Search Publications
Revealing the Photodissociation Region: HST/NICMOS Imaging of NGC 7027
Bieging, John H.; Hora, Joseph L.; Dayal, Aditya +4 more
We report results from a Hubble Space Telescope (HST) and Near-Infrared Camera and Multiobject Spectrometer (NICMOS) program to study the distribution of hot neutral (molecular hydrogen) and ionized circumstellar material in the young planetary nebulae NGC 7027. HST/NICMOS provided very high spatial resolution imaging in line and continuum emissio…
UVCS WLC Observations of Compressional Waves in the South Polar Coronal Hole
Romoli, M.; Poletto, G.; Noci, G. +2 more
Recent SOHO Ultraviolet Coronagraph Spectrometer (UVCS) white light channel (WLC) observations of the south polar coronal hole plumes and interplume regions produce signatures of quasi-periodic variations in the polarized brightness (pB) at a heliocentric distance of 1.9 solar radii (Rsolar). The Fourier power spectrum of the pB time se…
Observational Upper Limits to Low-Degree Solar g-Modes
Kosovichev, A. G.; Hoeksema, J. T.; Scherrer, P. H. +12 more
Observations made by the Michelson Doppler Imager (MDI) and Variability of solar IRradiance and Gravity Oscillations (VIRGO) on the Solar and Heliospheric Observatory (SOHO) and by the ground-based Birmingham Solar Oscillations Network (BiSON) and Global Oscillations Network Group (GONG) have been used in a concerted effort to search for solar gra…
Mining the Metal-rich Stars for Planets
Laughlin, Gregory
We examine the correlation between stellar metallicity and the presence of short-period planets. It appears that approximately 1% of dwarf stars in the solar neighborhood harbor short-period planets characterized by near-circular orbits and orbital periods P<20 days. However, among the most metal-rich stars (defined as having [Fe/H]>0.2 dex)…
Hubble Space Telescope Studies of the WLM Galaxy. II. The Star Formation History from Field Stars
Dolphin, Andrew E.
HST F555W and F814W photometry of a portion of the WLM galaxy is presented. The distance modulus is determined via fitting of the entire color-magnitude diagram to be (m-M)0=24.88+/-0.09, which is consistent with the red giant branch tip distance. The galaxy's measurable star formation history appears to have begun no more than 12 Gyr a…
Resolved Spectroscopy of the Narrow-Line Region in NGC 1068. III. Physical Conditions in the Emission-Line Gas
Crenshaw, D. Michael; Kraemer, Steven B.
The physical conditions in the inner narrow-line region (NLR) of the Seyfert 2 galaxy NGC 1068 are examined using ultraviolet and optical spectra and photoionization models. The spectra were taken with the Hubble Space Telescope Space Telescope Imaging Spectrograph (STIS), through the 0.1"×52.0" slit, covering the full STIS 1200-10000 Å waveband. …
Identification of Spectral Lines in the 500-1600 Å Wavelength Range of Highly Ionized Ne, Na, Mg, Ar, K, Ca, Ti, Cr, Mn, Fe, Co, and Ni Emitted by Flares (Te>=3×106 K) and Their Potential Use in Plasma Diagnostics
Wilhelm, K.; Curdt, W.; Landi, E. +1 more
On 1999 May 9 the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer on the Solar and Heliospheric Observatory (SOHO) recorded spectra from a high-temperature region located in the solar corona above the west limb. These spectra contain lines from rather less-abundant elements in solar plasmas. In this paper we present identi…
Spatial Variability in the Ratio of Interstellar Atomic Deuterium to Hydrogen. II. Observations toward γ2 Velorum and ζ Puppis by the Interstellar Medium Absorption Profile Spectrograph
Tripp, Todd M.; Jenkins, Edward B.; Vidal-Madjar, Alfred +4 more
High-resolution far-ultraviolet spectra of the early-type stars γ2 Vel and ζ Pup were obtained to measure the interstellar deuterium abundances in these directions. The observations were made with the Interstellar Medium Absorption Profile Spectrograph (IMAPS) during the ORFEUS-SPAS II mission in 1996. IMAPS spectra cover the wavelength…
Gravitational Lensing of Distant Supernovae in Cold Dark Matter Universes
Madau, Piero; Porciani, Cristiano
Ongoing searches for supernovae (SNe) at cosmological distances have recently started to provide large numbers of events with measured redshifts and apparent brightnesses. Compared to quasars or galaxies, Type Ia SNe represent a population of sources with well-known intrinsic properties and could be used to detect gravitational lensing even in the…
B Stars as a Diagnostic of Star Formation at Low and High Redshift
Heckman, Timothy M.; Leitherer, Claus; de Mello, Duília F.
We have extended the evolutionary synthesis models by Leitherer et al. by including a new library of B stars generated from the IUE high-dispersion spectra archive. We present the library and show how the stellar spectral properties vary according to luminosity classes and spectral types. We have generated synthetic UV spectra for prototypical you…