The Arecibo Remote Command Center at UWM: Searching for ... · What are gravitational waves? •...

The Arecibo Remote Command Center at UWM: Searching for gravitational waves using pulsars

Xavier Siemens

Sunday, November 13, 2011

What are gravitational waves?

• Predicted by Einstein in 1918, ripples in space and time analogous to electromagnetic waves

• Gravitational waves act in two directions at once!

GW direction

• The strain produced by a gravitational waveh

h =δL

L

L

δL

Astrophysical strains we expect

h ∼ 10−21

L ∼ 4 lyδL ∼ 10−5 m

+

diameter of a human hair!

Credit: Warren Anderson


Why bother trying to detect them?

• As we have added more frequencies with electromagnetic telescopes we have discovered amazing new things about the universe

• The idea is gravitational waves will lead us to similarly revolutionary growth in our understanding of the universe


Burst sources-Cosmic strings, Supermassive BBH fly-bys, unknown unkowns

NASA

Types of gravitational wave sources

NASA



Binary black hole inspirals: continuous waves



Stochastic background

NASA

Gravitational analog of cosmic microwave backgroundSunday, November 13, 2011

Stochastic Backgrounds

Gravitational radiation produced by an extremely large number of weak, independent and unresolved gravity-wave sources.

Credit: Jolien Creighton• Astrophysical Sources:

Black Hole Binaries, NS Binaries, White Dwarf Binaries...

• Cosmological Sources: Inflation, Cosmic Strings, Preheating, Phase Transitions...


Pulsars Beams of radio waves

Magnetic field

Pulsars are a type of neutron star: Common end products of stellar evolution

Pulsar mass ~ 1 solar mass, size = 10 km

Pulsars are extremely dense (nuclear density) 1 teaspoon weighs 10 million tons


Adresse Paris

paris - Google Maps http://maps.google.fr/maps?hl=fr&q=paris&ie=UTF8&hq=&hn...

1 of 1 4/27/11 3:05 PM


Pulsars Beams of radio waves

Magnetic field

Pulsars appear to us to emit short bursts (pulses) of radio waves

Pulsars are a type of neutron star: Common end products of stellar evolution

Pulsar mass ~ 1 solar mass, size = 10 km

Pulsars are extremely dense (nuclear density) 1 teaspoon weighs 10 million tons


How do we detect gravitational waves with pulsars?

• Because pulsars are extremely dense they rotate stably. We use them as clocks to construct a galactic scale GW detector

• Gravitational waves are ripples in space-time that change the arrival times of the steady train of radio pulses emitted by the pulsar

gravitational waves


Searches for gravitational waves using pulsars• We can predict when a particular pulse from a pulsar will arrive at our

radio telescope.

• But we don’t get it quite right, there are small differences between what when we expect the pulse and when it actually arrives at our radio telescope.

Arrival of pulse

A year later

Predicted arrival Actual arrival

Train of pulses 1 year ago Train of pulses today

• Gravitational waves change the time of arrival of pulses so we can look for gravitational waves in those differences


Searches for gravitational waves in pulsar timing data

• Can do these measurements very accurately, a few times a month for a few years

Jenet, Lommen, Larson, and Wen (2004)

• Lowest frequency GW we’re sensitivty to set by observation length T

• Highest frequency by Nyquist theoremSunday, November 13, 2011

Would like to build a pulsar timing array: A network of pulsars with which to look for GWs

There are about 2000 known pulsars in our galaxy.

Only a handful suitable for gravitational wave detection, Arecibo Remote Command Center at UWM ARCC@UWM activities

focused on finding more pulsars

David Champion


PTAs around the world and the IPTA

NANOGrav

PPTA

EPTA

Credit: Brian Burtsee also Hobbs et al 2010


ARCC@UWM

Justin EllisUWM Graduate

Student

Kathy GustavsonScience teacher

Nicolet HS

Jean CreightonUWM Planetarium

director

Dawn ErbFaculty

David KaplanFaculty

Beth SpearScience teacher Kenosha HS

Brian VlcekUWM Graduate

Student

Sydney ChamberlinUWM Grad Student


Research Activities Remote observing

Green Bank, WVArecibo, PR


Pulsars discovered by us (finding pulsars is hard!)

• Arecibo data

• GBT data (Fermi pulsar)

• In the last 9 months we (UWM) discovered 6-7 new pulsars (one of which is very interesting), confirmed two new millisecond pulsars


Research Activities Data analysis

• Looked at over 400,000 of these


Other activities

• Following up interesting candidates (radio, X-ray, gamma ray)

• Using neural networks (teach machines to do some of our work) to sort through pulsar candidates.

• Have a very large computing cluster called Nemo (~4000 CPUs), analyze the radio data we collect


The Arecibo Remote Command Center at UWM: Searching for ... · What are gravitational waves? •...

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