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Proceedings of High Energy Astrophysics in Southern Africa — PoS(HEASA2018)最新文献

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Constraining the star formation history withFermi-LAT observations of the gamma-ray opacity of the universe 约束恒星形成历史的费米- lat观测宇宙的伽马射线不透明度
Proceedings of High Energy Astrophysics in Southern Africa — PoS(HEASA2018) Pub Date : 2019-07-29 DOI: 10.22323/1.338.0003
Ashlynn Merial Le Ray, A. Chen
{"title":"Constraining the star formation history withFermi-LAT observations of the gamma-ray opacity of the universe","authors":"Ashlynn Merial Le Ray, A. Chen","doi":"10.22323/1.338.0003","DOIUrl":"https://doi.org/10.22323/1.338.0003","url":null,"abstract":"The star formation history (SFH) of the Universe is of fundamental importance to cosmology, not only to galactic formation itself but also for ongoing efforts to determine cosmological parameters and matter content of the Universe [1]. Measurements of the extragalactic background light (EBL) as a function of redshift can constrain models of the SFH, including the initial mass function(IMF) and dust extinction [1]. The gamma-ray spectra of AGN allows us to study the extragalactic background light (EBL) through γ − γ absorption of high-energy photons. In this work, we will produce constraints on models of SFH using a sample of AGN observed by the Fermi-LAT instrument by investigating the imprint of the EBL on the observed spectra of high-redshift Fermi-LAT AGN above ∼ 10 GeV.","PeriodicalId":192581,"journal":{"name":"Proceedings of High Energy Astrophysics in Southern Africa — PoS(HEASA2018)","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125162122","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
VHE gamma-ray emission from radio galaxies 射电星系的甚高频伽玛射线发射
Proceedings of High Energy Astrophysics in Southern Africa — PoS(HEASA2018) Pub Date : 2019-07-29 DOI: 10.22323/1.338.0010
D. Prokhorov
{"title":"VHE gamma-ray emission from radio galaxies","authors":"D. Prokhorov","doi":"10.22323/1.338.0010","DOIUrl":"https://doi.org/10.22323/1.338.0010","url":null,"abstract":"","PeriodicalId":192581,"journal":{"name":"Proceedings of High Energy Astrophysics in Southern Africa — PoS(HEASA2018)","volume":"57 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123039708","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Polarization of Gravitational Waves from Binary Systems 双星系统引力波的极化
Proceedings of High Energy Astrophysics in Southern Africa — PoS(HEASA2018) Pub Date : 2019-07-29 DOI: 10.22323/1.338.0029
Lutendo Nyadzani, S. Razzaque
{"title":"Polarization of Gravitational Waves from Binary Systems","authors":"Lutendo Nyadzani, S. Razzaque","doi":"10.22323/1.338.0029","DOIUrl":"https://doi.org/10.22323/1.338.0029","url":null,"abstract":"Gravitational waves (GWs) are one of the key predictions of Einstein’s theory of general relativity (GR). Scientists have been looking for evidence of GWs since their prediction by Einstein in 1916. The first direct detection was achieved by LIGO in 2015, 100 years after their prediction, from merging of two black holes in a binary into one. According to GR gravitational waves have two independent polarization states. In this paper, we study the power radiated and the strain of GW along the two polarization states from a compact binary system with its general orbital properties.","PeriodicalId":192581,"journal":{"name":"Proceedings of High Energy Astrophysics in Southern Africa — PoS(HEASA2018)","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115917318","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 1
Exploiting High-Energy Polarization in Blazars 利用耀变体的高能偏振
Proceedings of High Energy Astrophysics in Southern Africa — PoS(HEASA2018) Pub Date : 2019-07-29 DOI: 10.22323/1.338.0025
L. Dreyer, M. Böttcher
{"title":"Exploiting High-Energy Polarization in Blazars","authors":"L. Dreyer, M. Böttcher","doi":"10.22323/1.338.0025","DOIUrl":"https://doi.org/10.22323/1.338.0025","url":null,"abstract":"The spectral energy distributions (SEDs) and variability of astrophysical sources can be modeled in many different ways, in particular, the production of X-rays and γ-rays in the SEDs of blazars. High-energy polarimetry can probe the most active jet regions with the most efficient particle accelerations, and thus serve as a powerful tool to distinguish between models. We summarize the scientific potential and model predictions for high-energy polarization of blazar jets. The advantages of using Monte Carlo methods to study high-energy polarization from anisotropic Compton scattering, by thermal and non-thermal particles, will be discussed. This will reinforce the use of measurements of polarization signatures to suggest observational strategies in future projects and to use polarization as a diagnostic to distinguish between leptonic and hadronic highenergy emission from blazars.","PeriodicalId":192581,"journal":{"name":"Proceedings of High Energy Astrophysics in Southern Africa — PoS(HEASA2018)","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128428980","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 1
