Proceedings of 5th Annual Conference on High Energy Astrophysics in Southern Africa — PoS(HEASA2017)最新文献

{"title":"SALT observations of X-ray transients","authors":"D. Buckley, P. Charles, A. Rajoelimanana, L. Townsend","doi":"10.22323/1.319.0004","DOIUrl":"https://doi.org/10.22323/1.319.0004","url":null,"abstract":"This paper presents some highlights of results on X-ray transients which have been obtained as part of the SALT Large Science Programme on transient followup. These include both High and Low Mass X-ray binaries with either accreting neutron stars or black holes, as well the white dwarf accreting Super Soft Sources.","PeriodicalId":366250,"journal":{"name":"Proceedings of 5th Annual Conference on High Energy Astrophysics in Southern Africa — PoS(HEASA2017)","volume":"17 3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130647264","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}

{"title":"Centaurus A: Hard X-ray and soft gamma-ray lightcurve correlation","authors":"I. Davids, M. Böttcher, Michael Backes","doi":"10.22323/1.319.0010","DOIUrl":"https://doi.org/10.22323/1.319.0010","url":null,"abstract":"Centaurus A (Cen A), powered by a 55 million solar mass supermassive black hole, has been intensively monitored in all accessible wavelength ranges of the electromagnetic spectrum. However, its gamma-ray flux, both in the H.E.S.S. very-high and the Fermi-LAT high-energy gamma-ray regimes, is relatively faint, hampering lightcurve analyses. Yet, the extensive long-term light curve data from Fermi-LAT and Swift-BAT (hard X-rays) allows for cross-correlation studies. We find a hint that X-ray emission from Cen A precedes the gamma rays by 25 days. If this lag is real and related to a gamma-gamma absorption effect in the broad-line region (BLR) around the central source, then we can constrain the size of the BLR using light-travel time arguments. These are first results of extended light curve correlation studies between high-energy gamma rays and X-rays from Cen A.","PeriodicalId":366250,"journal":{"name":"Proceedings of 5th Annual Conference on High Energy Astrophysics in Southern Africa — PoS(HEASA2017)","volume":"72 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127329313","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}

{"title":"Correlation between intrinsic peak luminosity and spectral peak energy for energetic Fermi GRBs","authors":"F. Dirirsa, S. Razzaque","doi":"10.22323/1.319.0002","DOIUrl":"https://doi.org/10.22323/1.319.0002","url":null,"abstract":"We select energetic GRBs detected by Fermi-LAT/GBM with known redshift and compute the correlation between the intrinsic peak luminosity ($L_{rm iso}$) and peak energy ($E_{rm i,p}$) of the $nu F_{nu}$ energy spectrum, known as the Yonetoku relation, in the 1 keV-10 MeV and 1 keV-30 MeV energy ranges. This correlation has the potential to make GRBs standard candles, similar to type Ia supernovae, but extending to high redshift. We explore parameters of the Lambda-Cold-Dark- Matter cosmological model at high redshift using Yonetoku relation for our sample of GRBs.","PeriodicalId":366250,"journal":{"name":"Proceedings of 5th Annual Conference on High Energy Astrophysics in Southern Africa — PoS(HEASA2017)","volume":"116 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117352616","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}

{"title":"Study of the Very High Energy emission of the Pulsar Wind Nebula in MSH 15-5 2","authors":"M. Tsirou, Y. Gallant, R. Terrier, R. Zanin","doi":"10.22323/1.319.0023","DOIUrl":"https://doi.org/10.22323/1.319.0023","url":null,"abstract":"The composite supernova remnant (SNR) MSH 15-52 comprises the bright X-ray pulsar wind nebula (PWN) of PSR B1509-58, surrounded by a shell which is a prominent object in the radio domain. H.E.S.S. had discovered extended very-high-energy (VHE) gamma-ray emission coincident with the PWN. With additional H.E.S.S. observations performed since the 2005 discovery paper, we study the properties of the emission in greater detail. We compare the VHE gamma-ray morphology of the PWN with that in synchrotron emission,obtained from archival X-ray observations, and discuss the implications on the magnetic field in the nebula. In particular, we discuss potential extended gamma-ray emission beyond the X-ray PWN, which may allow for conclusions on scenarios of PWNe as sources of cosmic ray electrons and positrons.","PeriodicalId":366250,"journal":{"name":"Proceedings of 5th Annual Conference on High Energy Astrophysics in Southern Africa — PoS(HEASA2017)","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128448443","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}

