We present new optical emission-line images of the young SNR 1E 0102-7219 in the SMC obtained with the ACS on HST. This object is a member of the oxygen-rich class of SNRs showing strong oxygen, neon, and other metal-line emissions in its optical and X-ray spectra, and an absence of hydrogen and helium. The progenitor of 1E 0102-7219 may have been a Wolf-Rayet star that underwent considerable mass loss prior to exploding as a Type Ib/c or IIL/b supernova. The ejecta in this SNR are generally fast-moving (V > 1000 km s-1) and emit as they are compressed and heated in the reverse shock. In 2003 we obtained optical [O III], Hα, and continuum images with the ACS Wide Field Camera. The [O III] image through the F475W filter captures the full velocity range of the ejecta and shows considerable high-velocity emission projected in the middle of the SNR that was Doppler-shifted out of the narrow F502N bandpass of a previous WFPC2 image from 1995. Using these two epochs separated by ~8.5 yr, we measure the transverse expansion of the ejecta around the outer rim in this SNR for the first time at visible wavelengths. From proper-motion measurements of 12 ejecta filaments, we estimate a mean expansion velocity for the bright ejecta of ~2000 km s-1 and an inferred kinematic age for the SNR of ~2050 ± 600 yr. The age we derive from HST data is about twice that inferred by Hughes et al. from X-ray data, although our 1 σ error bars overlap. Our proper-motion age is consistent with an independent optical kinematic age derived by Eriksen et al. in 2003 using spatially resolved [O III] radial-velocity data. We derive an expansion center that lies very close to conspicuous X-ray and radio hot spots, which could indicate the presence of a compact remnant (neutron star or black hole).

We analyze HST/GHRS spectra of AB Doradus, the prototypical ultra-rapidly 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. The quiescent line profiles of the chromospheric and transition region lines show narrow cores superposed on very broad wings. The broad wings of the Mg II k h lines and of the transition region lines can be explained by emission from gas co-rotating with the star and extending out to near the Keplerian co-rotation radius (2.8 stellar radii). While this is not a unique solution, it is consistent with previous studies of H-alpha emission that are naturally explained by large co-rotating prominences. We find no evidence for rotational modulation of the emission line fluxes. The density diagnostics suggest that the transition region is formed at constant pressure, with an electron density 2-3 E12 /cm^3 at a temperature of 30,000 K. The electron pressure is about 100 times larger than that for the quiet Sun. The emission measure distribution shows a minimum between log(T) = 5 and 5.5. The Mg II line exhibits three interstellar absorption components along the 15 pc line of sight. We identify the lowest velocity component with the G cloud, but the other components are not identified with any interstellar clouds previously detected from other lines of sight.

Goddard High Resolution Spectrograph observations of the nucleus of the bright, nearby Seyfert galaxy NGC 4151 are presented and briefly described.

Observations of the ultra–sharp-lined, chemically peculiar star χ Lupi taken by the Goddard High Resolution Spectrograph in echelle mode are presented. Thirty-six intervals of the spectral region between 1249 and 2688 Å are covered with resolving powers in the range 75,000–93,000. Line identifications are provided, and the observed spectra are compared with synthetic spectra calculated using the SYNTHE program and associated line lists with changes to the line lists. The significance of these spectra for the χ Lupi Pathfinder Project and the closely related atomic physics effort is discussed in a companion paper.

Goddard High Resolution Spectrograph echelle-mode observations of the interstellar absorption lines of Mg II, Si IV, C IV, and N V toward mu Columbae (HD 38666) are presented. The observations have a spectral resolution of 3.5 km s(-1) and signal-to-noise ratios (S/Ns) of 20-200. The mu Col sight line (l = 237.degrees 3, b = -27.degrees 1, d = 0.40 kpc, z = -0.18 kpc) extends though the Local Bubble and the warm neutral, warm ionized, and hot ionized phases of the interstellar medium (ISM). The high-ionization column densities toward mu Col are log N(Si IV) = 12.16 +/- 0.05, log N(C IV) = 12.88 +/- 0.02, and log N(N V) = 11.8-12.3. Profile fits to Copernicus satellite measures of O VI absorption toward mu Col yield log N(O VI) = 13.82+/-0.01 and b = 38.7 km s(-1). This implies N(C IV)/N(O VI) = 0.11 +/- 0.01, which is typical of the values found for the hot ISM of the Galactic disk. The O vr profile is twice as broad as the C rv and N V profiles, even though these species have roughly similar average velocities. Some of the C IV, N V, and O VI absorption toward mu Col may occur at the interface of the Local Cloud and Local Bubble, although additional contributions to these ions probably also occur in more distant gas along the sight line. A substantial part of the Si Iv absorption likely arises in warm photoionized gas in an H II region surrounding mu Col. The profile width differences among the high-ionization lines of C IV, N V, and O VI could be produced if the line of sight passes through a highly evolved supernova remnant. The observations for mu Col and for other stars observed at high resolution with the GHRS reveal that multiple gas types (warm and hot) contribute to the absorption by the highly ionized atoms along both nearby and distant sight lines. Disentangling the relative contributions from the different gas types requires high-resolution and high-S/N observations. The Mg II observations, combined with a solar Mg reference abundance, imply that the Mg depletion toward mu Col is -0.31 dex. As observed for other sight lines through the warm neutral medium, the gas-phase observations of Mg, when combined with results for Fe and Si, suggest that Mg and Fe are more deficient from the gas phase than one would expect if these elements are only contained in silicate dust grains.

