Neutron Star Normal Modes LSC Meeting Baton Rouge

Neutron Star Normal Modes LSC Meeting, Baton Rouge, March 2004 LIGO-G 040141 -00 -Z B. S. Sathyaprakash and Bernard Schutz Cardiff University and AEI Neutron Star Normal Modes Sathyaprakash and Schutz March 10, 2004

Neutron Stars • Great interest in detecting radiation: physics of such stars is poorly understood. – After 35 years we still don’t know what makes pulsars pulse or glitch. – Interior properties not understood: equation of state, superfluidity, superconductivity, solid core, source of magnetic field. – May not even be neutron stars: could be made of strange matter! Neutron Star Normal Modes Sathyaprakash and Schutz March 10, 2004 2

Gravitational Waves from Pulsating Neutron Stars NS Formation Secular Instabilities Andersson, Jones & KK (2002) Neutron Star Normal Modes Sathyaprakash and Schutz Dimmelmeier, Font & Mueller (2002) NS merger Shibata & Uryu (2002) March 10, 2004 3

Stellar Modes Neutron Star Normal Modes Sathyaprakash and Schutz • G-modes or gravity-modes: buoyancy is the main restoring force • P-modes or pressure-modes: main restoring force is the pressure • F-mode or fundamental-mode: (surface waves) has an intermediate character of p - and g-mode • W-modes: pure space-time modes (only in GR, space-time curvature is the restoring agent) • Inertial modes (r-mode) : main restoring force is the Coriolis force (σ~2Ω/3) • Superfluid modes: Deviation from chemical equilibrium provides the main restoring agent March 10, 2004 4

Asteroseismology Normal mode frequencies and damping times have the same dependence on R and M Andersson-Kokkotas (1996 -98) Neutron Star Normal Modes Sathyaprakash and Schutz March 10, 2004 5

Asteroseismology Unique estimation of Mass and Radius and Eo. S Neutron Star Normal Modes Sathyaprakash and Schutz March 10, 2004 6

Signal Strengths of Normal Modes • Glitch the energy – Crab/Vela glitches could deposit energy in normal modes as high as 10– 12 Msun • Energy in normal modes when a neutron star forms could be as high as 10– 8 Msun • Normal modes excited due to glitches in Vela will have an amplitude of 10– 24 • It is possible that a newly born NS can be observed in normal modes in our own Galaxy Neutron Star Normal Modes Sathyaprakash and Schutz March 10, 2004 7

F- and W- modes in Interferometers Neutron Star Normal Modes Sathyaprakash and Schutz March 10, 2004 8

Analysis Plan • Make a catalogue of potential sources of normal modes (T. Regimbau) – Glitches in radio pulsars, especially Crab and Vela • Set up collaborations with Radio, Gamma and X-ray Astronomers to set up time-windows to search for normal modes – Accretion onto neutron stars could produce seismic disturbances that could lead to intermittent emission of normal modes. • Should coordinate with X-ray/Gamma-ray observations • Use existing LAL codes to set up a search pipeline (R. Balasubramanian) – Add a piece to carry out triggered searches for NS modes – Explore if we can use the existing triggered search codes Neutron Star Normal Modes Sathyaprakash and Schutz March 10, 2004 9

Coordinated Searches with Radio Data • Why pulsars glitch – 3 decades after pulsars are discovered we don’t fully understand why pulsars pulse or glitch – Observing normal modes in neutron stars, combined with radio observations, could teach us about glitches, equation-of-state of high-density neutrons (or other matter) • Collaborate with Jodrell Bank – Jodrell and can provide glitch data on PSR B 0833 -45, The Vela Pulsar and PSR B 0531+21, The Crab Pulsar – Jodrell also has unpublished data on pulsars showing peculiarities in pulse periods – could be looked in coincidence with GW data Neutron Star Normal Modes Sathyaprakash and Schutz March 10, 2004 10

Benefits from the study • Independent (maybe unique) estimation of stellar parameters (mass, radius, EOS, rotation) • Understanding of the microphysics in the early stages of NS formation • Discovering exotic EOS Neutron Star Normal Modes Sathyaprakash and Schutz March 10, 2004 11