Search Publications
MV Lyrae in Low, Intermediate, and High States
Szkody, Paula; Sion, Edward M.; Hoard, D. W. +4 more
Archival IUE spectra of the VY Sculptoris system MV Lyrae, taken during an intermediate state, can be best fit by an isothermal accretion disk extending half-way to the tidal cutoff radius. In contrast, a recent HST spectrum, while MV Lyr was in a high state, can be best fit with a standard T(R) profile for an accretion disk extending from an inne…
Chandra Observations of NGC 4261 (3C 270): Revealing the Jet and Hidden Active Galactic Nucleus in a Type 2 LINER
Zezas, A.; Fabbiano, G.; Birkinshaw, M. +2 more
We present results from a Chandra ACIS-S observation of the type 2 low-ionization nuclear emission-line region (LINER) radio galaxy NGC 4261 (3C 270). The X-ray data show that this galaxy hosts a heavily obscured (NH~8×1022 cm-2) active galactic nucleus (AGN) with an intrinsic luminosity of 2.4×1041 ergs…
Do Young Galaxies Exist in the Local Universe? Red Giant Branch Detection in the Metal-poor Dwarf Galaxy SBS 1415+437
Leitherer, C.; Tosi, M.; van der Marel, R. P. +3 more
We present results from an HST/ACS imaging study of the metal-poor blue compact dwarf galaxy SBS 1415+437. It has been argued previously that this is a very young galaxy that started to form stars only <~100 Myr ago. However, we find that the optical color-magnitude diagram prominently reveals asymptotic giant branch and red giant branch (RGB) …
New Elemental Abundances for V1974 Cygni
Shore, S. N.; Starrfield, S.; Wagner, R. M. +2 more
We present a new analysis of existing optical and ultraviolet spectra of the ONeMg nova V1974 Cygni 1992. Using these data and the photoionization code Cloudy, we have determined the physical parameters and elemental abundances for this nova. Many of the previous studies of this nova have made use of incorrect analyses, and hence a new study was r…
Constraining the Distribution of L and T Dwarfs in the Galaxy
Hathi, N. P.; Ryan, R. E., Jr.; Windhorst, R. A. +1 more
We estimate the thin-disk scale height of the Galactic population of L and T dwarfs based on star counts from 15 deep parallel fields from the Hubble Space Telescope. From these observations, we have identified 28 candidate L and T dwarfs based on their i'-z' color and morphology. By comparing these star counts with a simple Galactic model, we est…
XTE J1550-564: INTEGRAL Observations of a Failed Outburst
Shrader, C. R.; Sturner, S. J.
The well-known black hole X-ray binary transient XTE J1550-564 underwent an outburst during the spring of 2003, which was substantially underluminous in comparison to previous periods of peak activity in that source. In addition, our analysis shows that it apparently remained in the hard spectral state over the duration of that outburst. This is a…
FUSE Determination of a Low Deuterium Abundance along an Extended Sight Line in the Galactic Disk
Moos, H. W.; Chayer, P.; Dupuis, J. +5 more
We present a study of the deuterium abundance along the extended sight line toward HD 90087 with the Far Ultraviolet Spectroscopic Explorer (FUSE). HD 90087 is a O9.5 III star located in the Galactic disk at a distance of ~2.7 kpc away from the Sun. Both in terms of distance and column densities, HD 90087 has the longest and densest sight line obs…
Sculpting a Pre-planetary Nebula with a Precessing Jet: IRAS 16342-3814
Sahai, R.; Sánchez Contreras, C.; Le Mignant, D. +2 more
We have imaged the bipolar pre-planetary nebula IRAS 16342-3814 with the Keck adaptive optics (AO) system in four near-infrared bands in the 1.6-4.7 µm range. The lobes, which showed smoothly varying brightness distributions in previous optical images taken with the Hubble Space Telescope, have a limb-brightened appearance in the AO images, …
Isothermal Bias of the ``Filter Ratio'' Method for Observations of Multithermal Plasma
Schmelz, J. T.; DeLuca, E. E.; Weber, M. A. +1 more
An early result from the Transition Region and Coronal Explorer (TRACE) was that the EUV filter ratios for many narrow coronal loops (widths of a few arcseconds) were found to cluster within the small range 0.50-1.70, as functions of position along loop length. The most common interpretation is that the temperature along the loop is in fact nearly…
Abundances and Depletions of Interstellar Oxygen
Snow, Theodore P.; Rachford, Brian L.; Jensen, Adam G.
We report on the abundance of interstellar neutral oxygen (O I) for 26 sight lines, using data from the Far Ultraviolet Spectroscopic Explorer, the International Spectroscopic Explorer, and the Hubble Space Telescope. O I column densities are derived by measuring the equivalent widths of several ultraviolet absorption lines and subsequently fittin…