pages, 10 figures, Proc. of 36th ICRC, Madison, WI

The flat spectrum radio quasar PKS 1510-089 is a monitored target in many wavelength bands due to its high variability. It was detected as a very-high-energy (VHE) $\gamma$-ray emitter with H.E.S.S. in 2009, and has since been a regular target of VHE observations by the imaging Cherenkov observatories H.E.S.S. and MAGIC. In this paper, we summarize the current state of results focusing on the monitoring effort with H.E.S.S. and the discovery of a particularly strong VHE flare in 2016 with H.E.S.S. and MAGIC. While the source has now been established as a weak, but regular emitter at VHE, no correlation with other energy bands has been established. This is underlined by the 2016 VHE flare, where the detected optical and high-energy $\gamma$-ray counterparts evolve differently than the VHE flux., Comment: 11 pages, 8 figures, conference paper for the workshop "Monitoring the non-thermal Universe 2018" held in Cochem in September 2018

The energetic pulsar, PSR J2032+4127, has been recently discovered in the direction of the unidentified HEGRA TeV gamma-ray source (TeV J2032+4130). It is proposed that this pulsar forms a binary system with the Be type star, MT91 213, expected to reach the periastron late in 2017. We performed detailed calculations of the gamma-ray emission produced close to the binary system's periastron passage by applying a simple geometrical model. Electrons accelerated at the collision region of pulsar and stellar winds initiate anisotropic Inverse Compton electron-positron pair cascades by scattering soft radiation from the massive companion. The gamma-ray spectra, from such a comptonization process, are confronted with the measurements of the extended TeV gamma-ray emission from the HEGRA TeV gamma-ray source. We discuss conditions within the binary system, at the periastron passage of the pulsar, for which the gamma-ray emission from the binary can overcome the extended, steady TeV gamma-ray emission from the HEGRA TeV gamma-ray source., Comment: 19 pages, 8 figures, Journal of Physics G, accepted

BL Lacertae is a blazar at the redshift of z = 0.069, eponym of the BL Lac blazar type. It is also a prototype of the low-frequency-peaked BL Lac (LBL) subclass. It was first detected in sub-TeV gamma-ray range by MAGIC in 2005. In 2015, MAGIC observations of BL Lacertae were triggered by the Fermi-LAT analysis report in the MAGIC group, and were performed during 10 individual nights between 15th and 28th June for a total of 8.6 h. The measured gamma-ray flux varied from 40\% to 10\% of the Crab nebula flux above 200 GeV in the nights from 15th to 17th June. In particular, a fast variability was found during the nights of 15th and 17th June. % with a halving time scale of (33+/-9) minutes, statistical errors only. We also performed multi-wavelength (MWL) observations in the radio, optical, UV, X-ray and gamma-ray bands, and %the MWL light curves indicate that the very high energy gamma-ray flare was a so-called orphan flare, %i.e. no simultaneous activity in other wavebands was observed. the MWL light curves indicate that no apparent simultaneous activity in other wavebands accompanying the very high energy gamma-ray flare in June 2015 like an another occurrence of an orphan very high energy flare. In this proceedings we will present the results of the campaign and discuss their implications on our understanding of the object., Comment: Proceedings of the 35th International Cosmic Ray Conference (ICRC2017), Bexco, Busan, Korea. All MAGIC contributions are collected at arxiv.org/abs/1708.05153"

There are several types of Galactic sources that can potentially accelerate charged particles up to GeV and TeV energies. We present here the results of our observations of the source class of gamma-ray binaries and the subclass of binary systems known as novae with the MAGIC telescopes. Up to now novae were only detected in the GeV range. This emission can be interpreted in terms of an inverse Compton process of electrons accelerated in a shock. In this case it is expected that protons in the same conditions can be accelerated to much higher energies. Consequently they may produce a second component in the gamma-ray spectrum at TeV energies. The focus here lies on the four sources: nova V339 Del, SS433, LS I +61 303 and V404 Cygni. The binary system LS I +61 303 was observed in a long-term monitoring campaign for 8 years. We show the newest results on our search for superorbital variability, also in context with contemporaneous optical observations. Furthermore, we present the observations of the only super-critical accretion system known in our galaxy: SS433. Finally, the results of the follow-up observations of the microquasar V404 Cygni during a series of outbursts in the X-ray band and the ones of the nova V339 Del will be discussed in these proceedings., Comment: Proceedings of the 35th International Cosmic Ray Conference (ICRC 2017), Bexco, Busan, Korea (arXiv:1708.05153)

