Accretion Disk Line Emission from X0614+09

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Session 7 -- X-Ray Binaries and Gamma-Ray Binaries
Display presentation, Monday, 9:20-6:30, Heller Lounge Room

[7.08] Accretion Disk Line Emission from X0614+09

J.H.Swank, N.E.White (NASA/GSFC), D.J.Christian (UMD)

A series of X-ray observations of the low mass X-ray binary X0614+091 was made in 1979 with the non-dispersive moderate resolution Solid State Spectrometer on the Einstein Observatory and simultaneously with the Monitor Proportional Counter. During a period of relatively high source flux (0.5-20 keV) corresponding to an X-ray luminosity of $8x10^{36} ergs s^{-1}$ for an assumed distance of 5 kpc, several components of low energy emission can be distinguished, in particular an emission structure in one or several lines in a band of about 200 eV around 0.77 keV, to which OVII-OVIII and FeXVII-FeXIX would contribute. Observations in the preceding 6 months confirm the presence of the emission feature for continuum fluxes lower by a factor of 2. A total equivalent width of $27^{+ 5}_{-4} eV$ in a single line or divided among several is relatively high among the spectra of low mass X-ray binaries. Line emission adds to the similaries of X0614+091 to the set of bright burst sources with X-ray luminosities in the range $10^{36}-10^{37} ergs s^{-1}$, from which line emission has been reported from grating spectrometer results. An accretion disk corona is expected to be excited by the central source and soft X-ray lines should be emitted by some of the coronal gas. To explain the observed feature either most of the corona needs to contribute or other sources of emission are comparable. The corona for a moderate luminosity source would be less thick to Compton scattering than the coronas heated by the more luminous low mass X-ray binaries, and possibly would allow enhanced contributions of the base of the corona and an outer rim. An indication of an absorption edge in the spectrum suggests the possibility that better observations could confirm the outer part of the corona.

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