Forefront of neutron star science Precision astrometry using the VLBA Bowshocks and jets

26 Apr 2005 U. Illinois

• Forefront of neutron star science• Precision astrometry using the VLBA• Bowshocks and jets• Pulsar velocities:

• Bimodality• Kick mechanisms: tie-ins to cosmology?

• ALFA: A massive pulsar survey at Arecibo• SKA: toward a full Galactic census of pulsars

Pulsars in Motion:Astrometry, Kicks, ALFA and the SKA

Jim Cordes, Cornell University


Pulsars…• embody physics of the EXTREME

– surface speed ~0.1c– 10x nuclear density in center– some have B > Bq = 4.4 x 1013 G– Voltage drops ~ 1012 volts– FEM = 109Fg = 109 x 1011FgEarth

– Tsurf ~ million K• …relativistic plasma physics in action• …probes of turbulent and magnetized ISM• …precision tools, e.g. - Period of B1937+21: P = 0.00155780649243270.0000000000000004 s - Orbital eccentricity of J1012+5307: e<0.0000008


Pulsar Populations: P – Pdot diagram• Canonical

• P~ 20ms – 5s• B ~ 1012±1 G

• Millisecond pulsars (MSPs)• P ~ 1.5 – 20ms• B ~ 108 – 109 ms

• High field• P ~ 5 – 8 s

• B ~ few x 1013 G

• Braking index n:

• Pdot P2-n, n=3 magnetic dipole

radiation

• Death line

• Strong selection effects

log

Per

iod

deriv

ativ

e (s

s-1)

Period (sec)


Forefronts in NS Science

• Understanding NS populations and their physical differences

• Radio pulsars and their progenitors• Magnetars• Radio quiet/Gamma-ray loud objects• Branching ratios in supernovae

• The physics of NS runaway velocities

• Are “neutron stars” neutron stars?


Forefronts in NS Science

• Finding compact relativistic binary pulsars for use as laboratories

• Gravity• Relativistic plasma physics in strong B

• Finding spin-stable MSPs for use as gravitational wave detectors ( ~ light years)

• h ~ TOA T-1 (T = data span length)

• Complete surveys of the transient radio sky• pulsars as prototype coherent radio emission


First Double Pulsar: J0737-3939

• Pb=2.4 hrs, d/dt=17 deg/yr

• MA=1.337(5)M, MB=1.250(5)M

Lyne et al.(2004)

002.0000.1exp

obs

s

sTesting GR:

Kramer et al.(2004)

Now to 0.1%


Velocity Distribution

• Gunn and Ostriker 1970• Early estimates using interstellar scintillation

measurements of radio pulsars• Millisecond pulsars:

• High velocity by stellar standards• Slow by comparison to high-B objects (V~100 km s-1)

• Canonical pulsars:• <V> ~ 400 km s-1 (Lyne and Lorimer 1994)• Bimodal PDF (Cordes and Chernoff 1998)


Bow ShocksManifestations of high NS velocities

Probe relativistic winds from NS

Probe microstructure in the ISM

Guitar Nebula:• Ordinary pulsar

• P = 0.68 s

• B = 2.6 x 1012 G

• s = 1.1 Myr

• E = I 1033.1 erg s-1

• D 1.9 kpc (from DM)

• 1600 km s-1 at nominal distance

• Will escape the Milky Way

1994

2001

·˙

· ·

Palomar Hα Image

HST WFPC2 Hα


A: pulsar wind cavity

B: shocked pulsar wind

C: shocked ISM

TS: termination shock

CD: contact discontinuity

BS: bow shock

1100

1/2-ISMkpc

1100

1/2-ISM

2/1

2arcsec27.0AU271

4

VnDVn

Vc

ERs

Standoff radius for an isotropic, relativistic wind:

Consistent with all known NS bow shocks modulo ISM density and inclination (Chatterjee & Cordes 2002). No evidence for wind anisotropy in measured bowshock contours

Rs

Edot


Bow ShocksGuitar Nebula:

• Ordinary pulsar

• P = 0.68 s

• B = 2.6 x 1012 G• = 1.1 Myr• E = I 1033.1 erg s-1

• D 1.9 kpc (from DM)• 1600 km s-1 at nominal distance• Will escape the Milky Way

1994

2001

Palomar H image

Radius of curvature of bowshock nose increased from 1994 to 2001, corresponding to a 33% decrease in ISM density

The pulsar is emerging from a region of enhanced density

HST WFPC2 H

Chatterjee & Cordes 2004


Bow ShocksMSPs

Low V

High Edot

B1957+20 (Kulkarni & Hester; Gaensler et al. J0437-47 (Fruchter et al.)

