scholarly journals Complex emission patterns: fluctuations and bistability of polar-cap potentials

2020 ◽  
Vol 492 (4) ◽  
pp. 5987-5993
Author(s):  
P B Jones
Keyword(s):  
Characteristic Time ◽  
Unstable State ◽  
Electromagnetic Shower ◽  
Polar Cap ◽  
X Ray ◽  
Ion Proton ◽  
Vela Pulsar ◽  
Γ Ray ◽  
Small Increments

ABSTRACT Development of the ion-proton pulsar model extends it to the limit of large unscreened polar-cap potentials, for example, as in the Vela pulsar, in which ion charges differ only by small increments from their complete screening values. It is shown that the atomic number Z of an ion following its passage from the canonical Z0 = 26 value through the electromagnetic shower region to the surface is not necessarily time-independent but can vary between fixed limits in an irregular or quasi-periodic way in a characteristic time of the order of 104 s. Thus, at a certain Z the system may transition to an unstable state of higher electric potential and it is argued that this is the physical basis for mode-changes, long-term nulls, periodic or otherwise. The model requires an orientation of magnetic dipole moment relative to rotational spin giving a positive corotational charge density. Success of the model would fix the particle composition of the remaining parts of the magnetosphere, including the Y-point and is therefore relevant to X-ray and γ-ray emission processes.

scholarly journals Long-term multiwavelength view of the blazar 1ES 1218+304

2019 ◽  
Vol 489 (4) ◽  
pp. 5076-5086 ◽  
Author(s):  
K K Singh ◽  
B Bisschoff ◽  
B van Soelen ◽  
A Tolamatti ◽  
J P Marais ◽  
...  
Keyword(s):  
High Energy ◽  
Host Galaxy ◽  
Energy Bands ◽  
X Ray ◽  
Very High Energy ◽  
Γ Ray ◽  
Activity State ◽  
Low Activity ◽  
Very High

ABSTRACT In this work, we present a multiwavelength study of the blazar 1ES 1218+304 using near simultaneous observations over 10 yr during the period 2008 September 1 to 2018 August 31 (MJD 54710–58361). We have analysed data from Swift-UVOT, Swift-XRT, and Fermi-LAT to study the long term behaviour of 1ES 1218+304 in different energy bands over the last decade. We have also used the archival data from OVRO, MAXI, and Swift-BAT available during the above period. The near simultaneous data on 1ES 1218+304 suggest that the long term multiwavelength emission from the source is steady and does not show any significant change in the source activity. The optical/UV fluxes are found to be dominated by the host galaxy emission and can be modelled using the pegase code. However, the time averaged X-ray and γ-ray emissions from the source are reproduced using a single zone leptonic model with log-parabolic distribution for the radiating particles. The intrinsic very high energy γ-ray emission during a low activity state of the source is broadly consistent with the predictions of the leptonic model for blazars. We have investigated the physical properties of the jet and the mass of the supermassive black hole at the centre of the host galaxy using long term X-ray observations from the Swift-XRT which is in agreement with the value derived using blackbody approximation of the host galaxy. We also discuss the extreme nature of the source on the basis of X-ray and γ-ray observations.

scholarly journals MAXIINVESTIGATION INTO THE LONG-TERM X-RAY VARIABILITY FROM THE VERY-HIGH-ENERGY γ-RAY BLAZAR Mrk 421

2014 ◽  
Vol 798 (1) ◽  
pp. 27 ◽  
Author(s):  
Naoki Isobe ◽  
Ryosuke Sato ◽  
Yoshihiro Ueda ◽  
Masaaki Hayashida ◽  
Megumi Shidatsu ◽  
...  
Keyword(s):  
High Energy ◽  
X Ray ◽  
Very High Energy ◽  
Γ Ray ◽  
Very High

scholarly journals The uncorrelated long-term γ-ray and X-ray variability of blazars and its implications on disc–jet coupling

2013 ◽  
Vol 431 (2) ◽  
pp. 1618-1624 ◽  
Author(s):  
Debbijoy Bhattacharya ◽  
Ranjeev Misra ◽  
A. R. Rao ◽  
P. Sreekumar
Keyword(s):  
X Ray ◽  
Γ Ray

DEPENDENCE OF THE X-RAY LUMINOSITY AND PULSAR WIND NEBULA ON DIFFERENT PARAMETERS OF PULSARS AND THE EVOLUTIONARY EFFECTS

