Neutron Stars and Debris Disks

1
Neutron Stars and Debris Disks

• Andy Shearer and Vitaly Neustroev
• Centre for Astronomy
• NUI, Galway
• Ireland

2
Debris Disks and Pulsar Theory

• Underlying pulsar theory unchanged for 40 years
• rapidly rotating magnetised neutron star
• radio energy emission - coherent synchrotron
• high energy emission - incoherent synchrotron or
  curvature radiation
• No agreement on how.
• Probably the only point of agreement between all
  these theories is the association of pulsars with
  magnetized, rotating neutron stars - Lyutikov,
  M., Blandford, R., Machabeli, G., 1999, MNRAS,
  305, 338
• Understanding now helped by
• Rotating Radio Transients - RRATs
• AXPs
• Transient pulsars and transient phenomena
• .....

3
Some Background

• Pulsar-disk systems have been proposed for over
  25 years
• Debris Disks - either
• fossil disk created during the supernova event
• Michel Dessler, 1981, ApJ, 251, 654, Pulsar
  Disk System
• Michel, Nature, 1988, 333, 644, Neutron star
  disk formation from supernova fall-back and
  possible observational consequences
• continually fed from the ISM
• e.g. Popov, Colpi, Treves, Turolla, Lipunov,
  Prokhorov, 2000, ApJ, 530, 896
• pulsar planetary system first discovered in 1992
  - and to date the lowest mass planet
• Wolszczan, A. Frail, D. A., 1992, Nature, 355,
  145

4
Some more background - Spin History
But n2.4 - PSR B0540-69 1.4 - Vela
2.51 - Crab 2.91 PSR J1119-6127 2.837
PSR B1509-58
Additional torque from a fall-back disk Menou,
Perna Hernquist, ApJ, L63, 554 (2001) Mass in
flow 10-6 M? / year for the Crab But requires
limitations on the radial extent of the disk to
avoid optical detection
An additional source of torque for Vela? Possibly
a fall-back/debris disk?
5
First observation of a neutron star disk - AXP-
4U 014261
unpulsed
Wang et al, 2006, Nature, 440, 772
Pulsed
UltraCam observations - Dhillon et al, MNRAS,
363, 609, 2005
6
Other evidence for debris disks?
Shibanov, Y. A, et al, 2006, AA, 448, 313
7
(No Transcript)
8
Not a new idea ... Perna, Hernquist Narayan,
2000, ApJ, 54, 344
9
Spitzer - NICMOS - Subaru Image PSR
B065615 Spitzer 3.6µm
Spitzer 5.8µm
Subaru B
NICMOS 160W
Subaru -Shibanov et al., AA, 448, 313
(2006) Nicmos - Koptsevich et al, AA., 370, 1004
(2001) Spitzer - Spitzer archive.
10
Predicted Debris Disk Fluxes for Normal
Pulsars rinner light cylinder
radius router1R?
11
Rotating RAdio Transients - RRATs
Transient phenomena - Debris Disk hints?

• To date 10 pulsars show transient behaviour
• McLaughlin et al, Nature, 2006, 439, 817
• At least one with an X-ray counterpart
• Reynolds et al, 2006, ApJ, 639, L71
• Accreting material triggering magneto-spheric
  activity?
• Li, 2006, ApJ, 646, L139, also PSR B193124

12
Other stochastic emitters - Giant Radio
PulseGRPs Pulsars

• A few pulsars emit GRPs where the randomly
  occurring pulses have a flux many thousand times
  greater than the normal

13
Ground based AO Observations
arXiv0712.4171v2
Possible interpretations X-ray heated fossil
debris disk Viscously heated disk
14
Summary - why near IR observations are important

• At least one young neutron star, 4U 014261, has
  been observed to have a debris-disk, but
• how many others do?
• how long does a disk last?
• are such disks suitable for planet formation?
• disks or rings?
• How many young normal pulsars have associated
  debris disks?
• t lt 100,000 years Vela, Crab ......
• middle aged pulsars - PSR B065614, Geminga,
• Can debris disks explain
• Stochastic pulsar behaviour?
• Spin evolution and birth spin period?

15
Summary - Why SM4 will be important

• ACS
• Visible polarisation
• WFC3
• NIR imaging for 0.1µJy fluxes
• NICMOS
• NIR imaging and polarimetry
• compare LONG and SHORT polarisation fluxes
• Observations at 2 microns
• Need multi-wavelength studies
• X-Ray - IR variability for AXP disks
• WFC3 and ground based adaptive optic observations
  ELTs