Pulsar Timing with the GBT Scott Ransom National
Pulsar Timing with the GBT Scott Ransom National Radio Astronomy Observatory
Why NRAO's GBT for pulsars? 100 -m fully steerable telescope in West Virginia The GBT provides: Sensitivity 2 -5 x more sensitive than Jodrell Bank or Parkes (Arecibo is ~3 -4 x 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%)
Pulsar Timing with the GBT Approx 10 projects: ~50 millisecond pulsars (MSPs) in clusters ~12 high-precision MSPs 5 -6 interesting binaries (e. g. J 0737 -3039) 1 -2 young pulsars (e. g. G 21. 5 -0. 9) 1 radio-loud magnetar 10 -15 “normal” PSRs
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 (10010, 000 stars/ly 3) 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
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 (e>0. 2) binaries 2+ with main sequence companions? (Ter 5 ad and Ter 5 P – the 1 st and 5 th fastest MSPs known) 7 eclipsing systems Timing precisions typically 20 -50 μs (~1% pulse period) Terzan 5 (32 timing solns)
Fastest Millisecond Pulsars: Are many of the fastest-spinning pulsars hidden? Pulsar Name Spin Freq. (Hz) Eclipse Fraction Location J 1748 -2446 ad 716 0. 4 Terzan 5 B 1937+21 642 Isolated Gal. Plane B 1957+20 622 0. 1 Gal. Plane J 1748 -2446 O 596 0. 05 Terzan 5 J 1748 -2446 P 578 0. 4 Terzan 5 J 1843 -1113 542 Isolated Gal. Plane J 0034 -0534 533 None Gal. Plane J 1748 -2446 Y 488 None Terzan 5 J 1748 -2446 V 483 None Terzan 5 J 0023 -7203 J 476 0. 1 47 Tucanae 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
Pulsar Timing with the GBT Approx 10 projects: ~50 millisecond pulsars (MSPs) in clusters ~12 high-precision MSPs 5 -6 interesting binaries (e. g. J 0737 -3039) 1 -2 young pulsars (e. g. G 21. 5 -0. 9) 1 radio-loud magnetar 10 -15 “normal” PSRs
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 ~100 ns-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)
Current GBT PTA Status
Pulsar Timing with the GBT Approx 10 projects: ~50 millisecond pulsars (MSPs) in clusters ~12 high-precision MSPs 5 -6 interesting binaries (e. g. J 0737 -3039) 1 -2 young pulsars (e. g. G 21. 5 -0. 9) 1 radio-loud magnetar 10 -15 “normal” PSRs
The Double-Pulsar Binary: J 0737 -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
Pulsar Timing with the GBT Approx 10 projects: ~50 millisecond pulsars (MSPs) in clusters ~12 high-precision MSPs 5 -6 interesting binaries (e. g. J 0737 -3039) 1 -2 young pulsars (e. g. G 21. 5 -0. 9) 1 radio-loud magnetar 10 -15 “normal” PSRs
Young Pulsar in G 21. 5 -0. 9 PSR J 1833 -1034 61. 8 ms, likely <1000 yo Very weak: ~70 μJy (Camilo et al 2005) 2 nd highest Edot in galaxy (3 x 1037 ergs/s) Very stable timing for a such a young PSR More likely due to GLAST
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
- Slides: 17