共查询到20条相似文献，搜索用时 15 毫秒
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Pritchard Tobin Clark & Guinan 《Monthly notices of the Royal Astronomical Society》1998,299(4):1087-1096
Using improved techniques, high-quality CCD uvbyVI photometry has been obtained for the eclipsing binary HV 982 in the Large Magellanic Cloud (LMC). International Ultraviolet Explorer ultraviolet spectrophotometry was also obtained. These data have been analysed using the Wilson–Devinney synthetic light-curve code and Kurucz low-metallicity model atmospheres as well as the EBOP code. The system is detached and the orbit is eccentric. Apsidal motion is detected with apsidal period 205 ± 7 yr. The effective temperatures of the components are found via flux fitting to be T eff,1 = 28 000 ± 5000 K and T eff,2 = 27 200 ± 5000 K. The large errors result from uncertainties over the appropriate interstellar extinction correction. The system plausibly comprises two ∼ 8 M stars of radius 6–7 R separated by ∼ 30 R. For pedagogical and historical interest, the near simultaneity of the eclipse minima at different wavelengths is used to constrain the constancy of the speed of light with wavelength and the mass of the photon, yielding m γ < 10−41 kg. Because of the great distance to HV 982, this limit is some 102 times smaller than previously achieved with eclipse timings, but it is nevertheless 10 orders of magnitude less stringent than that which is provided by satellite measurements of planetary magnetic fields. 相似文献
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S. Nishida T. Tanabé Y. Nakada S. Matsumoto K. Sekiguchi I. S. Glass 《Monthly notices of the Royal Astronomical Society》2000,313(1):136-140
We report on the light variations of the infrared stars that were discovered recently in the Magellanic clusters NGC 419, 1783 and 1978. Their periods, of 528, 458 and 491 days, are among the longest known for carbon-rich Mira variables in the Clouds. All three IR stars were found to lie on the extension of the period– M bol relation derived from the shorter-period C-rich Miras while they were 0.45–0.70 mag fainter than the extension of the period– M K relation. Their main sequence masses were determined by isochrone fitting to be 1.5–1.6 M⊙ , consistent with the prediction of the evolutionary models of Vassiliadis & Wood. 相似文献
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Pritchard Tobin Clark & Guinan 《Monthly notices of the Royal Astronomical Society》1998,297(1):278-290
Using improved techniques, high-quality CCD uvbyVI C photometry has been obtained for the 14th magnitude eclipsing binaries HV 1620 in the Small Magellanic Cloud (SMC) and HV 2241 in the Large Magellanic Cloud (LMC). IUE ultraviolet spectrophotometry was also obtained. These data have been analysed using the Wilson & Devinney synthetic light-curve code and Kurucz model atmospheres. Both systems are semi-detached and appear to have undergone mass exchange. In HV 1620 the mass ratio and the effective temperatures of the primary and secondary are q = M 2 / M 1 = 0.68 ± 0.03, T eff,1 = 33 000 ± 4500 K and T eff,2 = 24 000 ± 3500 K. The corresponding values for HV 2241 are 0.53 ± 0.01, 27 000 ± 3000 K and 20 200 ± 1500 K. Using the radial-velocity curves obtained by Niemela & Bassino with a 1-m telescope, we find that both systems are massive, as expected. Reddening considerations suggest both systems may lie towards the rear of their respective Clouds. 相似文献
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G. Bono † F. Caputo M. Marconi 《Monthly notices of the Royal Astronomical Society》2001,325(4):1353-1358
We present a new set of Cepheid, full amplitude, non-linear, convective models which are pulsationally unstable in the second overtone (SO). Hydrodynamical models were constructed by adopting a chemical composition typical of Cepheids in the Small Magellanic Cloud (SMC) and for stellar masses ranging from 3.25 to 4 M⊙ . Predicted φ 21 Fourier parameters agree, within current uncertainties, with empirical data for pure first- and second-overtone variables as well as for first-/second-overtone (FO/SO) double-mode Cepheids collected by Udalski et al. in the SMC. On the other hand, predicted I -band amplitudes are systematically larger than the observed ones in the short-period range, but attain values that are closer to the empirical ones for log P SO ≥−0.12 and log P FO ≥0.1 . We also find, in agreement with empirical evidence, that the region within which both second and first overtones attain a stable limit cycle widens when moving towards lower luminosities. Moreover, predicted P SO / P FO and P FO / P F period ratios agree quite well with empirical period ratios for FO/SO and fundamental/FO double-mode SMC Cepheids.
