Search Publications
HST/GHRS Observations of the beta Pictoris System: Basic Parameters of the Age of the System
Hubeny, Ivan; Heap, Sara R.; Lanz, Thierry
We have reevaluated the basic parameters and age of the A5 IV--V star, beta Pictoris, making use of new observations obtained by the Goddard High-Resolution Spectrograph aboard the Hubble Space Telescope and using modern methods of atmospheric modeling and spectral synthesis. We derive stellar parameters appropriate to its spectral type (Teff = 82…
The Incidence of Damped LY alpha Systems in the Redshift Interval 0 < Z < 4
Turnshek, David A.; Rao, Sandhya M.; Briggs, Franklin H.
The determination of the incidence and column density distribution of damped Lyα systems from QSO absorption-line surveys in the redshift interval 0 < z < 1.65 is crucial for constraining the evolution of neutral gas in galaxies. This redshift interval corresponds to a time interval of ∼62% of the age of the universe for q0 = 0 (7…
New "Einstein Cross" Gravitational Lens Candidates in Hubble Space Telescope WFPC2 Survey Images
Im, Myungshin; Griffiths, Richard E.; Ratnatunga, Kavan U. +1 more
We report the serendipitous discovery of "Einstein cross" gravitational lens candidates using the Hubble Space Telescope (HST). We have so far discovered two good examples of such lenses, each in the form of four faint blue images located in a symmetric configuration around a red elliptical galaxy. The high resolution of HST has facilitated the di…
The Mass Ratios of Cepheid Binaries
Evans, Nancy Remage
The distribution of mass ratios in binary systems is important for comparison with star formation calculations but has been difficult to obtain observationally. This study uses IUE spectra of the hot companions of classical Cepheids with observed orbital motion to determine the companion types and hence their masses. Combining these with Cepheid m…
Of-Type Stars HD 16691 and HD 190429 Show WN-like Spectra in Infrared K Band
Conti, Peter S.; Morris, Patrick W.; Willis, Allan J. +2 more
We present 2 micrometer K-band spectra of two early-type Of stars that have infrared emission-line morphology similar to that of WN stars. Archival International Ultraviolet Explorer (IUE) spectra of these two stars indicate they appear to be Of type, rather than WN. Recently acquired optical spectra of these stars are quantitatively similar to th…
High-Speed Photometer Observations of the LMC Pulsar B0540-69
Dolan, J. F.; Boyd, P. T.; Nelson, M. J. +6 more
The High-Speed Photometer (HSP) on board the Hubble Space Telescope (HST) observed the 50 ms pulsar B0540-69 in the Large Magellanic Cloud on 1993 August 26 for 1 hr in a passband extending from 1600 Å to 7000 Å. The pulse profile resembles both that in the optical region alone and in the X-ray region. The pulsed fraction in the UV-plus-visible pa…
Interaction of a Stellar Wind with Clumpy Stellar Ejecta in A30
Borkowski, Kazimierz J.; Tsvetanov, Zlatan I.; Harrington, J. Patrick
Clumpy, hydrogen-depleted material in the planetary nebula Abell 30 was ejected by its central star ~1000 yr ago. We present observations of Abell 30 showing compact, hydrogen-poor knots with wind-blown tails, obtained with the Wide Field Planetary Camera (WFPC2) on board the Hubble Space Telescope, which offer an unprecedented view of the interac…
The IUE MEGA Campaign: Modulated Structure in the Wind of HD 64760 (B0.5 Ib)
Massa, Derck; Prinja, Raman K.; Fullerton, Alexander W.
We highlight systematic variability in the stellar wind of the early B type supergiant, HD 64760, whose UV line profiles were monitored for almost 16 days in 1995 January as part of the IUE "MEGA Campaign." The extensive coverage reveals a pattern of rapidly evolving discrete optical depth changes which typically migrate from ~-200 km s-1 to ~-150…
Detection of the Hot White Dwarf in the Magnetic Nova V1500 Cygni with the Hubble Space Telescope
Liebert, James; Schmidt, Gary D.; Stockman, H. S.
A comprehensive investigation of the AM Herculis-like nova system V1500 Cyg is presented, featuring time-resolved spectrophotometry with the Faint Object Spectrograph (FOS) of the Hubble Space Telescope (HST), coeval optical circular spectropolarimetry and spectrophotometry, and new broadband polarimetry. A revised ephemeris for the rotating white…
Discovery of Highly Ionized High-Velocity Clouds toward Markarian 509
Sembach, Kenneth R.; Savage, Blair D.; Lu, Limin +1 more
We present Goddard High Resolution Spectrograph measurements of the Milky Way halo gas absorption toward Mrk 509 (1 = 36°.0, b = -29°.9) in the 1233-1268 and 1521-1558 Å spectral regions at a resolution of ≈15 km s-1. We detect high-velocity (υLSR -340 to -170 km s-1 absorption in both members of the C IV λλ1548, 1…