The extragalactic background light (EBL) is the radiation accumulated through the history of the Universe in the wavelength range from the ultraviolet to the far infrared. Local foregrounds make the direct measurement of the diffuse EBL notoriously difficult, while robust lower limits have been obtained by adding up the contributions of all the discrete sources resolved in deep infrared and optical galaxy observations. Gamma-ray astronomy has emerged in the past few years as a powerful tool for the study of the EBL: very-high-energy (VHE) photons traversing cosmological distances can interact with EBL photons to produce e$^+$e$^-$ pairs, resulting in an energy-dependent depletion of the gamma-ray flux of distant sources that can be used to set constraints on the EBL density. The study of the EBL is one of the key scientific programs currently carried out by the MAGIC collaboration. We present here the results of the analysis of 32 VHE spectra of 12 blazars in the redshift range 0.03 - 0.94, obtained with over 300 hours of observations with the MAGIC telescopes between 2010 and 2016. A combined likelihood maximization approach is used to evaluate the density and spectrum of the EBL most consistent with the MAGIC observations. The results are compatible with state-of-the-art EBL models, and constrain the EBL density to be roughly within $\simeq 20\%$ of the nominal value in such models. The study reveals no anomalies in gamma-ray propagation in the large optical depth regime - contrary to some claims based on meta-analyses of published VHE spectra., Comment: Proceedings of the 35th International Cosmic Ray Conference (ICRC 2017), Bexco, Busan, Korea (arXiv:1708.05153)

MAGIC is a system of two Cherenkov telescopes designed to perform observations of gamma rays with energies from about 50 GeV to tens of TeV. A low energy threshold and an excellent low energy performance make it a powerful instrument for studies of high energy processes in Active Galactic Nuclei (AGN). The MAGIC Collaboration dedicates about 40% of the telescopes' time to such observations, both monitoring of known emitters, and Target of Opportunity observations of flaring events. In this presentation we will discuss the recent highlights of the MAGIC AGN program. In particular, multi year monitoring of radio galaxies, such as M87, and strong peculiar blazars, such as PG 1553+113, will be presented together with new discoveries based on the Target Of Opportunity program., Comment: Proceedings of the 35th International Cosmic Ray Conference (ICRC 2017), Bexco, Busan, Korea, (arXiv:1708.05153)

PKS1510-089 is a flat spectrum radio quasar located at a redshift of 0.36. It is one of only a few such sources detected in very-high-energy (VHE, >100 GeV) gamma rays. Though PKS1510-089 is highly variable at GeV energies, until recently no variability has been observed in the VHE band. In 2015 May PKS1510-089 showed a high state in optical and in the GeV range. A VHE gamma-ray flare was detected with MAGIC at that time, showing the first instance of VHE gamma-ray flux variability on the time scale of days in this source. We will present the MAGIC results from this observation, discuss their temporal and spectral properties in the multi-wavelength context and present modelling of such emission in the external Compton scenario., Comment: Proceedings of the 35th International Cosmic Ray Conference (ICRC 2017), Bexco, Busan, Korea (arXiv:1708.05153)

PKS 1510-089 (z=0.361) is one of only a handful of flat spectrum radio quasars that have been detected at very high energy (VHE, $E>100\,$GeV) gamma rays. It is a very active source across the entire electromagnetic spectrum. VHE observations in May 2016 with H.E.S.S. and MAGIC revealed an exceptionally strong flare, which lasted for less than two nights, and exhibited a peak flux of about 0.8 times the flux of the Crab Nebula above $200\,$GeV. The flare provides the first evidence of intranight variability at VHE in this source. While optical observations with ATOM reveal a counterpart at optical frequencies, Fermi-LAT observations reveal only low flux variability at high energy (HE, $E>100\,$ MeV) gamma rays. Interestingly, the HE spectral index significantly hardens during the peak of the VHE flare, indicating a strong shift of the peak frequency of the high energy component. Given the expected strong absorption due to the broad-line region, the VHE emission region cannot be located deep within that region., Comment: To appear in Proceedings of 35th ICRC, Busan (Korea) 2017

