Observations of compact binaries
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Observations of compact binaries using XMM-Newton. Gavin Ramsay. What is a compact binary?. Two stars orbiting around each other on timescales less than ~few hrs. One star a white dwarf the other a star similar to the Sun but less massive. How compact are they?. The Sun!.

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Observations of compact binaries using XMM-Newton

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Observations of compact binaries using xmm newton

Observations of compact binaries

using XMM-Newton

Gavin Ramsay


Observations of compact binaries using xmm newton

What is a compact binary?

Two stars orbiting around each

other on timescales less than ~few hrs

One star a white dwarf the other a star

similar to the Sun but less massive


Observations of compact binaries using xmm newton

How compact are they?

The Sun!

A compact binary with 2hr orbital period


Observations of compact binaries using xmm newton

Characteristics depend on the magnetic

field of the white dwarf

B<10^4G

B~10^6G

B>10^7G


Observations of compact binaries using xmm newton

XMM-Newton


Observations of compact binaries using xmm newton

XMM-MSSL polar survey

A survey of 40 strongly magnetic binary systems

Surprise was that so many were in

low accretion states: ~half of the systems

Not there!

Important input for population synthesis models

Ramsay et al (2004)


Observations of compact binaries using xmm newton

EP Dra - an eclipsing polar


Observations of compact binaries using xmm newton

EP Dra - accretion dip and eclipse

Ramsay et al (2004)


Observations of compact binaries using xmm newton

The X-ray spectra of polars

Long been the subject of great

controversy. Standard model suggests

L_soft/Lhard~1/2


Observations of compact binaries using xmm newton

Survey suggests that most polars show

X-ray spectrum consistent to that predicted

by standard model. However….

Ramsay & Cropper (2004)


Observations of compact binaries using xmm newton

EU UMa - shows very little hard X-ray flux

Some systems, however, show

emission properties not

predicted by the standard

accretion model. One proposal

is that dense blobs of material

are present in the accretion

flow which do not generate

hard X-rays. Not clear why

some systems have blobs while

others do not. Not related to

magnetic field strength.

Ramsay et al (2004)


Observations of compact binaries using xmm newton

XMM-Newton observations of Intermediate Polars

B<10^4G

B~10^6G

B>10^7G


Observations of compact binaries using xmm newton

FO Aqr: P_spin=20.9min, Porb=4.9hrs

Evans et al (2004)


Observations of compact binaries using xmm newton

FO Aqr: X-ray spectrum

Huge absorption dip due accretion ‘curtain’

Evans et al (2004)


Observations of compact binaries using xmm newton

Disc accreting binaries

B<10^4G

B~10^6G

B>10^7G


Observations of compact binaries using xmm newton

YZ Cnc: Porb~2.1hrs

Hakala et al (2004)


Observations of compact binaries using xmm newton

YZ Cnc: X-ray spectrum

Hakala et al (2004)


Observations of compact binaries using xmm newton

Evidence for jets?

Model with no-blue shift

Model with blue shift of

1200km/s

Hakala et al (2004)


Observations of compact binaries using xmm newton

ULTRA-compact binary: Porb<10min

Jupiter

Ultra-compact

binary


Observations of compact binaries using xmm newton

RX J1914+24: Porb 569 sec (9.5min)

Ramsay et al (2005)


Observations of compact binaries using xmm newton

Models fall into accretion and

non-accreting model.

Accreting models predict it would

spin down over time.

Non-accreting model suggests it

would spin-up over time (the electric

star model).


Observations of compact binaries using xmm newton

RX J1914+24: spinning up

Ramsay et al (2005)


Observations of compact binaries using xmm newton

Spining up at a rate of 6.6x10^-12s/s

Ramsay et al (2005)


Observations of compact binaries using xmm newton

What is the electric star model?

Sounds far fetched - but!….


Observations of compact binaries using xmm newton

We know it operates on Jupiter


Observations of compact binaries using xmm newton

RX J1914+24: X-ray spectrum

Very odd!

Ramsay et al (2005)


Observations of compact binaries using xmm newton

Both ultra-compacts have been discovered

in X-rays. Search for more!

Programme to search for ultra-compact

systems in XMM-Newton and Chandra

archives.

Have yet to find one but have discovered

lots of flare stars!


Observations of compact binaries using xmm newton

Trenholme, Ramsay & Foley (2004)


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