2001ApJ...563..941S -
Astrophys. J., 563, 941-949 (2001/December-3)
Double-peaked X-ray lines from the oxygen/neon-rich accretion disk in 4U 1626-67.
SCHULZ N.S., CHAKRABARTY D., MARSHALL H.L., CANIZARES C.R., LEE J.C. and HOUCK J.
Abstract (from CDS):
We report on a 39 ks observation of the 7.7 s low-mass X-ray binary pulsar 4U 1626-67 with the High Energy Transmission Grating Spectrometer (HETGS) on the Chandra X-Ray Observatory. This ultracompact system consists of a disk-accreting magnetic neutron star and a very low mass, hydrogen-depleted companion in a 42 minute binary. We have resolved the previously reported Ne/O emission line complex near 1 keV into Doppler pairs of broadened (~2500 km.s–1 FWHM) lines from highly ionized Ne and O. In most cases, the blue and red line components are of comparable strength, with blueshifts of 1550-2610 km.s–1 and redshifts of 770-1900 km.s–1. The lines appear to originate in hot (~106 K), dense material just below the X-ray-heated skin of the outer Keplerian accretion disk, or else possibly in a disk wind driven from the pulsar's magnetopause. The observed photoelectric absorption edges of Ne and O appear nearly an order of magnitude stronger than expected from interstellar material and are likely formed in cool, metal-rich material local to the source. Based on the inferred local abundance ratios, we argue that the mass donor in this binary is probably the 0.02 M☉ chemically fractionated core of a C-O-Ne or O-Ne-Mg white dwarf which has previously crystallized.
Abstract Copyright:
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Journal keyword(s):
Accretion, Accretion Disks - Stars: Binaries: Close - stars: individual (4U 1626-67) - Stars: Neutron - Techniques: Spectroscopic - X-Rays: Stars
CDS comments:
p.946 : 1E 1740.1-2947 misprint for 1E 1740.7-2942 ??
Simbad objects:
4
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