scholarly journals The permanent ellipticity of the neutron star in PSR J1023+0038

2020 ◽  
Vol 498 (1) ◽  
pp. 728-736 ◽  
Author(s):  
Sudip Bhattacharyya
Keyword(s):  
Gravitational Waves ◽  
Accretion Disc ◽  
Millisecond Pulsar ◽  
Pulsar Magnetosphere ◽  
Additional Source ◽  
X Ray ◽  
Γ Rays ◽  
Mass Quadrupole ◽  
Parameter Values ◽  
The Waves

ABSTRACT A millisecond pulsar having an ellipticity, which is an asymmetric mass distribution around its spin-axis, could emit continuous gravitational waves, which have not been detected so far. An indirect way to infer such waves is to estimate the contribution of the waves to the spin-down rate of the pulsar. The transitional pulsar PSR J1023+0038 is ideal and unique for this purpose because this is the only millisecond pulsar for which the spin-down rate has been measured in both accreting and non-accreting states. Here, we infer, from our formalism based on the complete torque budget equations and the pulsar magnetospheric origin of observed γ-rays in the two states, that PSR J1023+0038 should emit gravitational waves due to a permanent ellipticity of the pulsar. The formalism also explains some other main observational aspects of this source in a self-consistent way. As an example, our formalism naturally infers the accretion disc penetration into the pulsar magnetosphere, and explains the observed X-ray pulsations in the accreting state using the standard and well-accepted scenario. This, in turn, infers the larger pulsar spin-down power in the accreting state, which, in our formalism, explains the observed larger γ-ray emission in this state. Exploring wide ranges of parameter values of PSR J1023+0038, and not assuming an additional source of stellar ellipticity in the accreting state, we find the misaligned mass quadrupole moment of the pulsar in the range of (0.92–1.88) × 1036 g cm2, implying an ellipticity range of (0.48–0.93) × 10−9.

scholarly journals Erratum: X-ray coherent pulsations during a sub-luminous accretion disc state of the transitional millisecond pulsar XSS J12270–4859

2015 ◽  
Vol 453 (1) ◽  
pp. L63-L63
Author(s):  
A. Papitto ◽  
D. de Martino ◽  
T. M. Belloni ◽  
M. Burgay ◽  
A. Pellizzoni ◽  
...  
Keyword(s):  
Accretion Disc ◽  
Millisecond Pulsar ◽  
X Ray

scholarly journals X-ray coherent pulsations during a sub-luminous accretion disc state of the transitional millisecond pulsar XSS J12270−4859

2015 ◽  
Vol 449 (1) ◽  
pp. L26-L30 ◽  
Author(s):  
A. Papitto ◽  
D. de Martino ◽  
T. M. Belloni ◽  
M. Burgay ◽  
A. Pellizzoni ◽  
...  
Keyword(s):  
Accretion Disc ◽  
Millisecond Pulsar ◽  
X Ray

scholarly journals The internal conversion of gamma-rays.—Part II

1928 ◽  
Vol 121 (787) ◽  
pp. 447-456
Keyword(s):  
Magnetic Field ◽  
Quantum Mechanics ◽  
Wave Equation ◽  
Gamma Rays ◽  
Internal Conversion ◽  
Scalar Potential ◽  
X Ray ◽  
Electro Magnetic Field ◽  
Γ Rays ◽  
Electro Magnetic

In a previous paper the absorption of γ-rays in the K-X-ray levels of the atom in which they are emitted was calculated according to the Quantum Mechanics, supposing the γ-rays to be emitted from a doublet of moment f ( t ) at the centre of the atom. The non-relativity wave equation derived from the relativity wave equation for an electron of charge — ε moving in an electro-magnetic field of vector potential K and scalar potential V is h 2 ∇ 2 ϕ + 2μ ( ih ∂/∂ t + εV + ih ε/μ c (K. grad)) ϕ = 0. (1) Suppose, however, that K involves the space co-ordinates. Then, (K. grad) ϕ ≠ (grad . K) ϕ , and the expression (K . grad) ϕ is not Hermitic. Equation (1) cannot therefore be the correct non-relativity wave equation for a single electron in an electron agnetic field, and we must substitute h 2 ∇ 2 ϕ + 2μ ( ih ∂/∂ t + εV) ϕ + ih ε/ c ((K. grad) ϕ + (grad. K) ϕ ) = 0. (2)

scholarly journals Gravitational waves from mountains in newly born millisecond magnetars

