Soft gamma repeaters (SGRs) and anomalous X-ray pulsars (AXPs) are thought to be magnetars: neutron stars powered by extreme magnetic fields. These rare objects are characterized by repeated and sometimes spectacular gamma-ray bursts. The burst mechanism might involve crustal fractures and excitation of non-radial modes which would emit gravitational waves (GWs). We present the results of a search for GW bursts from six galactic magnetars that is sensitive to neutron star f-modes, thought to be the most efficient GW emitting oscillatory modes in compact stars. One of them, SGR 0501+4516, is likely ∼1kpc from Earth, an order of magnitude closer than magnetars targeted in previous GW searches. A second, AXP 1E 1547.0-5408, gave a burst with an estimated isotropic energy > 1044erg which is comparable to the giant flares. We find no evidence of GWs associated with a sample of 1279 electromagnetic triggers from six magnetars occurring between 2006 November and 2009 June, in GW data from the LIGO, Virgo, and GEO600 detectors. Our lowest model-dependent GW emission energy upper limits for band- and time-limited white noise bursts in the detector sensitive band, and for f-mode ringdowns (at 1090Hz), are 3.0 x 1044 d21 erg and 1.4 x 1047 d21 erg, respectively, where and d1 = d0501/ 1 kpc and d0501 is the distance to SGR 0501+4516. These limits on GW emission from f-modes are an order of magnitude lower than any previous, and approach the range of electromagnetic energies seen in SGR giant flares for the first time.
J. Abadie et al., "Search for Gravitational Wave Bursts from Six Magnetars," Astrophysical Journal Letters, vol. 734, no. 2 PART 2, Institute of Physics - IOP Publishing, Jun 2011.
The definitive version is available at https://doi.org/10.1088/2041-8205/734/2/L35
Keywords and Phrases
Gravitational waves; Stars: Magnetars
International Standard Serial Number (ISSN)
Article - Journal
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