Neon Line Emission in the ASCA X-ray spectrum of the 7s pulsar 4U1626-67
Session 62 -- Supernova Remnants and Pulsars
Oral presentation, Tuesday, 10, 1995, 10:00am - 11:30am

## [62.06] Neon Line Emission in the ASCA X-ray spectrum of the 7s pulsar 4U1626-67

L. Angelini, N.E. White, T.R. Kallman (LHEA/GSFC), F. Nagase (ISAS), A. Yoshida, T. Takeshima (RIKEN), C. Becker (MIT)

Using the ASCA Observatory we have discovered a strong 1kev Neon emission line complex in X-ray spectra of the 7s X-ray pulsar 4U1626-67. The Ly--$\alpha$, Ly--$\beta$, and Helium-like-$\alpha$ lines are detected at 1.05, 1.10 and 0.95 keV, respectively as well as a L-$\alpha$ Ne recombination edge at 1.20 keV. This is the first time a recombination line has been detected from a cosmic X-ray source. The strength of the neon emission compared to the expected iron L complex implies a factor of $\sim$ 10 Neon overabundance relative to iron. 4U1626-67 is a low mass X-ray binary, LMXRB, system with an orbital period of 2485s, and is unusual in that it is one of the few LMXRB to contain an X-ray pulsar. Neon is a by-product of Helium burning and its overabundance in this system indicates that the companion star is burning, or has in the past burnt Helium. This supports the evolutionary scenario for 4U1626-67 where the donor star is a helium-burning star.