Strong gravitational lensing leads to an occurrence of multiple images, with different magnifications, of a lensed source. Those magnifications can in turn be modified by microlensing on smaller mass scales within the lens. Recently, measurements of the changes in the magnification ratio of the individual images have been proposed as a powerful tool for estimation of the size and velocity of the emission region in the lensed source. The changes of the magnification ratios in blazars PKS1830-211 and QSO B0218+357, if interpreted as caused by a microlensing on individual stars, put strong constraints on those two variables. These constraints are difficult to accommodate with the current models of gamma-ray emission in blazars. In this paper we study if similar changes in the magnification ratio can be caused by microlensing on intermediate size structures in the lensing galaxy. We investigate in details three classes of possible lenses: globular clusters (GC), open clusters (OC) and giant molecular clouds (GMC). We apply this scenario to the case of QSO B0218+357. Our numerical simulations show that changes in magnifi- cations with similar time scales can be obtained for relativistically moving emission regions with sizes up to 0.01 pc in the case of microlensing on the cores of GCs or clumps in GMCs. From the density of such structures in spiral galaxies we estimate however that lensing in giant molecular clouds would be more common., Comment: 9 pages, 9 figures, accepted for publication in MNRAS

The nearby active galaxy IC 310, located in the outskirts of the Perseus cluster of galaxies is a bright and variable multi-wavelength emitter from the radio regime up to very high gamma-ray energies above 100 GeV. Originally, the nucleus of IC 310 has been classified as a radio galaxy. However, studies of the multi-wavelength emission showed several properties similarly to those found from blazars as well as radio galaxies. In late 2012, we have organized the first contemporaneous multi-wavelength campaign including radio, optical, X-ray and gamma-ray instruments. During this campaign an exceptionally bright flare of IC 310 was detected with the MAGIC telescopes in November 2012 reaching an averaged flux level in the night of up to one Crab above 1 TeV with a hard spectrum over two decades in energy. The intra-night light curve showed a series of strong outbursts with flux-doubling time scales as fast as a few minutes. The fast variability constrains the size of the gamma-ray emission regime to be smaller than 20% of the gravitational radius of its central black hole. This challenges the shock acceleration models, commonly used to explain gamma-ray radiation from active galaxies. Here, we will present more details on the MAGIC data and discuss several possible alternative emission models., Comment: 8 pages, 5 figures, Proceedings of the 34th International Cosmic Ray Conference, 30 July - 6 August, 2015, The Hague, The Netherlands

QSO B0218+357 is a blazar located at a cosmological redshift of z=0.944. It is gravitationally lensed by a spiral galaxy at a redshift of z=0.68. The blazar and its lens are well studied in the radio through X-ray bands, and several blazar outbursts were detected by Fermi-LAT at energies above 100 MeV. Strong gravitational lensing was invoked to explain the two components appar- ent in the radio and GeV light curves, separated by 10-12 days. In July 2014 another outburst was observed by Fermi-LAT, triggering follow-up observations with the MAGIC telescopes at energies above 100 GeV. The observations were scheduled at the expected time of arrival of the component delayed by the strong gravitational field of the lens, resulting in a firm detection of QSO B0218+357. Using the combined Fermi-LAT and MAGIC data sets, we report on variability of this unique blazar, the most distant among all currently known very high energy sources., Comment: 8 pages, 2 figures, Proceedings of the 34th International Cosmic Ray Conference, 30 July- 6 August, 2015, The Hague, The Netherlands

