Observations of compact binaries

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
Blt104G
B106G
Bgt107G
5
XMM-Newton
6
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)
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/Lhard1/2
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
Blt104G
B106G
Bgt107G
13
FO Aqr P_spin20.9min, Porb4.9hrs
Evans et al (2004)
14
FO Aqr X-ray spectrum
Huge absorption dip due accretion curtain
Evans et al (2004)
15
Disc accreting binaries
Blt104G
B106G
Bgt107G
16
YZ Cnc Porb2.1hrs
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 Porblt10min
Jupiter
Ultra-compact binary
20
RX J191424 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 J191424 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 J191424 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)