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The UV-brightest Stars of M33 and Its Nucleus: Discovery, Photometry, and Optical Spectroscopy
Massey, Philip; Bianchi, Luciana; Hutchings, John B. +1 more
We investigate the UV-brightest sources in the nearby galaxy M33. Our catalog of 356 sources is constructed from far-ultraviolet (FUV; 1500 A) and near-ultraviolet (NUV; 2400 A) images obtained with the Ultraviolet Imaging Telescope (UIT) matched with ground-based UBV data. We find that our survey is limited by the FUV flux and is complete to F
The Speedy Magnetic Propeller in the Cataclysmic Variable AE Aquarii
Eracleous, Michael; Horne, Keith
We present a spectroscopic study of the unusual flaring activity of the cataclysmic variable AE Aqr, which makes use of time-resolved, ultraviolet spectra obtained with the Hubble Space Telescope in November of 1992. This study complements our earlier investigation of the coherent, 33 s oscillations of AE Aqr using the same data. Its scientific ob…
On the Balmer Line Problem
Werner, K.
The so-called Balmer line problem describes the failure to achieve a consistent fit to the Balmer line spectrum of any hot sdO star whose effective temperature exceeds ~70,000 K. Results of Teff determinations drastically deviate, up to a factor of 2, depending on which Balmer line is examined. This problem was uncovered a few years ago during non…
Detection of a LY alpha Emission-Line Companion to the z=4.69 Quasar BR 1202$-0725
McMahon, Richard G.; Egami, Eiichi; Hu, Esther M.
We report the detection of a nearby emission-line companion to the z = 4.695 quasar BR 1202-0725. Deep narrowband exposures on this field from the University of Hawaii 2.2 m telescope show a Ly alpha flux of 1.5 x 10-16 ergs cm-2 s-1. High-resolution imaging in the F814W filter band with the Hubble Space Telescope Wide Field Planetary Camera (WFPC…
Ultraviolet Extinction by Interstellar Dust in External Galaxies: M31
Massey, Philip; Clayton, Geoffrey C.; Hutchings, J. B. +2 more
Hubble Space Telescope (HST) Faint Object Spectrograph (FOS) spectra of stars in OB associations of M31 are used to derive the UV extinction by interstellar dust in M31 by three different methods: (1) comparing spectra of M31 star pairs, (2) comparing spectra of M31 stars to those of Galactic standard stars, and (3) comparing M31 star spectra to a…
The Cosmological Density and Ionization of Hot Gas: O VI Absorption in Quasar Spectra
Burles, Scott; Tytler, David
We have conducted the first survey for O VI 1032, 1038 A absorption lines in QSO spectra. We used medium-resolution (R ~ 1300) high signal- to-noise (~20) Faint Object Spectrograph spectra of 11 QSOs (0.53 <= z_em_ <= 2.07) from the Hubble Space Telescope archive. We use simulated spectra to determine the significance of the line identificat…
K Giants in 47 Tucanae: Detection of a New Class of Variable Stars
Gilliland, Ronald L.; Edmonds, Peter D.
We report the discovery of variability among K giants in the globular cluster 47 Tucanae, using a time series of U exposures with the Hubble Space Telescope. The variables lie along a narrow band in the color-magnitude diagram, joining the faint end of the asymptotic giant branch to the red giant branch. The variations, if coherent, mostly have pe…
Hubble Space Telescope Observations of the Double Nucleus of NGC 4486B
Gebhardt, Karl; Richstone, Douglas; Kormendy, John +7 more
Hubble Space Telescope WFPC2 images show that the low-luminosity elliptical galaxy companion to M87, NGC 4486B, has a double nucleus that resembles the one discovered in M31. The NGC 4486B nucleus comprises two peaks separated by ~0."15 or 12 pc. Neither peak is coincident with the galaxy photocenter, which falls between them. The nuclear morpholo…
Hubble Space Telescope Ultraviolet Spectrum of ARP 102B, the Prototypical Double-peaked Emission-Line AGN
Filippenko, Alexei V.; Eracleous, Michael; Halpern, Jules P. +1 more
UV spectra of the nucleus of the elliptical galaxy Arp 102B were obtained with the HST's Faint Object Spectrograph in order to investigate the UV emission-line counterparts of its unusual double-peaked Balmer lines. Broad Mg II λ2798 is present with nearly the same profile as the Balmer lines (peaks separated by ~12,000 km s^-1^), and a typical Mg…
EUVE Observations of U Geminorum in Outburst
Szkody, Paula; Raymond, John C.; Long, Knox S. +2 more
We have observed U Gem during the peak and declining phases of a wide outburst in 1993 December with the Extreme Ultraviolet Explorer (EUVE) satellite. At peak, U Gem was one of the brightest EUV sources in the sky. The spectrum of the source is complex. Fitted to a blackbody spectrum, the apparent temperature at peak is ∼140,000 K, the luminosity…