2,872 research outputs found
Physics from Time Variability of the VHE Blazar PKS 2155-304
No full textBlazars are the principal extragalactic sources of very high energy gamma-ray emission in the Universe. These objects constitute a sub-class of Active Galactic Nuclei whose
emission is dominated by Doppler boosted non-thermal radiation from plasma outflowing at relativistic speeds from the central engine. This plasma outflow happens in the
form of large-scale collimated structures called jets, which can extend for Mpc in length and transport energy from the central engine of the galaxy to the larger scale intergalac-
tic medium. Over thirty such sources have been discovered to date by ground-based gamma-ray telescopes such as H.E.S.S., and PKS 2155-304 is the prototypical southern-hemisphere representative of this population of objects.
In this thesis I have studied in detail some aspects of the temporal variability of the jet emission from PKS 2155-304, combining coordinated observations across the electromagnetic spectrum, from optical polarimetric measurements to X-ray and ground-based gamma-ray data. The temporal properties of the dataset allowed us to derive important physical information about the structure and emission mechanisms of the source and put constraints to the location of the sites of VHE emission and particle acceleration within the jet. We have also derived a sensitive statistical measure, called Kolmogorov distance,
which we applied to the large outburst observed from PKS 2155-304 in July 2006, to derive the most stringent constraints to date on limits for the violation of Lorentz invariance induced by quantum-gravity effects from AGN measurements
The Search For Pulsar Wind Nebulae in the Very High Energy Gamma-ray Regime
No full textThe aim of this Thesis is to study the development of pulsar wind nebulae in the TeV regime and in doing so uncover more sources which have as yet not been observed at these wavelengths. It is found that the extent of pulsar wind nebula in the TeV gamma-ray increases with its age while no developmental relationship is seen concerning
the luminosity or spectral index of the nebulae when observed in the TeV gamma-ray regime due to uncertainties in the measurements available.
TeV gamma-ray upper limits are calculated for several nebulae observed in the X-ray regime allowing the strength of their magnetic fields to be constrained but only one new source, which was previously confused with its companion, was discovered, the Eel Nebula.
Predictions of the fluxes of many of the sources for which upper limits are derived in this work have been calculated from observations of their emission in X-rays and some of these sources should be uncovered with the next generation CTA instrument
HESS Prize
No full textThomas was awarded the H.E.S.S. prize for his numerous and highly valuable contributions to H.E.S.S. in the past few years. He played, in particular, a major role in the maintenance of the H.E.S.S. data acquisition system (DAQ), and contributed to the development and implementation of a mono classification scheme for the large telescope (CT5), which is the basis of the low-energy real-time analysis (RTA). This classification provides the fast and reliable backbone for the mono RTA, used to trigger follow-up observations of known variable sources like Active Galactic Nuclei (AGN) or the recently detected Gamma Ray Burst GRB 190829A, and to search for emission from new transients. In addition to his technical contributions to the H.E.S.S. collaboration, he participated in the data analysis and interpretation of several astrophysical sources, such as the binary system PSR B1259-63 with H.E.S.S.-I and H.E.S.S.-II data. His most significant achievement in the past months was his role in the successful implementation of the HESS DAQ cluster upgrade, which will ensure continued stable and reliable operation of H.E.S.S. in the coming years
The status of the HESS project
No full textThe High Energy Stereoscopic System (HESS) is a system of four, 107 m2 mirror area, imaging Cherenkov telescopes under construction in the Khomas Highland of Namibia (1800 m asl). The HESS system is characterised by a low threshold (~100 GeV) and a ~1% Crab flux sensitivity resulting from the good angular resolution and background rejection provided by the stereoscopic technique.
The first two telescopes are operational and first results are reported here. The remaining two telescopes (of HESS Phase-I) will be commissioned early in 2004
Working internationally: Crossing the boundaries of wound care
No full textWound care is an international area of nursing and medical expertise, and one where care intervention is truly inter-professional. Clinicians in all countries can collaborate with one another to improve patient care, ensuring that the patient’s journey is based on the best available evidence and research. With the growth of social media, video conferencing, Skype™, and other forms of virtual communication, it has never been easier for clinicians to communicate with one another, and become immersed in collaborative research and the sharing of best practice. Here, the authors present an insight into an effective collaboration between nurse academics based at universities in the UK and Australia
TeV Analysis of a Source-rich Region with the HAWC Observatory: Is HESS J1809-193 a Potential Hadronic PeVatron?