J2124-3358 Gaensler et al

Canonical pulsars

High V, low to high Edot

DuckMouse

RXJ1856

B0740-28

J0617


Velocity Distribution for Canonical Pulsars: bimodal

Cordes & Chernoff 1998 Arzoumanian, Chernoff & Cordes 2002

Escape from the Galaxy

Best-fit model:

two components


Uncertainties in the Velocity PDF

• Pulsar survey selection effects:• Beaming• Period dependence of pulsar luminosity• Frequency and period dependent selection effects

– ISM propagation (dispersion, scattering)

• Velocity selection in volume limited pulsar surveys• Low-Galactic latitude surveys miss high-V pulsars born in the

Galactic plane

• CC98 not corrected for selection effects, but high-V component ~ x5 too low

• ACC02 corrected for selection effects but uses distance estimates with large errors


Pulsar Distances Type Number Comments

Parallaxes: Interferometry

timing

optical

~13

~ 5

~ 1

1 mas @ 1 kpc

1.6 s @ 1 kpc

HST, point spread function

Associations SNRs 8

GCs 16

LMC,SMC ~8

false associations

HI absorption 74 bright pulsars, galactic rotation model

DM + ne model all radio pulsars

(~ 1700)

ISM perturbations


VLBI / VLBA


Pulsar astrometryScience Case

(Brisken et al. 2002, Chatterjee et al. 2001-2004)

• Pulsar Origins:• SNR associations• NS birth sites in stellar clusters / OB associations• True ages

• Astrophysics: • NS atmospheres, cooling curves etc. need absolute

distances

• Evolution: • NS distribution and population velocities

• Environments:• Galactic electron density• local ISM


In-Beam calibration• In-beam calibration:

– referencing to a source within the primary telescope beam• 20 arcmin at 1.4 GHz on the VLBA antennas

• less for e.g. AO and GBT and at higher frequency


Parallax / Proper Motion

• B1929+10– both at 1.4

and 5 GHz

• D = 361+10-8 pc

• V = 177+4-5 km/s

Chatterjee et al. 2004


Current Status of Large Astrometry Program Using the VLBA

• 26 pulsars observed at 8 epochs over 2 years • 2/3 use in-beam calibration• Expect 20 new parallaxes “soon”

(Brisken et al., Chatterjee et al., + applications, in preparation)

– http://www.astro.cornell.edu/~shami/psrvlb/

• Another set of pulsars is now being observed

http://www.astro.cornell.edu/~shami/psrvlb/


Ongoing Parallax Programs• 53 pulsars using VLBA antennas only at 1.4 GHz

(systematics: ionospheric phase)• Chatterjee, Brisken et al. (2002-2004)

• Currently can reach ~ 2 kpc

• 6 strong pulsars, VLBA-only at 5 GHz • Ionosphere less important

• Chatterjee, Vlemmings, Cordes et al. (2001-ongoing)

• VLBA + Arecibo + GBT + … • Initial tests

• Expect to do ~100 pulsars in 5 years, some to 5 kpc

• Future: SKA superior phase calibration, sensitivity, can reach >10 kpc


Separated at Birth • B2021+51 and

B2020+28 originate from same binary

• Disrupted in second SN explosion

– 1.9 Myr ago– c.f. spindown ages of

2.88 and 2.75 Myr

• Birth Location: the Cygnus Superbubble

• Birth velocities:– 200 km/s kick

• 150 km/s (B2021)• 500 km/s (B2020)

• Second created pulsar (B2020)

– P0 ~ 200 ms

Vlemmings, Cordes, Chatterjee (2004)


Cygnus 14o x 10o MSX Mid IR Image

Shaded band: kinematic constraints

Black pair of curves: spindown ages vs braking index for the two objects

Red, Green: P0 vs age for 3 values of braking index


B1508+55,b = 91.3o, 52.3o

D = 2.450.25 kpc

V = 1114-94 +132 km s-1

P = 0.74 s

B = 2x1012 G

s = P/2Pdot = 2.36 Myr

The highest measured velocity using direct distance measurement

2.5x further than electron density model based distance estimate (NE2001)

Chatterjee et al.