2021 ◽  
Vol 502 (4) ◽  
pp. 4680-4688
Author(s):  
Ankan Sur ◽  
Brynmor Haskell
Keyword(s):  
Gravitational Wave ◽  
Gravitational Waves ◽  
Massive Star ◽  
Gamma Ray ◽  
Dipole Radiation ◽  
X Ray ◽  
Binary Neutron Star ◽  
Spin Period ◽  
Lower Maximum ◽  
Wave Emission

ABSTRACT In this paper, we study the spin-evolution and gravitational-wave luminosity of a newly born millisecond magnetar, formed either after the collapse of a massive star or after the merger of two neutron stars. In both cases, we consider the effect of fallback accretion; and consider the evolution of the system due to the different torques acting on the star, namely the spin-up torque due to accretion and spin-down torques due to magnetic dipole radiation, neutrino emission, and gravitational-wave emission linked to the formation of a ‘mountain’ on the accretion poles. Initially, the spin period is mostly affected by the dipole radiation, but at later times, accretion spin the star up rapidly. We find that a magnetar formed after the collapse of a massive star can accrete up to 1 M⊙, and survive on the order of 50 s before collapsing to a black hole. The gravitational-wave strain, for an object located at 1 Mpc, is hc ∼ 10−23 at kHz frequencies, making this a potential target for next-generation ground-based detectors. A magnetar formed after a binary neutron star merger, on the other hand, accretes at the most 0.2 M⊙ and emits gravitational waves with a lower maximum strain of the order of hc ∼ 10−24, but also survives for much longer times, and may possibly be associated with the X-ray plateau observed in the light curve of a number of short gamma-ray burst.

Structural characterization of two K2SnX(PO4)3 (X=Fe,Yb) with langbeinite structure

2006 ◽  
Vol 21 (3) ◽  
pp. 214-219 ◽  
Author(s):  
Abderrahim Aatiq ◽  
Btissame Haggouch ◽  
Rachid Bakri ◽  
Youssef Lakhdar ◽  
Ismael Saadoune
Keyword(s):  
Solid State ◽  
Powder Diffraction ◽  
Room Temperature ◽  
Cell Parameter ◽  
Rietveld Analysis ◽  
Conventional Solid State Reaction ◽  
X Ray ◽  
Octahedral Sites ◽  
Parameter Values

Structures of two K2SnX(PO4)3(X=Fe,Yb) phosphates, obtained by conventional solid state reaction techniques at 950 °C, were determined at room temperature by X-ray powder diffraction using Rietveld analysis. The two materials exhibit the langbeinite-type structure (P213 space group, Z=4). Cubic unit cell parameter values are: a=9.9217(4) Å and a=10.1583(4) Å for K2SnFe(PO4)3 and K2SnYb(PO4)3, respectively. Structural refinements show that the two crystallographically independent octahedral sites (of symmetry 3) have a mixed Sn∕X (X=Fe,Yb) population although ordering is stronger in the Yb phase than in the Fe phase.

Gravitational waves: Some less discussed intriguing issues

2015 ◽  
Vol 24 (12) ◽  
pp. 1544023 ◽  
Author(s):  
C. Sivaram
Keyword(s):  
Gravitational Waves ◽  
Strong Field ◽  
Direct Detection ◽  
Recent Observation ◽  
High Redshift ◽  
Nonlinear Effects ◽  
Resonant Absorption ◽  
Compact Objects ◽  
The Waves ◽  
Very High

Attempts to detect gravitational waves is actively in progress with sophisticated devices like LIGO setup across continents. Despite being predicted almost 100 years ago, there has so far been no direct detection of these waves. In this work, we draw attention to some of the less discussed but subtle aspects arising, for example, from high orbital eccentricities, where emission near periastron could be millions of times more than that in the distant parts of the orbit. The strong field nonlinear effects close to the compact objects can substantially slow down and deflect the waves in the last (few) orbit(s) where much of the intensity is expected. Spin–orbit and other forces could be significant. There would also be plasma like resonant absorption (of kilohertz radiation) during the collapse. Recent observation of supermassive black holes at high redshift implies cluster collapse, where the gravitational wave intensity depends on very high powers of the mass. Any unambiguous claim of detection should perhaps consider several of these effects.

scholarly journals Simultaneous X-ray and radio observations of the transitional millisecond pulsar candidate CXOU J110926.4–650224

