scholarly journals RS CVn Systems: The High Energy Picture

1983 ◽  
Vol 71 ◽  
pp. 415-427 ◽  
Author(s):  
P.A. Charles
Keyword(s):  
Line Emission ◽  
High Energy ◽  
Close Binaries ◽  
Stellar Rotation ◽  
Active Systems ◽  
X Ray ◽  
Coronal Activity ◽  
Solar Abundances ◽  
Scaled Models ◽  
Einstein Observatory

AbstractThe discovery of X-ray emission from RS CVn systems by HEAO-1 and subsequent surveys by the Einstein Observatory have shown that these close binaries exhibit greatly enhanced coronal activity. Here we review the 3 main observational areas: (1) results of the X-ray surveys of RS CVn systems and other late-type stars which indicate how the X-ray luminosity is correlated with the binary period (and hence stellar rotation) and other coronal activity indicators. This will be discussed in the context of scaled models of the solar corona; (2) X-ray spectroscopy of the most active systems which show multitemperature spectra and line emission consistent with solar abundances of the heavy elements; (3) observations of X-ray “flare-type” activity that has been associated with several RS CVn systems.

scholarly journals Gamma-Ray and Neutrino Signals from Accretion Disk Coronae of Active Galactic Nuclei

Galaxies ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 36
Author(s):  
Yoshiyuki Inoue ◽  
Dmitry Khangulyan ◽  
Akihiro Doi
Keyword(s):  
Active Galactic Nuclei ◽  
Gamma Ray ◽  
Galactic Nuclei ◽  
High Energy ◽  
Thermal Activity ◽  
X Ray ◽  
Cascade Models ◽  
Coronal Activity ◽  
Ngc 1068 ◽  
High Energy Particles

To explain the X-ray spectra of active galactic nuclei (AGN), non-thermal activity in AGN coronae such as pair cascade models has been extensively discussed in the past literature. Although X-ray and gamma-ray observations in the 1990s disfavored such pair cascade models, recent millimeter-wave observations of nearby Seyferts have established the existence of weak non-thermal coronal activity. In addition, the IceCube collaboration reported NGC 1068, a nearby Seyfert, as the hottest spot in their 10 yr survey. These pieces of evidence are enough to investigate the non-thermal perspective of AGN coronae in depth again. This article summarizes our current observational understanding of AGN coronae and describes how AGN coronae generate high-energy particles. We also provide ways to test the AGN corona model with radio, X-ray, MeV gamma ray, and high-energy neutrino observations.

scholarly journals X-ray Properties of 3C 111: Separation of Primary Nuclear Emission and Jet Continuum

Universe ◽  
2020 ◽  
Vol 6 (11) ◽  
pp. 219
Author(s):  
Elena Fedorova ◽  
B.I. Hnatyk ◽  
V.I. Zhdanov ◽  
A. Del Popolo
Keyword(s):  
Accretion Disk ◽  
Power Law ◽  
Line Emission ◽  
High Energy ◽  
Power Law Model ◽  
X Ray ◽  
Additional Information ◽  
Observational Dataset ◽  
Simple Power ◽  
Photon Index

3C111 is BLRG with signatures of both FSRQ and Sy1 in X-ray spectrum. The significant X-ray observational dataset was collected for it by INTEGRAL, XMM-Newton, SWIFT, Suzaku and others. The overall X-ray spectrum of 3C 111 shows signs of a peculiarity with the large value of the high-energy cut-off typical rather for RQ AGN, probably due to the jet contamination. Separating the jet counterpart in the X-ray spectrum of 3C 111 from the primary nuclear counterpart can answer the question is this nucleus truly peculiar or this is a fake “peculiarity” due to a significant jet contribution. In view of this question, our aim is to estimate separately the accretion disk/corona and non-thermal jet emission in the 3C 111 X-ray spectra within different observational periods. To separate the disk/corona and jet contributions in total continuum, we use the idea that radio and X-ray spectra of jet emission can be described by a simple power-law model with the same photon index. This additional information allows us to derive rather accurate values of these contributions. In order to test these results, we also consider relations between the nuclear continuum and the line emission.

scholarly journals INVESTIGATION OF DENSE GAS TOWARDS RELATIVISTIC OUTFLOW SOURCES

