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Hubble Space Telescope Observations of the Very Low Mass Companion to Gliese 105A
Golimowski, David A.; Schroeder, Daniel J.; Uomoto, Alan +1 more
Hubble Space Telescope images of the astrometric binary Gl 105A confirm the previous ground-based detection of a faint, very red companion (Gl 105C) located 3."39 from Gl 105A at P.A. 290 deg. The instrumental magnitudes of Gl 105C are V555 = 16.86 and I814 = 13.54. The observed position of Gl 105C differs significantly from the positions expected…
Directivity and Its Energy Dependence in Solar Flare Energetic Emission
Li, Peng
We have studied 72 solar flares simultaneously observed by the Gamma-Ray Spectrometer (GRS, 0.3-1 MeV) and the Hard X-Ray Burst Spectrometer (HXRBS, 30-500 keV) on the Solar Maximum Mission (SMM). Using the spectral analysis results, we studied spectal and size distribution center-to-limb variations for both instruments. The GRS observations show …
Coronal Heating in Flare Stars: Resonant MHD Absorption?
Mullan, D. J.; Johnson, M.
We report on the occurrence of periodicity in X-rays from certain flare stars. Statistically significant periods in the range 70-200 s are present in Einstein data for EQ Vir, Proxima Cen, and AD Leo. Periodicities are also present (although with lower statistical significance) in ROSAT data for AD Leo, and in EXOSAT data for EQ Vir and AD Leo. In…
HST Images of the Eclipsing Pulsar B1957+20
Fruchter, Andrew S.; Bailyn, Charles D.; Bookbinder, Jay
We have obtained images of the eclipsing pulsar binary PSR~B1957+20 using the Planetary Camera of the Hubble Space Telescope. The high spatial resolution of this instrument has allowed us to separate the pulsar system from a nearby background star which has confounded ground-based observations of this system near optical minimum. Our images limit …
Multifrequency Observations of KAZ 102 during the ROSAT All-Sky Survey
Maraschi, L.; Tanzi, E. G.; Pian, E. +14 more
The bright quasar Kaz 102, which lies in the vicinity of the North Ecliptic Pole, was monitored during the ROSAT All Sky Survey for 121.5 days from 1990 July 30 to 1991 January 25. In the course of the survey, optical photometry with various filters was performed at several epochs, together with UV (IUE) and optical spectrophotometry. The spectral…
Discovery of Extreme-Ultraviolet Radiation from the Seyfert Galaxy Ton S180 (= EUVE J0057-223)
Thorstensen, John R.; Bowyer, Stuart; Vennes, Stephane +1 more
We report the detection of intense EUV radiation from the Seyfert 1 galaxy Ton S180. The source EUVE J0057-223, discovered in the Extreme-Ultraviolet Explorer all-sky survey, is only 25" away from its optical counterpart, well within the position error circle. We present a complete broadband energy distribution of Ton S180 using infrared (IRAS), o…
Structure and Photometry of an I < 20.5 Galaxy Sample from the Hubble Space Telescope Medium Deep Survey
Illingworth, Garth D.; Forbes, Duncan A.; Bershady, Matthew A. +5 more
A set of 100 faint galaxies from nine Hubble Space Telescope Wide Field Camera I-band images have been analyzed as part of the Medium Deep Survey (MDS) Key Project. This sample reaches a depth of I <~ 20.5 (corresponding to B ~ 22-23) and complements the first set of fainter galaxies analyzed by the MDS team. Images were deconvolved using the L…
The Threshold for Stellar Winds in Hot Main-Sequence Stars
Morrison, Nancy D.; Grigsby, James A.
The profiles of ultraviolet resonance lines of C IV were surveyed in a sample of 29 cluster and association members in the spectral type range O9-B2 III-V, together with a few field stars of interest. The temperatures and gravities of the stars were taken from the model atmosphere analysis by Grigsby, Morrison, & Anderson (1992), and the lumin…
The Ultraviolet Spectrum of the Gravitational Lens Candidate UM 425 = QSO 1120+019: Evidence for Broad Absorption Line (BAL) Structure
Michalitsianos, A. G.; Oliversen, R. J.
The UV line profile structure of high-ionization resonance lines found with the International Ultraviolet Explorer (IUE) in the brightest of four multiply imaged sources (image-A) in the `candidate gravitational lens UM 425 = QSO 1120+019 indicates broad absorption line (BAL) structure. The deep-broad trough associated with the O VI line extends t…
The Growth of Solids, Destruction of Molecules, and Shielding of Radiation in the Young Stellar Disk of HD 45677
Brown, Thomas M.; Grady, Carol; Buss, Richard, Jr. +1 more
Ultraviolet spectra (912-3300 Å) from the Astro-1 and lUE space missions of two Herbig Be stars, HD 45677 and HD 200775, show that the HD 200775 intrinsic continuum shape generally coincides with a T = 20,000 K Kurucz model and that the HD 45677 continuum exhibits additional line blanketing, extinction, and emission from gas and dust in its disk a…