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V. S. Niemela † R. C. Gamen †‡ 《Monthly notices of the Royal Astronomical Society》2005,356(3):974-978
From radial velocities determined in high signal-to-noise digital spectra, we report the discovery that the brightest component of the binary system HD 150136 is of spectral type O3. We also present the first double-lined orbital solution for this binary. Our radial velocities confirm the previously published spectroscopic orbital period of 2.6 d. He ii absorptions appear double at quadratures, but single lines of N v and N iv visible in our spectra define a radial velocity orbit of higher semi-amplitude for the primary component than do the He ii lines. From our orbital analysis, we obtain minimum masses for the binary components of 27 and 18 M⊙ . The neutral He absorptions apparently do not follow the orbital motion of any of the binary components, thus they most probably arise in a third star in the system. 相似文献
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P. Bartzakos A. F. J. Moffat †‡ V. S. Niemela ‡§ 《Monthly notices of the Royal Astronomical Society》2001,324(1):33-50
A search for evidence of colliding winds is undertaken among the four certain Magellanic Cloud WC/WO spectroscopic binaries found in the companion Paper I, as well as among two Galactic WC/WO binaries of very similar subtype. Two methods of analysis, which allow the determination of orbital inclination and parameters relating to the shock cone from spectroscopic studies of colliding winds, are attempted. In the first method, Lührs' spectroscopic model is fitted to the moderately strong C iii 5696-Å excess line emission arising in the shock cone for the stars Br22 and WR 9. The four other systems show only very weak C iii 5696-Å emission. Lührs' model follows well the mean displacement of the line in velocity space, but is unable to reproduce details in the line profile and fails to give a reliable estimate of the orbital inclination. In the second method, an alternative attempt is also made to fit the variation of more global quantities, full width at half-maximum and radial velocity of the excess emission, with phase. This method also gives satisfactory results in a qualitative way, but shows numerical degeneracy with orbital inclination. Colliding wind effects on the very strong C iv 5808-Å Wolf–Rayet emission line, present in all six binaries, are also found to behave qualitatively as expected. After allowing for line enhancement in colliding wind binaries, it now appears that all Magellanic Cloud WC/WO stars occupy a very narrow range in spectral subclass: WC4/WO3. 相似文献
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N.I. Morrell † R.H. Barbá † V.S. Niemela ‡ M.A. Corti § J.F. Albacete Colombo G. Rauw ¶ M. Corcoran T. Morel J.-F. Bertrand A.F.J. Moffat N. St-Louis 《Monthly notices of the Royal Astronomical Society》2001,326(1):85-94
A new high-quality set of orbital parameters for the O-type spectroscopic binary HD 93205 has been obtained combining échelle and coudé CCD observations. The radial velocity orbits derived from the He ii λ 4686 Å (primary component) and He i λ 4471 Å (secondary component) absorption lines yield semi-amplitudes of 133±2 and 314±2 km s−1 for each binary component, resulting in minimum masses of 31 and 13 M⊙ ( q =0.42) . We also confirm for the binary components the spectral classification of O3 V+ O8 V previously assigned. Assuming for the O8 V component a 'normal' mass of 22–25 M⊙ we would derive for the primary O3 V a mass of 'only' 52–60 M⊙ and an inclination of about 55° for the orbital plane. We have also determined for the first time a period of apsidal motion for this system, namely 185±16 yr using all available radial velocity data sets of HD 93205 (from 1975 to 1999). Phase-locked variations of the X-ray emission of HD 93205 consisting of a rise of the observed X-ray flux near periastron passage are also discussed. 相似文献
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G. Rauw † H. Sana I.I. Antokhin N.I. Morrell ‡ V.S. Niemela § J.F. Albacete Colombo ¶ E. Gosset &#; J.-M. Vreux 《Monthly notices of the Royal Astronomical Society》2001,326(3):1149-1160
We discuss the orbital elements of the multiple system Tr 16-104 which is usually believed to be a member of the open cluster Trumpler 16 in the Carina complex. We show that Tr 16-104 could be a hierarchical triple system consisting of a short-period (2.15 d) eclipsing O7 V+O9.5 V binary bound to a B0.2 IV star. Our preliminary orbital solution of the third body indicates that the B star most probably describes an eccentric orbit with a period of ∼285 or ∼1341 d around the close binary. Folding photometric data from the literature with our new ephemerides, we find that the light curve of the close binary exhibits rather narrow eclipses indicating that the two O stars must be well inside their Roche lobes. Our analysis of the photometric data yields a lower limit on the inclination of the orbit of the close binary of i ≥77° . The stellar radii and luminosities of the O7 V and O9.5 V stars are significantly smaller than expected for stars of this spectral type. Our results suggest that Tr 16-104 lies at a distance of the order of 2.5 kpc and support a fainter absolute magnitude for zero-age main-sequence O stars than usually adopted. We find that the dynamical configuration of Tr 16-104 corresponds to a hierarchical system that should remain stable provided that it suffers no strong perturbation. Finally, we also report long-term temporal variations of high-velocity interstellar Ca ii absorptions in the line of sight towards Tr 16-104. 相似文献
