scholarly journals Slugs and Snails and Puppy Dog Tails: jets from an unconventional angle

2014 ◽  
Vol 10 (S313) ◽  
pp. 199-207
Author(s):  
D. E. Harris
Keyword(s):  
Short Review ◽  
Active Galaxies ◽  
Electromagnetic Spectrum ◽  
Synchrotron Emission ◽  
X Rays ◽  
Current Experiment ◽  
Massive Black Holes ◽  
Extragalactic Jets ◽  
Inverse Compton ◽  
A Current

AbstractWe discuss some aspects of extragalactic jets originating from super massive black holes in the centres of active galaxies (and quasars). We start with a short review of sizes and flavors and then argue that the emission we detect across the electromagnetic spectrum does not come from the essence of the jet, but is rather a product of the jet. We go on to discuss some topics concerning synchrotron emission from jets, mainly aspects of knots. Finally we discuss the emission processes for the X-rays and describe a current experiment with LOFAR designed to test a requirement of inverse Compton models.

scholarly journals Structure and Emission of Parsec-Scale Jets in Quasars

1994 ◽  
Vol 159 ◽  
pp. 257-260
Author(s):  
Max Camenzind
Keyword(s):  
Synchrotron Emission ◽  
Relativistic Jets ◽  
Poynting Flux ◽  
The Core ◽  
Magnetic Surfaces ◽  
Inverse Compton ◽  
Shafranov Equation ◽  
Γ Rays ◽  
Jet Structure ◽  
A Current

The moving knots observed in VLBI of compact quasars are due to off-axis substructures in the parsec-scale jets which are dragged along by the underlying plasma flow. This is suggested by detailed MHD models for the structure of relativistic jets on the parsec–scale that are based on exact solutions of the nonlinear Grad–Schlüter–Shafranov equation in the asymptotic domain. These jet models are characterized by a current–carrying core and a current–free envelope. The corresponding core–radius Rc = upRL is related to the poloidal jet velocity up and the light cylinder radius RL generated by the rotation of the magnetic surfaces. The Poynting flux, which has an inhomogeneous distribution in the jet, provides an off–axis energy reservoir that could be tapped and converted into particle acceleration by non-axisymmetric instabilities in the core–jet structure. Evidence is presented that quasi-periodic synchrotron emission (in the IR–optical) and inverse Compton emission (in X– and γ–rays) from freshly accelerated electrons are due to a lighthouse effect of the rotating knots.

scholarly journals The Nova V5584 Sgr: A Short Review

2015 ◽  
Vol 2 (1) ◽  
pp. 234-237
Author(s):  
R. Poggiani
Keyword(s):  
Short Review ◽  
Electromagnetic Spectrum ◽  
X Rays ◽  
Infrared Observations ◽  
X Ray ◽  
Sgr A

The nova V5584 Sgr was discovered during 2009 October. It has been monitored in different domains of the electromagnetic spectrum: optical, infrared and X-rays. The optical and infrared observations suggest that V5584 Sgr is a Fe II nova that formed dust. No X-ray emission was observed around the time of maximum.

scholarly journals Unveiling the nature of extragalactic jets with Chandra observations

2010 ◽  
Vol 6 (S275) ◽  
pp. 160-163
Author(s):  
F. Massaro ◽  
C. C. Cheung ◽  
D. E. Harris
Keyword(s):  
Classification Scheme ◽  
Radio Sources ◽  
X Rays ◽  
Classification Criterion ◽  
New Classification ◽  
X Ray ◽  
Extended Radio ◽  
Extragalactic Jets ◽  
Inverse Compton ◽  
Basic Parameters

AbstractIn 1974 Fanaroff & Riley divided the extended radio sources into two classes, on the basis of their radio morphology and power. For several years we have been collecting basic parameters for extragalactic jets detected in the X-rays, looking for an extension of the classification criterion, based on their radio and X-rays properties. The fact that different processes have been proposed to explain their X-ray radiation, (synchrotron vs inverse Compton emission) suggests the possibility of a new classification scheme. However, comparing the radio-to-X-ray properties of the extragalactic jets, several aspects on their nature became unexpectedly unclear.

scholarly journals Multiwavelength morphological study of active galaxies

2019 ◽  
Vol 15 (S356) ◽  
pp. 295-298
Author(s):  
Betelehem Bilata-Woldeyes ◽  
Mirjana Pović ◽  
Zeleke Beyoro-Amado ◽  
Tilahun Getachew-Woreta ◽  
Shimeles Terefe
Keyword(s):  
Star Formation ◽  
Galaxy Formation ◽  
Formation Rate ◽  
Stellar Mass ◽  
Active Galaxies ◽  
Morphological Properties ◽  
X Rays ◽  
Host Galaxies ◽  
X Ray ◽  
Public Data

AbstractStudying the morphology of a large sample of active galaxies at different wavelengths and comparing it with active galactic nuclei (AGN) properties, such as black hole mass (MBH) and Eddington ratio (λEdd), can help us in understanding better the connection between AGN and their host galaxies and the role of nuclear activity in galaxy formation and evolution. By using the BAT-SWIFT hard X-ray public data and by extracting those parameters measured for AGN and by using other public catalogues for parameters such as stellar mass (M*), star formation rate (SFR), bolometric luminosity (Lbol), etc., we studied the multiwavelength morphological properties of host galaxies of ultra-hard X-ray detected AGN and their correlation with other AGN properties. We found that ultra hard X-ray detected AGN can be hosted by all morphological types, but in larger fractions (42%) they seem to be hosted by spirals in optical, to be quiet in radio, and to have compact morphologies in X-rays. When comparing morphologies with other galaxy properties, we found that ultra hard X-ray detected AGN follow previously obtained relations. On the SFR vs. stellar mass diagram, we found that although the majority of sources are located below the main sequence (MS) of star formation (SF), still non-negligible number of sources, with diverse morphologies, is located on and/or above the MS, suggesting that AGN feedback might have more complex influence on the SF in galaxies than simply quenching it, as it was suggested in some of previous studies.

