1. Transitional Millisecond pulsars as accretion probes
Caroline D’Angelo, Leiden University
August 3, 2014
Amruta Jaodand, Anne Archibald,
Jason Hessels, Alessandro Patruno, Slavko Bogdanov

2. Magnetospheric Accretion
B field
Spin Period
General picture: B, P_*, L(Mdot)

3. Magnetospheric Accretion
B field
Spin Period
General picture: B, P_*, L(Mdot)

4. 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

5. 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
Why are tMSP unique? What do they tell us about accretion physics? –good estimate of magnetic field strength (radio dipole spindown), precise timing solution (measure spindown in accretion state) – luminosity, B field, rotation rate, main physical parameters constrained, can ‘test’ mag. Accretion models, J1023: see *no change*, seems pulsar wind still active, accretion/ejection not important
From X-ray luminosity:

6. J1023+0038: Accretion Model Probe
Known B, P*
Known timing solution
Reasonable estimate of accretion rate
Accretion at “quiescent” luminosities
Pulsations – surface accretion
Why are tMSP unique? What do they tell us about accretion physics? –good estimate of magnetic field strength (radio dipole spindown), precise timing solution (measure spindown in accretion state) – luminosity, B field, rotation rate, main physical parameters constrained, can ‘test’ mag. Accretion models, J1023: see *no change*, seems pulsar wind still active, accretion/ejection not important

7. J1023+0038: Accretion Model Probe
Known B, P*
Known timing solution
Reasonable estimate of accretion rate
Accretion at “quiescent” luminosities
Pulsations – surface accretion
Why are tMSP unique? What do they tell us about accretion physics? –good estimate of magnetic field strength (radio dipole spindown), precise timing solution (measure spindown in accretion state) – luminosity, B field, rotation rate, main physical parameters constrained, can ‘test’ mag. Accretion models, J1023: see *no change*, seems pulsar wind still active, accretion/ejection not important
SEE AMRUTA JAODAND’S TALK ON THURSDAY

8. Magnetospheric Accretion
B field
Spin Period
General picture: B, P_*, L(Mdot)

9. What is accretion rate that sets inner disk edge at corotation?
Magnetospheric Accretion
B field
Spin Period
What is accretion rate that sets inner disk edge at corotation?
General picture: B, P_*, L(Mdot)

10. The ‘Critical' accretion rate
pressure balance; ξ < 1 for rotating thin disk
Angular momentum balance; η < 1 describes torque efficiency
Critical accretion rate uncertain by ~40
Boundary of accretion/propeller regime
Estimate Mdot so that Rin = Rc, accretion vs. barrier UNCERTAIN, depends on: magnetic field structure, disc/field interaction, disc structure (virialized flow)
Radial inflow vs. disk-like:
RIAF constraint

11. The ‘Critical' accretion rate
pressure balance; ξ < 1 for rotating thin disk
Angular momentum balance; η < 1 describes torque efficiency
What happens when rm > rc?
Critical accretion rate uncertain by ~40
Boundary of accretion/propeller regime
Estimate Mdot so that Rin = Rc, accretion vs. barrier UNCERTAIN, depends on: magnetic field structure, disc/field interaction, disc structure (virialized flow)
Radial inflow vs. disk-like:
RIAF constraint

12. Simulations often Show transient accretion
Lii et al. 2014
Make a picture of propeller outflow

13. Efficiency of outflow
Constraints on RIAF solution

18. Propeller
Trapped disc
Strong outflow dominates
Weak outflow; gas accretes
Narrow 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

19. Transitional Pulsars can be used to test these models
Propeller
Trapped disc
Strong outflow dominates
Weak outflow; gas accretes
Narrow 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

20. Simulations of strong accretion outflows
how much mass outflows? How energetic? How much angular momentum is lost?
use MHD simulations (unfortunately M. Romanova & collaborators couldn’t come present), some numerical limitations, but rough idea of inflow vs. outflow
see intermittent bursts of accretion on v. fast timescales (few rotation periods)

21. Efficiency of propeller
Constraints on RIAF solution

22. Efficiency of propeller
Constraints on RIAF solution

23. 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**
Why are tMSP unique? What do they tell us about accretion physics? –good estimate of magnetic field strength (radio dipole spindown), precise timing solution (measure spindown in accretion state) – luminosity, B field, rotation rate, main physical parameters constrained, can ‘test’ mag. Accretion models, J1023: see *no change*, seems pulsar wind still active, accretion/ejection not important
From X-ray luminosity:

24. 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**
Why are tMSP unique? What do they tell us about accretion physics? –good estimate of magnetic field strength (radio dipole spindown), precise timing solution (measure spindown in accretion state) – luminosity, B field, rotation rate, main physical parameters constrained, can ‘test’ mag. Accretion models, J1023: see *no change*, seems pulsar wind still active, accretion/ejection not important
From X-ray luminosity:

25. 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?

26. 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**
Why are tMSP unique? What do they tell us about accretion physics? –good estimate of magnetic field strength (radio dipole spindown), precise timing solution (measure spindown in accretion state) – luminosity, B field, rotation rate, main physical parameters constrained, can ‘test’ mag. Accretion models, J1023: see *no change*, seems pulsar wind still active, accretion/ejection not important
From X-ray luminosity:

27. 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**
Why are tMSP unique? What do they tell us about accretion physics? –good estimate of magnetic field strength (radio dipole spindown), precise timing solution (measure spindown in accretion state) – luminosity, B field, rotation rate, main physical parameters constrained, can ‘test’ mag. Accretion models, J1023: see *no change*, seems pulsar wind still active, accretion/ejection not important
From X-ray luminosity:

28. 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)?

29. 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
Add picture of propeller vs. trapped disk
Spell out again uncertainty on accretion rate (based on luminosity), uncertainty on Mdot for Rm

30. J1023+0038: Limits on propeller SPIN
Higher accretion rate
thinner disk

31. J1023+0038: Limits on propeller SPIN
Higher accretion rate
thinner disk

32. CONstraints on trapped disk picture?

33. CONstraints on trapped disk picture?

34. CONstraints on trapped disk picture?
Max spin down:
‘Typical’ values
(assumed in DS10):

35. Constraints from outflows?
Flat radio spectrum: evidence for a jet? (Adam Deller)
Other outflows? (Hernandez-Santisteban, Knigge)
Can energy/outflow rate be constrained?
Deller et al. 2015
Picture of Deller result – a strong outflow(?), Knigge/student? Energetic constraints, angular momentum loss constraints?

36. How much field is open? Pulsar wind shielded from disc ?
Open field line region should be ~5 times larger in accreting state
How strong is radio outflow?
Constraints on spin up/down, propeller vs. trapped disc.
For ms pulsar

37. 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?