1. Observations of compact binaries using XMM-Newton
Gavin Ramsay

2. 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

3. How compact are they? The Sun!
A compact binary with 2hr orbital period

4. Characteristics depend on the magnetic
field of the white dwarf
B<10^4G
B~10^6G
B>10^7G

5. XMM-Newton

6. XMM-MSSL polar survey Not there!
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)

7. EP Dra - an eclipsing polar

8. EP Dra - accretion dip and eclipse
Ramsay et al (2004)

9. The X-ray spectra of polars
Long been the subject of great
controversy. Standard model suggests
L_soft/Lhard~1/2

10. Survey suggests that most polars show
X-ray spectrum consistent to that predicted
by standard model. However….
Ramsay & Cropper (2004)

11. 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)

12. XMM-Newton observations of Intermediate Polars
B<10^4G
B~10^6G
B>10^7G

13. FO Aqr: P_spin=20.9min, Porb=4.9hrs
Evans et al (2004)

14. FO Aqr: X-ray spectrum Huge absorption dip due accretion ‘curtain’
Evans et al (2004)

15. Disc accreting binaries
B<10^4G
B~10^6G
B>10^7G

16. YZ Cnc: Porb~2.1hrs
Hakala et al (2004)

17. YZ Cnc: X-ray spectrum
Hakala et al (2004)

18. Evidence for jets? Model with no-blue shift Model with blue shift of
1200km/s
Hakala et al (2004)

19. ULTRA-compact binary: Porb<10min
Jupiter
Ultra-compact
binary

20. RX J : Porb 569 sec (9.5min)
Ramsay et al (2005)

21. 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).

22. RX J : spinning up
Ramsay et al (2005)

23. Spining up at a rate of 6.6x10^-12s/s
Ramsay et al (2005)

24. What is the electric star model?
Sounds far fetched - but!….

25. We know it operates on Jupiter

26. RX J : X-ray spectrum
Very odd!
Ramsay et al (2005)

27. 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!

28. Trenholme, Ramsay & Foley (2004)