scholarly journals Optical Flares from the Tidal Disruption of Stars by Massive Black Holes

2009 ◽  
Vol 5 (S267) ◽  
pp. 337-337 ◽  
Author(s):  
Linda E. Strubbe ◽  
Eliot Quataert
Keyword(s):  
Galactic Nuclei ◽  
Stellar Dynamics ◽  
Theoretical Models ◽  
X Rays ◽  
Tidal Disruption ◽  
Massive Black Hole ◽  
Detection Rates ◽  
Massive Black Holes ◽  
Near Ir ◽  
Nuclear Regions

A star that wanders too close to a massive black hole (BH) is shredded by the BH's tidal gravity. Stellar gas falls back to the BH, releasing a flare of energy. In anticipation of upcoming transient surveys, we predict the light curves and spectra of tidal flares as a function of time, highlighting the unique signatures of tidal flares in the optical and near-IR. Some of the gas initially bound to the BH is likely blown away when the fallback rate is super-Eddington at early times. This outflow produces an optical luminosity comparable to that of a supernova (Figure 1, left panel); such events have durations of ~ 10 days and may have been missed in supernova searches that exclude the nuclear regions of galaxies. When the fallback rate subsides below Eddington, the gas accretes onto the BH via a thin disk whose emission peaks in the UV to soft X-rays. Some of this emission is reprocessed by the unbound stellar debris, producing a spectrum of very broad emission lines, with no corresponding narrow forbidden lines (center panel). These lines are strongest for BHs with MBH ~ 105–106M⊙ and thus optical surveys are particularly sensitive to the lowest mass BHs in galactic nuclei. Calibrating our models to ROSAT and GALEX observations, we predict detection rates for Pan-STARRS, Palomar Transit Factory, and LSST (right panel) and highlight observational challenges in the optical. Pan-STARRS should detect at least several events per year — many more if current theoretical models of super-Eddington outflows are correct. These surveys will significantly improve our knowledge of stellar dynamics in galactic nuclei, the physics of super-Eddington accretion, the demography of intermediate mass BHs, and the role of tidal disruption in the growth of massive BHs.

Visualization of microvessels by angiography using inverse-Compton scattering X-rays in animal models

2014 ◽  
Vol 21 (6) ◽  
pp. 1327-1332 ◽  
Author(s):  
Toshiharu Fujii ◽  
Naoto Fukuyama ◽  
Chiharu Tanaka ◽  
Yoshimori Ikeya ◽  
Yoshiro Shinozaki ◽  
...  
Keyword(s):  
Compton Scattering ◽  
Photon Number ◽  
High Gain ◽  
Image Sensor ◽  
Clinical Settings ◽  
X Rays ◽  
X Ray ◽  
Inverse Compton Scattering ◽  
Small Vessels ◽  
Inverse Compton

The fundamental performance of microangiography has been evaluated using the S-band linac-based inverse-Compton scattering X-ray (iCSX) method to determine how many photons would be required to apply iCSX to human microangiography. ICSX is characterized by its quasi-monochromatic nature and small focus size which are fundamental requirements for microangiography. However, the current iCSX source does not have sufficient flux for microangiography in clinical settings. It was determined whether S-band compact linac-based iCSX can visualize small vessels of excised animal organs, and the amount of X-ray photons required for real time microangiography in clinical settings was estimated. The iCSX coupled with a high-gain avalanche rushing amorphous photoconductor camera could visualize a resolution chart with only a single iCSX pulse of ∼3 ps duration; the resolution was estimated to be ∼500 µm. The iCSX coupled with an X-ray cooled charge-coupled device image sensor camera visualized seventh-order vascular branches (80 µm in diameter) of a rabbit ear by accumulating the images for 5 and 30 min, corresponding to irradiation of 3000 and 18000 iCSX pulses, respectively. The S-band linac-based iCSX visualized microvessels by accumulating the images. An iCSX source with a photon number of 3.6 × 103–5.4 × 104times greater than that used in this study may enable visualizing microvessels of human fingertips even in clinical settings.

scholarly journals Nested Kirkpatrick–Baez (Montel) optics for hard X-rays

2015 ◽  
Vol 48 (2) ◽  
pp. 558-564 ◽  
Author(s):  
Giacomo Resta ◽  
Boris Khaykovich ◽  
David Moncton
Keyword(s):  
Ray Tracing ◽  
Compton Scattering ◽  
Analytical Procedure ◽  
X Rays ◽  
Multilayer Mirrors ◽  
Comprehensive Description ◽  
X Ray ◽  
Inverse Compton Scattering ◽  
Inverse Compton ◽  
Proper Orientation

A comprehensive description and ray-tracing simulations are presented for symmetric nested Kirkpatrick–Baez (KB) mirrors, commonly used at synchrotrons and in commercial X-ray sources. This paper introduces an analytical procedure for determining the proper orientation between the two surfaces composing the nested KB optics. This procedure has been used to design and simulate collimating optics for a hard-X-ray inverse Compton scattering source. The resulting optical device is composed of two 12 cm-long parabolic surfaces coated with a laterally graded multilayer and is capable of collimating a 12 keV beam with a divergence of 5 mrad (FWHM) by a factor of ∼250. A description of the ray-tracing software that was developed to simulate the graded multilayer mirrors is included.

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