* Astronomy

Blobrana · L

RE: Magnetar

Blobrana · L

Title: Friedel crystals and the outer crust of magnetars
Authors: Paulo F. Bedaque, Simin Mahmoodifar, Srimoyee Sen (University of Maryland)

The strong magnetic fields found on the surface of magnetars are known to have profound effects in the physics of atoms in magnetar envelopes. We argue that the Friedel oscillations in the Coulomb force between the ions due to electron shielding can, for certain values of the parameters, be the dominant effect determining the crystal structure in the outer crust of magnetars. We estimate the densities and magnetic fields for which this occurs, compute some of the elastic moduli and lattice phonon dispersion relations in this "Friedel crystal" phase.

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Blobrana · L

Magnetars

Blobrana · L

Title: Pulsars are Born as Magnetars
Authors: Ricardo Heras

This paper suggests the idea that all neutron stars experienced at birth an ultrafast decay of their magnetic fields from their initial values to their current surface values. If the electromagnetic energy radiated during this field decay is converted into kinetic energy of the neutron star via the radiation reaction mechanism then the decay time is of the order of 10^(-4)s provided that the initial magnetic fields lie in the range of 10^(14)-10^(16)G. This means that all neutron stars are born with magnetic fields typical of magnetars. According to this model the neutron stars acquire their observed high space velocities during the birth ultrafast decay of their magnetic fields. The origin of this field decay points to magnetic instabilities occurring at the end of the birth process.

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Blobrana · L

RE: Magnetar

Blobrana · L

Cosmic blasts hint at inner magnetars

Powerful, mysterious and brief, -ray bursts are the flash bulbs of the cosmos. The brightest bursts outshine a million galaxies, then fade within minutes or hours. Only an extraordinarily energetic and localized event could generate such a brilliant flash. Most -ray bursts (GRBs) are thought to be triggered by the collapse or merger of stars to form black holes.
Until now, the short timescales and considerable variation among GRBs have made it hard to understand the physical processes at work. But recent observations from NASA's Fermi Gamma-ray Space Telescope, launched in 2008, and the Swift satellite, launched in 2004 and still going strong, have allowed astronomers to unpick the details of the explosions. Each mission has now detected more than 500 bursts, and results presented this week at the Gamma Ray Bursts 2010 Conference in Annapolis, Maryland, have added a twist to the standard fireball-to-black-hole plot.
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Blobrana · L

Magnetars

Blobrana · L

Title: The Twin Magnetars: SGR 1627-41 and 1E 1547-5408
Authors: S. Mereghetti, A. Tiengo, P. Esposito, G. Vianello, A. De Luca, D. Gotz, G. Weidenspointner, A. von Kienlin, G.L. Israel, L. Stella, N. Rea, R. Turolla, S. Zane

We report on recent results obtained thanks to Target of Opportunity observations of the two galactic sources SGR 1627-41 and 1E 1547-5408. These two transient sources present several similarities which support the interpretation of Anomalous X-ray Pulsars and Soft Gamma-ray Repeaters as a single class of strongly magnetised neutron stars.

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Blobrana · L

Title: Recent results on magnetars
Authors: Sandro Mereghetti

Several observations obtained in the last few years indicate that Soft Gamma-ray Repeaters (SGRs) and Anomalous X-ray Pulsars (AXPs) are basically a single class of isolated neutron stars. Their properties are well explained by the magnetar model, based on neutron stars powered by magnetic fields as high as 10^14 -10^15 G. Here I report some recent results obtained for the transient Soft Gamma-ray Repeater SGR 1627-41, that started a new outburst after about 10 years from the previous one, and for the Anomalous X-ray Pulsar 1E 1547.0-5408. The latter source recently showed a remarkable bursting activity, that reinforces the similarity between AXPs and SGRs.

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Blobrana · L

UvA-astronomer finds swarm of electrons around magnetars
For the first time astronomers have measured the physical processes through which so-called magnetars radiate X-rays. A team of researchers led by UvA-astronomer Nanda Rea found evidence for large electric currents around all known magnetars based on data from ESA's XMM-Newton X-ray satellite and the gamma telescope Integral.
Magnetars are young neutron stars with an ultra-strong magnetic field. Neutron stars are the remnants of heavy stars (10 to 50 solar masses) and consist for the most part of neutrons. A neutron star has a diameter of 20 km, but is heavier than the sun. A teaspoon of neutron star material weighs approximately 100 million tons. Other characteristics of a neutron star are a rapid rotation and a strong magnetic field. Magnetars are a separate class of neutron stars, their magnetic field is 1000 times stronger than that of ordinary neutron stars. They are the most powerful magnets in the cosmos. 15 magnetars have been found so far.

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