Nordita Astrophysics seminars

QPOs from magnetar giant flares

by Cecilia Chirenti

The possibility of doing neutron star (NS) asteroseismology is full of promises for a deeper understanding of NS composition and equation of state. The quasiperiodic oscillations (QPOs) detected so far in the tail of three giant flares in soft gamma repeaters have offered a first opportunity to identify the observed frequencies as stellar modes of oscillation. However, a clear cut solution of the inverse problem is made difficult by uncertainties in the nature of the oscillations and the many unknowns in the modeling of the star: mass, equation of state, magnetic field strength and geometry, etc. I will discuss recent results obtained from a re-analysis of the SGR 1806-20 data, which are consistent with a picture of numerous independently-excited modes that decay within a few tenths of a second. This has interesting implications for the rapidity of decay of the QPOs, which could occur by the previously-suggested mechanism of coupling to the MHD continuum.