The nearby active galaxy IC 310 (z=0.019), located in the Perseus cluster of galaxies is a bright and variable multi-wavelength emitter from the radio regime up to very high gamma-ray energies above 100 GeV. Very recently, a blazar-like compact radio jet has been found by parsec-scale VLBI imaging. Along with the unusually flat gamma-ray spectrum and variable high-energy emission, this suggests that IC 310 is the closest known blazar and therefore a key object for AGN research. As part of an intense observing program at TeV energies with the MAGIC telescopes, an exceptionally bright flare of IC 310 was detected in November 2012 reaching a flux level of up to >0.5 Crab units above 300 GeV. We have organized a multi-wavelength follow-up program, including the VLBA, Effelsberg 100 m, KVA, Swift, INTEGRAL, Fermi/LAT, and the MAGIC telescopes. We present preliminary results from the multi-wavelength follow-up program with the focus on the response of the jet to this exceptional gamma-ray flare., Comment: Proceedings of the 33rd ICRC 2013, Rio de Janeiro, contribution #336

MAGIC is a system of two Imaging Atmospheric Cherenkov Telescopes located at the Canary Island of La Palma, designed to observe gamma rays with energies above 50 GeV. Recently it has undergone an upgrade of the camera, digital trigger and readout systems. The upgrade has led to an improvement in the performance of the telescopes, especially in the lower energy range. We evaluate the performance of the upgraded MAGIC telescopes using Monte Carlo simulations and a large sample of Crab Nebula data. We study differential and integral sensitivity of the system, its angular resolution as well as its energy resolution., Comment: 4 pages, 5 figures, Proc. of 33rd ICRC, Rio de Janeiro, Brazil

The Fermi-LAT telescope has unexpectedly discovered GeV gamma-ray emission from the symbiotic Nova V407 Cygni. We investigate the radiation processes due to electrons and hadrons accelerated during the explosion of this Nova. We consider a scenario in which GeV gamma-ray emission observed by Fermi is produced by the electrons with energies of a few tens of GeV in the inverse Compton scattering of stellar radiation. On the other hand, the hadrons are expected to reach larger energies, due to the lack of radiation losses during acceleration process, producing TeV gamma-rays and neutrinos. We predict the fluxes of very high energy gamma-rays and neutrinos from Novae of the V407 type for two models of hadron acceleration and discuss their possible detectability by the present and future telescopes (e.g. IceCube, CTA), Comment: 7 pages, 5 figures, accepted for publication in Phys. Rev D

The two BL Lac objects, 1ES 1215+303 and 1ES 1218+304, separated by 0.8 degree, were observed with the MAGIC Cherenkov telescopes in 2010-2011. The January 2011 observations resulted in the first detection above 100 GeV of 1ES 1215+303 (known also as ON-325) which has been flagged as a promising Very High Energy (VHE, E > 100 GeV) gamma-ray source candidate by the Fermi-LAT Collaboration in October 2010. The January 2011 observations were triggered by the high optical state of the source, as reported by the Tuorla blazar monitoring program. A comparison with the 2010 data suggests that 1ES 1215+303 was also flaring in VHE gamma-rays. In addition, the Swift Target of Opportunity (ToO) observations in X-rays showed that the flux was almost doubled with respect to previous observations (December 2009). Instead, 1ES 1218+304 is a well known VHE gamma-ray emitter located in the same field of view, which was then simultaneously observed with MAGIC. In this contribution we present preliminary results of the MAGIC observations of these two VHE gamma-ray emitting AGNs., Comment: 2011 Fermi Symposium proceedings - eConf C110509

The MAGIC Cherenkov telescopes observed the Perseus cluster sky region in stereo mode for nearly 90 hr from October 2009 to February 2011. This campaign led to the discovery of very high energy Gamma-ray emission from the central radio galaxy NGC 1275 and the head-tail radio galaxy IC 310. Here we report the results on the most recent discovery of NGC 1275 which was detected at low energies in the 2010/2011 data. We also present latest results on IC 310, which had been detected in the 2009/2010 data., Comment: Proceedings of the 32nd International Cosmic Ray Conference (Beijing)

