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The Identification of Highly Ionized Metal Species in the Hot DA1 White Dwarf G191-B2B with the Hubble Space Telescope Faint Object Spectrograph

Sion, Edward M.; Bohlin, Ralph C.; Tweedy, Richard W. +1 more

On the Certification of AM Canum Venaticorum as a Cataclysmic Variable

Halpern, Jules P.; Raymond, John C.; Patterson, Joseph +1 more

The evidence that the peculiar faint blue star AM CVn (= HZ 29) is an ultrashort-period cataclysmic binary is reexamined. The existence of at least two noncommensurate short periods in the light curve, plus the recent discovery of the class of pulsating DB white dwarfs, suggests a need for reappraisal of the binary star model. New photometry and s…

Gravitational Lensing of Quasars as Seen by the Hubble Space Telescope Snapshot Survey

Maoz, D.; Lahav, O.; Schneider, D. P. +4 more

As part of the ongoing HST Snapshot Survey, 152 additional high- luminosity z > 1 quasars were observed, bringing the total to 184 quasars. Each exposure was searched for evidence of gravitational lensing. Only one quasar among those observed, 1208+1011, is a candidate lens system with subarcsecond image separation. Six other quasars have point…

New Calibrators for the Cepheid Period-Luminosity Relation

Evans, Nancy R.

IUE spectra of six Cepheids have been used to determine their absolute magnitudes from the spectral types of their binary companions. The stars observed are U Aql, V659 Cen, Y Lac, S Nor, V350 Sgr, and V636 Sco. The absolute magnitude for V659 Cen is more uncertain than for the others because its reddening is poorly determined and the spectral typ…

Deep Hubble Space Telescope Imaging of a Compact Radio Galaxy at Z = 2.390

Windhorst, Rogier; Keel, William C.; Mathis, Douglas F.

We present deep 4 hr HST/WFC images in V and I of the LBDS radio galaxy 53W002, a weak and compact narrow-line galaxy recently discovered at z = 2.390. After deconvolution, the resolution is 0.2" FWHM. Its I- band structure is quite compact with 30% +/- 10% of its flux in the central <~ 1 kpc, presumably from its AGN. This is surrounded by a cl…

Highly Ionized Atoms toward HD 93521

Fitzpatrick, Edward L.; Spitzer, Lyman, Jr.

Results are reported from the HST High Resolution Spectrograph observations of absorption features of C IV and Si IV in the spectrum of the high-latitude O star HD 93521 (l = 183 deg; b = 62 deg). A comparison of Si IV and C IV profiles showed that the FWHM of both features is about 50 km/sec, in contrast to the 7 km/sec found for one of the sever…

The Coolest DA White Dwarfs Detected at Soft X-Ray Wavelengths

Barstow, M. A.; Wesemael, F.; Holberg, J. B. +2 more

New soft X-ray/EUV photometric observations of the DA white dwarfs KPD 0631 + 1043 = WD 0631 + 107 and PG 1113 + 413 = WD 1113 + 413 are analyzed. Previously reported soft X-ray detections of three other DAs and the failure to detect a fourth DA in deep Exosat observations are investigated. New ground-based spectra are presented for all of the obj…

Ultraviolet and Optical Spectral Morphology of Melnick 42 and Radcliffe 136a in 30 Doradus

Walborn, Nolan R.; Ebbets, Dennis C.; Parker, Joel Wm. +2 more

HST/GHRS ultraviolet spectrograms of the individual O3 If */WN6-A object Mk 42 in 30 Dor and the adjacent, central multiple system R136a are compared with each other and with an appropriate sequence of O3 If* and WN6-A standards from the IUE archive. The analogous spectral montages covering the blue-violet region, based on new, homogeneous, digita…

Far-Ultraviolet Observations of the Crab Nebula Using the Hopkins Ultraviolet Telescope

Blair, William P.; Kriss, Gerard A.; Davidsen, Arthur F. +5 more

Observations of the FUV spectrum of the central portion of the Crab Nebula SNR using the Hopkins Ultraviolet Telescope (HUT) aboard the Astro-1 space shuttle mission in December 1990 are reported. The C IV 1549-A emission line shows two resolved components representing the front and back sides of the shell expanding at roughly +/- 1100 km/s. The H…

Hubble Space Telescope Imaging of the Large-Redshift Gravitational Lens Candidate 1208+1011

Maoz, Dan; Schneider, Donald P.; Yanny, Brian +2 more

Four-color photometry obtained with the Hubble Space Telescope is consistent with the hypothesis that the light from the quasar 1208+1011 (z = 3.8) is gravitationally lensed. Guided exposures taken with the HST Planetary Camera resolve the quasar image into two point-source components separated by 0.476" +/- 0.004". The intensity ratio of the comp…