Proceedings of High Energy Astrophysics in Southern Africa — PoS(HEASA2018)最新文献_第2页

The intrinsic nuclear luminosities of a new sample of medium-distance Seyfert galaxies 一个中距离塞弗特星系新样本的本征核光度

Proceedings of High Energy Astrophysics in Southern Africa — PoS(HEASA2018) Pub Date : 2019-07-29 DOI: 10.22323/1.338.0015

H. Winkler

{"title":"The intrinsic nuclear luminosities of a new sample of medium-distance Seyfert galaxies","authors":"H. Winkler","doi":"10.22323/1.338.0015","DOIUrl":"https://doi.org/10.22323/1.338.0015","url":null,"abstract":"The ﬂux variation gradient technique has enabled the determination of the nuclear colours of many well-known AGN by comparing the total galaxy ﬂuxes at different epochs. It is now established that the intrinsic AGN nuclear colours in the optical are relatively constant throughout the class. This means that measured deviations from these colours are an indicator of partial obscuration and the resulting reddening of the nucleus. The degree of nuclear reddening determined in this manner therefore enables the estimation of the light loss due to circumnuclear matter. From this the intrinsic nuclear luminosity may be calculated. The author is engaged in a long-term observational campaign that seeks to secure photometric magnitudes of a large sample of comparatively rarely studied Seyfert galaxies during two epochs spaced apart by a period of typically 20 years. Initial results conﬁrm that most objects varied sufﬁciently between the two epochs to compute the ﬂux variation gradients, and hence to determine their intrinsic optical luminosity. This paper discusses the analytical processes necessary to maximise the accuracy of the nuclear luminosity determination. This includes the description of more sophisticated procedures to improve the nuclear component’s deconvolution and reddening, and the observational tests performed for this purpose.","PeriodicalId":192581,"journal":{"name":"Proceedings of High Energy Astrophysics in Southern Africa — PoS(HEASA2018)","volume":"15 4","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114007623","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

Did Dark Matter Kill the Dinosaurs? 暗物质杀死了恐龙吗?

Proceedings of High Energy Astrophysics in Southern Africa — PoS(HEASA2018) Pub Date : 2019-07-29 DOI: 10.22323/1.338.0032

M. Sarkis, G. Beck

{"title":"Did Dark Matter Kill the Dinosaurs?","authors":"M. Sarkis, G. Beck","doi":"10.22323/1.338.0032","DOIUrl":"https://doi.org/10.22323/1.338.0032","url":null,"abstract":"Potential links between astrophysical sources, such as Gamma-Ray Bursts (GRBs) and Supernovae (SN), and mass extinction events on Earth are of interest in the historical trajectory of life on our planet. There are strong arguments to suggest that these astrophysical sources can have several destructive effects, including depletion of atmospheric ozone and an increase in the radiation dose received by living organisms. Recent atmospheric simulations have shown that the fluence from a typical GRB at a distance of ∼2 kpc has the potential to deplete up to 38% of global atmospheric ozone, with as much as 74% localised depletion. In this work, it is hypothesised that the annihilation of Weakly Interacting Massive Particles (WIMPs) in the core of a clump of dark matter that passes through our solar system could be the source of a gamma-ray fluence at the surface of the Earth that is of a similar magnitude to nearby GRBs. It was found that extremely dense clumps of dark matter, so-called Ultra-compact Minihalos, can produce a much larger fluence, potentially enhancing this effect. The implications of this would be a large flux of solar UV-B radiation able to penetrate the atmosphere, leading to widespread cancer formation and DNA damage, as well as significant changes to climate. These effects are compatible with extinction patterns found from the Late Ordovician extinction event that occurred ∼443 My ago.","PeriodicalId":192581,"journal":{"name":"Proceedings of High Energy Astrophysics in Southern Africa — PoS(HEASA2018)","volume":"14 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":"131618351","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

An analytical hadronic synchrotron mirror model forblazars - Application to 3C279 blazars分析强子同步加速器镜面模型-在3C279上的应用

Proceedings of High Energy Astrophysics in Southern Africa — PoS(HEASA2018) Pub Date : 2019-07-29 DOI: 10.22323/1.338.0024

L. Oberholzer, M. Böttcher

引用次数: 0

Modelling the polarisation signatures detected from the first white dwarf pulsar AR Sco. 模拟从第一颗白矮星脉冲星AR Sco探测到的偏振特征。

Proceedings of High Energy Astrophysics in Southern Africa — PoS(HEASA2018) Pub Date : 2019-07-02 DOI: 10.22323/1.338.0027

L. Plessis, Z. Wadiasingh, C. Venter, A. Harding, S. Chandra, P. Meintjies

{"title":"Modelling the polarisation signatures detected from the first white dwarf pulsar AR Sco.","authors":"L. Plessis, Z. Wadiasingh, C. Venter, A. Harding, S. Chandra, P. Meintjies","doi":"10.22323/1.338.0027","DOIUrl":"https://doi.org/10.22323/1.338.0027","url":null,"abstract":"Marsh et al. detected radio and optical pulsations from the binary system AR Scorpii (AR Sco). This system, with an orbital period of 3.56 h, is composed of a cool, low-mass star and a white dwarf with a spin period of 1.95 min. Optical observations by Buckley et al. showed that the polarimetric emission from the white dwarf is strongly linearly polarised ( up to $sim40%$) with periodically changing intensities. This periodic non-thermal emission is thought to be powered by the highly magnetised ($ 5 times 10^{8} $ G) white dwarf that is spinning down. The morphology of the polarisation signal, namely the position angle plotted against the phase angle, is similar to that seen in many radio pulsars. In this paper, we demonstrate that we can fit the traditional pulsar rotating vector model to the optical position angle. We used a Markov-chain-Monte-Carlo technique to find the best fit for the model yielding a magnetic inclination angle of $alpha = (86.6^{+3.0}_{-2.8})^{circ}$ and an observer angle of $zeta = (60.5^{+5.3}_{-6.1})^{circ}$. This modelling supports the scenario that the synchrotron emission originates above the polar caps of the white dwarf pulsar and that the latter is an orthogonal rotator.","PeriodicalId":192581,"journal":{"name":"Proceedings of High Energy Astrophysics in Southern Africa — PoS(HEASA2018)","volume":"45 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132004369","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

