scholarly journals Gravitational waves from GRB core spindown

2021 ◽  
Author(s):  
I Contopoulos ◽  
A Strantzalis ◽  
D Papadopoulos ◽  
D Kazanas
Keyword(s):  
Magnetic Field ◽  
Gravitational Waves ◽  
Exponential Decay ◽  
Gamma Ray ◽  
Time Intervals ◽  
Sharp Rise ◽  
Linear Rise ◽  
The Magnetic Field ◽  
Prompt Emission ◽  
Fast Rotating

Abstract We investigate long Gamma-Ray Bursts (GRB) which manifest a sharp linear rise followed by an exponential decay in their γ-ray prompt emission observed with the BAT instrument on board the Swift satellite. We offer a simple electrodynamic model that may account for these particular characteristics. We associate the sharp rise with the winding of the magnetic field by the fast rotating core that formed in the interior of the stellar precursor. We also associate the subsequent exponential decay with the electromagnetic spindown of the core following the release of the electromagnetic jet from the stellar interior. Any non-axisymmetric distortion in the rotating core will generate gravitational waves with exponentially decreasing frequency, a so-called ‘down-chirp’. We obtain a detailed estimate of the gravitational wave profile if the distortion of spacetime is due to the winding of a non-axisymmetric component of the magnetic field during that particular phase of the burst. We offer 7 particular time intervals during which one may look into LIGO archival data for the presence of our particular predicted waveforms in order to test our interpretation.

scholarly journals Millimeter and Microwave Activity of the Sun

1990 ◽  
Vol 142 ◽  
pp. 457-465 ◽  
Author(s):  
M. R. Kundu ◽  
S. M. White
Keyword(s):  
Magnetic Field ◽  
Gamma Rays ◽  
Solar Flares ◽  
Gamma Ray ◽  
High Spatial Resolution ◽  
High Resolution Imaging ◽  
The Sun ◽  
Millimeter Wavelengths ◽  
Resolution Imaging ◽  
The Magnetic Field

The emission of solar flares at millimeter wavelengths is of great interest both in its own right and because it is generated by the energetic electrons which also emit gamma rays. Since high-resolution imaging at gamma-ray energies is not presently possible, millimeter observations can act as a substitute. Except for that class of flares known as gamma-ray flares the millimetric emission is optically thin. It can be used as a powerful diagnostic of the energy distribution of electrons in solar flares and its evolution, and of the magnetic field. We have carried out high-spatial-resolution millimeter observations of solar flares this year using the Berkeley-Illinois-Maryland Array (BIMA), and report on the preliminary results in this paper (Kundu et al 1990; White et al 1990). We also report some recent results obtained from multifrequency observations using the VLA (White et al 1990).

scholarly journals 2D and 3D turbulent magnetic reconnection

2009 ◽  
Vol 5 (H15) ◽  
pp. 434-435
Author(s):  
A. Lazarian ◽  
G. Kowal ◽  
E. Vishniac ◽  
K. Kulpa-Dubel ◽  
K. Otmianowska-Mazur
Keyword(s):  
Magnetic Field ◽  
Magnetic Reconnection ◽  
Large Scale ◽  
Gamma Ray ◽  
Three Dimensional ◽  
Turnover Time ◽  
Turbulent Fluid ◽  
Astrophysical Objects ◽  
Field Lines ◽  
The Magnetic Field

AbstractA magnetic field embedded in a perfectly conducting fluid preserves its topology for all times. Although ionized astrophysical objects, like stars and galactic disks, are almost perfectly conducting, they show indications of changes in topology, magnetic reconnection, on dynamical time scales. Reconnection can be observed directly in the solar corona, but can also be inferred from the existence of large scale dynamo activity inside stellar interiors. Solar flares and gamma ray busts are usually associated with magnetic reconnection. Previous work has concentrated on showing how reconnection can be rapid in plasmas with very small collision rates. Here we present numerical evidence, based on three dimensional simulations, that reconnection in a turbulent fluid occurs at a speed comparable to the rms velocity of the turbulence, regardless of the value of the resistivity. In particular, this is true for turbulent pressures much weaker than the magnetic field pressure so that the magnetic field lines are only slightly bent by the turbulence. These results are consistent with the proposal by Lazarian & Vishniac (1999) that reconnection is controlled by the stochastic diffusion of magnetic field lines, which produces a broad outflow of plasma from the reconnection zone. This work implies that reconnection in a turbulent fluid typically takes place in approximately a single eddy turnover time, with broad implications for dynamo activity and particle acceleration throughout the universe. In contrast, the reconnection in 2D configurations in the presence of turbulence depends on resistivity, i.e. is slow.

