Magnetospheric Accretion Shocks In The X-ray Spectrum Of The Ultra-compact Binary 4u 1626-67
Abstract
In 2008 the ultra-compact binary pulsar underwent another episode of torque reversal since the one in the early 1990. We observed the X-ray source one year after the event with the HETG spectrometer on board Chandra. While the light curve before torque reversal is featureless, it now shows enhanced flaring similar to observations before the first reversal episode. The X-ray continuum is fit by the same spectral model as before, but exhibits significantly larger black body temperatures and smaller emission radii. The spectrum for the first time shows a narrow Fe K fluorescence line. We show while a photo-ionized plasma cannot fit the Ne and O Doppler line emissions, a collisionally ionized plasma provides a better description of the data. We propose, that the nature of the Doppler line pairs can then be described as magnetospheric accretion shocks and shocked matter moving towards the magnetospheric poles.
- Publication:
-
AAS/High Energy Astrophysics Division #12
- Pub Date:
- September 2011
- Bibcode:
- 2011HEAD...12.4201S