No full textHESS J1809-193 is an unidentified TeV source, first detected by the High Energy Stereoscopic System (H.E.S.S.) collaboration. The emission originates in a source-rich region that includes several supernova remnants (SNRs) and pulsars including SNR G11.1+0.1, SNR G11.0-0.0, and the young radio pulsar PSR J1809-1917. Originally classified as a pulsar wind nebula candidate, recent studies show the peak of the TeV region overlapping with a system of molecular clouds. This resulted in the revision of the original leptonic scenario to look for alternate hadronic scenarios. Marked as a potential PeVatron candidate, this region has been studied extensively by H.E.S.S. due to its emission extending up to several tens of TeV. In this work, we use 2398 days of data from the High Altitude Water Cherenkov (HAWC) observatory to carry out a systematic source search of the HESS J1809-193 region. We were able to resolve emission detected as an extended component (modelled as a symmetric Gaussian with a 1σ radius of 0;21) with no clear cutoff at high energies and emitting photons up to 210 TeV. We model the multiwavelength observations for the region around HESS J1809-193 using a time-dependent leptonic model and a lepto-hadronic model. Our model indicates that both scenarios could explain the observed data within the region of HESS J1809-193
Flora Louise Hess Property
No full textEntry created by John H. Herrick January 7, 1974.John H. Herrick Archives: Documenting Structures at The Ohio State UniversityThe University Archives has determined that this item is of continuing value to OSU's history.The Flora Louise Hess Property was located at 2637 and 2703 Olentangy River Road. This property was never officially named by Board of Trustees action. It was purchased from Flora Louise and Elizabeth H. Hess. The author has never heard it referred to as anything, but the "Flora Louise Hess" property
Observation of the gamma-ray binary HESS J0632+057 with the H.E.S.S., MAGIC, and VERITAS telescopes - data release
No full textObservation of the gamma-ray binary HESS J0632+057 with the H.E.S.S., MAGIC, and VERITAS telescopes - data release The results of gamma-ray observations of the binary system HESS J0632+057 collected during 450 hours over 15 years, between 2004 and 2019, with the H.E.S.S., MAGIC, and VERITAS telescopes are presented in Observation of the gamma-ray binary HESS J0632+057 with the H.E.S.S., MAGIC, and VERITAS telescopes (ApJ, to be published). This repository provides access to all processed data presented in the publication in csv and ascii format. For a detailed description of analysis and data processing, see the associated primary publication. Please cite always the following primary reference when using these data: The Astrophysical Journal, 923:241 (30pp), 2021 December 20 arXiv:2109.11894 Data Publication Year: 2021 Citation: The VERITAS, MAGIC, and H.E.S.S. Collaborations (2021). Observation of the gamma-ray binary HESS J0632+057 with the HESS, MAGIC, and VERITAS telescopes - data release. DOI **[DOI to be added]** Additional information on the gamma-ray observatories: - H.E.S.S. ( https://www.mpi-hd.mpg.de/hfm/HESS/ ) and H.E.S.S. Auxiliary Data Page ( https://www.mpi-hd.mpg.de/hfm/HESS/pages/publications/auxiliary/auxinfo_hessj0632_HMVdata.html ) - MAGIC ( https://magic.mpp.mpg.de/ ) and MAGIC Data Page ( http://vobs.magic.pic.es/fits/ ) - VERITAS ( https://veritas.sao.arizona.edu/ ) and VERITAS Data Page ( https://github.com/VERITAS-Observatory/VERITAS-VTSCat ) This data repository is made available under the Public Domain Dedication and License v1.0 whose full text can be found at: http://opendatacommons.org/licenses/pddl/1.0/ ## List of data: (best to view with a markdown reader) 1. Gamma-ray and X-ray fluxes (Figures 2, 3, and 9): - Gamma-ray integral flux (>350 GeV) from H.E.S.S. observations: [Fig02_03_09/LightCurve-HESS.ecsv](Fig02_03_09/LightCurve-HESS.ecsv) - Gamma-ray integral flux (>350 GeV) from MAGIC observations: [Fig02_03_09/LightCurve-MAGIC.ecsv](Fig02_03_09/LightCurve-MAGIC.ecsv) - Gamma-ray integral flux (>350 GeV) from VERITAS observations: [Fig02_03_09/LightCurve-VERITAS.ecsv](Fig02_03_09/LightCurve-VERITAS.ecsv) - X-ray fluxes (0.3–10 keV) from Swift-XRT, Chandra, XMM, NuSTAR, Suzaku observations: [Fig02_03_09/LightCurve-XRay.ecsv](Fig02_03_09/LightCurve-XRay.ecsv) 2. Halpha observations (Figure 4): - Profile parameters of Halpha observations [Fig04/Halpha.ecsv](Fig04/Halpha.ecsv) 3. Gamma-ray - X-ray correlation (Figure 5): - Contemporaneous gamma-ray (>350 GeV) vs X-ray (0.3–10 keV) integral fluxes: [Fig05/LC-cross-Gamma-XRay.ecsv](Fig05/LC-cross-Gamma-XRay.ecsv) - Discrete cross-correlation function (DCF) between gamma- ray and X-ray data: [Fig05/DCF-cross-Gamma-XRay-HESSJ0632p057.ecsv](Fig05/DCF-cross-Gamma-XRay-HESSJ0632p057.ecsv) 4. Gamma-ray vs Optical and X-ray vs Optical correlations (Figure 6): - Halpha vs gamma-ray observations: [Fig06/Gamma-ray-Optical-Correlation.ecsv](Fig06/Gamma-ray-Optical-Correlation.ecsv) - Halpha vs X-ray observations: [Fig06/X-ray-Optical-Correlation.ecsv](Fig06/X-ray-Optical-Correlation.ecsv) 5. Spectral energy distributions (phase averaged; Figure 7 and 8) - SEDs from H.E.S.S. observations: [Fig07_08/HESS-phaserange04-spectrum.ecsv](Fig07_08/HESS-phaserange04-spectrum.ecsv), [Fig07_08/HESS-phaserange1-spectrum.ecsv](Fig07_08/HESS-phaserange1-spectrum.ecsv), [Fig07_08/HESS-phaserange2-spectrum.ecsv](Fig07_08/HESS-phaserange2-spectrum.ecsv), [Fig07_08/HESS-phaserange3-spectrum.ecsv](Fig07_08/HESS-phaserange3-spectrum.ecsv) - SEDs from MAGIC observations: [Fig07_08/MAGIC-phaserange04-spectrum.ecsv](Fig07_08/MAGIC-phaserange04-spectrum.ecsv), [Fig07_08/MAGIC-phaserange1-spectrum.ecsv](Fig07_08/MAGIC-phaserange1-spectrum.ecsv), [Fig07_08/MAGIC-phaserange2-spectrum.ecsv](Fig07_08/MAGIC-phaserange2-spectrum.ecsv) - SEDs from VERITAS observations: [Fig07_08/VERITAS-phaserange04-spectrum.ecsv](Fig07_08/VERITAS-phaserange04-spectrum.ecsv), [Fig07_08/VERITAS-phaserange1-spectrum.ecsv](Fig07_08/VERITAS-phaserange1-spectrum.ecsv), [Fig07_08/VERITAS-phaserange2-spectrum.ecsv](Fig07_08/VERITAS-phaserange2-spectrum.ecsv), [Fig07_08/VERITAS-phaserange3-spectrum.ecsv](Fig07_08/VERITAS-phaserange3-spectrum.ecsv) - SEDs from Swift-XRT observations: [Fig07_08/XRT-phaserange04-spectrum.ecsv](Fig07_08/XRT-phaserange04-spectrum.ecsv), [Fig07_08/XRT-phaserange1-spectrum.ecsv](Fig07_08/XRT-phaserange1-spectrum.ecsv), [Fig07_08/XRT-phaserange2-spectrum.ecsv](Fig07_08/XRT-phaserange2-spectrum.ecsv), [Fig07_08/XRT-phaserange3-spectrum.ecsv](Fig07_08/XRT-phaserange3-spectrum.ecsv) 