Search
Results
-
Relentless multi-wavelength variability of Mrk 421 and Mrk 501
(2022)PoS: Proceedings of Science ~ Proceedings of 37th International Cosmic Ray ConferenceMrk 421 and Mrk 501 are two close, bright and well-studied high-synchrotron-peaked blazars, which feature bright and persistent GeV and TeV emission. We use the longest and densest dataset of unbiased observations of these two sources, obtained at TeV and GeV energies during five years with FACT and Fermi-LAT. To characterize the variability and derive constraints on the emission mechanism, we augment the dataset with contemporaneous ...Conference Paper -
Protons Spectrum from MAGIC Telescopes data
(2022)PoS: Proceedings of Science ~ 37th International Cosmic Ray Conference (ICRC 2021)Imaging Atmospheric Cherenkov telescopes (IACTs) are designed to detect cosmic gamma rays. As a by-product, IACTs detect Cherenkov flashes generated by millions of hadronic air showers every night. We present the proton energy spectrum from several hundred GeV to several hundred TeV, retrieved from the hadron induced showers detected by the MAGIC telescopes. The protons are discriminated from He and other heavy nuclei by means of using ...Conference Paper -
Multi-wavelength study of Mrk 421 during a TeV flare
(2022)PoS: Proceedings of Science ~ 37th International Cosmic Ray Conference (ICRC 2021)The blazar Mrk 421 shows frequent, short flares in the TeV energy regime. Due to the fast nature of such episodes, we often fail to obtain sufficient simultaneous information about flux variations in several energy bands. To overcome this lack of multi-wavelength (MWL) coverage, especially for the pre- and post-flare periods, we have set up a monitoring program with the FACT telescope (TeV energies) and the Neil Gehrels Swift Observatory ...Conference Paper -
Relentless multi-wavelength variability of Markarian 421 and Markarian 501
(2022)PoS: Proceedings of Science ~ 37th International Cosmic Ray Conference (ICRC 2021)Mrk 421 and Mrk 501 are two close bright and well-studied high-synchrotron-peaked blazars, which feature bright and persistent GeV and TeV emission. We use the longest and densest dataset of unbiased observations of these two sources, obtained at TeV and GeV energies during 5 years with the FACT telescope and Fermi-LAT. To characterize the variability and derive constraints on the emission mechanism, we augment the dataset with contemporaneous ...Conference Paper -
Statistical properties of flux variations in blazar light curves at GeV and TeV energies
(2022)PoS: Proceedings of Science ~ 37th International Cosmic Ray Conference (ICRC 2021)Despite numerous detections of individual flares, the physical origin of the rapid variability observed from blazars remains uncertain. Using Bayesian blocks and the Eisenstein-Hut HOP algorithm, we characterize flux variations of high significance in the γ-ray light curves of two samples of blazars. Daily binned long-term light curves of TeV-bright blazars observed with the First G-APD Cherenkov Telescope (FACT) are compared to those ...Conference Paper -
FACT - Database-based Analysis and Spectrum Calculations
(2022)PoS: Proceedings of Science ~ 37th International Cosmic Ray Conference (ICRC 2021)The First G-APD Cherenkov Telescope (FACT) is located at the Observatory Roque de los Muchachos on the Canary island La Palma. It uses the imaging air Cherenkov technique to detect gamma rays. With the help of silicon based photosensors in the camera, FACT is an ideal instrument to monitor a small sample of sources with a good time coverage. The automatic operation of the telescope allows an increase of the duty cycle of the instrument. ...Conference Paper -
FACT - Highlights from more than Eight Years of Unbiased TeV Monitoring
(2022)PoS: Proceedings of Science ~ 37th International Cosmic Ray Conference (ICRC 2021)The First G-APD Cherenkov Telescope (FACT) has been monitoring blazars at TeV energies for more than eight years. Using solid state photo sensors and performing robotic operations results in a maximized duty cycle of the instrument and minimized observational gaps, providing an unprecedented data sample of more than 14700~hours of physics data. With an unbiased observing strategy, a small sample of sources is monitored. Results of an ...Conference Paper -
Periodicity Analysis of Mrk 501 and Mrk 421 in Gamma Rays
(2022)PoS: Proceedings of Science ~ 37th International Cosmic Ray Conference (ICRC 2021)Blazars, a subclass of active galactic nuclei (AGNs), are highly variable objects. Quasiperiodic oscillations (QPOs), which might originate from a binary black hole located at the AGN core,have been found in some blazar light curves. For the blazars Mrk 421 and Mrk 501, we test the possible QPO behavior using a variety of methods (generalized Lomb-Scargle periodogram,continuous-time autoregressive moving average models, wavelet scalograms, ...Conference Paper -
FACT - Multi-wavelength analysis of more than 30 flares of Mrk 421
(2021)PoS: Proceedings of Science ~ Proceedings of th 36th International Cosmic Ray Conference (ICRC 2019)Mrk 421 is a high-synchrotron-peaked blazar featuring bright and persistent GeV and TeV emission. We use multi-wavelength light curves of Mrk 421 spanning 5.5 years with FACT (TeV) and Fermi LAT (GeV) in the gamma rays, Swift BAT, Swift XRT and MAXI in the X-rays, together with optical and radio data and investigate the physical processes driving the emission and variability. Observations by FACT are continuous and not triggered, so the ...Conference Paper -
FACT - Probing the Periodicity of Mrk 421 and Mrk 501
(2021)PoS: Proceedings of Science ~ Proceedings of 36th International Cosmic Ray Conference (ICRC 2019)Markarian 421 and Markarian 501 are Active Galactic Nuclei and two of the most prominent sources of very high energetic gamma rays. In contrast to the predominantly stable Crab Nebula, the two blazars have extremely variable gamma-ray fluxes. Those could be caused by erratic accretion flow instabilities, but also by processes leading to quasi periodic oscillations (QPOs). Recently, hints of such a QPO of Mrk 501 with a period of about 322 ...Conference Paper