Interestingly enough, current models support the evidence that pure SO Cepheids and SO components in FO/SO Cepheids are good distance indicators. In fact, we find that the fit of the predicted period–luminosity–colour ( V , V – I ) relation to empirical SMC data supplies a distance modulus ( DM ) of 19.11±0.08 mag . The same outcome applies to pure FO Cepheids and FO components in FO/SO Cepheids, and indeed we find DM =19.16±0.19 mag . Current distance estimates do not account for, within current uncertainties on photometry and reddening, the so-called short distance scale. 相似文献
Interestingly enough, current models support the evidence that pure SO Cepheids and SO components in FO/SO Cepheids are good distance indicators. In fact, we find that the fit of the predicted period–luminosity–colour ( V , V – I ) relation to empirical SMC data supplies a distance modulus ( DM ) of 19.11±0.08 mag . The same outcome applies to pure FO Cepheids and FO components in FO/SO Cepheids, and indeed we find DM =19.16±0.19 mag . Current distance estimates do not account for, within current uncertainties on photometry and reddening, the so-called short distance scale. 相似文献
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M.J. Coe I. Negueruela D.A.H. Buckley N.J. Haigh S.G.T. Laycock 《Monthly notices of the Royal Astronomical Society》2001,324(3):623-627
We report observations that confirm the identities of the optical counterparts to the transient sources RX J0544.1–7100 and RX J0520.5–6932 . The counterparts are suggested to be B-type stars. Optical data from the observations carried out at ESO and SAAO, together with results from the OGLE data base, are presented. In addition, X-ray data from the RXTE All-Sky Monitor are investigated for long-term periodicities. A strong suggestion for a binary period of 24.4 d is seen in RX J0520.5–6932 from the OGLE data. 相似文献
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We present and discuss V BLUW photometry of eleven massive stars in the Magellanic Clouds: the SMC stars AzV121, AzV136 = HD5277 = R10, AzV197, AzV310 = R26 and AzV 369; the LMC stars GV80 = HD32034 = R62, GV91 = HDE 268 819, GV346 = HDE 269661 = R111, GV352 = HDE 269697, GV423 = HDE 269953 = R150 and GV460 = HDE 270111. Only one G0 Ia SMC supergiant is found to be variable, whereas all members of the LMC sample show definite variability. We find that roughly above M /M⊙ = 25, supergiants become photometrically unstable. The reddening‐independent metal‐index [B –L ] is used to investigate the metallicity of the late‐type supergiants in both galaxies relative to similar supergiants in the solar neighbourhood. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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M. A. T. Groenewegen P. R. Wood G. C. Sloan J. A. D. L. Blommaert M.-R. L. Cioni M. W. Feast S. Hony † M. Matsuura J. W. Menzies E. A. Olivier E. Vanhollebeke J. Th. van Loon P. A. Whitelock A. A. Zijlstra H. J. Habing E. Lagadec 《Monthly notices of the Royal Astronomical Society》2007,376(1):313-337
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Albert A. Zijlstra Mikako Matsuura Peter R. Wood G. C. Sloan Eric Lagadec Jacco Th. van Loon M. A. T. Groenewegen M. W. Feast J. W. Menzies P. A. Whitelock J. A. D. L. Blommaert M.-R. L. Cioni H. J. Habing S. Hony C. Loup L. B. F. M. Waters 《Monthly notices of the Royal Astronomical Society》2006,370(4):1961-1978
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Christopher J. Evans Ian D. Howarth 《Monthly notices of the Royal Astronomical Society》2008,386(2):826-834
We present radial velocities for 2045 stars in the Small Magellanic Cloud (SMC), obtained from the 2dF survey by Evans et al. The great majority of these stars are of OBA type, tracing the dynamics of the young stellar population. Dividing the sample into ad hoc 'bar' and 'wing' samples (north and south, respectively, of the line: δ=−77°50'+[4α]' , where α is the right ascension in minutes of time) we find that the velocities in the SMC bar show a gradient of 26.3 ± 1.6 km s−1 deg−1 at a position angle of 126°± 4°. The derived gradient in the bar is robust to the adopted line of demarcation between the two samples. The largest redshifts are found in the SMC wing, in which the velocity distribution appears distinct from that in the bar, most probably a consequence of the interaction between the Magellanic Clouds that is predicted to have occurred 0.2 Gyr ago. The mean velocity for all stars in the sample is +172.0 ± 0.2 km s−1 (redshifted by ∼20 km s−1 when compared to published results for older populations), with a velocity dispersion of 30 km s−1 . 相似文献