Abstract
Abstract Magnetar giant flares are rare and highly energetic phenomena observed in the transient sky whose emission mechanisms are still not fully understood. Depending on the nature of the excited modes of the magnetar, they are also expected to emit gravitational waves (GWs), which may bring unique information about the dynamics of the excitation. A few magnetar giant flares have been proposed to be associated with short gamma-ray bursts. In this paper we use a new gravitational-wave search algorithm to revisit the possible emission of GWs from four magnetar giant flares within 5 Mpc. While no gravitational-wave signals were observed, we discuss the future prospects of detecting signals with more sensitive gravitational-wave detectors. In particular, we show that galactic magnetar giant flares that emit at least 1% of their electromagnetic energy as GWs could be detected during the planned observing run of the LIGO and Virgo detectors at design sensitivity, with even better prospects for third-generation detectors.
Highlights
IntroductionHighly magnetized young neutron stars with surface fields often surpassing > 1014 G, are known to exhibit rare extraordinary flares characterized by micro-to-millisecond gamma-ray flashes of energies 1044 − 1047 erg (isotropic-equivalent) followed by quasi-thermal pulsing tails at ∼ 1044 erg s−1 lasting hundreds of seconds
Magnetars, highly magnetized young neutron stars with surface fields often surpassing > 1014 G, are known to exhibit rare extraordinary flares characterized by micro-to-millisecond gamma-ray flashes of energies 1044 − 1047 erg followed by quasi-thermal pulsing tails at ∼ 1044 erg s−1 lasting hundreds of seconds
We in particular show that galactic magnetar giant flares that emit at least 1% of their electromagnetic energy as gravitational waves could be detected during the planned observing run of the LIGO and Virgo detectors at design sensitivity, with even better prospects for third generation detectors
Summary
Highly magnetized young neutron stars with surface fields often surpassing > 1014 G, are known to exhibit rare extraordinary flares characterized by micro-to-millisecond gamma-ray flashes of energies 1044 − 1047 erg (isotropic-equivalent) followed by quasi-thermal pulsing tails at ∼ 1044 erg s−1 lasting hundreds of seconds. These magnetar giant flares are, in terms of energy, the most extreme phenomena known from isolated neutron stars. The recent observation of GRB 200415a in the NGC 253 galaxy at 3.57 Mpc (Svinkin et al 2021) has regenerated much discussion as to magnetar giant flares being a distinct class of short gamma-ray bursts. A limit of 2.1 × 1044 erg has been set on the GW energy emitted by SGR 1806–20 for 3 of the short bursts that occured during the Advanced LIGO’s second observing run (Abbott et al 2019)
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