We review changes to the characteristics of the Goddard High Resolution Spectrograph (GHRS) which resulted from the installation of the Corrective Optics Space Telescope Axial Replacement (COSTAR) on the Hubble Space Telescope. The introduction of two new optical elements into the light path altered the spectral distribution of the light, decreasing the amount of light striking the instrument by about 30% at wavelengths greater than 1200 Å and effectively eliminated all radiation at wavelengths less than 1130 Å. However, at the longer wavelengths the improved focus offset this loss when the Large Science Aperture (LSA) was used and increased the overall throughput of the Small Science Aperture (SSA) by a factor of 2. The improved focus also enhanced the spectral resolution of LSA observations and improved the ability of the instrument to observe in crowded fields.

The Space Telescope Imaging Spectrograph (STIS) was successfully installed into the Hubble Space Telescope (HST) in 1997 February, during the second HST servicing mission, STS-82. STIS is a versatile spectrograph, covering the 115-1000 nm wavelength range in a variety of spectroscopic and imaging modes that take advantage of the angular resolution, unobstructed wavelength coverage, and dark sky offered by the HST. In the months since launch, a number of performance tests and calibrations have been carried out and are continuing. These tests demonstrate that the instrument is performing very well. We present here a synopsis of the results to date.

Observations of the narrow-lined O-type star 10 Lacertae taken with the Goddard High Resolution Spectrograph in 1992 November are presented. The spectra cover the wavelength range 1181-1777 Angstrom with a resolution of 15 km s(-1) and signal-to-noise ratio greater than 100:1. Absorption lines arising in the interstellar medium, the photosphere, and the stellar wind are identified and discussed.

We present high-quality spectra of eta Car between 1203 and 1765 Angstrom obtained with the Goddard High Resolution Spectrograph on board the Hubble Space Telescope. A square entrance slit 0.'' 22 in diameter was used to isolate the brightest region of the core, ''component A,'' from the nearby knots of ejecta and the nebulosity in which it is embedded. The spectrum is that of an unusually dense stellar envelope, with a nearly flat continuum and numerous emission and absorption lines. Most lines exhibit the P Cygni type profiles characteristic of a stellar wind. Lines from a wide range of ionization stages, from N I through N v, are visible, most having very similar velocity structures. Wind lines from C, N, and O are all clearly visible, as are numerous metallic species. Most of the lines have two discrete, well-resolved absorption components, ore centered near -500 km s(-1) and the other near -1100 km s(-1). The overall morphology does not correspond to any one normal spectral type but suggests a composite of features seen in B-type supergiants in the range B2 Ia to B8 Ia, with additional lower temperature lines also present. The spectrum of eta Car is qualitatively similar to that of P Cyg in this wavelength range.

Observations of the quasar 3C 273 taken with the Goddard High Resolution Spectrograph in 1993 November and December are presented here. We have included both the fully-reduced spectra, and spectra combined with our earlier (1991) observations. There are a total of IO new medium resolution exposures covering four wavelength regions: 1164-1201 Angstrom, 1214-1251 Angstrom, 1537-1573 Angstrom, and 1633-1670 Angstrom. We confirm the suggestion of Morris et al. (1991, ApJ, 377, L21) that the galactic Si IV lambda 1393 line is blended with an extragalactic Ly alpha line by observing the Ly beta counterpart to this extragalactic line. We obtain an improved upper limit on the C IV/H I ratio in these weak low redshift Ly alpha absorption systems by coadding the corresponding C IV spectral regions. Improved line profiles for the galactic C IV and N V absorption are also presented and discussed. The improved measurements lead to a downward revision of the galactic C IV column density, log N(C IV) = 14.46+/-0.04. (C) 1997 American Astronomical Society.

We present an atlas and tabulation of weak interstellar absorption lines in the ultraviolet spectrum of zeta Ophiuchi in four selected wavelength regions observed with the Goddard High Resolution Spectrograph aboard the Hubble Space Telescope. The signal-to-noise ratio ranges from 150 to nearly 400, and the spectral resolving power exceeds 20 000, allowing 2 sigma detections of features as weak as W-lambda=0.8 m Angstrom. We report positive measurements of two lines of OH, and weak detections of P I, Tl II, and N V. Upper limits of W-lambda<1 m Angstrom are found for the molecules H2O, HCl, SiO, NO+, and CH2. Similar limits are found for heavy elements Te II, Co II, and Sb II. Three lines are present in our spectrum for which we have no identifications. They are found at wavelengths of lambda=1229.84, 1313.98, and 1314.23 Angstrom. However, none of the features reported by previous authors as unidentified absorption lines in the wavelength regions we have observed are present in our data. (C) 1996 American Astronomical Society.

