Search Publications

The Inferred Redshift Distribution of the Faint Blue Galaxy Excess

Driver, Simon P.; Windhorst, Rogier A.; Phillipps, Steven +1 more

We infer the redshift distribution of the faint blue galaxy excess (FBE) at mB = 23.5 by subtracting the predicted distribution of giant/normal galaxies from the observed N(z) distribution for all types. This is possible because of the recent deep Hubble Space Telescope (HST) WFPC2 morphological number counts that have convincingly demonstrated th…

Possible Association of a Quiescent X-Ray Source with a Gamma-Ray Burster

Cline, T.; Hurley, K.; Kouveliotou, C. +10 more

We report on the first repeatedly detected statistically significant coincidence (chance probability ≈10^-2-10^-3) between an X-ray source and a gamma-ray burst error box. We present three ROSAT observations of the field of the gamma-ray burst of 1992 May 1. The first, a 2000 5 target of opportunity observation, was carried out…

Detection of Accreting, Circumstellar Gas in a lambda Bootis Star: 131 Tauri

England, M. N.; McCollum, B.; Grady, C. A. +3 more

We present IUE high-dispersion spectra of the lambda Boo star, 131 Tau (HD 38545), confirming the presence of shell spectral features and also providing the first detection of accreting, circumstellar gas in the spectrum of a lambda Boo star. Accreting gas can be followed in the mid-UV Fe II transitions to +80 km s-1 relative to the star. Circumst…

IUE and Optical Observations of AM Herculis in Its Low State

Raymond, J. C.; Andronov, I. L.; Borisov, N. V. +3 more

Ten spectra of AM Herculis were obtained with the SWP instrument of the lUE over 2.5 orbital periods during a faint state in 1992 June. Significant periodic variability was seen in the UV flux and spectra. On the same day, UBVRI photometry was obtained at the 1.25 m optical telescope of the Crimean Astrophysical Observatory. A periodic brightening…

Interpretation of the Observed Plasma ``Turbulent'' Velocities as a Result of Magnetic Reconnection in Solar Flares

Antonucci, Ester; Benna, Carlo; Somov, Boris V.

One of the distinctive features of magnetic reconnection in current sheets, which has been proposed as the primary energy source in solar flares, is the presence of fast plasma outflows, or jets, whose velocities are nearly equal to the Alfvén speed and depend mainly on the electron and ion temperatures inside the current sheet. We briefly discuss…

The Density Profile of 47 Tucanae

Paresce, Francesco; Gilliland, Ronald L.; Bohlin, Ralph C. +2 more

We have used high-resolution HST-WF/PC images of the core of the globular cluster 47 Tucanae in the U-band to determine its radial density profile. The exceptional photometric quality of the data set ensures highly reliable measurements since no photometric completeness correction is required for stars at and above the turn-off luminosity over the…

Time-resolved Optical Spectroscopy of the Cataclysmic Variable PG 0859+415

Szkody, Paula; Hoard, D. W.

We present time-resolved, high-resolution (2 Å) spectra of the nova-like cataclysmic variable (CV) PG 0859+415. The average optical spectrum of this star displays a continuum slope that is steeper than expected for a steady state accretion disk this is attributed to the presence of a hot spot with T ∼ 12,000 K at the impact site of the accretion s…

A 21 Centimeter Absorber Identified with a Spiral Galaxy: Hubble Space Telescope Faint Object Spectrograph and Wide-Field Camera Observations of 3CR 196

Cohen, Ross D.; Junkkarinen, Vesa T.; Beaver, E. A. +3 more

We present imaging and spectroscopy of the quasar 3CR 196 (z_e = 0.871), which has 21 cm and optical absorption at z_a = 0.437.

We observed the region of Lyα absorption in 3CR 196 at z_a = 0.437 with the Faint Object Spectrograph on the Hubble Space Telescope. This region of the spectrum is complicated because of…

An Ultraviolet-Excess Optical Candidate for the Luminous Globular Cluster X-Ray Source in NGC 1851

Anderson, Scott F.; Margon, Bruce; Deutsch, Eric W. +1 more

The intense, bursting X-ray source in the globular cluster NGC 1851 was one of the first cluster sources discovered, but has remained optically unidentified for 25 years. We report here on results from Hubble Space Telescope WFPC2 multicolor images in NGC 1851. Our high spatial resolution images resolve ~200 objects in the 3" radius Einstein X-ray…

NE V and NE VI Lines in the Ultraviolet Spectrum of the Symbiotic Star RR Telescopii

Feibelman, W. A.; Keenan, F. P.; McKenna, F. C. +2 more

New theoretical Ne VI] electron density-sensitive ratios are presented for the intercombination transitions R₁ = I(1006.1 Å)/I(999.6 Å) and R₂ = 1(1010.6 Å)/I(999.6 Å). Temperature-sensitive ratios are also given for the Ne V] ratio R = 1(1137.0 Å)/I(1574.8 Å). We discuss the potential usefulness of these line ratios for stud…