The Crab Pulsar Wind Nebula is the best studied source of $\gamma$-ray astrophysics. The contribution of the various soft radiation fields to the Inverse Compton component of its high energy emission, the strenght of the internal magnetic field and the maximum energies reached by primary electrons are however still matter of study. The MAGIC stereoscopic system recorded almost 50 hours of Crab Nebula data in the last two years, between October 2009 and April 2011. Analysis of this data sample using the latest improvements in the MAGIC stereo software provided an unprecedented differential energy spectrum spanning three decades in energy, from 50 GeV up to 45 TeV. At low energies, the MAGIC results, combined with the Fermi/LAT data, yield a precise measurement of the Inverse Compton peak. In addition, we present light curves of the Crab Nebula at different time scales, including a measurement simultaneous to one of the Crab Nebula flares recently detected by both Fermi/LAT and AGILE. Using the MAGIC spectrum together with multiwavelength data, we discuss the implications for the modeling of the Crab Nebula., Comment: 4 pages, 6 figures, contribution to the 32nd International Cosmic Ray Conference, Beijing, China, August 2011

The two BL Lac objects 1ES 1215+303 and 1ES 1218+304, separated by 0.8 deg, were observed with the MAGIC telescopes in 2010 and 2011. The 20 hours of data registered in January 2011 resulted in the first detection at Very High Energy (>100 GeV) of 1ES 1215+303 (also known as ON-325). This observation was triggered by a high optical state of the source reported by the Tuorla blazar monitoring program. Comparison with the 25 hours of data carried out from January to May 2010 suggests that 1ES 1215+303 was flaring also in VHE gamma-rays in 2011. In addition, the Swift ToO observations in X-rays showed that the flux was almost doubled respect to previous observations (December 2009). Instead, 1ES 1218+304 is a well known VHE gamma-ray emitter lying in the same field of view, which was then simultaneously observed with the MAGIC telescopes. The overall observation time of nearly 45 hours has permitted to measure the spectrum of this source with a much higher precision than previously reported by MAGIC. Here, we present the results of the MAGIC and the multi-wavelength observations of these two VHE gamma-ray emitting AGNs., Comment: 4 pages, 5 figures, Proceedings of the 32nd ICRC (2011) Beijing

Microquasars have been expected to emit high energy gamma-rays due to their general similarities to the gamma-ray emitting blazars (evidences of relativistic jets, non-thermal radio to X-ray emission). In fact, the first source of this type, Cyg X-3, has been recently unambiguously discovered by the satellite telescopes. We study the features of the gamma-ray radiation produced in these sources by relativistic electrons, accelerated in the inner part of the jet. The electrons initiate an Inverse Compton e^\pm pair cascade in the radiation field of the accretion disk. Due to the anisotropy of the accretion disk radiation field, the spectra of gamma-rays show strong dependence on the observation angle, the location of the emission region within the jet and the details of the acceleration process. As an example, we confront our model with the observations of the microquasar Cyg X-3, which has been recently reported as a transient GeV gamma-ray source by the Agile and the Fermi Observatories. Satisfactory description of the gamma-ray spectra observed from Cyg X-3 are obtained in the case of the injection of electrons in the inner part of the jet (located within 300 inner disk radius from the jet base) provided that the observer is located at relatively small angle to the jet axis., Comment: 11 pages, 11 figures, accepted for publication in MNRAS

Very high energy gamma rays coming from extra-galactic sources can interact with intergalactic radiation fields. This process may result in electromagnetic cascades with the following cycle: the production of electron-positron pairs and then secondary gamma-rays due to inverse Compton scattering. Since electrons and positrons will be scattered in the intergalactic magnetic field, under certain conditions their radiation may be redirected towards the observer. Thus one can anticipate that the secondary gamma-ray emission may produce an apparent extended halo around the source. MAGIC is an Imaging Atmospheric Cerenkov Telescope located on Canary island of La Palma at Roque de los Muchachos Observatory (2200 m.a.s.l). Various source sizes and extended emission profiles within $1^\circ$ diameter have been studied by using dedicated Monte Carlo simulations for the MAGIC telescope. We present results of the study of a possible extended emission for Mrk 421 and Mrk501 done with the MAGIC telescope., Comment: Contribution to the 31st ICRC, Lodz, Poland, July 2009