Variable O VI and N V Emission from the X-ray Binary LMC X-3: Heating of the Black Hole Companion

Abstract

Based on high-resolution ultraviolet spectroscopy obtained with FUSE and COS, we present new detections of O VI and N V emission from the black-hole X-ray binary (XRB) system LMC X-3. We also update the ephemeris of the XRB using recent radial velocity measurements obtained with the echelle spectrograph on the Magellan-Clay telescope. We observe significant velocity variability of the UV emission, and we find that the O VI and N V emission velocities follow the optical velocity curve of the XRB. Moreover, the O VI and N V intensities regularly decrease between binary phase = 0.5 and 1.0, which suggests that the source of the UV emission is increasingly occulted as the B star in the XRB moves from superior to inferior conjunction. These trends suggest that illumination of the B-star atmosphere by the intense X-ray emission from the accreting black hole creates a hot spot on one side of the B star, and this hot spot is the origin of the O VI and N V emission. However, the velocity semiamplitude of the ultraviolet emission, K_{UV}~180 km/s, is lower than the optical semiamplitude; this difference could be due to rotation of the B star. If our hypothesis about the origin of the highly ionized emission is correct, then careful analysis of the emission occultation could, in principle, constrain the inclination of the XRB and the mass of the black hole.

To be published in the Astronomical Journal; 10 pages, 9 figures, 3 tables

References in corpus (3)

• CalFUSE v3: A Data-Reduction Pipeline for the Far Ultraviolet Spectroscopic Explorer
• An Extended FUSE Survey of Diffuse O VI Emission in the Interstellar Medium
• FUSE Observations of a Full Orbit of Hercules X-1: Signatures of Disk, Star, and Wind

Cited by in corpus (5)

• Mass Measurements of Stellar and Intermediate Mass Black-Holes
• The Mass of the Black Hole in LMC X-3
• Measuring the black hole masses in accreting X-ray binaries by detecting the Doppler orbital motion of their accretion disk wind absorption lines
• Modeling the Optical-X-ray Accretion Lag in LMC X-3: Insights Into Black-Hole Accretion Physics
• XMM-Newton/RGS Detection of the Missing Interstellar OVII Kalpha Absorption Line in the Spectrum of Cyg X-2