6. Spectral energy distributions (orbit 9 and 17; Figure 10): - SEDs from VERITAS observations: [Fig10/VERITAS-MJD55585-55600-spectrum.ecsv](Fig10/VERITAS-MJD55585-55600-spectrum.ecsv), [Fig10/VERITAS-MJD55600-55603-spectrum.ecsv](Fig10/VERITAS-MJD55600-55603-spectrum.ecsv), [Fig10/VERITAS-MJD55614-55623-spectrum.ecsv](Fig10/VERITAS-MJD55614-55623-spectrum.ecsv), [Fig10/VERITAS-MJD55624-55631-spectrum.ecsv](Fig10/VERITAS-MJD55624-55631-spectrum.ecsv), [Fig10/VERITAS-MJD58136-spectrum.ecsv](Fig10/VERITAS-MJD58136-spectrum.ecsv), [Fig10/VERITAS-MJD58141-spectrum.ecsv](Fig10/VERITAS-MJD58141-spectrum.ecsv), [Fig10/VERITAS-MJD58142-spectrum.ecsv](Fig10/VERITAS-MJD58142-spectrum.ecsv), [Fig10/VERITAS-MJD58143-spectrum.ecsv](Fig10/VERITAS-MJD58143-spectrum.ecsv), [Fig10/VERITAS-MJD58153-58154-spectrum.ecsv](Fig10/VERITAS-MJD58153-58154-spectrum.ecsv) - SEDs from MAGIC observations: [Fig10/MAGIC-MJD55585-55600-spectrum.ecsv](Fig10/MAGIC-MJD55585-55600-spectrum.ecsv) - SEDs from Swift-XRT observations: [Fig10/XRT-MJD55585-55600-spectrum.csv](Fig10/XRT-MJD55585-55600-spectrum.csv), [Fig10/XRT-MJD55600-55603-spectrum.csv](Fig10/XRT-MJD55600-55603-spectrum.csv), [Fig10/XRT-MJD55614-55623-spectrum.csv](Fig10/XRT-MJD55614-55623-spectrum.csv), [Fig10/XRT-MJD55624-55631-spectrum.csv](Fig10/XRT-MJD55624-55631-spectrum.csv), [Fig10/XRT-MJD58142-spectrum.csv](Fig10/XRT-MJD58142-spectrum.csv), [Fig10/XRT-MJD58143-spectrum.csv](Fig10/XRT-MJD58143-spectrum.csv), [Fig10/XRT-MJD58152-spectrum.csv](Fig10/XRT-MJD58152-spectrum.csv), [Fig10/XRT-MJD58153-spectrum.csv](Fig10/XRT-MJD58153-spectrum.csv) 7. Contemporaneous X-ray and gamma-ray spectral energy distribution (Appendix D) - SEDs from VERITAS observations: [Auxiliary/VERITAS*](Auxiliary/
HESS - The High Energy Stereoscopic System
No full textProceedings edition under the auspices of the International Union of Pure and Applied Physics (IUPAP)The HESS collaboration is planning to build a large Imaging Atmospheric Cherenkov Telescope (IACT) arrayin the Southern Hemisphere in the Khomas Highland of Namibia. In its final stage, the HESS experiment willhave up to 16 telescopes each with a 80 m reflector and a high resolution camera. The schedule foresees tostart with scientific operation of the first 4-telescope subsystem in 2002 (Phase 1).HESS will have a detection threshold of about 40 GeV and an angular resolution of less than a few arcmin-utes. The flux sensitivity above 100 GeV of 1
HESS - The High Energy Stereoscopic System
No full textProceedings edition under the auspices of the International Union of Pure and Applied Physics (IUPAP)The HESS collaboration is planning to build a large Imaging Atmospheric Cherenkov Telescope (IACT) arrayin the Southern Hemisphere in the Khomas Highland of Namibia. In its final stage, the HESS experiment willhave up to 16 telescopes each with a 80 m reflector and a high resolution camera. The schedule foresees tostart with scientific operation of the first 4-telescope subsystem in 2002 (Phase 1).HESS will have a detection threshold of about 40 GeV and an angular resolution of less than a few arcmin-utes. The flux sensitivity above 100 GeV of 1
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