Pulsar Science with the SKA
Dr. Michael Keith – University of Manchester, Jodrell Bank Centre for Astrophysics
On behalf of the CSP and SDP consortia and the Pulsar Science Working Group Thanks to M. Kramer and B. Stappers for many slides Pulsars…
…cosmic lighthouses …almost Black Holes: mass of ~1.4 Solar Mass within 20km …objects of extreme matter 10x nuclear density 13 B ~ Bcr = 4.4 x 10 Gauss Voltage drops ~ 1012 volts 10-12 FEM = 10 Fgravity High-temperature & superfluid superconductor …natural clocks with wide range of periods:
J1748-2446ad Period J2144-3933 1.4 ms 8.5 s
42,960 Rotations per Minute 7
è Lots of interesting precision physics… Already today, we can do amazing measurements…
Masses:
• Masses of neutron stars: m1 = 1.4398(2) M⊙ and m2 = 1.3886(2) M⊙ (Weisberg et al. 2010) • Mass of WD companions:
– Shapiro: 0.204(2) M⊙ (Jacoby et al. 2005)
– Optical: 0.181(7) M⊙ (Antoniadis et al. 2013)
• Mass of millisecond pulsar: 1.67(2) M⊙ (Freire et al. 2010)
• Main sequence star companion: 1.029(8) M⊙ (Freire et al. 2010) Spin parameters: • Period: 5.757451924362137(2) ms (Verbiest et al. 2008) = 2 atto seconds uncertainty! Orbital parameters: • Period: 0.102251562479(8) day (Kramer et al. in prep.) • Eccentricity: 3.5 (1.1) × 10−7 (Freire et al. 2012) Astrometry: • Distance: 157(1) pc (Verbiest et al. 2008) • Proper motion: 140.915(1) mas/yr (Verbiest e t al. 2008) GR tests: • Periastron advance: 4.226598(5) deg/yr (Weisberg et al. 2010) • Shrinkage due to GW emission: 7.152±0.008 mm/day (Kramer et al. in prep) • GR validity (obs/exp): 1.0000(5) (Kramer et al. in prep.)
But with the SKA…we can do so much more!!
So far, pulsar science hasn’t done badly…
• Pulsar astrophysics has a quite impressive track record of discoveries
• Large range of applications in the widest area of physics and astrophysics
from smallest (=solid states physics) to largest scales (=grav. physics)
• Don’t think that we have enough! … quite the opposite!
• The SKA is a superb instrument for pulsar research:
- large collecting area Never have enough of that..! - large fractional bandwidth
- large field-of-view Monitoring and searching with - multi-beaming capabilities excellent cadence & survey speed
• We have high expectations based on previous and recent experience Key Science and more…
• Key Science (“Gravity with pulsars and BHs”) described in Kramer et al. (2004) • Key Science capabilities enable a wide range of further exciting science, as described in Cordes et al. (2004) and other chapters: Cosmic census for pulsars: - Galactic population of radio emitting neutron stars (pulsars, magnetars etc.) - Galactic centre pulsars - Globular clusters & external galaxies Fundamental physics: - Tests of theories of gravity, incl. BH properties - Detection and study of gravitational waves, GW astronomy - Equation-of-state of super-dense matter, structure of neutron stars Relativistic plasma physics: Pulsar magnetospheres, emission physics. Mapping the Milky Way: interstellar medium, Galactic magnetic field. Properties of the intergalactic medium: giant pulses from extragalactic pulsars. Core-collapse supernova, formation of neutron stars, birth properties.
A simple recipe
1. Find them 2. Time them 3. VLBI them
In other words: Discovering is not enough.
To extract science, timing (follow-up) observations of all discovered pulsars are needed.
Lots of discoveries since SKA Science Book: “We’ve been busy…”
Animation by Cherry Ng
SKA science case written
• Currently, more than 2,300 pulsars, and nearly 300 millisecond pulsars • Since 2004 Science Book, nearly twice as many normal pulsars and three mes as many millisecond pulsars (digital signal processing!) Discoveries lead to excellent science! 1 Triple System 0.9 All pulsars Galac c centre Magnetar Millisecond Pulsars (P<30ms)J0348+0432 0.8 Thornton et al. Bursts 1st Pulsars via AI and Volunteer Compu ng 0.7 100th FERMI Pulsar 1st Blind-search radio magnetar 0.6 2-M¤ Pulsar Missing-link pulsar 0.5 Sub-100ns ming 0.4 “Lorimer Burst” Intermi ent pulsars
Cumulative Distribution 0.3 RRATs Fastest MSP! 0.2 Double Pulsar
0.1
0 1970 1975 1980 1985 1990 1995 2000 2005 2010 Year Discoveries lead to excellent science! 1 Triple System 0.9 All pulsars Galac c centre Magnetar Millisecond Pulsars (P<30ms)J0348+0432 0.8 Thornton et al. Bursts 1st Pulsars via AI and Volunteer Compu ng 0.7 100th FERMI Pulsar 1st Blind-search radio magnetar 0.6 2-M¤ Pulsar Missing-link pulsar 0.5 Sub-100ns ming 0.4 “Lorimer Burst” Intermi ent pulsars
Cumulative Distribution 0.3 RRATs Fastest MSP! 0.2 Double Pulsar
0.1
0 1970 1975 1980 1985 1990 1995 2000 2005 2010 Year
Exciting science ranging from solid-state physics to testing gravity. “…but that’s only the beginning!” 1
