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VRI CCD Photometry of Supergiant Stars in the Barred Galaxies NGC 925 and NGC 1637
Davidge, T. J.; Sohn, Young-Jong
V, R, and I CCD images obtained with the Canada-France-Hawaii Telescope are used to investigate the bright stellar content of the barred spiral galaxies NGC 925 and NGC 1637. Not counting objects located in H ii regions, we detect 295 supergiants in NGC 925 and 266 in NGC 1637. Comparisons with theoretical isochrones indicate that massive star for…
On the Multiplicity of η Carinae
Walborn, Nolan R.; Livio, Mario; Panagia, Nino +1 more
The nebula around the luminous blue variable (LBV) η Car is extremely N rich and C and O poor, which is indicative of CNO-cycle products. On the other hand, the recent Hubble Space Telescope-Goddard High-Resolution Spectrograph observation of the nucleus of η Car shows the spectrum of a star with stellar-wind lines of C II, C IV, Si II, Si IV, etc…
The Direct Amplification of Electromagnetic Waves by Electron Beams: An Alternate Explanation for Solar Type III Bursts
Huang, Guangli
The direct amplification of electromagnetic (EM) waves by the beam-plasma instability is proposed as an alternative for solar type III bursts in corona and planetary space, the main properties of type III bursts at meter bands are compared to this model, including the cutoff frequency, the timescale, the relative bandwidth, the polarization sense …
Gamma-Ray Burst Arrival Time Localizations: Simultaneous Observations by Pioneer Venus Orbiter, Compton Gamma-Ray Observatory, and ULYSSES
Hurley, K. C.; Fishman, G. J.; Kouveliotou, C. +9 more
Between the Compton Gamma Ray Observatory (CGRO) launch in 1991 April and the Pioneer Venus Orbiter (PVO) demise in 1992 October, concurrent coverage by CGRO, PVO, and Ulysses was obtained for several hundred gamma-ray bursts (GRBs). Although most of these were below the PVO and Ulysses thresholds, 37 were positively detected by all three spacecra…
Hubble Space Telescope Fine Guidance Sensor Astrometry of the Low-Mass Binary L722-22
Hershey, John L.; Taff, L. G.
The M dwarf star L722-22 (LHS 1047, GJ 1005) was discovered to be a binary in 1979. Analysis of ground-based data indicated a mass near 0.06 M_⊙ for the secondary star, well below the nominal stellar mass limit of 0.08 M_⊙. The close, faint binary was near the limit for ground-based astrometry and was approved for Hubble Space Telescope Fine Guida…
Discovery of a new 170 S X-ray pulsar 1SAX J1324.4-6200
Parmar, A. N.; Mineo, T.; Angelini, L. +2 more
We report the discovery with BeppoSAX of a new 170.84 +/- 0.04 s X-ray pulsar, XB 1323-619b, found serendipitously in the field of the X-ray binary XB 1323-619 in 1997 August. The source and periodicity are also detected in archival ASCA data taken in 1994. The X-ray spectrum is modeled by a power-law with a photon index of 1.0 +/- 0.4 and absorpt…
Spatial Interpolation for Four Spacecraft: Theory
Chanteur, Gérard
Multiplicity among peculiar A stars. I. The AP stars HD 8441 and HD 137909, and the AM stars HD 43478 and HD 96391
Carrier, F.; Udry, S.; North, P. +2 more
We present the first results of a radial-velocity survey of cool Ap and Am stars. HD 8441 is not only a double system with P = 106.357 days, but is a triple one, the third companion having an orbital period larger than 5000 days. Improved orbital elements are given for the classical Ap star HD 137909 = beta CrB by combining our radial velocities w…
The symmetry of the heliospheric current sheet as observed by Ulysses during the Fast Latitude Scan
Balogh, André; Erdős, Géza
The position of the heliospheric current sheet is investigated, based on Ulysses observations during the fast latitude scan from the South pole (in September, 1994) to the North pole (in July, 1995). The location of the current sheet on the source surface was calculated by mapping back the magnetic field vectors measured by Ulysses along the solar…
Spatially resolved optical spectroscopy of the Herbig Ae/Vega-like binary star HD 35187
Crawford, I. A.; Dunkin, S. K.
We report on observations of the young binary system HD 35187 (SAO 77144). For the first time, we have obtained spatially resolved optical spectra of the individual stars. Analysis of their effective temperatures indicates that the stars have spectral types of A2 (HD 35187B) and A7 (HD 35187A). Analysis of the Hγ Balmer line indicates a luminosity…