The design and specification of space-based detectors generally requires considerable analysis together with experimental simulation to characterize and minimize the influence of the dynamic space environment on the detector performance. We present the results of an extensive investigation of the in-orbit performance of the Digicon detectors in the Goddard High Resolution Spectrograph (GHRS), conducted as part of the commissioning phase of the Hubble Space Telescope (HST). This paper includes results on the background noise, sensor stability, orbital management of detector activities, and relevant GHRS astronomy applications.

An atlas of observations of the late-type supergiant a Orionis taken with the Goddard High Resolution Spectrograph in 1992 September is presented. We have included identifications of the major features along with the fully reduced spectrum. The 33 exposures consist of 3 high resolution (R∼80,000) and 30 medium resolution (R ∼20,000∼35,000) observations. The latter provide complete wavelength coverage from 1980 to 3300 Å.

The Goddard High Resolution Spectrograph (GHRS), currently in Earth orbit on the Hubble Space Telescope (HST), operates in the wavelength range 1150-3200 angstrom with spectral resolutions (lambda/deltalambda) of approximately 2 x 10(3), 2 X 10(4), and 1 X 10(5). The instrument and its development from inception, its current status, the approach to operations, representative results in the major areas of the scientific goals, and prospects for the future are described.

We report the observation of transient narrow absorption components (NACs) in the stellar wind of the O giant xi Per. Two sets of GHRS observations of the Si IV ultraviolet resonance doublet have been obtained. These features are extremely weak, with column densities of approximately 10(12) cm-2 and optical depths of order 0. 1. The features are narrow, less-than-or-equal-to 30 km s-1, and seem to occur in groups. If the NACs are due to the 1393 angstrom component, they represent previously undetected low-velocity discrete absorption components at v(rad) < -600 km s-1. If they are high-velocity features on the 1402 angstrom doublet component, they may represent the decay phase of the discrete absorption components at the terminal velocity. In either case, they are a new aspect of the NAC phenomenon that could not have been detected with previous ultraviolet spectrographs.

We report on the detection of the weak intersystem transition of C II] lambda2325 angstrom in the sight line toward zeta Oph using the Ech-B mode (3.5 km s-1 resolution) of the Goddard High-Resolution Spectrograph. The high-quality spectrum is characterized by an empirically measured signal-to-noise of 450, in excellent agreement with that expected from photon statistics. The measured equivalent width of the C II] line is W(lambda) = 0.52 +/- 0.12 mangstrom, implying a C II column density of 1.80(+/- 0.42) x 10(17) atoms cm-2 and (C/H)zeta Oph = 1.32(+/- 0.32) x 10(-4). This C/H is 1.9 +/- 0.7 smaller than that measured toward xi Per by Cardelli et al. (1991a). We find that some of this difference may be attributable to inhomogeneities in the cosmic abundance of carbon. However, a comparison between specific aspects of the observed extinction curves (e.g., integrated 2175 angstrom bump and far-UV extinction optical depths per H atom) for the zeta Oph and xi Per sight lines, indicates that at least part of this difference may also be consistent with some conversion of carbon grains and/or PAHs to gas phase C II.

Stellar-wind variability in the archetypal nonradially pulsating O star zeta Oph (O9.5 V) is discussed on the basis of new time-series IUE and HST spectroscopy and archival results. Time-variable ''discrete absorption components'' are first observed at high velocities (greater than or similar to 10(3) km s-1 congruent-to 0.8v(infinity)) and then migrate blueward; the recurrence time scale for the phenomenon is approximately 20 hr. This is the first record of this type of variability in a luminosity-class V star and provides support for the previously inferred ubiquity of such behavior across the O-star regime. The accelerations are slower than predicted by steady state wind models and are unlikely to represent the time-averaged velocity law of the outflow. The UV results are discussed in the context of simultaneous optical observations (Paper II); no evidence is found to suggest that nonradial pulsations have any direct role in determining the gross observational characteristics of discrete absorption components, on either long (years) or short (hours) time scales. The line-driven instability provides a promising mechanism to account for variability observed in the UV P Cygni profiles of zeta Oph, and, by extension, in all other O stars.

We report on an analysis of observations made with the Goddard High Resolution Spectrograph (GHRS) aboard the Hubble Space Telescope for the purpose of calibrating the effects of scattered light. The data were obtained during the first 2 years of flight operations as part of the Science Verification, Science Assessment Observations, and Guaranteed Time Observations programs. Data from the two high-resolution echelle modes, three of the four medium-resolution gratings, and both science apertures have been studied. Both the general level of background light near the spectra and the filling in of the cores of saturated interstellar absorption lines have been determined as functions of grating, order, wavelength, and aperture. The behavior is in accordance with our detailed analysis of prelaunch laboratory data and validates both the observing procedures and the data reduction developed on the basis of that experience. We present and discuss the use of a background (scattered light) removal algorithm designed to produce net spectra properly corrected for the effects of grating scattered light. The coefficients of the scattered light removal algorithm have been determined, and recommended numerical values are presented. Results of using the algorithm are presented for a diverse group of stellar, circumstellar, and interstellar spectra which demonstrate the utility of these techniques and illustrate the quality of data attainable with the GHRS and the HST.