Search Publications
Improved Laboratory Transition Probabilities for Pt I and Application to the Platinum Abundances of BD +17°3248 and the Sun
Sneden, C.; Beers, T. C.; Lawler, J. E. +3 more
Radiative lifetimes, accurate to +/-5%, have been measured for 58 odd-parity levels of Pt I using laser-induced fluorescence. The lifetimes were combined with branching fractions measured using grating and Fourier transform spectrometry to determine transition probabilities for 127 lines of Pt I. The new Pt lifetime measurements were found to be i…
Modelling cosmic ray intensities along the Ulysses trajectory
Ferreira, S. E. S.; Potgieter, M. S.; Heber, B. +1 more
Time dependent cosmic ray modulation in the inner heliosphere is studied by comparing results from a 2-D, time-dependent cosmic ray transport model with Ulysses observations. A compound approach, which combines the effects of the global changes in the heliospheric magnetic field magnitude with drifts to establish a realistic time-dependence, in th…
The supermassive black hole in the Seyfert 2 galaxy NGC 5252
Marconi, A.; Capetti, A.; Axon, D. +1 more
We present results from HST/STIS long-slit spectroscopy of the gas motions in the nuclear region of the Seyfert 2 galaxy NGC 5252. The observed velocity field is consistent with gas in regular rotation with superposed localized patches of disturbed gas. The dynamics of the circumnuclear gas can be accurately reproduced by adding to the stellar mas…
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…
Radial variation of whistler-mode chorus: first results from the STAFF/DWP instrument on board the Double Star TC-1 spacecraft
Santolík, O.; Yearby, K. H.; Cornilleau-Wehrlin, N. +2 more
We use the first measurements of the STAFF/DWP instrument on the Double Star TC-1 spacecraft to investigate whistler-mode chorus. We present initial results of a systematic study on radial variation of dawn chorus. The chorus events show an increased intensity at L parameter above 6. This is important for the possible explanation of intensificatio…
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…
Discovery of two M 32 twins in Abell 1689
Infante, L.; Blakeslee, J. P.; Hilker, M. +5 more
The M 31 satellite galaxy M 32 has long been considered an object of unique properties, being the most extreme example of the very rare compact elliptical galaxy class. Here we present the spectroscopic discovery of two M 32 twins in the massive galaxy cluster Abell 1689. As these objects are so rare, this is an important step towards a better und…