0.9 All pulsars Millisecond Pulsars (P<30ms) SKA 0.8
0.7
0.6
0.5 So far, only a modest prelude!
0.4
Cumulative Distribution 0.3
0.2 Today!
0.1 Original SKA Science Book
0 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 2020 2025 Year • We can expect to find about 30,000 active (visible) pulsars • Among those will be about 2000 millisecond pulsars • A dramatic increase in the number of known sources! All too easy?
• Unknown dispersion measure… ~5000 trials • Unknown orbit… ~200 trials • So 1 million trials (per beam), in real time (~600s) • 600 us per trial, 8Mpt FFT + analysis • Need ~10 petaFLOP/s! ~MWatt • Cost increases as cube of integration time
– So need to maximise Aeff/Tsys • Cost increases as square of core radius – So need compact core (~1km) Potential of SKA and pathfnders
SKA1, SKA1, LOFAR, SKA1, JVLA MeerKAT ASKAP mid survey NL low ? ? ? ?
Aeff/Tsys m2/K 265 321 1630 65 391 61 1000
Survey>FoV deg2 0.14 0.48 0.39 30 18 6 6
Survey>Speed> 21 41 deg m 0.98×104 5.0×104 1.0×106 1.3×105 2.8×106 2.2×104 6.0×106 FoM K22
Resolution arcsec 1.4 11 0.22 7 0.9 5 11
Beams to cover 2200 96 1 sq degree (1km core) @1.4GHz @0.3GHz Science increase is enabled mostly by increased instantaneous sensi vity… But number of beams to le sky is also directly propor onal to computa on cost SKA1 will already be an excellent search machine
We can find nearly 50% of all pulsars with a combination of SKA1-Low and SKA1-Mid. (We can expect to find about 30,000 pulsars)
Stappers (priv. comm.) Normal – SKA1-mid Normal – SKA1-low MSP – SKA1-mid
Note: Remember – all sky with Low requires far fewer beams • = less observing me SKA2 does not add as much to pulsar surveys since majority of extra dishes = less compu ng are outside the core. = less power requirements • BUT - SKA2 will be needed to realise the full potential of all these discoveries. Timing of these pulsars will achieve important SKA science goals:
ü Tests of gravity with pulsars ü Radio pulsars in the Galactic Centre ü Gravitational wave astronomy ü Cosmic census of radio emitting neutron stars ü Understanding the neutron star population ü Properties of super-dense matter, e.g. neutron star equation of state ü Understanding pulsar magnetospheres and the physics behind them ü Understanding Galactic structure (incl. ISM & magnetic feld)
ü PLUS: Fast transients (different science, but “BOGOF” with pulsars) UK involvement in “Non-imaging” part of SKA Purple boxes are UK lead (Uni. Manchester) Oxford are also heavily involved in “Non-imaging” work
SADT = signal and data transport… a big part of making SKA work! (also led from Manchester) SADT
Central Signal Processing Science Data Processor
Transient Correlator Data Analysis Pulsar SADT SEARCH Pulsar Search Beam- Data Analysis former Pulsar Pulsar Timing TIMING Data Analysis
(Calibra on/imaging not shown!) UK involvement in Pulsar Science
• Ben Stappers (Manchester) and Michael Kramer (MPIfR & Manchester) chair SKA Pulsar Science Working Group. • Manchester and Oxford have direct involvement in LOFAR/MEERKAT projects for pulsars which are pathfinding for SKA. So the UK is at the heart of pulsar science with the SKA! Get in touch if you have ideas/questions/ proposals/etc. Conclusion
• Pulsars remain key science for the SKA – Fundamental physics (gravitation) – Exciting and exotic new astrophysics – 2000 pulsars have given us so many astonishing results… 30000 will • UK institutes are central to the design of the pulsar (and fast transient) instruments for SKA – We are designing to maximize the science potential – Need to maximize collecting area in the inner 1km of SKA1 • Te UK is at the heart of pulsar science with SKA – We are best placed to exploit the design work we are leading