Gamma-ray bursts prompt emission spectrum: an analysis of a photosphere model

2007 ◽  
Vol 365 (1854) ◽  
pp. 1171-1175 ◽  
Author(s):  
Asaf Pe'er ◽  
Peter Mészáros ◽  
Martin J Rees
Keyword(s):  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Dissipation Process ◽  
Internal Shock ◽  
Peak Energy ◽  
Wide Range ◽  
Low Energies ◽  
Steep Slopes ◽  
The Magnetic Field ◽  
Prompt Emission

A thermal radiative component is likely to accompany the first stages of the prompt emission of gamma-ray bursts (GRBs) and X-ray flashes. We analyse the effect of such a component on the observable spectrum, assuming that the observable effects are due to a dissipation process occurring below or near the thermal photosphere. For comparable energy densities in the thermal and leptonic components, the dominant emission mechanism is Compton scattering. This leads to a nearly flat energy spectrum ( νF ν ∝ ν 0 ) above the thermal peak at approximately 10–100 keV and below 10–100 MeV, for a wide range of optical depths 0.03≲ τ ≲100, regardless of the details of the dissipation mechanism or the strength of the magnetic field. For higher values of the optical depth, a Wien peak is formed at 100 keV to 1 MeV. In particular, these results are applicable to the internal shock model of GRBs, as well as to slow dissipation models, e.g. as might be expected from reconnection, if the dissipation occurs at a sub-photospheric radii. We conclude that dissipation near the thermal photosphere can naturally explain (i) clustering of the peak energy at sub-MeV energies at early times, (ii) steep slopes observed at low energies, and (iii) a flat spectrum above 10 keV at late times. Our model thus provides an alternative scenario to the optically thin synchrotron–synchrotron self-Compton model.

scholarly journals Afterglow light curves from magnetized GRB flows

2010 ◽  
Vol 6 (S275) ◽  
pp. 358-362
Author(s):  
Petar Mimica ◽  
Dimitrios Giannios ◽  
Miguel Ángel Aloy
Keyword(s):  
Magnetic Field ◽  
Radiative Transfer ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Light Curves ◽  
Reverse Shock ◽  
The Magnetic Field

AbstractUsing the RMHD code MRGENESIS and the radiative transfer code SPEV we compute multiwavelength afterglow light curves of magnetized ejecta of gamma-ray bursts interacting with a uniform circumburst medium. We are interested in the emission from the reverse shock when ejecta magnetization varies from σ0 = 0 to σ0 = 1. For typical parameters of the ejecta, the emission from the reverse shock peaks for magnetization σ0 ~ 0.01 − 0.1, and is suppressed for higher σ0. We fit the early afterglow light curves of GRB 990123 and 090102 and discuss the possible magnetization of the outflows of these bursts. Finally we discuss the amount energy left in the magnetic field which is available for dissipation at later afterglow stages.

scholarly journals How many solar wind data are sufficient for accurate fluxgate magnetometer offset determinations?

2019 ◽  
Vol 8 (2) ◽  
pp. 285-291 ◽  
Author(s):  
Ferdinand Plaschke
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Field Measurements ◽  
Wind Data ◽  
Fluxgate Magnetometer ◽  
Time Intervals ◽  
Sensor Position ◽  
Magnetic Field Measurements ◽  
Wind Measurements ◽  
The Magnetic Field

Abstract. Accurate magnetic field measurements by fluxgate magnetometers onboard spacecraft require ground and regular in-flight calibration activities. Therewith, the parameters of a coupling matrix and an offset vector are adjusted; they are needed to transform raw magnetometer outputs into calibrated magnetic field measurements. The components of the offset vector are typically determined by analyzing Alfvénic fluctuations in the solar wind if solar wind measurements are available. These are characterized by changes in the field components, while the magnetic field modulus stays constant. In this paper, the following question is answered: how many solar wind data are sufficient for accurate fluxgate magnetometer offset determinations? It is found that approximately 40 h of solar wind data are sufficient to achieve offset accuracies of 0.2 nT, and about 20 h suffice for accuracies of 0.3 nT or better if the magnetometer offsets do not drift within these time intervals and if the spacecraft fields do not vary at the sensor position. Offset determinations with uncertainties lower than 0.1 nT, however, would require at least hundreds of hours of solar wind data.

