Search Publications
AB Dor in '94. I. Hubble Space Telescope Goddard High Resolution Spectrogaph Observations of the Quiescent Chromosphere of an Active Star
Savage, B. D.; Ebbets, D. C.; Carpenter, K. G. +15 more
We analyze Hubble Space Telescope/Goddard High Resolution Spectrograph spectra of AB Doradus, the prototypical, ultrarapidly rotating K dwarf. We observed chromospheric (Mg II) and transition-region (C II, Si IV, C IV, and N V) lines periodically throughout the stellar rotation period and provide a low-dispersion stellar atlas of 78 emission lines…
Hubble Space Telescope STIS Spectroscopy of VW Hydri during Early Quiescence following a Superoutburst
Szkody, Paula; Sion, Edward M.; Hubeny, Ivan +3 more
Hubble Space Telescope Space Telescope Imaging Spectrograph (STIS) observations of VW Hydri 2 and 7 days after the end of a superoutburst reveal a heated white dwarf with deep broad Lyα, narrow metallic absorption features and evidence of a hotter Keplerian-broadened component. We confirm the existence of enhanced abundances of odd-numbered nuclea…
Nuclear Turnoff Times for ONEMG Novae Determined Using Ultraviolet Spectral Evolution
Shore, Steven N.; Starrfield, Sumner; Vanlandingham, Karen M. +1 more
Classical novae go through a phase of constant bolometric luminosity as any remaining hydrogen in the accreted layers on the white dwarf is converted to helium. The length of this phase is dependent on many factors, including the amount of mass left on the white dwarf after the explosive phase of the outburst, the white dwarf's mass, and the effic…
Millihertz Optical/Ultraviolet Oscillations in 4U 1626-67: Evidence for a Warped Accretion Disk
O'Donoghue, Darragh; Chakrabarty, Deepto; Homer, Lee +1 more
We have detected large-amplitude 0.3-1.2 mHz quasi-periodic oscillations (QPOs) from the low-mass X-ray binary pulsar 4U 1626-67/KZ TrA, using UV photometry from the Hubble Space Telescope and ground-based optical photometry. These 1 mHz QPOs, which have coherence (ν/Δν)~8, are entirely distinct from the 130 mHz pulsar spin frequency, a previously…
Far Ultraviolet Spectroscopic Explorer Observations of Interstellar Gas toward the Small Magellanic Cloud Star Sk 108
Savage, B. D.; Shull, J. M.; Sembach, K. R. +10 more
We discuss the interstellar absorption lines found in Far Ultraviolet Spectroscopic Explorer spectra of the Wolf-Rayet binary Sk 108, which is located in the northeastern part of the main ``bar'' of the Small Magellanic Cloud. The spectra cover the 988-1187 Å wavelength range at a resolution of about 12,000 and a signal-to-noise ratio of 20-40. We…
Discovery of the Galaxy Proximity Effect and Implications for Measurements of the Ionizing Background Radiation at Low Redshifts
Chen, Hsiao-Wen; Lanzetta, Kenneth M.; Webb, John K. +1 more
We present an analysis of galaxy and quasi-stellar object (QSO) absorption line pairs toward 24 QSOs at redshifts between z~0.2 and 1 in an effort to establish the relationship between galaxies and absorption lines in physical proximity to QSOs. We demonstrate the existence of a galaxy proximity effect, in that galaxies in the vicinities of QSOs d…
Near-Infrared Spectroscopy and Hubble Space Telescope Imaging of a Dusty Starburst Extremely Red Object
Kneib, J. -P.; Smith, Graham P.; Treu, Tommaso +3 more
We present near-infrared spectroscopy and Hubble Space Telescope (HST) imaging of ERO J164023+4644, an Extremely Red Object (ERO) with (R-K)=5.9 at z=1.05 that has been detected by Infrared Space Observatory (ISO) at 15 µm. ERO J164023 resembles a disk galaxy, with an optical/infrared spectral energy distribution that is strongly reddened by…
Stellar luminosity functions of rich star clusters in the Large Magellanic Cloud
Santiago, B.; Gilmore, G. F.; Beaulieu, S. +1 more
We show the results of deep V and I HST photometry of 6 rich star clusters in the Large Magellanic Cloud with different ages and metallicities. The number of stars with measured magnitudes in each cluster varies from about 3000 to 10 000 stars. We build stellar density and surface brightness profiles for the clusters and extract half-light radii a…
New Hubble Space Telescope Spectra of QSO PG 1718+4807: No Evidence for Strong Deuterium Absorption
O'Meara, John M.; Burles, Scott; Tytler, David +6 more
The zabs~0.701 absorption system toward QSO PG 1718+4807 is the only example of a QSO absorption system which might have a deuterium/hydrogen ratio approximately 10 times the value found toward other QSOs. We have obtained new Space Telescope Imaging Spectrograph spectra from the Hubble Space Telescope of the Lyα and Lyman limit regions…
Sunspot Plumes and Flow Channels
Wilhelm, K.; Fredvik, T.; Kjeldseth-Moe, O. +2 more
It is well known that sunspots are dark. This statement is not correct in the sunspot atmosphere between the chromosphere and the corona, where sunspots often are brighter than their surroundings. The brightest feature in the sunspot transition region is called a sunspot plume. Not all sunspots contain a plume. We find that 20 out of 21 sunspots s…