Pulsar Timing with the GBT

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Pulsar Timing with the GBT
Scott Ransom National Radio Astronomy Observatory
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Why NRAO's GBT for pulsars?
100-m fully steerable telescope in West
Virginia The GBT provides Sensitivity 2-5x
more sensitive than Jodrell Bank or
Parkes (Arecibo is 3-4x better) Sky
Coverage 85 of total sky 65-75 for Parkes
and JB 33 for Arecibo National Radio-Quiet
Zone Does not provide Extremely large amounts
of dedicated pulsar time (currently 20)
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Pulsar Timingwith the GBT
Approx 10 projects 50 millisecond
pulsars (MSPs) in clusters 12 high-precision
MSPs 5-6 interesting binaries (e.g.
J0737-3039) 1-2 young pulsars (e.g.
G21.5-0.9) 1 radio-loud magnetar 10-15 normal
PSRs
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Pulsars in Globular Clusters

• Clusters of ancient stars (9-12 billion years
  old) that orbit our galaxy
• Contain 105-106 stars, many of which have binary
  companions
• Very high densities (100-10,000 stars/ly3) result
  in stellar encounters and collisions!
• They are effectively millisecond pulsar factories
  (and exotic ones at that!)
• Number known has more than tripled since 2000

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Globular Cluster MSP Timing

• Almost all of the new pulsars are MSPs (50-716
  Hz)
• Approx half are isolated (this is a selection
  effect)
• Many exotic systems
• 10 highly eccentric (egt0.2) binaries
• 2 with main sequence companions? (Ter5ad and
  Ter5P the 1st and 5th fastest MSPs known)
• 7 eclipsing systems
• Timing precisions typically 20-50 µs (1 pulse
  period)

Terzan 5 (32 timing solns)
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Fastest Millisecond PulsarsAre many of the
fastest-spinning pulsars hidden?
Are the frequencies limited by gravitational
radiation?
5 of the 10 fastest-spinning pulsars show
eclipses. 5 of the 10 fastest-spinning pulsars
are found in Terzan 5
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Pulsar Timingwith the GBT
Approx 10 projects 50 millisecond
pulsars (MSPs) in clusters 12 high-precision
MSPs 5-6 interesting binaries (e.g.
J0737-3039) 1-2 young pulsars (e.g.
G21.5-0.9) 1 radio-loud magnetar 10-15 normal
PSRs
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High-Precision Timing A Pulsar Timing Array for
GW Detection

• Currently a large group including people from
  Berkeley, UBC, NRL, Bryn Mawr, NRAO, etc...
• Need 12-20 MSPs spread across the full sky
• Requires timing precisions of 100ns-1µs
  10-4-10-3 in phase
• Competing projects at Parkes and in Europe
• Will likely become a true international effort
  within the next couple years
• Long-term project (5-10 yrs)

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Current GBT PTA Status
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Pulsar Timingwith the GBT
Approx 10 projects 50 millisecond
pulsars (MSPs) in clusters 12 high-precision
MSPs 5-6 interesting binaries (e.g.
J0737-3039) 1-2 young pulsars (e.g.
G21.5-0.9) 1 radio-loud magnetar 10-15 normal
PSRs
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The Double-Pulsar Binary J0737-3039

• This system has two visible pulsars and is
  currently being studied primarily with the GBT.
  At least 5 tests of General Relativity have
  already been made, to a precision of better than
  0.05!

From Kramer et al., 2005, astro-ph/0503386
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Pulsar Timingwith the GBT
Approx 10 projects 50 millisecond
pulsars (MSPs) in clusters 12 high-precision
MSPs 5-6 interesting binaries (e.g.
J0737-3039) 1-2 young pulsars (e.g.
G21.5-0.9) 1 radio-loud magnetar 10-15 normal
PSRs
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Young Pulsar in G21.5-0.9

• PSR J1833-1034
• 61.8ms, likely lt1000 yo
• Very weak 70 µJy
• (Camilo et al 2005)

2nd highest Edot in galaxy (3x1037 ergs/s) Very
stable timing for a such a young PSR More likely
due to GLAST
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Outlook for the future...

• Prospects for new discoveries with the GBT are
  good
• Many more clusters to observe and search
• Upcoming all-sky surveys (many more MSPs)
• We really want more Holy Grails
• MSP-MSP binary
• PSR-BH binary
• sub-MSP
• Longer term, an Arecibo in the South would find
  and time hundreds of new cluster MSPs... (FAST?)
• Even longer term, the Square Kilometer Array will
  find thousands of new pulsars