Characterizing the aerosol atmosphere above the Observatorio del Roque de los Muchachos by analysing seven years of data taken with an GaAsP HPD-readout, absolutely calibrated elastic LIDAR

We present a new elastic LIDAR concept, based on a bi-axially mounted Nd:YAG laser and a telescope with HPD readout, combined with fast FADC signal digitization and offline pulse analysis. The LIDAR return signals have been extensively quality checked and absolutely calibrated. We analyse seven years of quasi-continuous LIDAR data taken during those nights when the MAGIC telescopes were operating. Characterization of the nocturnal ground layer yields zenith and azimuth angle dependent aerosol extinction scaleheights for clear nights. We derive aerosol transmission statistics for light emitted from various altitudes throughout the year and separated by seasons. We find further seasonal dependencies of cloud base and top altitudes, but none for the LIDAR ratios of clouds. Finally, the night sky background light is characterized using the LIDAR photon backgrounds.The financial support of the Spanish grant PID2019-107847RB-C42, funded by the Spanish Ministry of Science and Innovation (MCIN)/AEI/10.13039/501100011033, the German Federal Ministry of Education and ResearchBMBF and the German Max-Planck-Gesellschaft (MPG), and by the Croatian Science Foundation (HrZZ) Project IP-2016-06-9782 and the University of Rijeka Project uniri-prirod-18-48 is gratefully acknowledged.Peer reviewe

STRAW-b (STRings for Absorption length in Water-b): the second pathfinder mission for the Pacific Ocean Neutrino Experiment

Since 2018, the potential for a high-energy neutrino telescope, named the Pacific Ocean Neutrino Experiment (P-ONE), has been thoroughly examined by two pathfinder missions, STRAW and STRAW-b, short for short for Strings for Absorption Length in Water. The P-ONE project seeks to install a neutrino detector with a one cubic kilometer volume in the Cascadia Basin's deep marine surroundings, situated near the western shores of Vancouver Island, Canada. To assess the environmental conditions and feasibility of constructing a neutrino detector of that scale, the pathfinder missions, STRAW and STRAW-b, have been deployed at a depth of 2.7 km within the designated site for P-ONE and were connected to the NEPTUNE observatory, operated by Ocean Networks Canada (ONC). While STRAW focused on analyzing the optical properties of water in the Cascadia Basin, \ac{strawb} employed cameras and spectrometers to investigate the characteristics of bioluminescence in the deep-sea environment. This report introduces the STRAW-b concept, covering its scientific objectives and the instrumentation used. Furthermore, it discusses the design considerations implemented to guarantee a secure and dependable deployment process of STRAW-b. Additionally, it showcases the data collected by battery-powered loggers, which monitored the mechanical stress on the equipment throughout the deployment. The report also offers an overview of STRAW-b's operation, with a specific emphasis on the notable advancements achieved in the data acquisition (DAQ) system and its successful integration with the server infrastructure of ONC.Comment: 20 pages, 11 figures, 2 table

Limits to dark matter annihilation cross-section from a combined analysis of MAGIC and Fermi-LAT observations of dwarf satellite galaxies

We present the first joint analysis of gamma-ray data from the MAGIC Cherenkov telescopes and the Fermi Large Area Telescope (LAT) to search for gamma-ray signals from dark matter annihilation in dwarf satellite galaxies. We combine 158 hours of Segue 1 observations with MAGIC with 6-year observations of 15 dwarf satellite galaxies by the Fermi-LAT. We obtain limits on the annihilation cross-section for dark matter particle masses between 10 GeV and 100 TeV - the widest mass range ever explored by a single gamma-ray analysis. These limits improve on previously published Fermi-LAT and MAGIC results by up to a factor of two at certain masses. Our new inclusive analysis approach is completely generic and can be used to perform a global, sensitivity-optimized dark matter search by combining data from present and future gamma-ray and neutrino detectors.Comment: 19 pages, 3 figures. V2: Few typos corrected and references added. Matches published version JCAP 02 (2016) 03

