origin of outburst x-ray emission
DESCRIPTION
Origin of outburst X-ray emission. Peter Wheatley, University of Warwick. Dwarf nova X-ray emission. Optical. EUV. X-ray. Wheatley, Mauche & Mattei 2003. outburst. quiescence. Patterson & Raymond 1985. X-ray eclipse in quiescence. HT Cas with ASCA. Mukai et al., 1997. - PowerPoint PPT PresentationTRANSCRIPT
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Origin of outburst X-ray emission
Peter Wheatley, University of Warwick
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Dwarf nova X-ray emission
Wheatley, Mauche & Mattei 2003
Optical
EUV
X-ray
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outburstquiescence
Patterson & Raymond 1985
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X-ray eclipse in quiescence
Mukai et al., 1997HT Cas with ASCA
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Z Cha in quiescence with XMM-NewtonHickman et al., in prep
B band
0.2-12 keV
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WD eclipse
Z Cha optical eclipse Hickman et al., in prep
B band
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1.2-10 keV
0.2-1.2 keV
Hickman et al., in prepZ Cha X-ray eclipse
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X-ray spectra
quiescence outburst
Patterson & Raymond 1985
Confirmed
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Reis et al., in prep
1029 erg s-1 ~ 1012 g s-1 ~ 10-14 MSun yr-1
X-ray luminosities of white-dwarf dominated CVs
Reis et al., in prep
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X-ray spectra
quiescence outburst
Patterson & Raymond 1985
Confirmed
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Naylor et al. 1988
OY Car in outburst with EXOSAT LE
7-250 Å
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EUV spectra of dwarf novae in outburst
Mauche 2004
WZ Sgehigh inclination
SS Cyglow inclination
Lbl~1034 erg s-1 NH~3x1019 cm-2 V~2500 km s-1
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X-ray spectra
quiescence outburst
Patterson & Raymond 1985
Confirmed Confirmed?
NH~3x1019 cm-2
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OY Car in outburst with ROSAT - no X-ray eclipse
Pratt et al., 1999
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Z Cha in outburst with XMM-Newton
outburst
quiescence
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XMM-Newton spectra of Z Cha
outburst
quiescence
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X-ray scattering?
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UX UMa with XMM-Newton
Pratt et al., 2004
• Nova-like used as proxy for outburst state
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Not X-ray scattering
Wheatley & Kallman 2006
UX UMa Pratt et al., 2004
NH=5x1020 cm-2
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Nature of outburst X-ray emission
• Properties– Spectrum is unabsorbed optically-thin thermal emission
• weighted to low temperatures compared with quiescence
– Not eclipsed– Not scattered– Only present in outburst– Lx ~ 1031 erg s-1 ~ 10-3 Ldisc
• Origin– Boundary layer - No
• Not eclipsed, not scattered
– Secondary star - No• Too luminous, turns off in quiescence
– Disc hotspot - No• Not eclipsed, turns off in quiescence
– Accretion disc corona - Maybe– Shocks in radiatively-driven wind - Maybe
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WZ Sge with Chandra LETG
Wheatley & Mauche 2005
Outburst
Outburst
Quiescence
kT <= 1 keV
v=840 km/s
RKep~2x1010cm
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Lx ~ 1031 erg s-1 ~ 10-3 Ldisc
Lx <= 10-3 Lstar
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Z Cha in outburst with XMM-Newton
outburst
quiescence
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Conclusions
• Eclipses confirm that all quiescent X-ray emission from BL– Useful for estimating instantaneous accretion rates
• Outburst EUV spectra and lack of EUV eclipse consistent with BL dominating outburst emission as well
• However, outburst X-ray spectra and lack of X-ray eclipses are NOT consistent with origin in BL
• Properties of outburst X-ray emission only consistent with a disc corona– Disc corona only only in outburst points to magneto-rotational instability
– Outburst X-rays may provide the best observational handle on the MRI
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Magneto-rotational instability (MRI)
Adapted from Balbus & Hawley 1998
Balbus & Hawley 1991
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