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

Search for very-high-energy emission from pulsars and tests of Lorentz invariance using the MAGIC telescopes

Desde su descubrimiento, los púlsares han sido un laboratorio esencial en muchas ramas diferentes de la astrofísica y la física porque son objetos ultra densos, de giro rápido y emisores de múltiples longitudes de onda. Han ampliado nuestra comprensión de la evolución estelar y los estudios de objetos compactos, así como temas de física fundamental como la relatividad general y el modelo estándar. Los mecanismos de emisión de los púlsares aún no se conocen del todo. Aunque la historia de los estudios de púlsares en bandas de radio se remonta a la década de 1960, los estudios de púlsares con rayos gamma de muy alta energía son relativamente más recientes. Por lo tanto, detectar nuevos púlsares y aumentar nue stro conocimiento sobre los descubiertos juega un papel crucial en la astrofísica de púlsares. Los telescopios Cherenkov son excelentes sistemas para estudiar fotones de muy alta energía provenientes de los púlsares. Debido al hecho de que los púlsares son fuentes débiles en comparación con otras fuentes de rayos gamma, como los núcleos galácticos activos o las explosiones de rayos gamma, la calidad de los datos es de gran importancia para los resultados del análisis de datos, y uno de los efectos más considerables proviene de la condiciones atmosféricas. Por lo tanto, los sistemas de escaneo atmosférico como los Raman LIDAR que trabajan con los telescopios Cherenkov son sistemas cruciales para el análisis de datos. El enfoque principal de este estudio son los estudios de púlsar con los telescopios MAGIC y el uso de los datos para las pruebas de Violación de Invariancia de Lorentz (LIV). Para ello, se han analizado y utilizado diez años de datos de Crab Pulsar para la prueba LIV. Además, se ha realizado por primera vez una búsqueda de emisión de VHE de un púlsar de milisegundos, PSR J0218 + 4232, en el modo estereoscópico de los telescopios MAGIC. Se ha analizado e incluido en este estudio una fuente BL Lac intermedia, 3C66A, en el campo de visión del púlsar de milisegundos. Además del análisis de la fuente astrofísica, en este estudio también se incluyeron algunos resultados de las pruebas del CTA Pathfinder Raman LIDAR y las pruebas de puesta en servicio. La tesis sigue este esquema: El capítulo 1 es una introducción a los púlsares. Se discuten los mecanismos de formación, evolución y emisión. El Capítulo 2 ofrece una descripción general de los estudios de Violación de In variancia de Lorentz con púlsares. El Capítulo 3 describe la técnica IACT, los telescopios MAGIC y el análisis de datos. El capítulo 4 ofrece una descripción general de los sistemas LIDAR utilizados para la caracterización atmosférica trabajando con los telescopios Cherenkov e incluye algunos resultados de las pruebas del Barcelona Raman LIDAR, "pathfinder" del "Cherenkov Telescope Array". El capítulo 5 se centra en la búsqueda de emisiones de VHE del púlsar de milise gundos PSR J0218 + 4232 y el análisis de la fuente IBL Lac 3C66A en el campo de visión. El Capítulo 6 se centra en el análisis de datos del Crab Pulsar 2009-2020 y el estudio sobre la emisión más alta hasta energías TeV. El Capítulo 7 muestra los resultados de la prueba LIV realizada con los datos mostrados en el capítulo anterior. Finalmente, se discutirán las observaciones finales y los aspectos futuros.Since their discovery, pulsars have been an essential laboratory in many different astrophysics and physics branches because they are ultra-dense, fast spinning, and multiwavelength emitting objects. They have widened our understanding of stellar evolution and compact object studies, as well as fundamental physics topics such as General Relativity and the Standard Model. The emission mechanisms of pulsars are still not fully known. Although the history of pulsar studies in radio bands starts back in the 1960s, very high-energy (VHE) gamma-ray studies of pulsars are relatively newer. Therefore detecting new pulsars and increasing our knowledge on the discovered ones plays a crucial role in pulsar astrophysics. Cherenkov telescopes are excellent systems for studying very high-energy photons coming from the pulsars. Due to the fact that pulsars are faint sources compared to the other gamma-ray sources such as active galactic nuclei or gamma-ray bursts, data quality is of great importance for the data analysis results, and one of the most considerable effects comes from the atmospheric conditions. Therefore atmospheric scan systems such as Raman LIDARs working with the Cherenkov telescopes are supportive systems for the data analysis. The primary focus of this study is pulsar studies with the MAGIC telescopes and using the data for Lorentz Invariance Violation (LIV) tests. For this purpose, ten years of Crab Pulsar data has been analyzed and used for the LIV test. Moreover, a VHE emission search of a millisecond pulsar, PSR J0218+4232, has been performed for the first time in the stereoscopic mode of MAGIC telescopes. An intermediate BL Lac source, 3C66A, in the field of view (FoV) of the millisecond pulsar has been analyzed and included in this study. Apart from the astrophysical source analysis, some CTA pathfinder Raman LIDAR tests results and commissioning tests were included in this study, too. The thesis follows this outline: Chapter 1 is an introduction to Pulsars. The formation, evolution, and emission mechanisms are explained. Chapter 2 gives an overview of Lorentz Invariance Violation studies with pulsars. Chapter 3 describes the IACT technique, MAGIC Telescopes, and the data analysis. Chapter 4 gives an overview of LIDAR systems used for atmospheric characterization working with Cherenkov Telescopes and includes some tests results of the Barcelona Raman LIDAR, Cherenkov Telescope Array's path. Chapter 5 focuses on searching VHE emission from the millisecond pulsar PSR J0218+4232 and analysis of IBL Lac source 3C66A in the FoV. Chapter 6 focuses on 2009-2020 Crab Pulsar data analysis and the study on the highest emission up to TeV energies. Chapter 7 shows the results of the LIV test performed with the data shown in the previous chapter. Finally, the conclusion remarks, and future aspects will be discussed