Inverse Compton radiation from GRB afterglows in the VHE range 伽玛暴余辉在VHE范围内的逆康普顿辐射
Proceedings of High Energy Astrophysics in Southern Africa — PoS(HEASA2018) Pub Date : 2019-07-29 DOI: 10.22323/1.338.0020
J. Joshi, S. Razzaque
{"title":"Inverse Compton radiation from GRB afterglows in the VHE range","authors":"J. Joshi, S. Razzaque","doi":"10.22323/1.338.0020","DOIUrl":"https://doi.org/10.22323/1.338.0020","url":null,"abstract":"The observation of Gamma-ray bursts (GRBs) can be classified into prompt and afterglow emission. The prompt emission is observed for up to 100s of seconds after the trigger of the event while a delayed and long-lasting afterglow emission is followed after this phase. The prompt emission dominates in the γ -rays (keV-MeV-GeV), while the afterglow emission mainly occurs in X-ray, UV, optical, radio wavelengths and possibly in γ -rays. In this work, we study the signature of inverse Compton emission in the afterglow emission of GRBs. We consider the expansion of an adiabatic blast wave into a constant density medium and use the observation of GRB 130427A afterglow to constrain the model parameters. The flux produced via inverse-Compton mechanism have been discussed and also possible detection by the Cherenkov Telescope Array mainly in the range 30 GeV- 1 TeV have been discussed.","PeriodicalId":192581,"journal":{"name":"Proceedings of High Energy Astrophysics in Southern Africa — PoS(HEASA2018)","volume":"43 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128173030","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Particle-in-cell simulations of shear boundary layersin relativistic jets 相对论射流中剪切边界层的粒子胞内模拟
Proceedings of High Energy Astrophysics in Southern Africa — PoS(HEASA2018) Pub Date : 2019-07-29 DOI: 10.22323/1.338.0046
T. Chand, M. Böttcher, P. Kilian
{"title":"Particle-in-cell simulations of shear boundary layersin relativistic jets","authors":"T. Chand, M. Böttcher, P. Kilian","doi":"10.22323/1.338.0046","DOIUrl":"https://doi.org/10.22323/1.338.0046","url":null,"abstract":"The supermassive black holes in the centres of active galaxies (AGN) eject powerful relativistic jets which propagate over kpc scales, showing no significant momentum loss. Both observational evidence as well as theoretical considerations from MHD simulations of jets suggest that they are radially stratified, with a fast inner spine surrounded by a slower-moving outer sheath. The resulting relativistic shear layers are a prime candidate for the site of relativistic particle acceleration in the jets of AGN and gamma-ray bursts (GRBs). We present results of particle-in-cell simulations of magnetic-field generation in the relativistic shear boundary layers of jets in AGN and GRBs. We outline future plans to include a self-consistent calculation of radiation produced by the particles accelerated at these shear boundary layers.","PeriodicalId":192581,"journal":{"name":"Proceedings of High Energy Astrophysics in Southern Africa — PoS(HEASA2018)","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115009457","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
The ASTRI Dual-Mirror Small-Size Cherenkov Telescope 应科院双镜小尺寸切伦科夫望远镜
Proceedings of High Energy Astrophysics in Southern Africa — PoS(HEASA2018) Pub Date : 2019-07-29 DOI: 10.22323/1.338.0008
C. Arcaro, Cta Astri
{"title":"The ASTRI Dual-Mirror Small-Size Cherenkov Telescope","authors":"C. Arcaro, Cta Astri","doi":"10.22323/1.338.0008","DOIUrl":"https://doi.org/10.22323/1.338.0008","url":null,"abstract":"The ASTRI dual-mirror small-size telescope (ASTRI-Horn) is an imaging atmospheric Cherenkov telescope that was developed by the Italian National Institute of Astrophysics (INAF) within the framework of the Cherenkov Telescope Array (CTA) project, the next-generation ground-based very-high-energy gamma-ray observatory. The CTA observatory will consist of two sites configured in two arrays of telescopes of different sizes. They will be located in the Northern and Southern Hemispheres to cover the full sky. ASTRI (Astrofisica con Specchi a Tecnologia replicante Italiana) is the Italian proposal for the small-size telescopes and its design is based on a Schwarzschild-Couder configuration. To fulfill the required plate scale, the camera is based on a new technology involving the use of Silicon-photomultipliers. With its wide field of view of 10 degrees, it is optimized for gamma-ray observations in the range from few TeV up to several tens of TeV. The ASTRI prototype is installed at Serra La Nave at 1735 m a.s.l. in Sicily, Italy, and is currently going through the science validation phase. A further development of the program foresees the construction of a set of nine ASTRI telescopes proposed as pathfinder for the CTA array. In this contribution, the main features of the ASTRI telescope will be described and an update on the latest news on the prototype activities and the mini-array will be presented.","PeriodicalId":192581,"journal":{"name":"Proceedings of High Energy Astrophysics in Southern Africa — PoS(HEASA2018)","volume":"91 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124665854","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