In preparation

Possibly born in Cyg OB 7


NE2001: Galactic Distribution of Free Electrons + Fluctuations

Paper I = the model (astro-ph/0207156)

Paper II = methodology & particular lines of sight (astro-ph/0301598)

Based on ~ 1500 lines of sight to pulsars and extragalactic objects

Code + driver files + papers:www.astro.cornell.edu/~cordes/NE2001


Local ISM Components of NE2001

B1508+55 is further than its DM implies most likely because it is viewed through one or more Galactic chimneys (supernova blowouts)


Pulsar Velocity Distribution Using only Parallax Distances

• Likelihood analysis for birth parameters:– using pulsars with

accurate astrometry– 1 component model

V1 = 175 km/s• hz = 0.2 kpc

– 2 component model V1 = 86 km/s V2 = 296 km/s• hz = 0.16 kpc


Understanding the Velocity Distribution

• Two components suggest 2 processes• E.g. orbital disruption + asymmetric supernovae

• But two independent processes will not produce a bimodal PDF

• Convolution unimodal PDF

• Need “kick” processes to be selective• Extreme case: Bombaci and Popov (2004):

– Low V NS are hadronic

– High V “NS” are quark stars that undergo two kicks (including one corresponding to phase transition to quark matter)


Pulsar Jets• Magnetospheric Jets

• Along spin axis • Nearly ║ to V

• 0.1 to 1 pc in length

Chandra images

Crab pulsar P = 33 ms

Vela pulsar P = 89 ms


Pulsar Jets• Guitar Nebula Jet

• Chandra 50 ksec ACIS obs• Misaligned from Guitar axis proper motion direction

Cordes et al. in preparation


Pulsar Jets• Guitar Nebula Jet

• Chandra 50 ksec ACIS obs• Misaligned from Guitar axis

proper motion direction• Jet luminosity is much larger

fraction of Edot than in Crab and Vela pulsars

• One-sided = two-sided + relativistic beaming?

• Jet is straight for ~1pc• Consistent with synchrotron

energy losses, ~0.3c and jet within 30o of LOS

• Explanation: magnetic reconnection in bow-shock nose

Cordes et al. 2005 (in prep)


Simulated Bow Shocks

Romanova, Chulsky & Lovelace 2001, 2005


Pulsar Jets• J2124-3358

• MSP: P = 4.93s• B = 3.2x108 Gs = 3.8 Gyr

• Probably a magnetospheric jet• Bent by the shocked ISM flow

• Chatterjee et al. in preparation

Gaensler et al 2002Hα

Chandra


Pulsar KicksPulsar space velocity:

• Present day pulsar motions require that large contributions from disrupted orbital motion and from near instantaneous natal “kicks”

• Most pulsars are isolated though most originated in binary stellar systems

• Symmetric supernova explosions unbind binaries if Mlost > ½ pre-supernova total system mass (Blaauw mechanism)

•NS velocity = pre-SN orbital velocity

•Maximum NS velocity 103 km s-1 (but will be rare)

• Natal kicks:

•Can unbind binaries with less mass loss

•Manifestations depend on time scale kick relative to

• Porbital

• Pspin (of proto NS)

VPSR = VGal + Vpeculiar = VGal + Vprogenitor + Vkick, orb + Vkick, natal

Spruit & Phinney 1998

Lai et al. 2001


Evidence for NS Kicks

Large NS Velocities (>> progenitors’ velocities ~ 30 km/s):

Characteristics of NS Binaries (kicks are required, not just binary breakup):

• Pulsar-MS binaries: Orbital plane precession and orbital decay PSR J0045-7319 binary (Kaspi et al. 1996; Lai et al. 1995; Lai 1996; Kumar & Quataert 1997) PSR J1740-3052 (Stairs et al. 2003)

• Double NS Binaries: Geodetic precession, orbital eccentricities, systemic motion PSR B1913+16 (Kramer 1998; Wex et al. 2000; Weisberg & Taylor 2002); PSR B1534+12 PSR J0737-3039 (Dewi & van den Heuvel 2004; Willems et al 2004; Ransom et al. 2004)

• High-Mass X-ray Binaries: High eccentricities of Be/X-ray binaries (Verbunt & van den Heuvel 1995; but Pfahl et al. 2002) High radial velocity (430 km/s) of Circinus X-1 (Tauris et al. 1999)

