Transcript G040141-00 - DCC

Neutron Star Normal Modes
LSC Meeting, Baton Rouge, March 2004
LIGO-G040141-00-Z
B.S. Sathyaprakash and Bernard Schutz
Cardiff University and AEI
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
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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)
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Stellar Modes
Neutron Star Normal Modes
Sathyaprakash and Schutz
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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
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Asteroseismology
Normal mode frequencies and damping times have the same dependence on R and M
M 13.4
(sec)  4
f
R10
1

M 1.4 
22
.
85

14
.
65


R
10 

Andersson-Kokkotas (1996-98)
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Asteroseismology
Unique estimation of Mass and Radius and EoS
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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
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March 10, 2004
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F- and W- modes in
Interferometers
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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
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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 B0833-45, The Vela
Pulsar and PSR B0531+21, The Crab Pulsar
– Jodrell also has unpublished data on pulsars showing peculiarities
in pulse periods – could be looked in coincidence with GW data
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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
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