Other
Scientific paper
Nov 1993
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993aj....106.2081e&link_type=abstract
Astronomical Journal (ISSN 0004-6256), vol. 106, no. 5, p. 2081-2095
Other
5
B Stars, Ionized Gases, Mass Ratios, Photosphere, Stellar Spectra, Stellar Winds, Velocity Distribution, Binary Stars, Doppler Effect, Hydrogen, Interstellar Gas, Iron, Iue, Magnesium, Silicon
Scientific paper
I have followed photospheric and wind absorptions in International Ultraviolet Explorer (IUE) spectra over much of the orbit of this K4 Ib+B3-4 binary system, using interstellar lines to transform all the velocities to a scale with the interstellar medium at -10.1 km/s. Results are as follows: Interstellar Fe II lines give NL (Fe(+)) = 1-2 x 1014/sq cm with a Doppler width of 7 km/s; depletions of heavy elements along the line of sight to this star are similar to those for other stars with low interstellar densities. Photospheric lines yield a new velocity amplitude for the B star, KB = 23.2 +/- 1.0 km/s, which gives the mass ratio MK/MB = 1.66 and masses MB = 7.1 solar mass and MK = 11.7 solar mass. Existing photometry gives RK = 197 solar radius, RB = 5.2 solar radius, and i = 87.19 deg. Breadths of photospheric lines imply the rotational velocity of the B star is V sin i = 70-80 km/s. Most of the wind features are formed in a shell much larger than the binary system for which the terminal velocity seems to be 73 +/- 2 km/s, but it may be as high as approximately 90 km/s. The Doppler width (approximately 13 km/s) of Fe II shell lines likely results from acceleration of the wind, although it could reflect orbital motion of the K supergiant. Shell lines of Mg II and Si II are roughly consistent with Fe II, although their strengths are phase dependent, while S II requires a somewhat thicker shell in S(+) than in Fe(+) with a greater spread in expansion velocity. Shell lines of O I and N I are abnormally weak, if detected at all, and this implies that hydrogen is ionized throughout much of the wind. Lines of highly ionized species (C IV, Si Iv, and N V) appear sporadically in the spectrum and have inverse P Cyg profiles implying collapse (probably of an accretion disk) onto the B star. They do not seem to be isolated at particular phases as might be expected for formation in a conical shock front around an accretion column. I argue that the wind is roughly isotopic and is accelerated slowly, in agreement with existing ideas about winds.
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