• Evolutionary studies of NS population (e.g., Dewey & Cordes 1987; Fryer & Kalogera 1997; Fryer, Burrows & Benz 1998)

• Pulsar proper motion V ~ 200-500 km/s, some with V>103 km/s (Hansen & Phinney 1997; Lorimer et al. 1997; Cordes & Chernoff 1998; Arzoumanian et al. 2002)

• Bow shock from fast moving pulsars in ISM

(e.g., PSR 2224+65 V>800 km/s; Cordes et al.1993; Chatterjee & Cordes 2002)

• NS-SNR association large NS velocity up to ~ 103 km/s


S

L

PSR 1913+16A

S Vkick

S L

He star

SB

PSR B

SB

SB

Assume SB was aligned ==> Vkick must not be aligned with SB.

PSR B spin period? ~ 1s

Similarly for doublepulsar J0737-3939

Geodetic precession (spin-orbit GR effect)


Clues about Kicks

• Bimodality of the net velocity distribution• Includes combined effects of orbital disruption and

natal kicks

• The proper motion is nearly aligned with jets seen in the Crab and Vela pulsars

• + a few other objects• common or chance?• Intrinsic to the kick mechanism or imposed by

rotation? (Spruit & Phinney 1998; Lai et al. 2001)


Mechanism Time ScaleVmax

(km s-1)

Alignment

( and V)

Binary disruption

(Blaauw)<< Porb 1000

Evanescent NS binary (Colpi & Wasserman 2002)

sec - min 1000

Hydrodynamical seconds 100-200Random +

Rotational averaging

-driven seconds ~ 50 B15Parallel if rotational averaging

EM Rocket

(Harrison-Tademaru)months 1400 R10

2 Pms-2 parallel

Kick Mechanisms (after Bombaci and Popov 2004)


Adapted from Janka et al

Convection in the the shocked mantle (and in proto-NS) can lead to asymmetric matter ejection and associated neutrino emission.How much?


Numerical experiments of Scheck et al.(2004)

Adjust L(t) from proto-NS so that explosion sets in slowly(100’s ms--seconds)

Slow explosion leads to large kick (100’s km/s)


Toward a Galactic Census of Radio Pulsars

The first 30 years of pulsars:~ 700 radio pulsars~ 1% binaries

Parkes Multibeam Survey 1997-2004:~ 800 new pulsars

+ Other surveys:~ 100 MSPs

6 relativistic binary pulsars (NS-NS)No PSR-BH binary (yet)

c.f. ~105 active radio pulsars (20% beamed to us)


Why more pulsars?Extreme Pulsars:

• P < 1 ms P > 5 sec

• Porb < hours B >> 1013 G (link to magnetars?)

• V > 1000 km s-1

• Population & Stellar Evolution Issues

• NS-NS & NS-BH binaries: strong gravity effects probed with pulse timing

• The high-energy connection (e.g. GLAST)

• Physics payoff (EOS of NS matter, GR, LIGO, GRBs…)

• Serendipity (strange stars, transient sources)

• Mapping the Galactic magnetoionic medium

• New instruments (AO, GBT, SKA) can dramatically increase the volume searched (Galactic & extragalactic)


Arecibo + SKA Surveys




ALFA Galactic Plane SurveySurvey Galactic Plane

– |b| < 5o = 32o-77o and = 168o-214o

– 300 s / sky position (~30s needed to match PMB sensitivity)– Greater sensitivity to MSPs (narrower frequency channels)– 2000 hr telescope time over a 3-5 year period

103 new pulsars – Reach edge of Galactic population for much of luminosity function– High sensitivity to millisecond pulsars and binary pulsars– Dmax = 2 to 3 times greater than for Parkes MB

Sensitivity to transient sourcesData management:

– Keep all raw data (~ 1 Petabyte after 5 years) at the Cornell Theory Center Database of raw data, data products, end products

– Web based tools for Linux-Windows interface (mysql ServerSql)– VO linkage (in future)


Blue: known pulsars Blue: known pulsars

(prior to Parkes MB)(prior to Parkes MB)

Red: Parkes MB Red: Parkes MB

Green: PALFA Green: PALFA

simulated pulsarssimulated pulsars


The First ALFA Pulsar


A pulsar found A pulsar found through its single-through its single-pulse emission, not its pulse emission, not its periodicity (c.f. Crab periodicity (c.f. Crab giant pulses).giant pulses).