White Dwarf Pulsars as Possible Gamma-Ray Sources 白矮星脉冲星是可能的伽马射线源
Proceedings of High Energy Astrophysics in Southern Africa — PoS(HEASA2018) Pub Date : 2019-07-29 DOI: 10.22323/1.338.0037
P. Meintjes, Q. Kaplan, Krishna Kumar Singh, H. V. Heerden, F. Ramamonjisoa
{"title":"White Dwarf Pulsars as Possible Gamma-Ray Sources","authors":"P. Meintjes, Q. Kaplan, Krishna Kumar Singh, H. V. Heerden, F. Ramamonjisoa","doi":"10.22323/1.338.0037","DOIUrl":"https://doi.org/10.22323/1.338.0037","url":null,"abstract":"The newly discovered white dwarf binary system AR Scorpii (AR Sco) with its fascinating nonthermal dominated multi-frequency emission has sparked renewed interest in potential high energy gamma-ray emission from white dwarf pulsars. Recent studies revealed that the optical and X-ray components of the emission in AR Sco can be powered entirely by the spin-down luminosity of the white dwarf in the absence of any mass accretion in this system. The Spectral Energy Distribution (SED) below and above optical shows a clear indication of a non-thermal synchrotron component, with pulsed emission in optical and X-ray bands at the white dwarf spin period as well as a beat with the binary period. From an energy perspective the highly magnetic rotating white dwarf can accelerate particles to TeV energies. In this study, a search for high energy gamma-ray emission was conducted between 100 MeV - 500 GeV by analysing the newly available Fermi-LAT Pass 8 data with the new Fermi 1.0.1 Science Tools. We find low significance (4.89 s) integrated gamma-ray activity between 100 MeV - 500 GeV at a photon flux level of 1.076±0.318×10−8photons cm−2s−1 from the selected Region of Interest (ROI) centred on AR Sco’s position. However, the close-by unidentified source (∼ 0.576◦) 4FGLJ1623.7−2315 may also contribute to this emission. AR Sco’s location inside the Rho Ophiuchi (Rho Oph) molecular cloud complex combined with the poor spatial resolution of Fermi-LAT complicates any unambiguous identification of the source of low-level gamma-ray activity at the location that coincides with the position of AR Sco.","PeriodicalId":192581,"journal":{"name":"Proceedings of High Energy Astrophysics in Southern Africa — PoS(HEASA2018)","volume":"123 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122282400","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 1
Early Science with MeerKAT 早期科学与MeerKAT
Proceedings of High Energy Astrophysics in Southern Africa — PoS(HEASA2018) Pub Date : 2019-07-29 DOI: 10.22323/1.338.0041
S. Goedhart
{"title":"Early Science with MeerKAT","authors":"S. Goedhart","doi":"10.22323/1.338.0041","DOIUrl":"https://doi.org/10.22323/1.338.0041","url":null,"abstract":"The MeerKAT telescope celebrated its inauguration on 13 July 2018. While it is still being commissioned, and more correlator capabilities are expected to be rolled out, it has already demon-strated its potential to produce high dynamic range images with high fidelity, as shown with its inaugural image of the Galactic Centre. A technical overview of MeerKAT, its measured perfor-mance, current status and future capabilities is provided and first light images are shown.","PeriodicalId":192581,"journal":{"name":"Proceedings of High Energy Astrophysics in Southern Africa — PoS(HEASA2018)","volume":"66 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125867739","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Fits to the spectra of broad-line region of active galactic nuclei and opacities for two-photon pair production. 适用于活动星系核宽线区域的光谱和双光子对产生的不透明。
Proceedings of High Energy Astrophysics in Southern Africa — PoS(HEASA2018) Pub Date : 2019-07-29 DOI: 10.22323/1.338.0049
Mfuphi Ntshatsha, S. Razzaque, R. Britto
{"title":"Fits to the spectra of broad-line region of active galactic nuclei and opacities for two-photon pair production.","authors":"Mfuphi Ntshatsha, S. Razzaque, R. Britto","doi":"10.22323/1.338.0049","DOIUrl":"https://doi.org/10.22323/1.338.0049","url":null,"abstract":"Based on the spectral analysis of a composite Hubble Space Telescope (HST) spectrum made of 184 quasar data, we model the emission lines of the broad-line region (BLR) using analytic functions. For simplicity of this paper we neglect effects of the continuum emission, which may be resulting from emission by the accretion disk, and assume the emission of the BLR to be composed of the most prominent emission lines that form as a result of ionization and recombination processes within regions of the BLR. We also calculate opacities for gamma-rays propagating in the BLR and interacting with the modeled emission to produce electron-positron ($e^{pm}$) pairs.","PeriodicalId":192581,"journal":{"name":"Proceedings of High Energy Astrophysics in Southern Africa — PoS(HEASA2018)","volume":"59 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121753261","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
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