Search Publications
The Ultraviolet Absorption Spectrum of the Quasar PKS 0405-12 and the Local Density of Lyman-Alpha Absorption Systems
Schneider, Donald P.; Jannuzi, Buell T.; Bahcall, John N. +1 more
A sample of 32 absorption lines has been identified in the ultraviolet spectrum of the z = 0.57 quasar PKS 0405 - 12. The observations were obtained using three R = 1300 gratings of the Faint Object Spectrograph of the Hubble Space Telescope. The data cover the wavelength range 1190- 3260 A. The sample was constructed by requiring that all include…
On the nature of the 25-min periodicity from 4U 0142+614 : a nearby, slowly spinning neutron star/Be system ?
Mereghetti, S.; Stella, L.; de Nile, F.
The unidentified X-ray source 4U 0142+614 has an unusually soft spectrum and has shown a periodic modulation at approximately 25 minutes, which could be interpreted as the orbital period of a Low Mass X-ray Binary. Recently a new X-ray source, probably a Be/neutron star system, has been discovered at an angular distance of only 24 arcmin from 4U 0…
JHK Photometry of WD 0950+139
Liebert, James; Fulbright, Michael S.
We present results from several nights of JHK photometry of the hot DA white dwarf 0950+139. It has a significant infrared excess over the expected flux from the white dwarf alone, confirming a previous finding by Zuckerman et al. (1991). The infrared excess corresponds to an upper limit on the spectral type of a companion of M4 V. We consider two…
Extreme Ultraviolet Observations of HZ 43 and the Local H/He Ratio with the Hopkins Ultraviolet Telescope
Feldman, Paul D.; Kimble, Randy A.; Davidsen, Arthur F. +1 more
We present a spectrum of the hot DA white dwarf HZ 43 in the EUV, near the 504-A ionization edge of neutral helium, obtained with the Hopkins Ultraviolet Telescope (HUT) during the 1990 December Astro-1 mission. The interstellar column densities derived from this spectrum rule out the anomalous interstellar absorption model proposed by Heise et al…
Jovian electron jets in interplanetary space
Ferrando, P.; Raviart, A.; Ducros, R. +1 more
The COSPIN/KET experiment onboard Ulysses has been monitoring the flux of ∼ 3-20 MeV electrons in interplanetary space since the launch of Ulysses in October 1990. The origin of these electrons has been known for a long time to be the Jovian magnetosphere. Propagation models assuming interplanetary diffusion of these electrons in the ideal Parker …
Solar wind composition measurements by the Ulysses SWICS experiment during transient solar wind flows
Geiss, J.; Galvin, A. B.; Ipavich, F. M. +3 more
For the March/April 1991 time period, the alpha/proton abundance ratio, the proton kinetic temperature and speed distributions, and the relative abundance of O+7 to O+6 is determined over each 13-minute duty cycle of the Solar Wind Ion Composition Spectrometer (SWICS) experiment on Ulysses. The ratio (as a relative measure of ionization temperatur…
Colliding Wind Binary Systems: Monte Carlo Simulations of Line-Profile Variability
Stevens, Ian R.
We investigate the line-profile variability observed in colliding wind binary systems. In these systems the ultraviolet P Cygni line profiles show marked orbital variability; the nature of which differs between individual lines and binaries. We present results of three-dimensional Monte Carlo simulations of the radiative transfer and line formatio…
30 Doradus: Ultraviolet and Optical Stellar Photometry
Cheng, Kwang-Ping; O'Connell, Robert W.; Bohlin, Ralph C. +7 more
Stellar photometry is presented for 314 stars in a 9.7' x 9.7' field in the 30 Dor nebula centered on R136. Magnitudes are computed from Ultraviolet Imaging Telescope images in up to 4 bands with effective wave-lengths from 1615 to 2558 A, and from a ground-based CCD image in the B band. Spectral types and extinctions are estimated using a least- …
ROSAT/IUE discovery of a white dwarf companion to HD 33959C.
Barstow, M. A.; Hodgkin, S. T.; Pye, J. P. +2 more
We report the discovery, from the ROSAT EUV and X-ray all-sky surveys, and from IUE spectra, of a white dwarf (WD) companion to HD 33959C. RE 0515 + 324 is among the 10 brightest EUV sources in the sky in the 100-200 A band. It is also a strong soft X-ray source. IUE observations of candidate objects have revealed a previously uncataloged hot DA W…
Measurements of the interstellar gas
Lallement, R.
Two types of interstellar gas observations are considered; namely those made in the local interstellar medium on paths to nearby stars, and those obtained from the study of solar system gas. Optical measurements, and in particular Hubble Space Telescope spectra of the star Capella, have recently confirmed detection of the Local Interstellar Cloud …