Collisional Ionization and Doppler Lines in the Ultra-compact Binary 4U1626-6750 years or X-ray Binaries, Chandra Workshop, July 10-12, 2012, Boston MA

Collisional Ionization and Doppler Lines in the Ultra-compact Binary 4U1626-67 Ionization properties in X-ray Binaries: Reflection, ADC Emissions, Jets, Discs, and

- Properties of 4U 1626-67: Torque Reversals, X-rayVariability, Doppler and Fe Lines Fe Line Fluorescence before and after the 2008 Torque Reversal

- Fitting Ionization Models: Photo-ionization vs Collisional Ionization

- Possible Interpretations: Fe in the System, Ultracompact CO Disks, Magnetospheres

50 years or X-ray Binaries, Chandra Workshop, July 10-12, 2012, Boston MA

Previous HETG Observations of the the Ultra-compact Binary 4U1626-67Previous HETG GTO observations: - Schulz et al. 2001: Double Peaked X-ray Lines from the O/Ne-rich Accretion Disk in 4U 1626-67: OBSIDs 104, 39 ksec - Krauss et al. 2007: High Resolution X-ray Spectroscopy of the Ultra-compact LMXB Pulsar 4U 1626-67: OBSIDs 104, 39 ksec 3504, 97 ksec

X-ray Spectra and Long-term Lightcurve of the Ultra-compact Binary 4U1626-67New HETG GTO observations:Chakrabarty & Schulz 2009 Cycle 11 GO time: OBSIDs 11058, 80 ksec, Jan 14. 2010Camero-Arranz et al. 2012Schulz et al. 2012

Continuum Properties of the Ultra-compact Binary 4U1626-67 before and after Torque Reversal Tbnew (Powerlaw + Bbodyrad):NH = 1.2x1021 cm-1 AG = 0.0084 ph cm-2 s-1= 0.80Abb = 593 (R2km / D2kpc)kTbb = 0.20 keV

Tbnew (Powerlaw + Bbodyrad):NH = 1.2x1021 cm-1 (0.2) AG = 0.0384 ph cm-2 s-1= 1.19 (0.90)Abb = 83 (R2km / D2kpc)kTbb = 0.48 keV (0.52)

Camero-Arranz et al. 2012Schulz et al. 2012

Fe Fluorescence in the Ultra-compact Binary 4U1626-67 before and after Torqure ReversalSchulz et al. 2012Camero-Arranz et al. 2012

Fe Fluorescence in the Ultra-compact Binary 4U1626-67Schulz et al. 2012

Flares and Dips in the New Light Curve of 4U1626-67Obsid 11058:

Obsid 3504:

Schulz et al. 2012

Doppler Lines in the Ultra-compact Binary 4U1626-67 before and after 2008 Torque Reversal

Doppler Lines in the Ultra-compact Binary 4U1626-67Schulz et al. 2012

Ionization Model Fits to the X-ray Spectrum of 4U1626-67Photo-ionized modeling:

Collisional-ionized modeling:

Aped_density = 13:

Collisional Ionization Model Fits to the X-ray Spectrum of 4U1626-67Schulz et al. 2012

Pure C/O/Ne disk?:

Cannot maintain C I/Ne I/O I : log x > 2 @ r~109 cm

Pure C/O disk model predicts T = 28000 K @ 20000 km (Werner et al. 2006)

Model CO Disk Properties in the Ultra-compact Binary 4U1626-67

Magnetospheric Accretion Shocks in the Ultra-compact Binary 4U1626-67Emission Volumes:

In conclusion we propose the following:

Doppler Lines in the Ultra-compact Binary 4U1626-67Magnetospheric Accretion ShocksRco = 8.5x108 cm

Rco = Rmag

Vshift ~ 2000 km/s

~ Vco

Vco ~ Vshock

Tjump < 60 MK

CO plasma< 20 deg impact

Vshift = Vion

Tshock < 10 K

In conclusion we propose the following:

Doppler Lines in the Ultra-compact Binary 4U1626-67 The light curve before torque reversal is featureless. The light curve after torque reversal shows enhance variability which includes type II flaring, intensity dips, and periods of quiescence.

The X-ray flux at the time of the observation in 2009 is at about the same level as it was in 1994.

The X-ray continuum after torque reversal is fit by the same spectrum as before, however with a higher blackbody temperature and a smaller emission radius. The spectrum shows a narrow Fe K fluorescence line, which was not observed before torque reversal.

A photo-ionized plasma cannot fit the Ne and O Doppler line emissions.

The large ratio between the Ne X L line and the upper limit to the Ne X L line rules out significant contributions due to resonance scattering. A collisions ionized plasma fits both Ne and O line ratios very well with enhanced plasma densities and plasma temperature between 1 MK and 10 MK.Magnetospheric Accretion Shocks

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