Caroline D’Angelo, Leiden University

August 3, 2014

Amruta Jaodand, Anne Archibald,

Jason Hessels, Alessandro Patruno, Slavko Bogdanov

TRANSITIONAL MILLISECOND PULSARS AS ACCRETION PROBES

MAGNETOSPHERIC ACCRETION

Spin Period

B field

MAGNETOSPHERIC ACCRETION

Spin Period

B field

MAGNETICALLY REGULATED ACCRETION: WHAT DETERMINES SPIN RATE?

• Spin up: accretion

• Spin down:

• Magnetically-launched outflows? (AE Aqr)

• Pulsar wind? (Parfrey, Spitkovsky talks)

• Transferred to accretion disk? (This work)

Behaviour depends on Magnetic field strength, Spin rate, Accretion rate

J1023+0038: ACCRETION MODEL PROBE

• Known B, P*

• Known timing solution• Reasonable estimate of

accretion rate• Accretion at “quiescent”

luminosities • Pulsations – surface

accretion in “propeller” regime

From X-ray luminosity:

J1023+0038: ACCRETION MODEL PROBE

• Known B, P*

• Known timing solution• Reasonable estimate of

accretion rate• Accretion at “quiescent”

luminosities• Pulsations – surface

accretion

J1023+0038: ACCRETION MODEL PROBE

• Known B, P*

• Known timing solution• Reasonable estimate of

accretion rate• Accretion at “quiescent”

luminosities• Pulsations – surface

accretion

SEE AMRUTA JAODAND’S TALK ON THURSDAY

MAGNETOSPHERIC ACCRETION

Spin Period

B field

MAGNETOSPHERIC ACCRETION

Spin Period

B field

What is accretion rate that sets inner disk edge at

corotation?

THE ‘CRITICAL' ACCRETION RATE

pressure balance; ξ < 1 for rotating thin disk

Angular momentum balance; η < 1 describes torque efficiency

Boundary of accretion/propeller regime

Critical accretion rate uncertain by ~40

Radial inflow vs. disk-like:RIAF constraint

THE ‘CRITICAL' ACCRETION RATE

pressure balance; ξ < 1 for rotating thin disk

Angular momentum balance; η < 1 describes torque efficiency

Boundary of accretion/propeller regime

Critical accretion rate uncertain by ~40

Radial inflow vs. disk-like:RIAF constraint

What happens when rm > rc?

SIMULATIONS OFTEN SHOW TRANSIENT ACCRETION

Lii et al. 2014

EFFICIENCY OF OUTFLOW

Propeller Trapped discStrong outflow dominates Weak outflow; gas

accretesNarrow range of produce pulsations

Pulsations to low accretion rates

Accretion flow dominates emission

Stellar surface dominates emission

Luminosity drops rapidly as accretion rate declines

Luminosity drops gradually

Propeller Trapped discStrong outflow dominates Weak outflow; gas

accretesNarrow range of produce pulsations

Pulsations to low accretion rates

Accretion flow dominates emission

Stellar surface dominates emission

Luminosity drops rapidly as accretion rate declines

Luminosity drops gradually

Transitional Pulsars can be used to test these

models

EFFICIENCY OF PROPELLER

EFFICIENCY OF PROPELLER

J1023+0038: AN AMAZING PROBE OF ACCRETION MODELS

• Low accretion state: propeller?, radiatively-inefficient?)

• Pulsations – surface accretion *

• Known B, P*

• Known timing solution• Reasonable estimate of

accretion rate**

From X-ray luminosity:

J1023+0038: AN AMAZING PROBE OF ACCRETION MODELS

• Low accretion state: propeller?, radiatively-inefficient?)

• Pulsations – surface accretion *

• Known B, P*

• Known timing solution• Reasonable estimate of

accretion rate**

From X-ray luminosity:

CAVEATS

* Pulsations = surface accretion? Energy budget does not exclude X-rays generated by pulsar spin down. Could unchanged spin down suggest disk stays outside Light Cylinder?

J1023+0038: AN AMAZING PROBE OF ACCRETION MODELS

• Low accretion state: propeller?, radiatively-inefficient?)

• Pulsations – surface accretion *

• Known B, P*

• Known timing solution• Reasonable estimate of

accretion rate**

From X-ray luminosity:

J1023+0038: AN AMAZING PROBE OF ACCRETION MODELS

• Low accretion state: propeller?, radiatively-inefficient?)

• Pulsations – surface accretion *

• Known B, P*

• Known timing solution• Reasonable estimate of

accretion rate**

From X-ray luminosity:

CAVEATS

* Pulsations = surface accretion? Energy budget does not exclude X-rays generated by pulsar spin down. Could unchanged spin down suggest disk stays outside Light Cylinder?

** Is X-ray luminosity really a good probe of accretion rate? (generate luminosity from spin down, lose mass to outflows, uncertain bolometric corrections)?

COMPARE SPINDOWN PREDICTIONS

• Measured spin change:

• Accretion torques add >10% to spin-down rate:

• Limit on spin down (from enhanced pulsar wind, disk interaction, magnetically-launched wind):

• Predicted spin down depends on: spin-down source model, critical accretion rate, observed accretion rate

J1023+0038: LIMITS ON PROPELLER SPIN

thinner disk

Higher accretion rate

J1023+0038: LIMITS ON PROPELLER SPIN

thinner disk

Higher accretion rate

CONSTRAINTS ON TRAPPED DISK PICTURE?

CONSTRAINTS ON TRAPPED DISK PICTURE?

CONSTRAINTS ON TRAPPED DISK PICTURE?

Max spin down:

‘Typical’ values (assumed in DS10):

CONSTRAINTS FROM OUTFLOWS?

Deller et al. 2015

Flat radio spectrum: evidence for a jet? (Adam Deller)Other outflows? (Hernandez-Santisteban, Knigge)

Can energy/outflow rate be constrained?

HOW MUCH FIELD IS OPEN?

For ms pulsar

• Pulsar wind shielded from disc ?• Open field line region should be ~5 times

larger in accreting state• How strong is radio outflow?

CONCLUSIONS

• Transitional MSPs offer strong constraints on magnetospheric accretion models

• J1023 spin-down identical to dipole case• Strong outflow predicts larger spin-down than constrained• Trapped disc can work, on edge of parameter space• Constraint on open field line region? • Is something else going on?