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M. P. E. Schurch M. J. Coe K. E. McGowan V. A. McBride D. A. H. Buckley J. L. Galache R. H. D. Corbet M. Still P. Vaisanen A. Kniazev K. Nordsieck 《Monthly notices of the Royal Astronomical Society》2007,381(4):1561-1568
We investigate the optical counterparts of recently discovered Be/X-ray binaries in the Small Magellanic Cloud (SMC). In total four sources, SXP101, SXP700, SXP348 and SXP65.8 were detected during the Chandra survey of the wing of the SMC. SXP700 and SXP65.8 were previously unknown. Many optical ground-based telescopes have been utilized in the optical follow-up, providing coverage in both the red and blue bands. This has led to the classification of all of the counterparts as Be stars and confirms that three lie within the Galactic spectral distribution of known Be/X-ray binaries. SXP101 lies outside this distribution and is the latest spectral type known. Monitoring of the Hα emission line suggests that all the sources barring SXP700 have highly variable circumstellar discs, possibly a result of their comparatively short orbital periods. Phase-resolved X-ray spectroscopy has also been performed on SXP65.8, revealing that the emission is indeed harder during the passage of the X-ray beam through the line of sight. 相似文献
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Harris W. M. Nordsieck K. H. Scherb F. Mierkiewicz E. J. 《Earth, Moon, and Planets》1997,78(1-3):161-167
We report on the reduction and analysis of UVpolarimetric images of CI (λ1657 Å) and dust continuum (2696 Å emissions from C/1995 O1 (Hale-Bopp) taken using the Wide Field Imaging Survey Polarimeter (WISP) sounding rocket on 8 April, 1997. These observations represent the first imaging polarimetry of comets in the UV, and were performed in consort with ground based measurements of gas and dust polarization and distribution. The continuum results show 9% polarization across the image field with a polarization phase angle close to the 129° prediction. Comparison with ground based data implies minimal color dependence for Hale-Bopp in either the degree of polarization and in the position angle. The carbon polarimetry implies that most production occurs in the dense inner coma, and that it leaves that area in thermodynamic equilibrium. Its radial profile further constrains the carbon outflow speed to be sufficient to travel ≥5 × 106 km without photoionization. 相似文献
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G. K. Fox A. D. Code C. M. Anderson B. L. Babler K. S. Bjorkman J. J. Johnson M. R. Meade K. H. Nordsieck A. J. Weitenbeck & N. E. B. Zellner 《Monthly notices of the Royal Astronomical Society》1998,298(1):303-309
Portions of the Moon were observed by the Wisconsin Ultraviolet Photopolarimeter Experiment ( WUPPE ) on 1995 March 12, 14 and 17, and represent the first ultraviolet (UV) spectropolarimetric observations of the Moon. The polarimetric observations confirm that a change in the dominant scattering process occurs in the UV, changing from volume scattering in the near-UV to surface scattering in the far-UV. The data are investigated empirically. It is found that Umov's relationship holds when the polarization is perpendicular to the scattering plane. It is also found that the degree of polarization can be modelled by a phase-angle-dependent polarization modified by a wavelength-dependent depolarization factor. The scattering function for each observation is determined. 相似文献
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Spectropolarimetric observations from 5000 to 8000 Å have been obtained for comets P/Austin (1982g) and P/Churyumov-Gerasimenko (1982f). The observations were spaced over phase angles of 50–125° for comet Austin and 10–40° for comet Churyumov-Gerasimenko. The use of spectropolarimetry allowed an evaluation of continuum polarization without molecular line contamination. Especially for comet Churyumov-Gerasimenko, the curve of polarization versus phase angle resembles curves for asteroids, where the polarization is negative (electric vector maximum parallel to the scattering plane) for phase angles less than 20° and the most negative polarization is from ?1 to ?2%. The negative polarization at backscattering angles may be due to multiple scattering in agglomerated grains, as assumed for asteroids, or to Mie scattering by small dielectric particles. If multiple scattering is important in comet dust, polarization measurements may imply a low albedo, less than 0.08. The polarization of comet Austin remained steady during a large change in the dust production rate. Both comets increased continuum flux by a factor of 2 near perihelion. The continuum of comet Churyumov-Gerasimenko had the shape of the solar spectrum with derivations less than 5%. The equivalent width of spectral features of C2, NH2, and O varied as r?2. 相似文献
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P. A. Woudt D. Kilkenny E. Zietsman B. Warner N. S. Loaring C. Copley A. Kniazev P. Väisänen M. Still R. S. Stobie E. B. Burgh K. H. Nordsieck J. W. Percival D. O'Donoghue D. A. H. Buckley 《Monthly notices of the Royal Astronomical Society》2006,371(3):1497-1502
We report the serendipitous discovery of the Sloan Digital Sky Survey (SDSS) star SDSS J160043.6+074802.9 to be a very rapid pulsator. The variation is dominated by a frequency near 8380 μHz (period = 119.33 s) with a large amplitude (0.04 mag) and its first harmonic at 16760 μHz (59.66 s; 0.005 mag). In between these frequencies, we find at least another eight variations with periods between 62 and 118 s and amplitudes between about 0.007 and 0.003 mag; weaker oscillations might also be present. Preliminary spectrograms from the performance verification phase of the Southern African Large Telescope indicate that SDSS J160043.6+074802.9 is a spectroscopic binary consisting of an sdO star and a late-type main-sequence companion. This makes it the first unambiguous detection of such an sdO star to pulsate, and certainly the first found to exhibit multifrequency variations. 相似文献
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