Monday, July 22, 2013

1307.5074 (M. Malheiro et al.)

Describing SGRs/AXPs as fast and magnetized white dwarfs    [PDF]

M. Malheiro, J. G. Coelho
Over the last decade, observational evidence has mounted that SGRs/AXPs belong to a particular class of pulsars. Furthermore, fast and very magnetic white dwarfs have been observed, and recently two SGRs with low magnetic fields $B\sim(10^{12}-10^{13})$ G, namely SGR 0418+5729 and Swift J1822.3-1606 were discovered with a period of $P\sim9.08$ s and $P\sim8.44$ s, respectively. These new discoveries opens the question of the nature of SGRs/AXPs, emerging alternative scenarios, in particular the white dwarf (WD) pulsar model. These astronomical observations have based an alternative description of the SGRs/AXPs expressed on rotating highly magnetized and very massive WDs. In this new description, several observational properties are easy understood and well explained as a consequence of the large radius of a massive white dwarf that manifests a new scale of mass density, moment of inertia, rotational energy, and magnetic dipole moment in comparison with the case of neutron stars. In this contribution, we will show that these recent discoveries of SGRs with low magnetic field share some properties with the recent detected fast WD pulsar AE Aquarii, and also with RXJ 0648.0-4418, and EUVE J0317-855, supporting the understanding of at least these SGRs with low-B as belonging to a class of very fast and magnetic massive WDs. Furthermore, these recent astronomical observations suggest that we should revisit the real nature of AXP/SGRs: are they really magnetars or very fast and massive white dwarfs?
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