Recent Results in Pulsars: A Pulsar Renaissance. Scott Ransom

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1 Recent Results in Pulsars: A Pulsar Renaissance Scott Ransom NRAO Charlottesville NAIC/NRAO Single-Dish Summer School 2005

2 What s a Pulsar? Discovered in 1967 by Jocelyn Bell and Antony Hewish at Cambridge We observe regular pulses of radio emission due to a lighthouse type effect Some pulsars emit high-energy light as well (e.g. optical, X-rays, γ-rays) Spin-down power up to 10,000 times more than the Sun's output! B~ G

3 Pulsar Flavors Normal PSRs Young (average B, slow spin) High B Young PSRs (high B, fast spin, very energetic) Millisecond PSRs (low B, very fast, very old, very stable spin, best for basic physics tests) Old Low B

4 Pulsar Recycling Start with a slow pulsar or neutron star in a binary system The companion evolves to become a red giant Matter from the companion transfers onto the NS, spinning it up During the process, the system is bright in x-rays (LMXB) Left with a binary millisecond pulsar

5 Some Physics from Pulsars (see Blandford, 1992, PTRSLA, 341, 177 for a review) Astrophysics (e.g. stellar masses and evolution) Newtonian and relativistic dynamics (e.g. binary pulsars) Gravitational wave physics (e.g. NS-NS binaries) Plasma physics (e.g. magnetospheres, pulsar eclipses) Fluid dynamics (e.g. supernovae collapse) Magnetohydrodynamics (MHD; e.g. pulsar winds) Relativistic electrodynamics (e.g. pulsar magnetospheres) Atomic physics (e.g. NS atmospheres) Solid state physics (e.g. NS crust properties) Physics at nuclear density (e.g. NS equations of state)

6 Physics of Matter at Very High Densities Observations of neutron stars (usually by high time resolution observations of radio MSPs) are currently the only way to probe matter at densities much greater than that found in atomic nuclei. (Density) M. Rho, 2000, nucl-th/

7 Folding Pulsar Data for Timing Original time series Shift and add the pulses A strong average profile that can be cross correlated to get a Time-of-Arrival (TOA)

8 Timing Observations All of the science comes from long-term timing Account for every single rotation of the pulsar Fit the arrival times of the pulse to a simple polynomial model after transforming the time: Accounts for pulsar spin, orbital, and astrometric parameters and Roemer, Einstein, and Shapiro delays in the Solar System and pulsar system Extraordinary precision for MSP timing

9 Timing Example

10 So why the new Renaissance? Low-noise, wide BW, receivers from 1-2 GHz Can see much deeper into the Galaxy (i.e. volume) Greatly reduced scattering and/or smearing Better telescope systems: Parkes Multibeam system Arecibo upgrade GBT Much better pulsar backends Faster sampling Better frequency resolution Improved computational resources

11 Parkes Multibeam Survey for Pulsars System: 13 beam L-band receiver system Survey Area: -260 < l < 50 deg, -5 < b < 5 deg Center Freq: 1374 MHz Bandwidth: 288 MHz (96 chan x 3 MHz x 2 pol) Sampling Rate: 0.25 ms x 1 bit/chan Integration Time: 35 min per pointing Sensitivity: ~7 times better than previous 400 MHz surveys Started in 1997 and results are still coming!

12 Parkes Multibeam Survey Results More than 700 new pulsars discovered! Many young pulsars ~12 Vela-like Several SNR assoc Near Magnetars J J Exotic Binaries J J (double NS systems) J (B-star) J (relativistic, young with massive WD) ~15 new MSPs

13 Pulsars in Globular Clusters Clusters of ancient stars (9-12 billion years old) that orbit our galaxy Usually contain stars, many of which have binary companions Very high core densities ( M /pc3) result in stellar encounters (tcross ~ 105 yrs) They are effectively factories for creating Millisecond Pulsars Number known has tripled in the last 10 yrs (47Tuc alone has 22)

14 Terzan 5 Very massive cluster with a high central density Verbunt and Hut (1987) calculated that it had one of the highest interaction rates of any cluster Distance ~ 8.5 ± 2 kpc (Cohn et al. 2001) Within ~ 1 kpc of Galactic center (l,b) = (3.8º, 1.7º) Deep VLA observations by Fruchter Interstellar electrons (i.e. S. Ortolani, I-band NTT image (ESO) and Goss (1990, 2000) found point Dispersion Measure or sources and ~ 2 mjy of diffuse DM) make deep searches quite difficult (e.g. emission in core: MSPs? scattering and smearing) From , though, only 3 MSPs were discovered

15 27 new MSPs in Terzan5 = 30 in total! Ransom et al., 2005, Science, 307, 892

16 Eclipsing Binary MSPs in Terzan 5 Ter5A Ter5O Ter5P Ppsr = ms Ppsr = 1.67 ms Ppsr = 1.73 ms Porb = 1.82 hrs Porb = 6.22 hrs Porb = 8.70 hrs Mc,min ~ M Mc,min ~ M Mc,min ~ 0.38 M

17 A Few Interesting Binary PSRs in Ter5 Ter5N Ter5E How is a such a wide binary surviving? Is this the first CO White Dwarf known in a GC? Ter5ad Is this (finally) a new fastest known MSP? Ppsr = 2.20 ms Ppsr = 8.67 ms Ppsr = 1.39 ms Porb = 60.06d (e~0.02) Porb = 9.25 hrs (e~4.6x10-5) Porb = 1.09 days Mc,min ~ 0.22 M Mc,min ~ 0.48 M Mc,min ~ 0.14 M