2014 ◽  
Vol 28 ◽  
pp. 1460198
Author(s):  
J. HAWKES ◽  
G. ROWELL ◽  
B. DAWSON ◽  
F. AHARONIAN ◽  
M. BURTON ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Line Emission ◽  
High Energy ◽  
Dense Gas ◽  
Relativistic Jets ◽  
Hii Region ◽  
X Ray ◽  
Stellar Cluster ◽  
Radio Recombination Line ◽  
Low Mass

We probe the interstellar medium towards the objects Circinus X-1, a low-mass X-ray binary with relativistic jets; and the highly energetic Westerlund 2 stellar cluster, which is located towards TeV gamma-ray emission and interesting arc- and jet-like features seen in Nanten 12CO data. We have mapped both regions with the Mopra radio telescope, in 7 mm and 12 mm wavebands, looking for evidence of disrupted/dense gas caused by the interaction between high energy outflows and the ISM. Towards Westerlund 2, peaks in CS(J=1-0) emission indicate high density gas towards the middle of the arc and the endpoint of the jet; and radio recombination line emission is seen overlapping the coincident HII region RCW49. Towards Circinus X-1, 12CO(J = 1-0) Nanten data reveals three molecular clouds that lie in the region of Cir X-1. Gas parameters for each cloud are presented here.

scholarly journals X-Ray Studies of Quasars and Active Galaxies with the Einstein Observatory

1980 ◽  
Vol 5 ◽  
pp. 677-687 ◽  
Author(s):  
William H.-M. Ku
Keyword(s):  
Statistical Tests ◽  
Cosmological Parameters ◽  
High Energy ◽  
Active Galaxies ◽  
X Ray ◽  
Upper Limits ◽  
Extensive Program ◽  
The Universe ◽  
Bl Lacs ◽  
Einstein Observatory

The launch of the Einstein Observatory has added a new and exciting dimension to the study of active galaxies. Not only have a large number of optical and radio active galaxies been detected, but many new examples of high energy activity have been found. The ease with which a large number of quasars may now be studied in the X-ray regime out to a redshift of at least four promises to improve our understanding of the nature of these tremendous powerhouses and the evolution of the universe.The Columbia Astrophysics Laboratory (CAL) is carrying out an extensive program to study active galaxies with the imaging proportional counter (IPC) on board the Einstein Observatory (Giacconi et al. 1979). These observations have already yielded a large number of positive detections including four Seyferts, five N galaxies, seven BL Lacs, and 17 quasars. Upper limits were obtained for eight additional quasars. Six new Seyfert I and/or quasars have been identified from X-ray observations (Chanan 1979). Preliminary results from the first six months of the CAL survey of active galaxies will be presented below. A few representative objects of interest will be discussed briefly. Simple statistical tests will be applied to determine whether X-ray properties can be used to understand the differences and similarities between the various classes of active galaxies. Particular emphasis will be placed on the quasars in our sample. Our results for the quasar survey will be compared with those discussed by Tananbaum et al. (1979). Finally, the implications of the discovery of a large number of quasars will be briefly discussed. (Cosmological parameters of qo = 0 and Ho = 50 km (s Mpc)-1 are used throughout.)

Polycapillary X-Ray Optics for Thin Film Strain and Texture Analysis

1997 ◽  
Vol 505 ◽  
Author(s):  
F. A. Hofmann ◽  
W. M. Gibson ◽  
S. M. Lee ◽  
C. A. Macdonald ◽  
J. B. Ullrich ◽  
...  
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Line Emission ◽  
System Optimization ◽  
High Energy ◽  
Film Stress ◽  
Characteristic Line ◽  
Background Suppression ◽  
Polycapillary Optics ◽  
X Ray

ABSTRACTPolycapillary optics, shaped arrays consisting of hundreds of thousands of hollow glass capillary tubes, can be used to redirect, collimate, or focus x-ray beams from conventional, laboratory-based sources. Multifiber polycapillary collimating optics were placed without system optimization into a number of diffractometer systems. Strain and texture measurements were performed. Measurements on thin films with and without the lens yielded gains of 8–100. Gains are higher in comparison with systems employing pinhole rather than one-dimensional slit collimation. The collimation also resulted in peak symmetrization, which simplified peak shape analysis.Focused beam optics provide even larger gains. Gains of 100 have been demonstrated using polycapillary optics with spot sizes as small 20 μm. This is of particular significance for providing spatial resolution for low signal applications such as thin films. The inverse dependence of the critical angle for total external reflection on photon energy also results in suppression of high energy photons. This suppression of Bremsstrahlung can allow use of higher tube potentials to increase characteristic line emission. Background suppression from a polycapillary optic ″soller slit″ is also enhanced due to the two dimensional collimation and much smaller acceptance angle of the polycapillary optics. Polycapillary optic alignment is also faster and more convenient than the usual parafocusing geometry. The combination of background suppression, intensity gain and increased tube emission by employing polycapillary optics greatly increases the signal to noise ratio for thin film stress analysis.

