Pulsar Array Gravitational-wave Observatory

Andrea N. LommenAssistant Professor of Physics and Astronomy

Head of Astronomy Program

Director of Grundy Observatory

Franklin and Marshall College

Lancaster, PA

Collaborators

• David Nice, Bryn Mawr College • Ingrid Stairs, U. British Columbia• Don Backer, UC Berkeley• Paul Demorest, NRAO• Rob Ferdman, U. British Columbia,• Dick Manchester, ATNF• Bill Coles, UC San Diego• George Hobbs, ATNF• Rick Jenet, UT Brownsville

20yrs of B1855+09

PSR J1713+0747 over 12 years

€

Ωgw ( f ) =2

3

π 2

H02f 2hc ( f )

2

fmin =1

dataspan

hc ( fmin ) ≤rms

dataspan

Ωgw ( f ) ≤rms2

dataspan4

From Jenet, Hobbs, van Straten, Manchester, Bailes, Verbiest, Edwards, Hotan, Sarkissian & Ord (2006)

Arecibo dominates by length of data set

Figure courtesy of George Hobbs

Some Possible Sources of Burst Radiation

• Formation of SMBH (Thorne and Braginski ‘76)

• Close encounters of massive objects (Kocsis 06)

• Highly eccentric SMBH binaries (Enoki and Nagashima ‘06)

• Cosmic Strings (Damour and Vilenkin ‘01)

The shape of the GW response

Thanks Bill Coles

Detection algorithm: Weighted sum of residuals

So what can we detect?• 20 pulsars, 1 microsecond RMS, daily obs, we

would detect a 0.70 microsecond maximum response about 93% of the time. For a 2-week burst we calculate the corresponding characteristic strain:

Max response (us)

Characteristic strain (h)

Percent detected

0.7 3.3e-13 93

0.5 2.3e-13 40

0.3 1.4e-13 2

Scaling that last slide

• Statistic scales as number of pulsars so e.g. measurable strains halve if number of pulsars doubles

• Response scales as burst length, so measurable strains halve if burst length doubles

• If 20 pulsars have 100 ns RMS, divide left two columns by 10

Sensitivity to a 0.75 s 2-week burst, daily observing, 20 pulsars

Sensitivity to a 0.75 s 2-week burst, daily observing, 20 pulsars

Sensitivity to a 0.75 s 2-week burst, daily observing, 20 pulsars

Sensitivity to a 0.75 s 2-week burst, daily observing, 20 pulsars + 3 more

Wish-list

• Back to 20 observations per year• Wide-band multi-frequency

observations (800MHz + Lband + Sband)

• Clone of NRAO pulsar “dream” machine. 800 MHz coherent dedispersion with FPGAs

• Observing system stream-lined.

Summary and Prospects

• Arecibo is needed for detection of GWs.• Arecibo is leading, and is poised to continue

to do so, but at one observing session every two months it will lose its edge.

• P-ALFA searches important for discovering new pulsars for the array.

• North American Pulsar Timing Array meeting next weekend

Detectability of a Waveform

• “Recall”

€

R(t) =1

21+ cosμ( ) r+ t( )cos 2ψ( ) + r× t( )sin 2ψ( )[ ]

r+,× t( ) = r+,×e − r+,×

p

r+,×e = h+,×

e τ( )0

t

∫ dτ

r+,×p = h+,×

p τ −d

c1− cosμ( )

⎡ ⎣ ⎢

⎤ ⎦ ⎥

0

t

∫ dτ

(Jenet, Lommen, Larson and Wen 2004)