Search Publications
Composition of Interstellar Clouds in the Disk and Halo. II. gamma 2 Velorum
Fitzpatrick, Edward L.; Spitzer, Lyman, Jr.
High-resolution observations of gamma2 Vel with the Goddard High-Resolution Spectrograph (GHRS) echelle on the Hubble Space Telescope reveal the presence of seven narrow absorption components, with LSR velocities between -23 and +9 km s-1. Three of these show column density ratios N(S(++))/N(S(+)) and N(P(++))/N(P+)) of about…
The X-Ray Spectra of Blazars Observed with EXOSAT
Giommi, Paolo; Barr, Paul; Sambruna, Rita M. +3 more
A systematic analysis of the X-ray spectra (0.1-10 keV) of all blazars observed with EXOSAT is presented. The objects include 16 X-ray-selected BL Lac objects (XBLs), five radio-selected BL Lac objects (RBLs), and five highly polarized quasars (HPQs). Comparing the results of single-power-law fits for the different classes, we find that XBLs have …
HST Images of Nearby Luminous Quasars
Schneider, Donald P.; Bahcall, John N.; Kirhakos, Sofia
Strong upper limits are placed on the visual-band brightnesses of galactic hosts for four luminous, radio-quiet quasars with redshifts between 0.16 and 0.24 that were studied with the HST's Wide Field/Planetary Camera 2 (WFPC2). Typical upper limits on the luminosities of galactic hosts are ~1.4 mag fainter than L^*^ for spirals and ~0.5 mag faint…
The Early Bolometric Evolution of Nova Cygni 1992
Shore, Steven N.; Sonneborn, George; Starrfield, Sumner +2 more
We report on combined ultraviolet and optical observations of early stages of the outburst of Nova Cygni 1992. We show that the initial optical rise and decline were produced by the dramatic increase in UV line opacity and its gradual subsequent lifting as the ejecta expand. The source of the Mv - t3 relation is easily unders…
The Discovery of NI V in the Photospheres of the Hot DA White Dwarfs RE 2214-492 and G191-B2B
Barstow, M. A.; Sion, E. M.; Holberg, J. B. +3 more
We have co-added six recently obtained International Ultraviolet Explorer (IUE) echelle spectra of the hot DA white dwarf RE 2214-492 and 10 existing archive spectra of the well-known hot DA, G191-B2B. We find that both stars contain numerous weak features due to Ni V. Nickel is thus the second iron-group element to be found in the spectra of the …
High-Velocity Plasma in the Transition Region of AU Microscopii: Evidence for Magnetic Reconnection and Saturated Heating during Quiescent and Flaring Conditions
Wood, Brian E.; Linsky, Jeffrey L.
We analyze high-resolution HST spectra of the dMOe flare star AU Mic, including the profiles of the C IV 1548.2 A, 1550.8 A and Si IV 1393.8 A, 1402.8 A lines obtained with the G160M grating of the Goddard High-Resolution Spectrograph. The quiescent profiles of the C IV and Si IV lines are broad, and not simple Gaussians in shape. Flux in the C IV…
High-Resolution Spectra of Jupiter's Northern Auroral Ultraviolet Emission with the Hubble Space Telescope
Trafton, L. M.; Gerard, J. C.; Munhoven, G. +1 more
The first spectroscopic observations of planetary aurora with the Hubble Space Telescope (HST) are reported. These include spectral regions centered on the H2 Lyman and Werner bands of a region of Jupiter's northern aurora. The observations were made with the Goddard High Resolution Spectrograph (GHRS) using the Large Science Aperture as part of a…
Elemental Abundances of the Supernova Remnant G292.0+1.8: Evidence for a Massive Progenitor
Singh, K. P.; Hughes, John P.
We present a comprehensive nonequilibrium ionization (NEI) analysis of X-ray spectral data from the Einstein Observatory and EXOSAT for the supernova remnant G292.0+1.8. The spectra are well described by a single-temperature, single-timescale NEI model with kT = 1.64-0.19+0.29 keV and net = (5.55-1.12
Probing the Galactic Disk and Halo. I. The NGC 3783 Sight Line
Sembach, Kenneth R.; Savage, Blair D.; Lu, Limin
We report a study of Galactic disk and halo absorption toward the Seyfert galaxy NGC 3783 which has Galactic coordinates l = 287.46 and b = +22.95. The data were obtained with the Goddard High Resolution Spectrograph operating at medium resolution with the Large Science Aperture, which produces a line spread function having a sharp core (FWHM ~ 20…
GHRS Observations of Cool, Low-Gravity Stars. I. The Far-Ultraviolet Spectrum of alpha Orionis (M2 Iab)
Brown, Alexander; Robinson, Richard D.; Linsky, Jeffrey L. +2 more
We present far-UV (1200-1930 A) observations of the prototypical red supergiant star alpha Ori, obtained with the Goddard High Resolution Spectrograph (GHRS) on the Hubble Space Telescope (HST). The observations, obtained in both low- (G140L) and medium- (G160/200M) resolution modes, unambiguously confirm that the UV 'continuum' tentatively seen w…