Following a previous study by Altamore et al. (1982, Paper I) of the ultraviolet spectrum of KQ Pup, and the spectral Atlas of this star by Altamore et al. (1991, Paper II), we analyze coude and CAT CES optical spectra of the object observed during 1969-1984, and compare with IUE data obtained in 1979. Besides the M-star photospheric absorptions, the optical spectrum shows sharp emissions of [S II], [Cu II], [Fe II], Fe II, and [Ni II]. They probably arise in an intermediate region of the M-star wind ionized by the hot star radiation, where also the P Cygni UV lines of ionized metals are formed. The region is more extended and closer to the M-star near periastron passage. The earlier Balmer lines present a double peaked emission with a sharp central absorption which in 1979 and 1983 appears double suggesting the presence of streams or clouds of matter in the system environment. The redshifted emission component disappears in the higher series members, giving rise to an inverse P Cygni profile. Some Balmer lines display very broad absorption components which are identified as the density broadened hot star photospheric lines. He I is probably present with a rotationally broadened absorption at 3819 angstrom largely hidden by the rich M-star spectrum. In the UV the resonance lines and the excited lines of the doubly ionized metals are broad and redshifted by about +37 km s-1 with respect to the M-star radial velocity, implying line formation in opaque and turbulent matter flowing near and towards the surface of the hot star. From the blue-IR colour indices and the 2200 angstrom interstellar band we derive for KQ Pup a colour excess of E(B-V) = 0.14 +/- 0.03. The ultraviolet to infrared energy distribution appears bimodal with the hot component dominating below about 3600 angstrom and the M star above 4000 angstrom. We have fitted the dereddened energy distribution with a combination of a 30 000 K black body and of a M-supergiant spectrum (alpha-Ori), and derived for KQ Pup a distance at 1400 +/- 200 pc. At this distance the hot component results a slightly underluminous BOV star with a radius of 4.35R.. The mass ratio of the components of the binary system seems to be close to unity. We propose for KQ Pup a binary model with a highly mass losing cool supergiant primary and an unevolved early-type secondary. The optical and UV emission lines are formed in the regions of the cool star wind which are ionized by the hot star radiation. A shock is probably produced near the hot star by the interaction of the cool star wind with the hot star wind. Instabilities probably occur near the shock which produce cool clouds from the M-star wind, which may penetrate the hot star wind and be accreted.
Rossi, C., Altamore, A., Baratta, G.b., Friedjung, M., Viotti, R. (1992). THE SPECTRUM OF THE VV-CEPHEI STAR KQ-PUPPIS (BOSS-1985) .3. A POSSIBLE MODEL. ASTRONOMY & ASTROPHYSICS, 256(1), 133-140.
THE SPECTRUM OF THE VV-CEPHEI STAR KQ-PUPPIS (BOSS-1985) .3. A POSSIBLE MODEL
ALTAMORE, Aldo;
1992-01-01
Abstract
Following a previous study by Altamore et al. (1982, Paper I) of the ultraviolet spectrum of KQ Pup, and the spectral Atlas of this star by Altamore et al. (1991, Paper II), we analyze coude and CAT CES optical spectra of the object observed during 1969-1984, and compare with IUE data obtained in 1979. Besides the M-star photospheric absorptions, the optical spectrum shows sharp emissions of [S II], [Cu II], [Fe II], Fe II, and [Ni II]. They probably arise in an intermediate region of the M-star wind ionized by the hot star radiation, where also the P Cygni UV lines of ionized metals are formed. The region is more extended and closer to the M-star near periastron passage. The earlier Balmer lines present a double peaked emission with a sharp central absorption which in 1979 and 1983 appears double suggesting the presence of streams or clouds of matter in the system environment. The redshifted emission component disappears in the higher series members, giving rise to an inverse P Cygni profile. Some Balmer lines display very broad absorption components which are identified as the density broadened hot star photospheric lines. He I is probably present with a rotationally broadened absorption at 3819 angstrom largely hidden by the rich M-star spectrum. In the UV the resonance lines and the excited lines of the doubly ionized metals are broad and redshifted by about +37 km s-1 with respect to the M-star radial velocity, implying line formation in opaque and turbulent matter flowing near and towards the surface of the hot star. From the blue-IR colour indices and the 2200 angstrom interstellar band we derive for KQ Pup a colour excess of E(B-V) = 0.14 +/- 0.03. The ultraviolet to infrared energy distribution appears bimodal with the hot component dominating below about 3600 angstrom and the M star above 4000 angstrom. We have fitted the dereddened energy distribution with a combination of a 30 000 K black body and of a M-supergiant spectrum (alpha-Ori), and derived for KQ Pup a distance at 1400 +/- 200 pc. At this distance the hot component results a slightly underluminous BOV star with a radius of 4.35R.. The mass ratio of the components of the binary system seems to be close to unity. We propose for KQ Pup a binary model with a highly mass losing cool supergiant primary and an unevolved early-type secondary. The optical and UV emission lines are formed in the regions of the cool star wind which are ionized by the hot star radiation. A shock is probably produced near the hot star by the interaction of the cool star wind with the hot star wind. Instabilities probably occur near the shock which produce cool clouds from the M-star wind, which may penetrate the hot star wind and be accreted.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