scholarly journals Sources of the X-Ray Background: Temporal Stability

1980 ◽  
Vol 92 ◽  
pp. 227-228
Author(s):  
Elihu Boldt
Keyword(s):  
Gamma Ray ◽  
High Redshift ◽  
Temporal Stability ◽  
High Energy ◽  
Energy Limit ◽  
X Ray ◽  
New Class ◽  
Order Of Magnitude ◽  
X Ray Background ◽  
Einstein Observatory

The A2 experiment on HEAO-1 was especially developed to make systematics-free measurements of the extragalactic X-ray background (Boldt et al. 1979) over the band (up to 60 keV) of maximum flux. The spectrum observed has a remarkably simple thermal form (Marshall et al. 1980) with a mean photon energy of about 40 keV, an order of magnitude above the high-energy limit of the Einstein Observatory (HEAO-2) telescope. If most of this hard X-ray flux is not diffuse, then the main sources of this background could be 1) unresolved objects of known classification (e.g. BL Lac type, quasars, active galaxies) at high redshift, 2) redshifted (z > 1) gamma-ray bursts and/or 3) a new class of X-ray objects peculiar to high redshifts. If we assume that the number of such sources that are highly variable is less than 106, then our first-cut analysis of the temporal stability measured for the X-ray background indicates that 1) their contribution is less than 15% if they are variable on scales less than 104 seconds, and 2) their contribution is less than 60% if they are variable on scales less than a half-year.

scholarly journals AstroSat observations of the first Galactic ULX pulsar Swift J0243.6+6124

2020 ◽  
Vol 500 (1) ◽  
pp. 565-575
Author(s):  
Aru Beri ◽  
Sachindra Naik ◽  
Kulinder Pal Singh ◽  
Gaurava K Jaisawal ◽  
Sudip Bhattacharyya ◽  
...  
Keyword(s):  
Power Law ◽  
Broad Band ◽  
Line Emission ◽  
High Energy ◽  
Emission Feature ◽  
Iron Line ◽  
Strong Function ◽  
X Ray ◽  
Broad Emission ◽  
The Continuum

ABSTRACT Swift J0243.6+6124, the first Galactic ultraluminous X-ray pulsar, was observed during its 2017–2018 outburst with AstroSat at both sub- and super-Eddington levels of accretion with X-ray luminosities of LX ∼ 7 × 1037 and 6 × 1038 erg s−1, respectively. Our broad-band timing and spectral observations show that X-ray pulsations at ${\sim}9.85~\rm {s}$ have been detected up to 150 keV when the source was accreting at the super-Eddington level. The pulse profiles are a strong function of both energy and source luminosity, showing a double-peaked profile with pulse fraction increasing from ∼$10{{{\ \rm per\ cent}}}$ at $1.65~\rm {keV}$ to 40–80 ${{\ \rm per\ cent}}$ at $70~\rm {keV}$. The continuum X-ray spectra are well modelled with a high-energy cut-off power law (Γ ∼ 0.6–0.7) and one or two blackbody components with temperatures of ∼0.35 and $1.2~\rm {keV}$, depending on the accretion level. No iron line emission is observed at sub-Eddington level, while a broad emission feature at around 6.9 keV is observed at the super-Eddington level, along with a blackbody radius ($121\!-\!142~\rm {km}$) that indicates the presence of optically thick outflows.

Polycapillary X-ray optics for microdiffraction

1999 ◽  
Vol 32 (2) ◽  
pp. 160-167 ◽  
Author(s):  
C. A. MacDonald ◽  
S. M. Owens ◽  
W. M. Gibson
Keyword(s):  
Line Emission ◽  
High Energy ◽  
Small Sample ◽  
Quality Data ◽  
Characteristic Line ◽  
X Rays ◽  
Glass Capillary ◽  
Data Set ◽  
Ray Optics ◽  
X Ray