MAGIC and H.E.S.S. detect VHE gamma rays from the blazar OT081 for the first time: a deep multiwavelength study

https://pos.sissa.it/395/815/pdfPublished versio

Broadband Multi-wavelength Properties of M87 during the 2017 Event Horizon Telescope Campaign

Abstract: In 2017, the Event Horizon Telescope (EHT) Collaboration succeeded in capturing the first direct image of the center of the M87 galaxy. The asymmetric ring morphology and size are consistent with theoretical expectations for a weakly accreting supermassive black hole of mass ∼6.5 × 109 M ⊙. The EHTC also partnered with several international facilities in space and on the ground, to arrange an extensive, quasi-simultaneous multi-wavelength campaign. This Letter presents the results and analysis of this campaign, as well as the multi-wavelength data as a legacy data repository. We captured M87 in a historically low state, and the core flux dominates over HST-1 at high energies, making it possible to combine core flux constraints with the more spatially precise very long baseline interferometry data. We present the most complete simultaneous multi-wavelength spectrum of the active nucleus to date, and discuss the complexity and caveats of combining data from different spatial scales into one broadband spectrum. We apply two heuristic, isotropic leptonic single-zone models to provide insight into the basic source properties, but conclude that a structured jet is necessary to explain M87’s spectrum. We can exclude that the simultaneous γ-ray emission is produced via inverse Compton emission in the same region producing the EHT mm-band emission, and further conclude that the γ-rays can only be produced in the inner jets (inward of HST-1) if there are strongly particle-dominated regions. Direct synchrotron emission from accelerated protons and secondaries cannot yet be excluded

Atmospheric monitoring in MAGIC and data corrections

A method for analyzing returns of a custom-made “micro”-LIDAR system, operated alongside the two MAGIC telescopes is presented. This method allows for calculating the transmission through the atmospheric boundary layer as well as thin cloud layers. This is achieved by applying exponential fits to regions of the back-scattering signal that are dominated by Rayleigh scattering. Making this real-time transmission information available for the MAGIC data stream allows to apply atmospheric corrections later on in the analysis. Such corrections allow for extending the effective observation time of MAGIC by including data taken under adverse atmospheric conditions. In the future they will help reducing the systematic uncertainties of energy and flux

Nitrous Oxide, N2O: Spectroscopic Investigations for Future Lidar Applications

Nitrous Oxide, N2O, is the third most important GHG contributing to human-induced global warming, after carbon dioxide and methane. Its growth rate is constantly increasing and its global warming potential is estimated to be 273 times higher than that of CO2 over 100 years. The major anthropogenic source is nitrogen fertilization in croplands. Soil N2O emissions are increasing due to interactions between nitrogen inputs and global warming, constituting an emerging positive N2O-climate feedback. The recent increase in global N2O emissions exceeds even the most pessimistic emission trend scenarios developed by the IPCC, underscoring the urgency of mitigating N2O emissions (Global Carbon Project, 2020). Estimating N2O emissions from agriculture is inherently complex and comes with a high degree of uncertainty, due to variability in weather and soil characteristics, in agricultural management options and in the interaction of field management with environmental variables. Further sources of N2O are processes in the chemical industry and combustion processes. The sink of N2O in the stratosphere increases the NOx concentration which catalytically depletes ozone. Better N2O measurements thus are urgently needed, particularly by means of remote sensing. Airborne or satellite based N2O lidar remote sensing combines the advantages of high measurement accuracy, large-area coverage and nighttime measurement capability. Past initial feasibility studies revealed that Integrated-Path Differential-Absorption (IPDA) lidar providing vertical column concentrations of N2O would be the method of choice. In this current study we use the latest HITRAN spectroscopic data in order to identify appropriate N2O absorption lines in the wavelength region between 2.9 and 4.6 µm. The infrared spectral region challenges both lidar transmission and detection options. On the transmitter side, the use of optical parametric conversion schemes looks promising, while HgCdTe avalanche photodiode (APD), superconducting nanowire single-photon (SNSPD) or upconversion detectors (UCD) could offer high-efficiency low-noise signal detection. These options are implemented into a lidar simulation model in order to identify the optimal lidar system configuration for measuring N2O from aircraft or satellite using state-of-the-art technology