2004 ◽  
Vol 13 (02) ◽  
pp. 197-213 ◽  
Author(s):  
OKTAY H. GUSEINOV ◽  
AŞKIN ANKAY ◽  
SEVINÇ O. TAGIEVA ◽  
M. ÖZGÜR TAŞKIN
Keyword(s):  
Magnetic Field ◽  
Neutron Stars ◽  
Characteristic Time ◽  
Rotational Energy ◽  
X Ray ◽  
Γ Ray ◽  
Pulsar Wind ◽  
Low X ◽  
The Magnetic Field ◽  
Relativistic Particles

Dependences of the X-ray luminosity (Lx) of young single pulsars, due to ejection of relativistic particles, on electric field intensity, rate of rotational energy loss (Ė), magnetic field, period, and some other parameters of neutron stars are discussed. Influence of the magnetic field and effects of some other parameters of neutron stars on the Lx-Ė and the Lx-τ (characteristic time) dependences are considered. Evolutionary factors also play an important role in our considerations. Only the pulsars with L2–10 keV >1033 erg/s have pulsar wind nebula around them. The pulsars from which γ-ray radiation has been observed have low X-ray luminosity in general.

scholarly journals THE HIGH-ENERGY PROPERTIES OF 3C 454.3: A FOUR-YEAR STUDY

2012 ◽  
Vol 08 ◽  
pp. 404-407 ◽  
Author(s):  
◽  
STEFANO VERCELLONE
Keyword(s):  
Gamma Ray ◽  
High Energy ◽  
Short Term ◽  
Multi Wavelength ◽  
Vela Pulsar ◽  
Short And Long Term ◽  
Γ Ray ◽  
Short Term Variability ◽  
Daily Time

The blazar 3C 454.3 has become the most active and brightest γ-ray source of the sky, earning the nickname of Crazy Diamond. The short-term variability in the γ-ray energy band and the extremely high peak fluxes reached during intense flaring episodes make 3C 454.3 one of the best targets to investigate the blazar jet properties. We will review four years of observational properties of this remarkable source, discussing both short- and long-term multi-wavelength campaigns, with particular emphasis on the recent flaring episode which occurred on 2010 November 20, when 3C 454.3 reached on a daily time-scale a gamma-ray flux (E > 100 MeV) higher than 6 × 10-5 photons cm-2 s-1, about six times the flux of the brightest γ-ray steady source, the Vela Pulsar.

scholarly journals Modelling X-ray and Gamma-ray Emission from Pulsars

2003 ◽  
Vol 214 ◽  
pp. 177-180
Author(s):  
B. Rudak ◽  
J. Dyks
Keyword(s):  
Space Charge ◽  
Gamma Ray ◽  
High Energy ◽  
Energy Spectra ◽  
Polar Cap ◽  
Unique Case ◽  
High Energy Radiation ◽  
Energy Radiation ◽  
X Ray ◽  
Γ Ray

Lightcurves and broadband energy spectra of the brightest X/γ-ray sources among the rotation powered pulsars exhibit unexpected richness of features, making each object almost a unique case. This contribution presents how our models of high-energy radiation within the framework of SCLF (space charge limited flow) polar-cap scenarios tackle with some of these challenges.

scholarly journals A full polar cap cascade model: pulsar γ-ray and X-ray luminosities

2000 ◽  
Vol 177 ◽  
pp. 481-482
Author(s):  
Bing Zhang ◽  
Alice K. Harding
Keyword(s):  
Synchrotron Radiation ◽  
Cascade Model ◽  
Polar Cap ◽  
X Ray ◽  
Inverse Compton ◽  
Primary Particles ◽  
Γ Ray

AbstractWe propose a full polar cap cascade model which includes the curvature and inverse Compton emission of the primary particles, and both synchrotron radiation and inverse Compton of the higher generation pairs. Such a full cascade model can reproduce both theLγ∝ (Lsd)1/2and theLx~ 10−3Lsddependences observed from the known spin-powered pulsars.

scholarly journals Modeling the broadband emission of 3C 454.3

2021 ◽  
Author(s):  
N Sahakyan
Keyword(s):  
Spectral Energy ◽  
Emission Region ◽  
Physical Parameters ◽  
X Ray ◽  
Broadband Emission ◽  
Line Region ◽  
Spectrum Radio ◽  
Γ Ray ◽  
Flux Increase

