Describing SGRs/AXPs as fast and magnetized white dwarfs

TL;DR

Recent observations of SGRs/AXPs with low magnetic fields and long periods suggest they may be better explained as fast, magnetized white dwarfs rather than traditional neutron star magnetars, challenging existing models.

Contribution

This paper proposes a white dwarf pulsar model for SGRs/AXPs, offering an alternative explanation based on recent low-field, fast-spinning white dwarf observations.

Findings

SGRs/AXPs with low magnetic fields share properties with fast white dwarf pulsars.

The white dwarf model explains observational properties more simply than neutron star models.

Recent discoveries support the classification of some SGRs/AXPs as massive, fast white dwarfs.

Abstract

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?