The Polarization of Cyg XR-1 and LMC X-3 in the UV

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Session 65 -- Interacting Binaries: Compact Stars
Oral presentation, Thursday, January 13, 2:15-3:45, Salon V Room (Crystal Gateway)

[65.07] The Polarization of Cyg XR-1 and LMC X-3 in the UV

J. F. Dolan, K. G. Wolinski, P. T. Boyd (Lab. Astron. Sol. Phys., NASA/GSFC)

Variable linear polarization has been observed in the visible from Cyg XR-1 = HDE226868 (Dolan, ApJ, 384, 249, 1992 and refs. therein), but no polarization measurements have been reported for LMC X-3. We present observations of the linear polarization of these two black-hole candidate systems around their 5.6 d (Cyg XR-1) and 1.7 d (LMC X-3) orbits, obtained in a bandpass centered at 2770 \AA with the High Speed Photometer on the Hubble Space Telescope. Cyg XR-1 shows variable polarization in the UV; its amplitude is ~ 2% peak to peak, consistent with the identification made from optical wavelength studies of Rayleigh scattering in a recombined gas stream as the mechanism producing it. The only other component of polarization detected is interstellar polarization. The amplitude of the variability of the linear polarization at 2770 \AA in LMC X-3 is $\stackrel{<}{\sim}$ 1% peak to peak. The inclination of the LMC X-3 system appears to be close to $90\deg$.

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