2021 ◽  
Vol 655 ◽  
pp. A52
Author(s):  
F. Coti Zelati ◽  
B. Hugo ◽  
D. F. Torres ◽  
D. de Martino ◽  
A. Papitto ◽  
...  
Keyword(s):  
Radio Emission ◽  
Flux Density ◽  
Millisecond Pulsar ◽  
Radio Emissions ◽  
X Ray ◽  
Link Type ◽  
Upper Limit ◽  
Variability Pattern ◽  
Average Flux ◽  
Compact Array

We present the results of simultaneous observations of the transitional millisecond pulsar (tMSP) candidate CXOU J110926.4–650224 with the XMM-Newton satellite and the MeerKAT telescope. The source was found at an average X-ray luminosity of LX ≃ 7 × 1033 erg s−1 over the 0.3−10 keV band (assuming a distance of 4 kpc) and displayed a peculiar variability pattern in the X-ray emission, switching between high, low and flaring modes on timescales of tens of seconds. A radio counterpart was detected at a significance of 7.9σ with an average flux density of ≃33 μJy at 1.28 GHz. It showed variability over the course of hours and emitted a ≃10-min long flare just a few minutes after a brief sequence of multiple X-ray flares. No clear evidence for a significant correlated or anticorrelated variability pattern was found between the X-ray and radio emissions over timescales of tens of minutes and longer. CXOU J110926.4–650224 was undetected at higher radio frequencies in subsequent observations performed with the Australia Telescope Compact Array, when the source was still in the same X-ray sub-luminous state observed before, down to a flux density upper limit of 15 μJy at 7.25 GHz (at 3σ). We compare the radio emission properties of CXOU J110926.4–650224 with those observed in known and candidate tMSPs and discuss physical scenarios that may account for its persistent and flaring radio emissions.

scholarly journals X-ray Dips in AGN and Microquasars – Collapse Timescales of Inner Accretion Disc

2020 ◽  
Author(s):  
Mayur B Shende ◽  
Prashali Chauhan ◽  
Prasad Subramanian
Keyword(s):  
Collisionless Plasma ◽  
Cosmic Ray ◽  
Outer Radius ◽  
Accretion Disc ◽  
Accretion Discs ◽  
X Rays ◽  
Temporal Behaviour ◽  
X Ray ◽  
Ray Diffusion ◽  
3C 120

Abstract The temporal behaviour of X-rays from some AGN and microquasars is thought to arise from the rapid collapse of the hot, inner parts of their accretion discs. The collapse can occur over the radial infall timescale of the inner accretion disc. However, estimates of this timescale are hindered by a lack of knowledge of the operative viscosity in the collisionless plasma comprising the inner disc. We use published simulation results for cosmic ray diffusion through turbulent magnetic fields to arrive at a viscosity prescription appropriate to hot accretion discs. We construct simplified disc models using this viscosity prescription and estimate disc collapse timescales for 3C 120, 3C 111, and GRS 1915+105. The Shakura-Sunyaev α parameter resulting from our model ranges from 0.02 to 0.08. Our inner disc collapse timescale estimates agree well with those of the observed X-ray dips. We find that the collapse timescale is most sensitive to the outer radius of the hot accretion disc.

scholarly journals Evaluation the Safety and Security Procedures used In X-ray Clinics in Al-Harthiya-Baghdad

2021 ◽  
Vol 2114 (1) ◽  
pp. 012009
Author(s):  
Thuraya A. Abdul Hussian ◽  
Anwar kh. Farman
Keyword(s):  
Ionizing Radiation ◽  
X Rays ◽  
X Ray ◽  
Beta Particles ◽  
Medical Clinics ◽  
Γ Rays ◽  
Health Laws ◽  
Different Sources ◽  
Α Particles ◽  
Security Procedures

Abstract Radiation is a form of energy, its emitted either in the form of particles such as α-particles and β-particles (beta particles including the electron and the positron) or waves such as sunlight, X-rays and γ-rays. Radiation found everywhere around us and it comes from many different sources naturally or man-made sources. In this study a questionnaire was distributed to people working in the field of X-rays that used for a medical imaging (X-ray and CT-scan) to evaluate the extent of awareness and knowledge in estimate the damage of ionizing radiation as a result of wrong use. The questionnaire was distributed to medical clinics in Al-Harithiya in Baghdad, which it’s considered as one of the important areas in Iraq to attract and treat patients. It’s found that most of the commitment of radiography clinics by safety and security procedures. Most of the radiology clinics abide by most of the Iraqi Ministry of Health laws. However, some clinics did not implement some of the security and safety conditions

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