Polycapillary optics,i.e.shaped arrays consisting of hundreds of thousands of hollow glass capillary tubes, can be used to redirect, collimate or focus X-ray beams. X-rays emitted over a large angular range from conventional laboratory-based sources can be transformed into a beam with a small angular divergence or focused onto a small sample or sample area. Convergent beams of X-rays, with convergence angles as high as 15°, have been produced using polycapillary X-ray optics. Focused-spot sizes as small as 20 µm have been achieved, with flux densities two orders of magnitude larger than that produced by pinhole collimation. This results in a comparable decrease in data collection times because of the increase in direct-beam intensity and reciprocal-space coverage. In addition, the optics can be employed to reduce background and provide more convenient alignment geometries. The inverse dependence of the critical angle for total external reflection on photon energy results in suppression of high-energy photons. This effect can be employed to allow the use of higher tube potentials to increase the characteristic line emission and has also been employed to increase significantly theKα/Kβ ratio in Cu radiation. Measurements of X-ray diffraction data and crystallographic analyses have been performed for systems ranging from elemental crystals to proteins. Data from a lysozyme protein `standard' with a slightly convergent beam, taken in 3 min per frame with 2° oscillation with a 2.8 kW source, refined to an intensity variance of 5% compared to a standard data set. High-quality data were also obtained with a 0.03 kW fixed-anode source and a 2° convergent lens in 5 min per frame.

scholarly journals A new radio molecular line survey of planetary nebulae

2019 ◽  
Vol 625 ◽  
pp. A101 ◽  
Author(s):  
J. Bublitz ◽  
J. H. Kastner ◽  
M. Santander-García ◽  
V. Bujarrabal ◽  
J. Alcolea ◽  
...  
Keyword(s):  
Line Emission ◽  
Planetary Nebulae ◽  
Central Star ◽  
High Energy ◽  
Clear Correlation ◽  
X Rays ◽  
Molecular Line ◽  
X Ray ◽  
Trace Species ◽  
New Radio

Certain planetary nebulae (PNe) contain shells, filaments, or globules of cold gas and dust whose heating and chemistry are likely driven by UV and X-ray emission from their central stars and from wind-collision-generated shocks. We present the results of a survey of molecular line emission in the 88–236 GHz range from nine nearby (<1.5 kpc) planetary nebulae spanning a range of UV and X-ray luminosities, using the 30 m telescope of the Institut de Radioastronomie Millimétrique. Rotational transitions of thirteen molecules, including CO isotopologues and chemically important trace species, were observed and the results compared with and augmented by previous studies of molecular gas in PNe. Lines of the molecules HCO+, HNC, HCN, and CN, which were detected in most objects, represent new detections for four planetary nebulae in our study. Specifically, we present the first detections of 13CO (1–0, 2–1), HCO+, CN, HCN, and HNC in NGC 6445; HCO+ in BD+30°3639; 13CO (2–1), CN, HCN, and HNC in NGC 6853; and 13CO (2–1) and CN in NGC 6772. Flux ratios were analyzed to identify correlations between the central star and/or nebular UV and X-ray luminosities and the molecular chemistries of the nebulae. This analysis reveals a surprisingly robust dependence of the HNC/HCN line ratio on PN central star UV luminosity. There exists no such clear correlation between PN X-rays and various diagnostics of PN molecular chemistry. The correlation between HNC/HCN ratio and central star UV luminosity demonstrates the potential of molecular emission line studies of PNe for improving our understanding of the role that high-energy radiation plays in the heating and chemistry of photodissociation regions.

scholarly journals Proxima Centauri – the nearest planet host observed simultaneously with AstroSat, Chandra, and HST

2020 ◽  
Vol 498 (3) ◽  
pp. 3658-3663
Author(s):  
S Lalitha ◽  
J H M M Schmitt ◽  
K P Singh ◽  
P C Schneider ◽  
R O Parke Loyd ◽  
...  
Keyword(s):  
Spectral Type ◽  
High Energy ◽  
Mass Star ◽  
Habitable Zone ◽  
High Energy Radiation ◽  
Energy Radiation ◽  
X Ray ◽  
Coronal Activity ◽  
Low Mass

ABSTRACT Our nearest stellar neighbour, Proxima Centauri, is a low-mass star with spectral type dM5.5 and hosting an Earth-like planet orbiting within its habitable zone. However, the habitability of the planet depends on the high-energy radiation of the chromospheric and coronal activity of the host star. We report the AstroSat, Chandra, and HST observation of Proxima Centauri carried out as part of the multiwavelength simultaneous observational campaign. Using the soft X-ray data, we probe the different activity states of the star. We investigate the coronal temperatures, emission measures and abundance. Finally, we compare our results with earlier observations of Proxima Centauri.

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