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Gravitational waves from isolated neutronstarsIan Jones
General Relativity Group, Southampton University
Ian Jones Gravitational waves from isolated neutron stars 1/11
Outline
The state of gravitational wave detection
Ways in which neutron stars can emit gravitational waves
Signal analysis difficulties
Astrophysical input for known sources
Astrophysical input for unknown sources
Ian Jones Gravitational waves from isolated neutron stars 2/11
Outline
The state of gravitational wave detection
Ways in which neutron stars can emit gravitational waves
Signal analysis difficulties
Astrophysical input for known sources
Astrophysical input for unknown sources
Ian Jones Gravitational waves from isolated neutron stars 2/11
Outline
The state of gravitational wave detection
Ways in which neutron stars can emit gravitational waves
Signal analysis difficulties
Astrophysical input for known sources
Astrophysical input for unknown sources
Ian Jones Gravitational waves from isolated neutron stars 2/11
Outline
The state of gravitational wave detection
Ways in which neutron stars can emit gravitational waves
Signal analysis difficulties
Astrophysical input for known sources
Astrophysical input for unknown sources
Ian Jones Gravitational waves from isolated neutron stars 2/11
Outline
The state of gravitational wave detection
Ways in which neutron stars can emit gravitational waves
Signal analysis difficulties
Astrophysical input for known sources
Astrophysical input for unknown sources
Ian Jones Gravitational waves from isolated neutron stars 2/11
The state of gravitational wave detection
The three US detectors, LIGO, have officially reached their initialdesign sensitivity.
The Anglo-German detector GEO600 is at design sensitivity atfrequencies above 200 Hz.
The fifth science run, taking coincident data, began in November,and will last about 18 months.
The Italian-French VIRGO is carrying out engineering runs, but isgetting close to science mode.
People are beginning to get jumpy...
Ian Jones Gravitational waves from isolated neutron stars 3/11
LIGO performance
Ian Jones Gravitational waves from isolated neutron stars 4/11
Ways in which neutron stars can emitgravitational waves
We are interested in continuous (approximately) monochromaticsources:
Fluid oscillations, e.g. r-modes
Free precession
Triaxialty:
h =
(
2
15
)1/2G
c48Ω2
dεI,
where ε = ∆I/I measures the fractional difference between twoperpendicular moments of inertia.
Ian Jones Gravitational waves from isolated neutron stars 5/11
Signal analysis difficulties
A continuous monochromatic source is specified by 7 parameters:
θ = (h0, f, α, δ, φ0, ι, ψ)
Real systems will probably require additional parameterisation,e.g. spin-down or binary-induced Doppler modulation.
The way search proceeds depends upon whether source isknown or unknown.
Ian Jones Gravitational waves from isolated neutron stars 6/11
Known sources: naive bounds onamplitude
Upper limits on GW emission from triaxial neutron stars can beused to decide which pulsars to target:
0 1 2 3 4
log10 frequency/Hz
-29
-28
-27
-26
-25
-24
-23
-22
log 10
of a
mpl
itude
and
11.
4*no
ise
for a
1-y
ear o
bser
vatio
n
Crab
Vela
J0537-6910
J1952+3252
Sco X-1
J0205+6449
J2229+6114J1913+1011
J0437-4715
GEO600Initial LIGOVIRGOAdvanced LIGOPulsarsLMXBs
Upper bounds on h from pulsar spin-down
Ian Jones Gravitational waves from isolated neutron stars 7/11
Known sources: more realistic bounds onamplitude
A more realistic picture is obtained if we assume ε can be nolarger than 10−7 (see Brynmor Haskell’s poster):
0 1 2 3 4
log10 frequency/Hz
-29
-28
-27
-26
-25
-24
-23
-22
log 10
of a
mpl
itude
and
11.
4*no
ise
for a
1-y
ear o
bser
vatio
n
CrabVela
J0537-6910
J1952+3252
Sco X-1
Crab
GEO600Initial LIGOVIRGOAdvanced LIGOPulsarsLMXBs
Upper bounds on h
Ian Jones Gravitational waves from isolated neutron stars 8/11
Known sources: astrophysicalinputs/issues
Find new stars, probably MSPs or young close stars
Can one extract further information from radio data, viz ι, theinclination angle via pulsar beam width (à la Rankin) or viapolarisation sweep? How reliable is this?
Is it worthwhile targeting isolated non-pulsating stars?
How secure is evidence that MSP spin-down iselectromagnetically driven?
