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 \sim 1 kpc 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 > 10 ^ { 44 } erg 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 November 2006 and June 2009 , 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 1090 Hz ) , are 3.0 \times 10 ^ { 44 } d _ { \mathrm { 1 } } ^ { 2 } erg and 1.4 \times 10 ^ { 47 } d _ { \mathrm { 1 } } ^ { 2 } erg respectively , where d _ { \mathrm { 1 } } = \frac { d _ { \mathrm { 0501 } } } { 1 \mathrm { kpc } } and d _ { \mathrm { 0501 } } 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 .