1. Very hard X-ray binaries containing white dwarfs
Marina Orio
Collaborators: D. de Martino, A. Bianchini, K. Mukai, T. Nelson, J. Sokoloski

2. Classes of interacting WD binaries emitting hard X-rays:
Symbiotics: a red, cool secondary. Not all symbiotics have WD… perhaps 90%? 7 NS stars symbiotics are hard. But… also 4 WD symbiotics are very hard sources.
Main sequence secondary: disk (low luminosity hard X-rays possible), magnetic mass transfer only (polars), magnetic accretion+disk (intermediate polars)
White dwarfs MS or RG with thermonuclear burning: novae, recurrent novae, “steady burners”?
High mass binaries: probably very soft only
Products of HMB evolution with brown dwarf, WD or NS: hard sources if they are merging? Probably not!
All these binaries, but specially novae and symbiotics, are detected in external galaxies. Novae can be indicators of binary star formation and pop. evolution.

3. Hard X-rays in outburst: RS Oph outburst on February 12 2006

4. RS Ophiuchi is a recurrent nova and a symbiotic
system (WD + red giant). It was observed in
outburst in 1898, 1933, 1958, 1967, 1985 and in
February of The AAVSO light curve is
shown above, and on the left is Williamina Fleming,
who studied the system after the first outburst.
RS Oph was also extensively studied by Annie Jump
Cannon AAVSO observations in 2000.

5. Early days of outburst: blast wave
1036 erg/s in hard X-rays! Initially >50 keV?
Deceleration after
1.7 days (low mass
shell) and rapid
cooling,
implications
for H-content of
SNe Ia.

6. Plot by J. Drake
February : rich emission line spectrum; resonance lines of He-l like and H-like ions of Fe, S, Si, Mg and Ne. Wide range of plasma temperatures: coolest transition O VIII Lyman alpha doublet at A (emissivity peak at T=3MK), hottest is Fe XXV 1s2p-1s2 resonance line (emissivity peak at T=60MK).
Broadening of the lines => approximately 2000 km/s at half maximum. Broadening increases with . Larger blue shift proportionate to ionization state and proportional to 
Interaction with red giant wind.

7. Quiescent evolution: CVs in hard X-ray surveys
SWIFT/BAT:
INTEGRAL IBIS:
421 sources (~5% are CVs)
461 sources (~6% are CVs) 7

8. Emission in post-shock region
For both magnetic and non magnetic accretion, hard X-rays. Stationary cooling flow, with highest T ~ gravitational potential well.
7 times deeper for 1.35 M than for 0.6 M WD
Hard X-rays are the best way to select potential Sne Ia candidates among WD systems!
MCV have “vertical” shocks and no radiation from disk.
IP’s have larger mdot and, due to lower B, no large blobs penetrating the post-shock region => much brighter in hard X-rays

9. Hard X-ray CVs
Most RXTE, INTEGRAL & SWIFT CVs are IP’s (Barlow et al. 2006; Bonnet-Bidaud et al.2006; 2007; Mukai et al.2007; Bodaghee et al. 2007; Shafter et al. 2008; Bonnet-Bidaud et al. 2009; de Martino et al. 2009……follow-up on-going…..) 9

10. MCVs: a hidden population of Galactic XRBs?
Chandra survey of the Galactic center (Muno et al.2004; Ruiter et al 2006):
over 2000 Faint Sources: Lx < 1031 – 1033 erg/s
- Hard spectra: kT > 8keV, Fe H-like and He-like emissions
- Affected by local absorption
- Variable: periods 300sec – 4.5hrs
=> IPs thought to be the dominant population: ~800 to be detected with NHXM
RXTE & INTEGRAL surveys of the Milky Way (Sazonov et al. 2006; Revnivtsev et al. 2008; 2009):
- XLF [2-10keV] at L<1034erg/s from coronal sorces (65%) and CVs (35%)
- XLF of CVs [2-12keV] similar to XLF[16-60keV]
=> Galactic Ridge emission at E>20keV dominated by MCVs 10

11. Most SDSS emission line objects Most Hard X-ray surveys
ORBITAL PERIOD DISTRIBUTION
Census: Polars IPs
Pre-Rosat (60%) (40%)
Post-Rosat (70%) (30%)
Today (54%) (46%)
Most SDSS emission line objects
Most Hard X-ray surveys

12. Polar CV emitting hard X-rays:
INTEGRAL & SWIFT hard X-ray polars
NAME
B (MG)
SYNCHRO
P_orb (hr)
V834 Cen 23
YES
1.7
SwiftJ ?
NO:
3.0
BY Cam 41 NO
3.4
V1432 Aql
28-35
The asynchronous polars are post-outburst novae?
(Massive WD yield novae more often) 12

13. WD Symbiotics
Kennea et al. 2009, Luna : 4 symbiotics with large X-ray luminosity
(several 1033 erg/s) detected with Swift-BAT up to 50 keV
T Cr Bor is a recurrent nova => surely a WD
Like the other 3 systems it does not show a spin period of the WD
Evidence hat they are all very massive WD with large( cm) disks
Type Ia SN progenitors?
stochastic variability,
“partial” absorber

14. Same criterion can be used to select massive WD in quiescent novae
CP Puppis is the hardest quiescent WD so far
Outburst consistent with very massive nova
Very luminous and only moderately fast => low mdot, not SN progenitor
Novae are far, we need deeper X-ray observations