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A Thermal Pulse in Progress in the Nucleus of the Large Magellanic Cloud Planetary Nebula N66
Pena, M.; Torres-Peimbert, S.; Ruiz, M. T. +2 more
Optical and UV spectrophotometric data, gathered in the 1987-1994 interval, are presented for the planetary nebula N66 (WS 35 or SMP 83) in the Large Magellanic Cloud. These data show that the central star has suffered dramatic changes. Before 1987 it showed a featureless continuum while its present spectrum shows intense W-R features and P-Cygni …
A Spectrum Synthesis Program for Binary Stars
Linnell, Albert P.; Hubeny, Ivan
A new program produces synthetic spectra of binary stars at arbitrary values of orbital longitude, including longitudes of partial or complete eclipse. The stellar components may be distorted, either tidally or rotationally, or both. Either or both components may be rotating nonsynchronously. We illustrate the program performance with two cases: E…
The X-Ray Selected Cataclysmic Variables H0459+246 and H0857-242
Buckley, D. A. H.; Schwartz, D. A.; Tuohy, I. R. +5 more
We report the discovery of two cataclysmic variables located with the assistance of X-ray positions from the HEAO 1 Modulation Collimator and the Large-Area Sky Survey. Each case is distinguished by evidence of two periodic modulations that appear to represent the orbital period and the spin period of the white dwarf, respectively. The first case,…
Spectroscopy of Chromospheric Lines of Giants in the Globular Cluster NGC 6752
Smith, Graeme H.; Dupree, A. K.; Hartmann, Lee +3 more
Spectroscopic observations of chromospheric transitions (Mg II, H-alpha, and Ca II K) from two red giants (A31 and A59) in the globular cluster NGC 6572 were made with the Goddard High Resolution Spectrograph on the Hubble Space Telescope and the coude spectrograph of the 1.9 m telescope at the Mount Stromlo Observatory. These measurements give ev…
Stellar Photometry Including Saturated Images: Results on M67 with WFPC2
Gilliland, Ronald L.
The Wide Field and Planetary Camera 2 (WFPC2) on Hubble Space Telescope (HST) is providing unsurpassed imaging capabilities and supporting accurate stellar photometry over large fields of view at high angular resolution. I discuss a feature of the WFPC2 CCD systems that nominally limits the dynamic range attainable with single exposures: a 12 bit …
Hot Degenerates in the Montreal-Cambridge-Tololo Survey. II. Two New Hybrid White Dwarfs, MCT 0128-3846 and MCT 0453-2933, and the Nature of the DAB Stars
Kepler, S. O.; Fontaine, G.; Bergeron, P. +7 more
We report the discovery, in the course of a survey for high-latitude, ultraviolet-excess objects in the southern hemisphere, of two new hybrid DAB stars. Both objects exhibit a weak He I 4471 A line superposed onto the usual Balmer line spectrum. Analysis of the Balmer series with both homogeneous and stratified models show these stars to have spe…
X-Ray Continuum and Iron K Emission Line from the Radio Galaxy 3C 390.3
Elvis, M.; Fabbiano, G.; Hayashida, K. +8 more
X-ray properties of the radio galaxy 3C 390.3 were investigated using the EXOSAT and Ginga satellites. Long-term, large-amplitude X-ray intensity changes were detected over a period extending from 1984 through 1991, and high-quality X-ray spectra were obtained especially with Ginga. The X-ray continuum spectra were described with power-law model w…
First Hubble Space Telescope Observations of the Brightest Stars in the Virgo Galaxy M100 = NGC 4321
Casertano, Stefano; Ballester, Gilda E.; Kennicutt, Robert C. +24 more
As part of both the Early Release Observations from the Hubble Space Telescope and the Key Project on the Extragalactic Distance Scale, we have obtained multiwavelength BVR WFPC2 images for the face-on Virgo cluster spiral galaxy M100 = NGC 4321. We report here preliminary results from those observations, in the form of a color-magnitude diagram f…
Ultraviolet Spectra of HZ Herculis/Hercules X-1 from HST: Hot Gas during Total Eclipse of the Neutron Star
Anderson, Scott F.; Blair, William P.; Halpern, Jules P. +3 more
The Faint Object Spectrograph (FOS) aboard Hubble Space Telescope (HST) has been used in the UV to observe the prototypical X-ray pulsar Her X-1 and its companion HZ Her. Optical spectra were also obtained contemporaneously at the Kitt Peak National Observatory (KPNO) 2.1 m. The FOS spectra encompass the 1150-3300 A range near binary orbital phase…
Conditions in the Z = 0.692 Absorber toward 3CR 286
Cohen, Ross D.; Junkkarinen, Vesa T.; Beaver, E. A. +3 more
We present HST/FOS^1^ ultraviolet and ground-based optical spectra of the z = 0.692 21 cm absorption system in the QSO 3CR 286. The strength of the damped Lyα absorption implies an H I column density, N(H I)~2 x 10^21^ cm^-2^. We derive a high spin temperature for the H I gas, T_s_~> 10^3^ K, as has been found for other high-redshift 21 cm abso…