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THE SPECTRUM OF THE VV-CEPHEI STAR KQ-PUPPIS (BOSS-1985) .3. A POSSIBLE MODEL
No full textFollowing 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
Analysis of the variability of the luminous emission line star MWC 314
No full textContext. We investigated the surroundings of MWC 314 in the framework of the study of hot emission line star environments using the SAC method. This star is either a B[e] supergiant or a luminous blue variable and appears to be extremely luminous and massive.
Aims. We determine the structure and physical conditions of the emitting region and study the possible variations.
Methods. We measured the absorption and emission line radial velocities and the emission line fluxes on high-resolution spectra obtained with Aurelie at the 1.52 m OHP telescope in July 1998, with Elodie at the 1.93 m OHP telescope at various epochs, and with echelle spectrographs of the Asiago and Loiano observatories (Italy) in 2006. We used the statistical approach of the self-absorption curve method (SAC) to derive physical parameters of the line-emitting region.
Results. We detected drastic variations of the photospheric absorption line radial velocities with time, while the emission line velocities appear to be stable. The Cr I
The symbiotic star BX Monocerotis
No full textThe nature of BX Mon, a peculiar star characterized by a composite spectrum and very long period photometric variability, has been investigated. The star has been included in an extensive program of ESO observations of emission line stars. New results are discussed based on coordinated optical (IDS) and infrared observations made in February 1983, on high resolution H alpha spectrophotometry made with CAT-CES in February 1984, and on infrared photometry of March 1985. The 1983 spectrum is composite with prominent hydrogen and weak He I emission lines, and a cool continuum with strong TiO absorptions. The red-infrared energy distribution, corrected for an interstellar extinction of (B-V) = 0.2, suggests for the cool component an M5 III spectral type in agreement with the strength of the TiO red bands. A distance of 2800 pc is estimated for the system. An excess with respect to the M continuum is present shortward of 600 nm and is attributed to a hotter component and to nebular emission. The 1984 H alpha profile is complex, with two-component emission, and a broad red red-shifted shell absorption probably produced in a wind from the cool giant with a velocity of 59 km/s. The observations indicate that presently the cool M-type component of BX Mon is rather stable - certainly not a Mira variable in agreement with its being an S-type symbiotic. The reported photometric variability could be attributed to the hot component
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
The X-ray spectrum of emission line stars (superluminous and symbiotic)
No full textThe observation of the X-ray spectrum of peculiar emission line stars, whose atmospheric envelopes are characterized by extreme physical conditions, represents an important tool to investigate the processes of formation of high temperature plasmas. The authors discuss the case of the superluminous object η Car showing both high and low temperature regions and an asymmetric wind. They present new EXOSAT observations of symbiotic stars. AG Draconis observed at a minimum phase shows a low temperature X-ray spectrum. A weak flux from the Mira variable R Aqr observed near maximum has been also detected
Ultraviolet and coordinated ground based observations of Z Andromedae
No full textHigh- and low-resolution UV spectrograms of the symbiotic star Z Andromedae were made during 1978-79 with the International Ultraviolet Explorer (IUE) and coordinated with ground-based observations. The spectrograms extend from 1200 to 3341 A and show a rich emission line spectrum with a wide range of ionization energy, from O I, Mg I and II and Fe II to He II, N V, O V, and Mg V. From the analysis of the emission lines, an electron density of 2 x 10 to the 10th/cu cm is derived, along with an emitting volume of 1 x 10 to the 37th/cu cm and a maximum line-of-sight thickness of 6 x 10 to the 10th cm. It is argued that the high-ionization emission lines are formed in a region which is not nebular, but in a solar-type transition zone around the cool star
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