18 Neutron Star Equations of State This region is excluded due to rotation Rapidly rotating pulsars (the fastest known, PSR B , rotates 641 Hz!) directly limit the maximum size of a NS for any given mass. Ter5ad (rotating at 716 Hz?) would push this limit by another ~10% towards stiffer EOSs From Lattimer and Prakash 2004, Science

19 Five (!) Eccentric Binary MSPs in Ter5 Ter5I Ter5J Ter5Q Ter5U Ter5X Ppsr = 9.57 ms Porb = 1.33 days Mc,min ~ 0.21 M Ppsr = 2.81 ms Porb = 1.10 days Mc,min ~ 0.34 M Ppsr = 2.81 ms Porb = 30 days Mc,min ~ 0.45 M Ppsr = 3.29 ms Porb = 1.8 days Mc,min ~ 0.02 M Ppsr = 3.00 ms Porb = 5.0 days Mc,min ~ 0.25 M ecc = 0.43 ecc = 0.35 ecc = 0.72 ecc = 0.27 ecc = 0.30

20 Ter5I and J: Eccentric and Relativistic Systems Ter5I Ter5J From measurement of the relativistic advance of periastron: Mtot = 2.17±0.02M Mtot = 2.20±0.04M

21 Neutron Star Equations of State NSs with Nucleons More exotic components From Ter5I and J Timing of several binary MSPs (including Ter5I and J) indicates that the NSs are more massive than normal, which rules out several EOSs. From Lattimer and Prakash 2001, ApJ

22 Archival Chandra Observation Public 40ks Chandra ACIS-S observation 35+ sources within cluster half-mass radius (0.83') Absorption is high: NH ~ 1022 cm '

23 1950 MHz Pulsar Luminosities For a given pulsar luminosity, Ter5 has ~3x more pulsars than 47 Tuc!

24 (Orbital Size) Tests of Relativity in Strong-Field Pulsars yet to be discovered... The best pulsar currently... The best we can do in the solar system... (Mass) Recently discovered binary pulsars (and pulsar+black hole binaries that we might detect in the future) allow tests of gravity that are impossible here in our Solar System From: Kramer et al., 2004, astro-ph/

25 Post-Keplerian Orbital Parameters Besides the normal 5 Keplerian parameters (Porb, e, asin(i)/c, T0, ω), General Relativity gives: (Orbital Precession) (Grav redshift + time dilation) (Shapiro delay: range and shape ) where: T GM /c3 = µs, M = m1 + m2, and s sin(i)

26 The Binary Pulsar: J Burgay et al., 2003, Nature, 426, 531: Discovered in an extension of the Parkes Multibeam Survey Immediately identified as a highly relativistic NS-NS binary B J Pspin ms 22.7 ms Porbit hrs 2.45 hrs a sin(i)/c eccentricity lt-s lt-s ω Merge time Precession Period 4.2 /yr 320 Myr 300 yr 16.9 /yr 85 Myr 75 yr Post-Keplerian 3 (ω, Porb, γ) 2+ (ω, γ, r?, s?)

27 PSR J is a Double Pulsar! Lyne et al., 2004, Science, 303, 1153: PSR B has a Pspin = 2.77 s and normal magnetic field Characteristic age ~1/4 of PSR A (50 Myr vs 210 Myr) Allowed immediate determination of mass ratio Orbit is nearly edge-on PSR A s spin-down dominates that of PSR B by ~3600x Many other strange things going on...

28 0737A Timing and Tests of GR Kramer et al. 2005: Inclinations < 90º ω = (2) /yr γ = 0.39(2) ms Shapiro Delay: r = 6.2(6) µs s = (4) ma/mb = 1.071(1) Pb = -1.2x % GR test! MA = 1.338(1) M MB = 1.249(1) M Future: perhaps ~10% measurement of NS moment of inertia

29 Shock+Magnetosphere+Magnetosheath A s wind effectively blows away some of B s magnetosphere: Bow shock Magnetosheath (high density and temp) = synchrotron absorption Open magnetotail All modulated by B s rotation Fig courtesy NASA For more info: Arons, Spitkovsky & Backer, in prep., and Lyutikov, 2005, MNRAS, 353, 1095

30 0737A Eclipses Kaspi et al, 2004, ApJ, 613, L137

31 Modulation of the A Eclipse by B McLaughin et al, 2004, ApJ, 616, L131

32 Time Evolution for 0737B 820 MHz One Orbit 1400 MHz

33 More(!) Time Evolution for 0737B Burgay et al, 2005, ApJ, 624, L113

34 Modulation of B s Pulses by A McLaughin et al, 2004, ApJ, 613, L57 Argue that A s EM-field is causing this modulation. Therefore most of A s spin-down energy is carried by The Poynting Flux of the magnetic-dipole radiation.

35 Diffractive Scintillation Modulated at the orbital period Ransom et al, 2004, ApJ, 609, L71 But the scintillation is anisotropic! Coles et al, 2005, ApJ, 623, 392

36 But there are more Holy-Grails to find! Pulsar-ALFA Survey Galactic plane and midlatitude surveys More sensitive than Parkes survey in ~60s! Should find hundreds of new pulsars (have already found 12)

37 Two interesting pulsars already... PSR J Ppsr = ms tchar = 82 kyr Edot = 1.6x1036 ergs/s EGRET Source? PSR J Ppsr = ms Porb = 3.98 hrs Mc,min > 0.9 M ecc = Relativistic binary 2nd born NS?