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V. S. Niemela † P. Massey ‡ G. Testor § S. Giménez Benítez ¶ 《Monthly notices of the Royal Astronomical Society》2002,333(2):347-352
We present a study of optical spectra of the Wolf–Rayet star AzV 336a (=SMC WR7) in the Small Magellanic Cloud. Our study is based on data obtained at several Observatories between 1988 and 2001. We find SMC WR7 to be a double-lined WN+O6 spectroscopic binary with an orbital period of 19.56 d. The radial velocities of the He absorption lines of the O6 component and the strong He ii emission at λ 4686 Å of the WN component describe anti-phased orbital motions. However, they show a small phase shift of ∼1 d. We discuss possible explanations for this phase shift. The amplitude of the radial velocity variations of He ii emission is twice that of the absorption lines. The binary components have fairly high minimum masses, ∼18 and 34 M⊙ for the WN and O6 components, respectively. 相似文献
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We present the discovery of OB type absorption lines superimposed to the emission line spectrum and the first double-lined orbital elements for the massive Wolf–Rayet binary HDE 318016 (=WR 98), a spectroscopic binary in a circular orbit with a period of 47.825 days. The semiamplitudes of the orbital motion of the emission lines differ from line to line, indicating mass ratios between 1 and 1.7 for
. 相似文献
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Guillermo Bosch †‡ Rodolfo Barbá ‡§ Nidia Morrell †‡§ Virpi Niemela †‡¶ Pablo Ostrov ‡ Marcelo Arnal § Cristina Cappa § Ricardo Morras § Guillermo Giménez de Castro 《Monthly notices of the Royal Astronomical Society》2003,341(1):169-178
We present new spectroscopy in the optical range and 21-cm H i data covering the Ruprecht 55 (Ru 55) field in the Puppis window where several authors have proposed the existence of one (or two) clusters.
We have determined new MK spectral types for about 50 stars in the region, finding 43 OB-type stars among them. LS 985 was found to be an O9 V + O9.5 III binary and it is the earliest type of star in our observed sample.
We have identified a stellar OB association (Ru 55), which is most likely related to a depletion detected in our H i data, as: (i) they are located at the same distance (6 kpc), within observational errors; (ii) both have similar radial velocities (∼67 km s−1 ); (iii) current OB stars could have provided the energy needed to blow the cavity; (iv) the dynamical time-scale for the hole buildup matches the age estimated for the earliest OB stars; and (v) LS 985 might be responsible for ionizing the H i cavity inner walls close to it. 相似文献
We have determined new MK spectral types for about 50 stars in the region, finding 43 OB-type stars among them. LS 985 was found to be an O9 V + O9.5 III binary and it is the earliest type of star in our observed sample.
We have identified a stellar OB association (Ru 55), which is most likely related to a depletion detected in our H i data, as: (i) they are located at the same distance (6 kpc), within observational errors; (ii) both have similar radial velocities (∼67 km s
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C. A. Olano † P. I. Meschin V. S. Niemela ‡ 《Monthly notices of the Royal Astronomical Society》2006,369(2):867-874
We have studied the kinematics and spatial distribution of the interstellar gas in the sky region 110°≤ l ≤ 135°, 10°≤ b ≤ 20° , using the extensive Leiden–Dwingeloo Survey of H i emission and the Columbia Survey of CO emission. The spectra show two main velocity components, namely feature A that has a mean local standard of rest (LSR) velocity of ∼0 km s−1 and is due to the Lindblad ring of the Gould belt, and feature C that has a mean LSR velocity of ∼−11 km s−1 and is associated to the local arm or Orion arm. The H i and CO distributions of feature A in the region trace a large complex of gas and dust known as the Cepheus Flare, which lies at a distance of 300 pc. The spectral line profiles of feature A, which are rather broad and often double-peaked, reveal that the Cepheus Flare forms part of a big expanding shell of interstellar matter that encloses an old supernova remnant associated with a void inside the Cepheus Flare. On the other hand, by analysing the distribution and velocity structure of feature C, we have detected a second large expanding shell in the region, located at a distance of 800 pc in the local arm. This shell surrounds the stellar association Cepheus OB4 and was probably generated by stellar winds and supernovae of Cepheus OB4. The radii, expansion velocities and H i masses of the two shells are approximately 50 pc, 4 km s−1 and 1.3 × 104 M⊙ for the Cepheus Flare shell and 100 pc, 4 km s−1 and 9.9 × 104 M⊙ for the Cepheus OB4 shell. Both shells have similar ages of the order of a few 106 yr. 相似文献