Search for quasi-periodic signals in magnetar giant flares

Abstract

Quasi-periodic oscillations (QPOs) discovered in the decaying tails of giant flares of magnetars are believed to be torsional oscillations of neutron stars. These QPOs have a high potential to constrain properties of high-density matter. In search for quasi-periodic signals, we study the light curves of the giant flares of SGR 1806-20 and SGR 1900+14, with a non-parametric Bayesian signal inference method called D${}^3$PO. The D${}^3$PO algorithm models the raw photon counts as a continuous flux and takes the Poissonian shot noise as well as all instrument effects into account. It reconstructs the logarithmic flux and its power spectrum from the data. Using this fully noise-aware method, we do not confirm previously reported frequency lines at $\nu \gtrsim 17$Hz because they fall into the noise-dominated regime. However, we find two new potential candidates for oscillations at $9.2$Hz (SGR 1806-20) and $7.7$Hz (SGR 1900+14). If these are real and the fundamental magneto-elastic oscillations of the magnetars, current theoretical models would favour relatively weak magnetic fields $\bar{B}\sim 6\times 10^{13}-3\times 10^{14}$G (SGR 1806-20) and a relatively low shear velocity inside the crust compared to previous findings.

References in corpus (42)

• The McGill Magnetar Catalog
• Discovery of Rapid X-ray Oscillations in the Tail of the SGR 1806-20 Hyperflare
• Discovery of Fast X-ray Oscillations During the 1998 Giant Flare from SGR 1900+14
• Global Seismic Oscillations in Soft Gamma Repeaters
• Neutron Star Asteroseismology. Axial Crust Oscillations in the Cowling Approximation
• The 2004 Hyperflare from SGR 1806-20: Further Evidence for Global Torsional Vibrations
• Detection with RHESSI of high frequency X-ray oscillations in the tail of the 2004 hyperflare from SGR 1806-20
• Magnetohydrodynamics of superfluid and superconducting neutron star cores
• Torsional Oscillations of Relativistic Stars with Dipole Magnetic Fields
• QPOs during magnetar flares are not driven by mechanical normal modes of the crust
• Magneto-elastic oscillations of neutron stars with dipolar magnetic fields
• On the theory of magnetar QPOs
• Constraints on Neutron Star Crusts From Oscillations in Giant Flares
• Shear Waves and Giant Flare Oscillations from Soft Gamma-Ray Repeaters
• Elastic or magnetic? A toy model for global magnetar oscillations with implications for QPOs during flares
• Alfvén QPOs in Magnetars
• Reconstruction of Gaussian and log-normal fields with spectral smoothness
• Magnetars oscillations in the presence of a crust
• Effect of superfluidity on neutron star crustal oscillations
• Magneto-elastic oscillations and the damping of crustal shear modes in magnetars
• The Denoised, Deconvolved, and Decomposed Fermi $\gamma$-ray sky - An application of the D${}^3$PO algorithm
• Alfven QPOs in magnetars in the anelastic approximation
• Magnetar Oscillations I: strongly coupled dynamics of the crust and the core
• Reconstruction of signals with unknown spectra in information field theory with parameter uncertainty
• On the Quasi-Periodic Oscillations of Magnetars
• Quasi-Periodic Oscillations in Short Recurring Bursts of the Soft-Gamma Repeater J1550-5418
• RESOLVE: A new algorithm for aperture synthesis imaging of extended emission in radio astronomy
• Quasi-periodic oscillations in superfluid magnetars
• Quasi-Periodic Oscillations in Short Recurring Bursts of the magnetars SGR 1806-20 and SGR 1900+14 Observed With RXTE
• Imprints of superfluidity on magneto-elastic QPOs of SGRs
• Torsional Oscillations of Magnetized Relativistic Stars
• Stratification, superfluidity and magnetar QPOs
• Possible identifications of newly observed magnetar quasi-periodic oscillations as crustal shear modes
• Magnetar Oscillations II: spectral method
• D${}^3$PO - Denoising, Deconvolving, and Decomposing Photon Observations
• Axial quasi-normal modes of neutron stars: Accounting for the superfluid in the crust
• Bayesian timing analysis of giant flare of SGR 1806-20 by RXTE PCA
• Coherent magneto-elastic oscillations in superfluid magnetars
• Intermittency and Lifetime of the 625 Hz QPO in the 2004 Hyperflare from the Magnetar SGR 1806-20 as evidence for magnetic coupling between the crust and the core
• Magnetar giant flare oscillations and the nuclear symmetry energy
• Dynamic system classifier
• Correlated signal inference by free energy exploration

Cited by in corpus (15)

• The Galactic Faraday depth sky revisited
• Constraints on the nuclear equation of state and the neutron star structure from crustal torsional oscillations
• Constraining properties of high-density matter in neutron stars with magneto-elastic oscillations
• On the Persistence of QPOs During the SGR 1806-20 Giant Flare
• Evidence for a strong 19.5 Hz flux oscillation in Swift BAT and Fermi GBM gamma-ray data from GRB 211211A
• Denoising, deconvolving and decomposing multi-domain photon observations- The D4PO algorithm
• Tangled magnetic field model of QPOs
• Torsional oscillations of magnetized neutron stars with mixed poloidal-toroidal fields
• Zeeman splitting of torsional oscillation frequencies of magnetars
• Selfsimilarity relations for torsional oscillations of neutron stars
• Powerful flares and magneto-elastic oscillations of magnetars
• Separating diffuse from point-like sources - a Bayesian approach
• Misidentification of Short GRBs as Magnetars in Nearby Galaxies
• Zeeman effect in oscillations of magnetars with toroidal magnetic fields
• Nonlinear coupling between magnetar QPOs