The blazar TXS 0506+056 associated with a high-energy neutrino: insights into extragalactic jets and cosmic ray acceleration

International audienceA neutrino with energy ∼290 TeV, IceCube-170922A, was detected in coincidence with the BL Lac object TXS 0506+056 during enhanced gamma-ray activity, with chance coincidence being rejected at ∼3σ level. We monitored the object in the very-high-energy (VHE) band with the Major Atmospheric Gamma-ray Imaging Cherenkov (MAGIC) telescopes for ∼41 hr from 1.3 to 40.4 days after the neutrino detection. Day-timescale variability is clearly resolved. We interpret the quasi-simultaneous neutrino and broadband electromagnetic observations with a novel one-zone lepto-hadronic model, based on interactions of electrons and protons co-accelerated in the jet with external photons originating from a slow-moving plasma sheath surrounding the faster jet spine. We can reproduce the multiwavelength spectra of TXS 0506+056 with neutrino rate and energy compatible with IceCube-170922A, and with plausible values for the jet power of . The steep spectrum observed by MAGIC is concordant with internal γγ absorption above ∼100 GeV entailed by photohadronic production of a ∼290 TeV neutrino, corroborating a genuine connection between the multi-messenger signals. In contrast to previous predictions of predominantly hadronic emission from neutrino sources, the gamma-rays can be mostly ascribed to inverse Compton upscattering of external photons by accelerated electrons. The X-ray and VHE bands provide crucial constraints on the emission from both accelerated electrons and protons. We infer that the maximum energy of protons in the jet comoving frame can be in the range ∼1014 – 1018 eV

Intensity interferometry with the MAGIC telescopes

Due to their large mirror size, fast response to single photons, sensitivity and telescope baselines in the order of 100 m, Imaging Atmospheric Cherenkov Telescopes are ideally suited to perform intensity interferometry observations. In 2019 a test readout setup was installed in the two 17-m diameter MAGIC telescopes to allow performing interferometry measurements with them. The first on-sky measurements were able to detect correlated intensity fluctuations consistent with the stellar diameters of three different stars: Adhara (n CMa), Benetnasch ([ UMa) and Mirzam (V CMa). After the upgrade of the setup in 2021, MAGIC is now equipped with a high-duty-cycle intensity interferometer, already in operation. A technical description of the interferometer and first performance results obtained by measuring several known stellar diameter are presented

Extreme blazars under the eyes of MAGIC

Extreme high-frequency-peaked BL Lac objects (EHBLs) are the most energetic persistent sources in the universe. This contribution reports on long-term observing campaigns of tens of EHBLs that have been organized by the MAGIC collaboration to enlarge their population at VHE and understand the origin of their extreme properties. EHBLs are characterized by a spectral energy distribution (SED) featuring a synchrotron peak energy above 1 keV. Several EHBLs display a hard spectral index at very high energies (VHE; E > 100 GeV), suggesting a gamma-ray SED component peaking significantly above 1 TeV. Such extreme properties are challenging current standard emission and acceleration mechanisms. Recent studies have also unveiled intriguing disparities in the temporal characteristics of EHBLs. Some sources seem to display a persistent EHBL behaviour, while others belong to the EHBL family only temporarily. Here, we present recent results of the first hard-TeV EHBL catalog. The MAGIC observations are accompanied by an extensive multiwavelength coverage to obtain an optimal determination of the SED. This allow us to investigate leptonic and hadronic scenarios for the emission. We also present the recent detection of the EHBL RX J0812.0+0237 in the VHE band by MAGIC. Finally, we discuss a broad multiwavelength campaign on the BL Lac type object 1ES 2344+514, which showed intermittent EHBL characteristics in August 2016