Simultaneous Fitting of the Spectral Energy Density, Energy-dependent Size, and X-ray Spectral Index vs.Radius of The Young Pulsar Wind Nebula PWNG0.9+0.1 年轻脉冲星风星云PWNG0.9+0.1的光谱能量密度、能量依赖大小和x射线光谱指数与半径的同时拟合

Proceedings of High Energy Astrophysics in Southern Africa — PoS(HEASA2018) Pub Date : 2019-05-17 DOI: 10.22323/1.338.0005

C. V. Rensburg, C. Venter

{"title":"Simultaneous Fitting of the Spectral Energy Density, Energy-dependent Size, and X-ray Spectral Index vs.Radius of The Young Pulsar Wind Nebula PWNG0.9+0.1","authors":"C. V. Rensburg, C. Venter","doi":"10.22323/1.338.0005","DOIUrl":"https://doi.org/10.22323/1.338.0005","url":null,"abstract":"We have constructed and calibrated a spherically-symmetric, spatially-dependent particle transport and emission code for young pulsar wind nebulae (PWNe). This code predicts the spectral energy distribution (SED) of the radiation spectrum at different positions in a PWN, thus yielding the surface brightness vs. radius and hence the nebular size as function of energy. It also predicts the X-ray spectral index at different radii from the central pulsar, depending on the nebular B-field profile and particle transport properties. We apply the code to PWN G0.9+0.1 and fit these three functions concurrently, thus maximizing the constraining power of the data. We use a Markov-chain-Monte-Carlo (MCMC) method to find best-fit parameters with accompanying errors. This approach should allow us to better probe the spatial behaviour of the bulk-particle motion, the $B$-field and diffusion coefficient, and break degeneracies between different model parameters. Our model will contribute to interpreting results by the future Cherenkov Telescope Array (CTA) that will yield many more discoveries plus morphological details of very-high-energy Galactic PWNe.","PeriodicalId":192581,"journal":{"name":"Proceedings of High Energy Astrophysics in Southern Africa — PoS(HEASA2018)","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-05-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125264004","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

Accretion onto deformed black holes via pseudo–Newtonian potentials 通过伪牛顿势对变形黑洞的吸积

Proceedings of High Energy Astrophysics in Southern Africa — PoS(HEASA2018) Pub Date : 2019-04-23 DOI: 10.22323/1.338.0001

A. John, Chris Stevens

引用次数: 0

Differential Observation Techniques for the SZE-21cm and radio sources SZE-21cm和射电源的差分观测技术

Proceedings of High Energy Astrophysics in Southern Africa — PoS(HEASA2018) Pub Date : 2019-03-29 DOI: 10.22323/1.338.0006

C. Takalana, P. Marchegiani, S. Colafrancesco

{"title":"Differential Observation Techniques for the SZE-21cm and radio sources","authors":"C. Takalana, P. Marchegiani, S. Colafrancesco","doi":"10.22323/1.338.0006","DOIUrl":"https://doi.org/10.22323/1.338.0006","url":null,"abstract":"The SZE-21cm has been proposed as an alternative probe for the Dark Ages (DA) and the Epoch of Reionization (EoR). The effect is produced when photons of the 21cm background are inverse Compton (up-)scattered by electrons residing in hot plasma of cosmic structures and can be studied through differential observations of the large-scale structure, towards and away a region of the radio sky containing the cosmic structure of interest. This work makes use of the 21cmFAST code to simulate low frequency radio observations of a galaxy cluster from which we then extract the SZE-21cm signal. We further explore uses of the differential technique to radio observations of active radio galaxies using radio observations from the MWA GLEAM survey. The differential techniques this work studies enable us to extract the SZE-21cm signal from simulated galaxy cluster observations, which can then be used to obtain the global features of the 21cm signal during the DA and EoR. The technique shows further benefits in source extraction and characterisation, and feature enhancement in radio observations particularly for low-surface brightness and extended radio sources.","PeriodicalId":192581,"journal":{"name":"Proceedings of High Energy Astrophysics in Southern Africa — PoS(HEASA2018)","volume":"235 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132507398","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

Blazar variability -- expect the unexpected Blazar的可变性——期待意想不到的事情

Proceedings of High Energy Astrophysics in Southern Africa — PoS(HEASA2018) Pub Date : 2019-03-06 DOI: 10.22323/1.338.0033

M. Zacharias

引用次数: 1

Dark matter gets DAMPE at high energies 暗物质在高能量下受到阻尼

Proceedings of High Energy Astrophysics in Southern Africa — PoS(HEASA2018) Pub Date : 2019-02-20 DOI: 10.22323/1.338.0013

G. Beck, S. Colafrancesco

引用次数: 0

Possible Dark Matter annihilation in the galaxy cluster A520 A520星系团中可能存在的暗物质湮灭

Proceedings of High Energy Astrophysics in Southern Africa — PoS(HEASA2018) Pub Date : 2018-08-01 DOI: 10.22323/1.338.0030

P. Marchegiani, S. Colafrancesco, N. Khanye

引用次数: 0