Lena Linhoff
A5000383309- Astrophysics and Cosmic Phenomena
- Gamma-ray bursts and supernovae
- Dark Matter and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- Particle Detector Development and Performance
- Neutrino Physics Research
- Particle Accelerators and Free-Electron Lasers
- Astrophysical Phenomena and Observations
- Pulsars and Gravitational Waves Research
- Particle physics theoretical and experimental studies
- Cosmology and Gravitation Theories
- Radiation Detection and Scintillator Technologies
- Astronomy and Astrophysical Research
- Astronomical Observations and Instrumentation
- Stellar, planetary, and galactic studies
- Gyrotron and Vacuum Electronics Research
- Geophysics and Gravity Measurements
- Advanced X-ray and CT Imaging
- Nuclear Physics and Applications
- Precipitation Measurement and Analysis
- Laser Design and Applications
- Geological and Geophysical Studies
- Noncommutative and Quantum Gravity Theories
- Terahertz technology and applications
- Radiation Therapy and Dosimetry
TU Dortmund University
2016-2024
Universidad de La Laguna
2021-2024
Instituto de Astrofísica de Canarias
2021-2024
Institut de Recherche sur les Lois Fondamentales de l'Univers
2023
CEA Paris-Saclay
2023
Université Paris-Saclay
2023
Commissariat à l'Énergie Atomique et aux Énergies Alternatives
2023
ETH Zurich
2021-2023
University of Würzburg
2023
École Polytechnique
2023
Extended and delayed emission around distant TeV sources induced by the effects of propagation gamma rays through intergalactic medium can be used for measurement magnetic field (IGMF). We search GeV from hard-spectrum blazar 1ES 0229+200 with goal to detect or constrain IGMF-dependent secondary flux generated during medium. analyze most recent MAGIC observations over a 5 year time span complement them historic data H.E.S.S. VERITAS telescopes along 12-year long exposure Fermi/LAT telescope....
The blazar TXS 0506+056 got into the spotlight of astrophysical community in September 2017, when a high-energy neutrino detected by IceCube (IceCube-170922A) was associated at 3 $\sigma$ level to $\gamma$-ray flare from this source. This multi-messenger photon-neutrino association remains, as per today, most significant one ever observed. poorly studied object before IceCube-170922A event. To better characterize its broad-band emission, we organized multi-wavelength campaign lasting 16...
Active Galactic Nuclei emit radiation over the whole electromagnetic spectrum up to TeV energies. Blazars are one subtype with their jets pointing towards observer. One of typical features is extreme variability on timescales, from minutes years. The fractional an often used parameter for investigating degree a light curve. Different detection methods and sensitivities instruments result in differently binned data curves gaps. As they can influence physics interpretation broadband...
The First G-APD Cherenkov Telescope (FACT) is monitoring blazars at TeV energies. Thanks to the observing strategy, automatic operation and usage of solid state photosensors (SiPM, aka G-APDs), duty cycle instrument has been maximized observational gaps minimized. This provides a unprecedented, unbiased data sample almost 9000~hours which 2375 hours were taken in 2016. An quick look analysis results with low latency on public website. More than 40 alerts have sent last three years based...
Context. The BL Lac object 1ES 0647+250 is one of the few distant γ -ray emitting blazars detected at very high energies (VHEs; ≳100 GeV) during a non-flaring state. It was with MAGIC telescopes period low activity in years 2009−2011 as well three flaring activities 2014, 2019, and 2020, highest VHE flux last epoch. An extensive multi-instrument data set collected part several coordinated observing campaigns over these years. Aims. We aim to characterise long-term multi-band variability...
The First G-APD Cherenkov Telescope (FACT) has been monitoring Active Galactic Nuclei (AGN) for the past five years. use of robust silicon photomultipliers (SiPMs) allows a continuous, unbiased sampling even during bright-light conditions. This dataset promises insights into core regions AGN by investigating periodicity sources. Periodic changes in flux could indicate binary nature supermassive black holes. A study using Lomb-Scargle periodogram to find monitored is presented. Repeating...
ABSTRACT The central galaxy of the Perseus cluster, 3C 84 or NGC 1275, hosts one closest and well-observed active galactic nuclei (AGNs) thus offered insights into a variety phenomena over past decades. Although close well observed, some key properties remain unknown. One these is inclination angle between jet line sight, for which wide range values can be found in publications. Previous studies have indicated precessing behaviour 84’s that could explain discrepancies. In this work, we...
The BL Lac 1ES 2344+514 is known for temporary extreme properties (e.g., a shift of the synchrotron SED peak energy $\nu_{synch,p}$ above 1keV). While those states were so far observed only during high flux levels, additional multi-year observing campaigns are required to achieve coherent picture. Here, we report longest investigation source from radio VHE performed far, focusing on systematic characterisation intermittent states. our results confirm that typically exhibits...
Imaging Air Cherenkov Telescopes (IACT) measure the faint flashes of light emitted by air-showers that are produced when charged particles or gamma rays hit atmosphere. Therefore, atmosphere above IACT is an integral part detector. Variations in performance itself, but also changes absorption and scattering due to clouds dust affect interpretation measured signals. information about status full system crucial combine measurements from different time periods. The First G-APD Telescope (FACT)...
