Cyclotron Spectroscopy of Polars

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Cyclotron Spectroscopy of Polars
Ryan Campbell, NMSU
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Outline

• Polars/Cyclotron Basics
• Models Used
• Constant Lambda
• Fischer Beuermann
• Objects
• EF Eri
• VV Pup
• MQ Dra

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A Polar

• Interacting binary star system.
• Named for high linear and circular polarization
  observed
• RLOF
• WD is highly magnetic (8-240 MG)
• Captured material transferred to pole

White Dwarf Primary
Late-Type Dwarf Secondary
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Accretion Region
Hot/Dense Core embedded in diffuse/cool region

• If mdot gt 1g/cm2/s Hydrodynamic shock formed

To, Vo
Precursor
4To, Vo/4
Post-Shock
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Cyclotron Emission
Cyclotron Humps!!
First detected in VV Pup (1979)

Velocity
Each electron does this Emitting radiation at
?ceB/(mrelC) Emission also at every n?c
Broad cyclotron harmonics!
mrel depends on the velocity of the particle,
producing.
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Constant Lambda (CL) Models

• Four Global parameters
• B- the magnetic field strength
• kT- The plasma temperature
• log? Ne/B
• 4) T- The viewing angle

B
Shock
log?
T
kT
WD surface
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Fischer Beuermann
mdot

• One Dimensional Radiative Hydrodynamic code
• Uses Normalized Velocity and Temperature profiles
  as inputs
• Radiative transfer done through shock of finite
  size
• Inputs B, mdot, D, Mwd,T

B
V
kT
T
D
WD surface
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Cyclotron Geometry

• Viewing angle is orbitally modulated
• iinclination tilts the center
• ßmagnetic co-latitude.
• forbital phase.
• cosT cos i cos ß sin i sin ß cos2p(f- fo)
• Use T modulation to determine geometry
• Local field line angle, b, often differs from the
  magnetic co-lat, ß

Rotation Axis
Accretion Region
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EF Eri

• Ultra-short period
• P 81 min
• Low state since 1997, but now bright again?
• B 13 MG, primary accretion spot
• Zeeman tomography gt zones and regions, high
  field spot. B 100 MG
• Used Schwope et al., 2007 WD (9750 K)

Two Accretion Spots?
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Two cyclotron components needed
B12.6, kT 4.5kev, log?5.5
B12.8, kT 6.0kev, log?6.5
Bluehot, dense. Redcool, diffuse. At different
colatitudes (ß 6 and 2)
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VV Pup

• Short period
• P 100 min
• Archetypal 2-pole polar B 32, 56 MG
• Variable states 14.5 ltVlt 19.5
• i75, ß 10, 155
• Multi-epoch dataset

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Brightens over the night
Extreme Low-State (VLT) kT4.0 keV, log?6.0 B
31.0 MG
Low-State (VLT) kT7.7-10 keV, log?
5.5, B 31.5
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B-kT Plane
high state
Fischer Beuermann (2001) kT mdotB(-2.6)
B-kT dependence of c, a proxy for mdot
Mid state
The brightness states are well partitioned in
B-kT space! (From CL Models, FB results coming..)
(more observations are planned)
low state
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MQ Dra (SDSS 1553)

• Long Period
• P 4.39 hr
• Archetypal Pre-Polar.
• Even cooler than LARPS havent warmed yet
• Variable states 14.5 ltVlt 19.5
• Modeled with CL and Fischer Beuermann
• Simple geometry (i68, ß8) doesnt work
• Lowest fluxes seen for phases with high T

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MQ Dra
Conditions for model maximum occur at cyclotron
minimum
Cyclo Min
Cyclo Max
-Fischer Beuermann models - B 58.5 MG, mdot
2.5e-3, Mwd0.6, D5.5e7 cm, d130 pc
-CL Models - B 59.0 MG, kT 1.8 keV, log?
3.8
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Solution Bent Field lines

• Simple geometry model doesnt work
• Instead of i68, constant beta i45, variable b

Phase modulated apparent area explained by
foreshortening
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Conclusions

• Have modeled cyclotron spectra for EF Eri, VV
  Pup, and MQ Dra
• Geometries as well as B, kT, log? (or B, mdot and
  Mwd) were determined
• Multi-Epoch datasets (e.g. VV Pup) are the future
• Beginning to compare CL and FB models

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EF Eri Galex

• Szkody et al. 2006 NUV/FUV shows suprising
  variablity
• Can be fit with cyclotron!!
• Co-add same WD with cyclotron models extrapolated
  to UB
• Higher B 115 MG, otherwise identical

BluePhoto. Max, RedPhoto. Min