Abstract The results of a long-term multiwavelength study of the powerful flat spectrum radio quasar 3C 454.3 using Fermi-LAT and Swift XRT/UVOT data are reported. In the γ-ray band, Fermi-LAT observations show several major flares when the source flux was >10−5 photon cm−2 s−1; the peak γ-ray flux above 141.6 MeV, (9.22 ± 1.96) × 10−5 photon cm−2 s−1 observed on MJD 55519.33, corresponds to 2.15 × 1050 erg s−1 isotropic γ-ray luminosity. The analysis of Swift XRT and UVOT data revealed a flux increase, although with smaller amplitudes, also in the X-ray and optical/UV bands. The X-ray emission of 3C 454.3 is with a hard spectral index of ΓX = 1.16–1.75, and the flux in the flaring states increased up to (1.80 ± 0.18) × 10−10 erg cm−2 s−1. Through combining the analyzed data, it was possible to assemble 362 high-quality and quasi-simultaneous spectral energy distributions of 3C 454.3 in 2008-2018 which all were modeled within a one-zone leptonic scenario assuming the emission region is within the broad line region, involving synchrotron, synchrotron self-Compton and external Compton mechanisms. Such an extensive modeling is the key for constraining the underlying emission mechanisms in the 3C 454.3 jet and allows to derive the physical parameters of the jet and investigate their evolution in time. The modeling suggests that during the flares, along with the variation of emitting electron parameters, the Doppler boosting factor increased substantially implying that the emission in these periods has most likely originated in a faster moving region.

Preparation And elemental analysis of ancient fibers

1987 ◽  
Vol 45 ◽  
pp. 410-411
Author(s):  
Allen Angel ◽  
Kathryn A. Jakes
Keyword(s):  
Cross Sections ◽  
Physical Structure ◽  
Energy Dispersive ◽  
Archaeological Sites ◽  
X Ray ◽  
Long Term Storage ◽  
Backscattered Electron ◽  
Electron Imaging

Fabrics recovered from archaeological sites often are so badly degraded that fiber identification based on physical morphology is difficult. Although diagenetic changes may be viewed as destructive to factors necessary for the discernment of fiber information, changes occurring during any stage of a fiber's lifetime leave a record within the fiber's chemical and physical structure. These alterations may offer valuable clues to understanding the conditions of the fiber's growth, fiber preparation and fabric processing technology and conditions of burial or long term storage (1).Energy dispersive spectrometry has been reported to be suitable for determination of mordant treatment on historic fibers (2,3) and has been used to characterize metal wrapping of combination yarns (4,5). In this study, a technique is developed which provides fractured cross sections of fibers for x-ray analysis and elemental mapping. In addition, backscattered electron imaging (BSI) and energy dispersive x-ray microanalysis (EDS) are utilized to correlate elements to their distribution in fibers.

Long-term variations in individual particle types in the aerosol of Phoenix, Arizona, as determined using automated electron microprobe analysis and multivariate statistical techniques

1993 ◽  
Vol 51 ◽  
pp. 742-743
Author(s):  
Karen A. Katrinak ◽  
James R. Anderson ◽  
Peter R. Buseck
Keyword(s):  
Electron Microprobe ◽  
Fine Fraction ◽  
Coarse Fraction ◽  
Motor Vehicles ◽  
Multivariate Statistical Methods ◽  
Multivariate Statistical ◽  
X Ray ◽  
Mineral Particles ◽  
Anthropogenic Air Pollutants

Aerosol samples were collected in Phoenix, Arizona on eleven dates between July 1989 and April 1990. Elemental compositions were determined for approximately 1000 particles per sample using an electron microprobe with an energy-dispersive x-ray spectrometer. Fine-fraction samples (particle cut size of 1 to 2 μm) were analyzed for each date; coarse-fraction samples were also analyzed for four of the dates.The data were reduced using multivariate statistical methods. Cluster analysis was first used to define 35 particle types. 81% of all fine-fraction particles and 84% of the coarse-fraction particles were assigned to these types, which include mineral, metal-rich, sulfur-rich, and salt categories. "Zero-count" particles, consisting entirely of elements lighter than Na, constitute an additional category and dominate the fine fraction, reflecting the importance of anthropogenic air pollutants such as those emitted by motor vehicles. Si- and Ca-rich mineral particles dominate the coarse fraction and are also numerous in the fine fraction.

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