DISTANCE INDICATORS OF GAMMA-RAY PULSARS

2013 ◽  
Vol 23 ◽  
pp. 289-294
Author(s):  
WEI WANG
Keyword(s):  
Magnetic Field ◽  
Gamma Ray ◽  
Physical Origin ◽  
Large Area ◽  
Distance Measurements ◽  
Distance Information ◽  
Cascade Processes ◽  
Gamma Ray Emission ◽  
Distance Indicators ◽  
The Magnetic Field

Distance measurements of gamma-ray pulsars are challenging questions in present pulsar studies. The Large Area Telescope (LAT) aboard the Fermi gamma-ray observatory discovered more than 100 gamma-ray pulsars including 24 new gamma-selected pulsars which nearly have no distance information. We study the relation between gamma-ray emission efficiency (η = Lγ/Ė) and pulsar parameters for young radio-selected gamma-ray pulsars with known distance information in the first gamma-ray pulsar catalog reported by Fermi/LAT. We have introduced three generation order parameters to describe gamma-ray emission properties of pulsars, and find the strong correlation of η – ζ3 a generation order parameter which reflects γ-ray photon generations in pair cascade processes induced by magnetic field absorption in pulsar magnetosphere. A good correlation of η – B LC the magnetic field at the light cylinder radius is also found. These correlations would be the distance indicators in gamma-ray pulsars to evaluate distances for gamma-selected pulsars. Distances of 25 gamma-selected pulsars are estimated, which could be tested by other distance measurement methods. Physical origin of the correlations may be also interesting for pulsar studies.

scholarly journals AXPs & SGRs: Magnetar or Quarctar?

2012 ◽  
Vol 8 (S291) ◽  
pp. 474-476
Author(s):  
Guojun Qiao ◽  
Xionwei Liu ◽  
Renxin Xu ◽  
Yuanjie Du ◽  
Jinlin Han ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Loss Rate ◽  
Gamma Ray ◽  
Radiation Energy ◽  
X Ray ◽  
Two Factors ◽  
Normal Method ◽  
The Magnetic Field

AbstractThe concept of a “magnetar” was proposed mainly because of two factors. First, the X-ray luminosity of Anomalous X-ray Pulsars (AXPs) and Soft Gamma-Ray Repeaters (SGRs) is larger than the rotational energy loss rate (Lx > Ėrot), and second, the magnetic field strength calculated from “normal method” is super strong. It is proposed that the radiation energy of magnetar comes from its magnetic fields. Here it is argued that the magnetic field strength calculated through the normal method is incorrect at the situation Lx > Ėrot, because the wind braking is not taken into account. Besides, the “anti-magnetar” and some other X-ray and radio observations are difficult to understand with a magnetar model.Instead of the magnetar, we propose a “quarctar”, which is a crusted quark star in an accretion disk, to explain the observations. In this model, the persistent X-ray emission, burst luminosity, spectrum of AXPs and SGRs can be understood naturally. The radio-emitting AXPs, which are challenging the magnetar, can also be explained by the quarctar model.

GROUND STATE RESONANCES OF A HYDROGEN ATOM IN AN INTENSE MAGNETIC FIELD

1995 ◽  
Vol 07 (03) ◽  
pp. 311-361 ◽  
Author(s):  
RICHARD FROESE ◽  
ROGER WAXLER
Keyword(s):  
Magnetic Field ◽  
Angular Momentum ◽  
Hydrogen Atom ◽  
Time Evolution ◽  
Complex Plane ◽  
Exponential Decay ◽  
Ground State ◽  
Stationary States ◽  
Intense Magnetic Field ◽  
The Magnetic Field

We consider a hydrogen atom in a constant and very large magnetic field. For bounded angular momentum about the direction of the magnetic field we consider resonances in the sense of dilation analyticity. We find a class of resonances corresponding to quasi-stationary states which behave in a certain sense like ground states. The position of these resonances in the complex plane is estimated. Further it is shown that under the time evolution generated by the Hamiltonian for this system these quasi-stationary states exhibit exponential decay in time.

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