Algorithm: matched Algorithm: matched filtering in the DM-t filtering in the DM-t plane.plane.

ALFA’s 7 beams ALFA’s 7 beams provide powerful provide powerful discrimination discrimination between celestial and between celestial and RFI transientsRFI transients



The Square Kilometer Array


The Collecting Area Plateau In Radio Astronomy


Five Key Science Areas for the SKA

Topic Goals

Dark Energy and Cosmic Structure1. Understand dark energy (eqn of state; W(z) = P/)

2. Understand structure formation and galaxy evolution

Gravity: Pulsars & Black Holes1. Use precision timing of pulsars to test theories of

gravity in the strong field limit

2. Pulsars with NS/BH companions (including Sgr A*)

Probing the Dark Ages

1. Map out structure formation using HI from the era of reionization (6 < z < 13)

2. Probe early star formation using high-z CO

3. Detect the first active galactic nuclei

Cosmic MagnetismDetermine the structure and origins of cosmic magnetic fields (in galaxies and in the intergalactic medium) vs. redshift z

The Cradle of Life

1. Understand the formation of Earth-like planets

2. Understand the chemistry of organic molecules and their roles in planet formation and generation of life

3. Detect signals from ET


Example of the SKA as a Pulsar-Search Machine

~104 pulsar detections with the SKA (assuming all-sky capability)

• rare NS-NS, NS-BH binaries for probing strong-field gravity

• millisecond pulsars < 1.5 ms• MSPs suitable for gravitational

wave detection• Galactic tomography of

electron density and magnetic field

• Spiral-arm definition


SKA Specifications Summary for Fundamental Physics from Pulsars

Required SpecificationRequired Specification

TopicTopict

(s)A/T

(m2/K)max

(GHz)Configuration

FOV Sampling

Polarization

Searching 50 2x104 fc

2.5

15 (GC)Core with large fc full

Total

Intensity

Timing 1 2x104 15Non-critical if

phasable100

beams/deg2

Full Stokes;

-40 dB isolation

Astrometry (VLB)

200 >2x103 8Intercontinental

baselines~ 3 beams

Total Intensity


327 MHz VLA image

Milky Way at 408 MHz


Axes of Discovery for the SKA


Giant pulse from the Crab pulsar

S ~ 160 x Crab Nebula

~ 200 kJy

Detectable to ~ 1.5 Mpc with Arecibo

The brightest pulses in the Universe

Cordes et al 2004


Phase Space for Transients: SpkD2 vs. W

W

WSpk

log

Sp

kD

2

log W


International SKA Project

• Active participation by US, Canada, China, India, Australia, Europe (esp. UK, Netherlands, Italy), South Africa

• Timeline for milestones: now to 2020• Site selection 2006• Technical concept 2008• Demonstrator array 2009 – 2012?• Full array 2015 – 2020?

• International SKA Steering Committee• 21 members • 7 US members reflects targeted 33% funding of SKA by the US


US SKA Consortium

Chair: Yervant Terzian (Cornell)Vice Chair: Jack Welch (UCB)


Architectures for the SKASmall paraboloids +

Point feeds

Focal plane arrays

US (ATA, TDP, DSN)

Australia, India, South Africa, US (TDP)

Cylindrical paraboloids + line feeds

Australia (Molonglo)

Large adaptive reflector + aerostat suspended FPA

Canada (CLAR)

Arecibo-like reflector + FPA China (FAST)

Aperture arrays Europe (EMBRACE)



Technology Development for the LNSD Concept by the USSKAC

• Allen Telescope Array• EVLA• Low frequency arrays (LWA, MWA)• NSF/ATI funding (2002-2005)• Technology Development Project

• Managed by NAIC for the USSKAC• Submitted to NSF for $32M 2004 March• Panel review 2004 October• Funding Post Senior Rev.




Summary

• Pulsars continue to live up to their utility as physics laboratories

• The best is yet to come with a full Galactic census for neutron stars

• Arecibo/ALFA will provide ~ 1000 new NS• SKA will finish the Galactic census and

begin extragalactic searches• The SKA will transform radio science and

astrophysics in other important ways


Extra Slides


Spin-Kick Connection

Documents

Forefront of neutron star science Precision astrometry using the VLBA Bowshocks and jets