{"title":"One and two dimensional interpolation schemes of atmospheric muon neutrino flux models","authors":"Luis Salvador Miranda Palacios, S. Razzaque","doi":"10.22323/1.319.0026","DOIUrl":"https://doi.org/10.22323/1.319.0026","url":null,"abstract":"High-energy cosmic rays from all directions in space enter the Earth’s atmosphere. Interaction of \u0000these cosmic rays in the atmosphere produces secondary particles, including neutrinos. Generally \u0000the behavior of atmospheric neutrino flux is accepted as a power-law function type, although the \u0000shape varies at different energies and zenith angles. Due to these complications, the fluxes from \u0000detailed numerical calculations are reported in energy and zenith angle bins. In this article we \u0000propose new interpolation schemes for the flux in energy bins or energy and zenith angle bins \u0000for any power-law type function. We apply these schemes to the atmospheric muon neutrino flux \u0000model H3a QGSJET-II-4.","PeriodicalId":366250,"journal":{"name":"Proceedings of 5th Annual Conference on High Energy Astrophysics in Southern Africa — PoS(HEASA2017)","volume":"173 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132107978","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}

{"title":"Multi-wavelength observations of the unusual soft X-ray transient ASASSN-16oh","authors":"A. Rajoelimanana, P. Charles, D. Buckley, P. Meintjes","doi":"10.22323/1.319.0003","DOIUrl":"https://doi.org/10.22323/1.319.0003","url":null,"abstract":"We present our results from the analysis of optical and X-ray observations of the unusual X-ray transient ASASSN-16oh. The optical light curve revealed that at quiescence the source was fainter ($I$ = 20.3) and brightened up to $I$ = 15 during the outburst. The outburst light curve looks remarkably symmetric, with a total duration of $sim$300 days. The optical spectra from SALT show a strong emission line of He II $lambda$4686, He I and some weak Balmer lines. The X-ray and near ultraviolet fluxes correlate with the optical brightness. Such behavior is unusual amongst the known supersoft sources (hereafter SSS), and is difficult to assimilate into the standard model, but whatever the cause, a period of significantly enhanced mass transfer from the donor is required.","PeriodicalId":366250,"journal":{"name":"Proceedings of 5th Annual Conference on High Energy Astrophysics in Southern Africa — PoS(HEASA2017)","volume":"43 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-10-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115181027","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}

{"title":"Studies of optical/gamma-ray flares of blazar 4C+01.02: recent updates from the 2016-2017 observations","authors":"R. Britto, M. Böttcher, H. Schutte, A. Falcone, J. P. Marais, B. V. Soelen, D. Buckley","doi":"10.22323/1.319.0013","DOIUrl":"https://doi.org/10.22323/1.319.0013","url":null,"abstract":"The flat spectrum radio quasar 4C +01.02 became one of the brightest active galactic nuclei detected at high redshift (z = 2.1) in gamma rays when it underwent a series of outbursts during several months in 2016. We monitored this source in gamma rays using the Large Area Telescope onboard of the Fermi spacecraft (Fermi-LAT), and in optical using the Las Cumbres Observatory (LCO). The highest peak flux detected was F(E > 100 MeV) = (2.8 +/- 0.3) 10^-6 ph cm^-2 s^-1 on \u000010 July 2016 (MJD 57579, daily average). We also obtained optical spectropolarimetry with the Robert Stobie Spectrograph on the Southern African Large Telescope (SALT-RSS) and observed a degree of linear polarisation of up to 10% during flaring states, and ~1% during a quiescent period. We report recent updates we obtained in our time-domain and spectral studies of this source in July-August 2016, November-December 2016, and July 2017.","PeriodicalId":366250,"journal":{"name":"Proceedings of 5th Annual Conference on High Energy Astrophysics in Southern Africa — PoS(HEASA2017)","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-10-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129735007","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}

