D. Buckley, P. Charles, A. Rajoelimanana, L. Townsend
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.
{"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}
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.
{"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}
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.
{"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}
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.
{"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}
Recent observations of distant gamma ray sources indicate that the universe may be more transparent to VHE-gamma-rays than expected. In this paper we study the reduction of the EBL gamma-gamma opacity due to the existence of underdense regions along the line of sight to VHE gamma-ray sources and the possibility of a Lorentz Invariance Violation (LIV) signature. Therefore, we study whether one or both of these effects could be suitable to explain the spectral hardening observed in a few VHE gamma-ray sources. We found that, although the cosmic opacity for VHE gamma rays with energy more than 10 TeV can be strongly reduced, the spectral hardening feature observed in some VHE gamma-ray blazars with energy from 300 GeV up to few TeVs (e.g. PKS 1424+240) still remains puzzling.
{"title":"Why the universe is unexpectedly transparent to very high energy gamma rays","authors":"H. Abdalla, M. Böttcher","doi":"10.22323/1.319.0028","DOIUrl":"https://doi.org/10.22323/1.319.0028","url":null,"abstract":"Recent observations of distant gamma ray sources indicate that the universe may be more transparent to VHE-gamma-rays than expected. In this paper we study the reduction of the EBL gamma-gamma opacity due to the existence of underdense regions along the line of sight to VHE gamma-ray sources and the possibility of a Lorentz Invariance Violation (LIV) signature. Therefore, we study whether one or both of these effects could be suitable to explain the spectral hardening observed in a few VHE gamma-ray sources. \u0000We found that, although the cosmic opacity for VHE gamma rays with energy more than 10 TeV can be strongly reduced, the spectral hardening feature observed in some VHE gamma-ray blazars with energy from 300 GeV up to few TeVs (e.g. PKS 1424+240) still remains puzzling.","PeriodicalId":366250,"journal":{"name":"Proceedings of 5th Annual Conference on High Energy Astrophysics in Southern Africa — PoS(HEASA2017)","volume":"17 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":"129995130","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}
High-energy cosmic rays from all directions in space enter the Earth’s atmosphere. Interaction of these cosmic rays in the atmosphere produces secondary particles, including neutrinos. Generally the behavior of atmospheric neutrino flux is accepted as a power-law function type, although the shape varies at different energies and zenith angles. Due to these complications, the fluxes from detailed numerical calculations are reported in energy and zenith angle bins. In this article we propose new interpolation schemes for the flux in energy bins or energy and zenith angle bins for any power-law type function. We apply these schemes to the atmospheric muon neutrino flux model H3a QGSJET-II-4.
高能宇宙射线从太空的各个方向进入地球大气层。这些宇宙射线在大气中的相互作用产生了次级粒子，包括中微子。一般来说，大气中微子通量的行为被接受为幂律函数类型，尽管其形状在不同的能量和天顶角下会发生变化。由于这些复杂性，从详细的数值计算通量报告在能量和天顶角箱。本文针对幂律型函数，提出了能量箱或能量和天顶角箱中通量的新插值格式。我们将这些格式应用于大气介子中微子通量模型H3a qgsjt - ii -4。
{"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}
A. Rajoelimanana, P. Charles, D. Buckley, P. Meintjes
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$4686, He I and some weak Balmer lines. The X-ray and near ultraviolet fluxes correlate with the optical brightness. Such behavior is unusual amongst the known supersoft sources (hereafter SSS), and is difficult to assimilate into the standard model, but whatever the cause, a period of significantly enhanced mass transfer from the donor is required.
我们提出了对不寻常的x射线瞬变ASASSN-16oh的光学和x射线观测分析的结果。光学光曲线显示，在静止时，光源较暗($I$ = 20.3)，在爆发时变亮至$I$ = 15。爆发光曲线看起来非常对称，总持续时间为$sim$ 300天。SALT的光谱显示出He II $lambda$ 4686、He I和一些弱的Balmer谱线的强发射线。x射线和近紫外通量与光学亮度相关。这种行为在已知的超软源(以下简称SSS)中是不寻常的，并且很难被同化到标准模型中，但无论原因是什么，都需要一段时间来显著增强供体的传质。
{"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}
R. Britto, M. Böttcher, H. Schutte, A. Falcone, J. P. Marais, B. V. Soelen, D. Buckley
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 10 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.
{"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}
Cataclysmic variables (CVs) have been studied for decades, but it is only during recent years that the importance of multi-wavelength studies of these sources have motivated dedicated surveys e.g. CRTS and MASTER. Multi-wavelength follow-up studies are required to fully constrain the properties and radiative processes of CVs, as these sources emit energy over almost the whole electromagnetic spectrum. A selection of results from a multi-wavelength follow-up study of CV systems, showing high levels of transient emission, will be discussed. This will also be used to demonstrate how essential dedicated radio and gamma-ray telescopes like MeerKAT and the forth-coming Cherenkov Telescope Array (CTA) are to complete our understanding of these sources and associated eruptive processes in general. Constraining non-thermal synchrotron emission processes in CVs and high energy outbursts are of special interest.
{"title":"Multi-wavelength follow-up studies of eruptive cataclysmic variables in the MeerKAT and CTA era","authors":"H. Szegedi, A. Odendaal, P. Meintjes","doi":"10.22323/1.319.0040","DOIUrl":"https://doi.org/10.22323/1.319.0040","url":null,"abstract":"Cataclysmic variables (CVs) have been studied for decades, but it is only during recent years that the importance of multi-wavelength studies of these sources have motivated dedicated surveys e.g. CRTS and MASTER. Multi-wavelength follow-up studies are required to fully constrain the properties and radiative processes of CVs, as these sources emit energy over almost the whole electromagnetic spectrum. A selection of results from a multi-wavelength follow-up study of CV systems, showing high levels of transient emission, will be discussed. This will also be used to demonstrate how essential dedicated radio and gamma-ray telescopes like MeerKAT and the forth-coming Cherenkov Telescope Array (CTA) are to complete our understanding of these sources and associated eruptive processes in general. Constraining non-thermal synchrotron emission processes in CVs and high energy outbursts are of special interest.","PeriodicalId":366250,"journal":{"name":"Proceedings of 5th Annual Conference on High Energy Astrophysics in Southern Africa — PoS(HEASA2017)","volume":"128 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":"132525492","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}
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.
第三次Fermi Hard Fermi- lat源目录(3FHL)共探测到1556个10 GeV以上的源，为H.E.S.S.望远镜后续观测寻找新的候选TeV源提供了重要资源。为了寻找潜在的TeV星系外源，我们使用SAAO 1.9 m望远镜观测了5个被归类为未知类型Blazars (BCU)的3FHL源和2个在其他波长没有关联的3FHL源。观测于2017年2月进行，SpUpNIC光谱仪安装在1.9米望远镜上。通过使用无线电、红外和x射线目录的存档多波长数据进行交叉匹配，确定了不相关源的可能对应物。对所有观测到的bcu进行了分类，并确定了其中两个bcu的红移。对观测到的两个不相关源的光学候选点进行了红移测量。需要进一步的分析来证实它们与3FHL γ射线源的关联。
{"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}
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