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Caroline D’Angelo, Leiden University
August 3, 2014
Amruta Jaodand, Anne Archibald,
Jason Hessels, Alessandro Patruno, Slavko Bogdanov
TRANSITIONAL MILLISECOND PULSARS AS ACCRETION PROBES
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
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?
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
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
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?
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