{"title":"Searching for new TeV blazars in the 3rd Fermi-LAT catalogue of hard gamma-ray sources","authors":"J. P. Marais, B. V. Soelen","doi":"10.22323/1.319.0014","DOIUrl":"https://doi.org/10.22323/1.319.0014","url":null,"abstract":"The 3rd Fermi catalogue of Hard Fermi-LAT Sources (3FHL), which detected 1556 sources above 10 GeV, provides an important resource for finding new candidate TeV sources for follow-up observations with the H.E.S.S. telescopes. To search for potential TeV emitting extragalactic sources, we observed a sample of five 3FHL sources classified as Blazars of unknown type (BCU) and two 3FHL sources without associations at other wavelengths with the SAAO 1.9-m telescope. The observations were performed during February 2017, with the SpUpNIC spectrograph on the 1.9-m telescope. Possible counterparts for the unassociated sources were determined by cross-matching objects using archival multi-wavelength data from Radio, Infrared and X-ray catalogues. Classifications were obtained for all the observed BCUs and redshifts were determined for two of them. Redshift measurements were obtained for the optical candidates of both the unassociated sources observed. Further analysis is necessary to confirm their association to the 3FHL γ-ray sources.","PeriodicalId":366250,"journal":{"name":"Proceedings of 5th Annual Conference on High Energy Astrophysics in Southern Africa — PoS(HEASA2017)","volume":"158 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114741755","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}

{"title":"Some things change, some don’t. An exploration of Seyfert galaxy luminosity changes over a generation","authors":"H. Winkler","doi":"10.22323/1.319.0011","DOIUrl":"https://doi.org/10.22323/1.319.0011","url":null,"abstract":"In the 1980's some of the first systematic photometric studies established that Seyfert galaxies are variable on typical timescales of months. In some instances the luminosity, and even some of the spectral characteristics have changed dramatically over the years. In contrast, other AGN also classified as broad-line Seyferts have proved to be much more photometrically stable. The paper presents re-observations of several AGN obtained at SAAO in 2016-2017. These are used with other recent data to highlight a potential correlation between the spectral characteristics and the variability pattern. The significance of this correlation is briefly explored.","PeriodicalId":366250,"journal":{"name":"Proceedings of 5th Annual Conference on High Energy Astrophysics in Southern Africa — PoS(HEASA2017)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128652752","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}

{"title":"Studying the dark matter annihilation in galaxy clusters through radio and gravitational lensing measures","authors":"P. Marchegiani, S. Colafrancesco","doi":"10.22323/1.319.0006","DOIUrl":"https://doi.org/10.22323/1.319.0006","url":null,"abstract":"Galaxy clusters are expected to be dominated by a component of Dark Matter (DM) of unknown nature. The annihilation of DM particles in a galaxy cluster can produce relativistic electrons and gamma rays, that can be used to test the properties of the DM particles and of the cluster itself. Gravitational lensing measures provide the spatial DM distribution in a cluster, and can be used to build detailed models to estimate the contribution of DM-produced electrons to the non-thermal diffuse emission observed in some galaxy clusters. Therefore putting together the information derived from radio and gravitational lensing measures in galaxy clusters can provide important information about the properties of DM and the physics of clusters. \u0000We apply this technique to two galaxy clusters where radio and gravitational lensing measurements are available. In the Bullet cluster a contribution of the DM to the diffuse radio emission is possible because of the spectral changes visible in the overall spectrum, that suggest that more than one component can be present; to better constrain this possibility information on the spectrum of the diffuse radio emission in smaller regions of the cluster is necessary. In the Coma cluster the distribution of the DM sub-halos closely resembles the radio halo surface brightness shape, and the overall radio halo spectrum is well reproduced by a DM model for the observed properties of the magnetic field, without violating the gamma ray upper limits in the cluster; however, there are open issues, like the values of the annihilation cross section and of the substructures boosting factor. \u0000On the basis of these results, we conclude that the combination of radio and gravitational lensing studies of galaxy clusters appears to be a very promising way to obtain information about the physics of galaxy clusters and the DM properties. Present results suggest that a contribution from DM to the total diffuse radio emission can be important, but require to study in detail the spectrum of the diffuse radio emission obtained in smaller regions of the clusters, and to have good contraints on the components of baryonic origin. The application of this technique to a higher number of clusters will be important to obtain better information and solve some open issues.","PeriodicalId":366250,"journal":{"name":"Proceedings of 5th Annual Conference on High Energy Astrophysics in Southern Africa — PoS(HEASA2017)","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130348695","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}