Highly-magnetized white dwarfs:Formation mechanisms and implications for PNe.

J. NordhausNSF FellowCenter for Computational Relativity and GravitationRochester Institute of Technology (USA)

High-field magnetic white dwarfs (HFMWD): BWD ⇠ 106 � 109 G

~10% of all white dwarfs are highly magnetized (same for neutron stars)

High-field magnetic white dwarfs (HFMWD): BWD ⇠ 106 � 109 G

~10% of all white dwarfs are highly magnetized (same for neutron stars)

High-field magnetic white dwarfs (HFMWD): BWD ⇠ 106 � 109 G

If the formation of HFMWDs is independent of binary evolution...

... then the fraction of HFMWDs in single stars should be the same as in binary systems.

0 20 40 60 80 100

0

5

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B (MG)

Kepler et al. 2013

SDSS DR7 Sample SDSS identified ~1,200 detached WD + M dwarf binaries

None are HMWDs

(see also Tout 08)

0 20 40 60 80 100

0

5

10

15

20

B (MG)

Kepler et al. 2013

SDSS DR7 Sample SDSS identified ~1,200 detached WD + M dwarf binaries

None are HMWDs

SDSS identified 149 single HFMWDs

Should we have found HFMWDs in binaries?

(see also Tout 08)

0 20 40 60 80 100

0

5

10

15

20

B (MG)

Kepler et al. 2013

SDSS DR7 Sample SDSS identified ~1,200 detached WD + M dwarf binaries

None are HMWDs

SDSS identified 149 single HFMWDs

Should we have found HFMWDs in binaries?

Within 20 pc, 109 WDs: 20% have a main-sequence companion

Probability of obtaining samples this different from the same underlying population is: 5.7⇥ 10�10 6.2�or

(see also Tout 08)

Nordhaus et al. 2011

HFMWD: no detached companion present.

non-magnetic WDs: detached companion present.

Two options:

1. Presence of detached, long-period companions prevents formation of HFMWD.

2. Orbiting companions were present but were destroyed during formation of HFMWD.

Formation of high-field magnetic white dwarfs from common envelopes

Nordhaus et al. 2011 PNAS 108, 8

Sarah Wellons (Harvard)Dave Spiegel (IAS)Brian Metzger (Columbia)Eric Blackman (Rochester)

Collaborators:

4 5 6 8 10 20 30 40 70 100 200 400 600

1

2

3

4

7

10

20

30

40

70

100

Mc (M

Jup)

P (

hr)

(assumes Ebind

= 1046 erg, MWD

= 0.5 Msun

)

a inner

(! CE=1)

a inner

(! CE=0.

25)

Allowed

ashred

Not Allowed("The Gap")

NGM11

Multiple

Inte

rior t

o "The

Gap

"

and K

nown S

yste

ms

0.005 0.01 0.02 0.05 0.1 0.2 0.5

Mc (M

Sun)

4 5 6 8 10 20 30 40 70 100 200 400 600

0.25!0.35

0.35!0.45

0.45!0.55

0.55!0.65

0.65!0.75

0.75!0.85

0.85!0.95

0.95!1.05

1.05!1.15

1.15!1.25

MWD

(MSun

)

Nordhaus & Spiegel MNRAS 2013 432, 500

Nordhaus et al. 2010 MNRAS 408, 631

0.1 AU1 AU

10 AU100 AU

Fates of KnownPlanetary Systems

ai, engulfed

ai, escapes

af, escapes

pi, engulfed

pi, escapes

ai, Jupiter now

af, Jupiter future

Nordhaus & Spiegel 2013

WD

Inflow Outfl

ow

Boundary Layer

Magnetized WD

Nordhaus et al. 2011 PNAS 108,8Nordhaus & Blackman 2006 MNRAS 370, 2004Nordhaus, Blackman & Frank 2007 MNRAS 376, 599

For shaping PNe see Reyes-Ruiz & Lopez 2001

Nordhaus et al. 2011

Important Points:

B-field amplification at convective-radiative boundary with downward diffusion not sufficient.

Companion disrupts; hypercritical accretion initially.

Fields amplify in disk, accrete onto WD surface, survive through termination of the AGB phase.

Important Caveats:

How long does the disk survive?

Hydrogen-rich material deposited in He-burning layer could trigger thermonuclear runaway.

Nordhaus & Di Lernia AstroBEAR

Nordhaus & Di Lernia AstroBEAR