The realtime follow-up of neutrino events is a promising approach to search for astrophysical sources. It has so far provided compelling evidence point source: the flaring gamma-ray blazar TXS 0506+056 was observed in coincidence with high-energy IceCube-170922A detected by IceCube. detection very-high-energy gamma rays (VHE, E > 100 GeV) from this source helped establish and constrained modeling emission at time IceCube event. four major imaging atmospheric Cherenkov telescope arrays...
Starting from the first announcement of unequivocal detection very high energy (VHE) emission a gamma-ray burst (GRB) by MAGIC telescopes (GRB 190114C), four additional detections VHE GRBs ground-based were reported. These observations have revealed new, energetic component that has become an probe to explore GRB physics. In order deepen our understanding origin this new component, and in general radiation GRBs, further instruments are crucial. work we report fast follow-up 201015A, detected...
Blazars are highly variable objects and their spectral energy distribution (SED) features two peaks. The emission at low energies is understood, however, the origin of TeV strongly debated. While snapshots SEDs usually can be explained with simple models, evolution challenges many models allows for conclusions on mechanisms. Leptonic expect a correlation between peaks, while hadronic accommodate more complex correlations. To study time-resolved SEDs, we set up target-of-opportunity program...
Blazars like Markarian 421 or 501 are active galactic nuclei (AGN), with their jets orientated towards the observer. They among brightest objects in very high energy (VHE) gamma ray regime (>100 GeV). Their emitted gamma-ray fluxes extremely variable, changing activity levels on timescales between minutes, months, and even years. Several questions part of current research, such as question emission regions engine AGN particle acceleration. A dedicated longterm monitoring program is...
For studying variable sources like blazars, it is crucial to achieve unbiased monitoring, either with dedicated telescopes in pointing mode or survey instruments. At TeV energies, the High Altitude Water Cherenkov (HAWC) observatory monitors approximately two thirds of sky every day. It uses water technique, which provides an excellent duty cycle independent weather and season. The First G-APD Telescope (FACT) a small sample better sensitivity, using imaging air technique. Thanks its camera...
ABSTRACT The FR-I galaxy 3C 84, that is identified with the misaligned blazar NGC 1275, well known as one of very few radio galaxies emitting gamma-rays in TeV range. Yet, gamma-ray emission region cannot be pinpointed and responsible mechanisms are still unclear. We calculate optical absorption depth high-energy photons broad-line 84 depending on their energy distance to central black hole. Based these calculations, a lower limit from hole can derived. These limits estimated for two...
Segmented imaging reflectors are a great choice for Imaging Atmospheric Cherenkov Telescopes (IACTs). However, the alignment of individual mirror facets is challenging. We align segmented reflector by observing and optimizing its Bokeh function. can already be done with very little resources preparation time. Further, anytime, even during day. present first usage on FACT, 4m IACT Canary Island La Palma, Spain further test CTA MST prototype in Brelin Adlershof.
Dwarf spheroidal galaxies (dSphs) are among the best candidates to perform indirect searches for DM, having highest known mass-to-light ratio and being free of astrophysical gamma-ray emitting sources. The Major Atmospheric Gamma Imaging Cherenkov (MAGIC) telescopes, located on Canary Island La Palma, have observed a fair amount optimal dSphs in recent years. This is outcome diversifying observation strategy order avoid possible biases target selection improve previous results. In this...
Imaging Atmospheric Cherenkov telescopes (IACTs) are designed to detect cosmic gamma rays. As a by-product, IACTs flashes generated by millions of hadronic air showers every night. We present the proton energy spectrum from several hundred GeV TeV, retrieved hadron induced detected MAGIC telescopes. The protons discriminated He and other heavy nuclei means using machine learning classification. estimation is based on specially developed deep neural network regressor. In last decade, Deep...
OT 081 is a well-known, luminous blazar that remarkably variable in many energy bands. We present the first broadband study of source which includes very-high-energy (VHE, $E>$100\,GeV) $\gamma$-ray data taken by MAGIC and H.E.S.S. imaging Cherenkov telescopes. The discovery VHE emission happened during high state activity July 2016, observed instruments from radio to $\gamma$-rays. identify four states source, one emission. Variability domain found on daily timescales. intrinsic spectrum...
Abstract OT 081 is a well-known, luminous blazar that remarkably variable in many energy bands. We present the first broadband study of source which includes very-high-energy (VHE, E >100 GeV) γ-ray data taken by MAGIC and H.E.S.S. imaging Cherenkov telescopes. The discovery VHE emission happened during high state activity July 2016, observed instruments from radio to γ-rays. identify four states source, one emission. Variability domain found on daily timescales. intrinsic spectrum...
The First G-APD Cherenkov Telescope (FACT) is pioneering the usage of silicon photo mul- tipliers (SiPMs also known as G-APDs) for imaging atmospheric technique. It located at Observatorio Roque de los Muchachos on Canary island La Palma. Since first light in October 2011, it monitoring bright TeV blazars northern sky. By now, FACT only telescope operating with S I PMs a nightly basis. Over course last five years, has been demonstrating their reliability and excel- lent performance....
Imaging Atmospheric Cherenkov Telescopes provide large gamma-ray collection areas > 10^4 m^2 and successfully probe the high energetic sky by observing extensive air showers during night. The First G-APD Telescope (FACT) explores silicon based photoelectric converters (called G-APDs or SiPMs) which more observation time with strong moonlight, a stable photon gain over years of observations, mechanically simpler imaging cameras. So far, signal extraction methods used for FACT originate from...