Gravitational waves from SGRs and AXPs as fast-spinning white dwarfs

TL;DR

This paper proposes that certain Soft Gamma Repeaters and Anomalous X-Ray Pulsars are fast-spinning white dwarfs, and predicts their gravitational wave signals could be detected by space-based observatories, supporting the white dwarf pulsar model.

Contribution

It introduces the novel idea that SGRs/AXPs can be modeled as white dwarf pulsars emitting detectable gravitational waves, a first in the literature.

Findings

Some SGRs/AXPs could be detected by BBO and DECIGO within 1-5 years.

Detection of GWs would support the white dwarf pulsar hypothesis.

Highly magnetized neutron star models are below detection sensitivity.

Abstract

Gravitational waves (GWs) emission due to magnetic deformation mechanism is applied for Soft Gamma Repeaters (SGRs) and Anomalous X-Ray Pulsars(AXPs), described as fast-spinning and magnetized white dwarfs (WDs). The emission is caused by the asymmetry around the rotation axis of the star generated by its own intense magnetic field. Thus, for the first time in the literature, it is estimated the GWs counterpart for SGRs/AXPs described as WD pulsars. We find that some SGRs/AXPs can be observed by the space detectors BBO and DECIGO. In particular, 1E 1547.0-5408 and SGR 1806-20 could be detected in 1 year of observation, whereas SGR 1900+14, CXOU J171405.7-381031, Swift J1834.9-0846 and SGR 1627-41 could be observed with a 5-year observation time. We also found that SGRs/AXPs as highly magnetized neutron stars are far below the sensitivity curves of BBO and DECIGO. This result indicates that a possible detection of continuous GWs originated from these objects would corroborate the WD pulsar model.