Ian Jones Gravitational waves from isolated neutron stars 9/11
Known sources: astrophysicalinputs/issues
Find new stars, probably MSPs or young close stars
Can one extract further information from radio data, viz ι, theinclination angle via pulsar beam width (à la Rankin) or viapolarisation sweep? How reliable is this?
Is it worthwhile targeting isolated non-pulsating stars?
How secure is evidence that MSP spin-down iselectromagnetically driven?
Ian Jones Gravitational waves from isolated neutron stars 9/11
Known sources: astrophysicalinputs/issues
Find new stars, probably MSPs or young close stars
Can one extract further information from radio data, viz ι, theinclination angle via pulsar beam width (à la Rankin) or viapolarisation sweep? How reliable is this?
Is it worthwhile targeting isolated non-pulsating stars?
How secure is evidence that MSP spin-down iselectromagnetically driven?
Ian Jones Gravitational waves from isolated neutron stars 9/11
Known sources: astrophysicalinputs/issues
Find new stars, probably MSPs or young close stars
Can one extract further information from radio data, viz ι, theinclination angle via pulsar beam width (à la Rankin) or viapolarisation sweep? How reliable is this?
Is it worthwhile targeting isolated non-pulsating stars?
How secure is evidence that MSP spin-down iselectromagnetically driven?
Ian Jones Gravitational waves from isolated neutron stars 9/11
Unknown sources: astrophysicalinputs/issues
Where to look? What are relative merits of Galactic centre, Gouldbelt, nearest portion of nearest spiral arm, supernova remnants?
How realistic is the Blandford argument, i.e. how plausible is itthat there exists a population of electromagnetically-quiet starsspinning down due to GW emission?
In particular, is it possible to use existing (non-)measurements toconstrain such a population?
Ian Jones Gravitational waves from isolated neutron stars 10/11
Unknown sources: astrophysicalinputs/issues
Where to look? What are relative merits of Galactic centre, Gouldbelt, nearest portion of nearest spiral arm, supernova remnants?
How realistic is the Blandford argument, i.e. how plausible is itthat there exists a population of electromagnetically-quiet starsspinning down due to GW emission?
In particular, is it possible to use existing (non-)measurements toconstrain such a population?
Ian Jones Gravitational waves from isolated neutron stars 10/11
Unknown sources: astrophysicalinputs/issues
Where to look? What are relative merits of Galactic centre, Gouldbelt, nearest portion of nearest spiral arm, supernova remnants?
How realistic is the Blandford argument, i.e. how plausible is itthat there exists a population of electromagnetically-quiet starsspinning down due to GW emission?
In particular, is it possible to use existing (non-)measurements toconstrain such a population?
Ian Jones Gravitational waves from isolated neutron stars 10/11
Summing up
There are many ways in which astrophysicists can aid GW searches.Of particular importance are:
Finding new targets
Extracting further information from radio data
Assessing GW interest of non-pulsating stars
Deciding where best to look for unknown sources
Assessing the likelihood of there being a sizable‘electromagnetically invisible’ neutron star population (à laBlandford).
Ian Jones Gravitational waves from isolated neutron stars 11/11
Summing up
There are many ways in which astrophysicists can aid GW searches.Of particular importance are:
Finding new targets
Extracting further information from radio data
Assessing GW interest of non-pulsating stars
Deciding where best to look for unknown sources
Assessing the likelihood of there being a sizable‘electromagnetically invisible’ neutron star population (à laBlandford).
Ian Jones Gravitational waves from isolated neutron stars 11/11
Summing up
There are many ways in which astrophysicists can aid GW searches.Of particular importance are:
Finding new targets
Extracting further information from radio data
Assessing GW interest of non-pulsating stars
Deciding where best to look for unknown sources
Assessing the likelihood of there being a sizable‘electromagnetically invisible’ neutron star population (à laBlandford).
Ian Jones Gravitational waves from isolated neutron stars 11/11
Summing up
There are many ways in which astrophysicists can aid GW searches.Of particular importance are:
Finding new targets
Extracting further information from radio data
Assessing GW interest of non-pulsating stars
Deciding where best to look for unknown sources
Assessing the likelihood of there being a sizable‘electromagnetically invisible’ neutron star population (à laBlandford).
Ian Jones Gravitational waves from isolated neutron stars 11/11
Summing up
There are many ways in which astrophysicists can aid GW searches.Of particular importance are:
Finding new targets
Extracting further information from radio data
Assessing GW interest of non-pulsating stars
Deciding where best to look for unknown sources
Assessing the likelihood of there being a sizable‘electromagnetically invisible’ neutron star population (à laBlandford).
Ian Jones Gravitational waves from isolated neutron stars 11/11
