Search Publications
A Self-occulting Accretion Disk in the SW Sextantis Star DW Ursae Majoris
Dhillon, V. S.; Szkody, Paula; Hoard, D. W. +2 more
We present the ultraviolet spectrum of the SW Sextantis star and nova-like variable DW Ursae Majoris in an optical low state, as observed with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope (HST). The data are well described by a synthetic white dwarf (WD) spectrum with Teff=46,000+/-1000 K, logg=7.60+/-0.1…
Interstellar dust properties derived from mass density, mass distribution, and flux rates in the heliosphere
Kimura, Hiroshi; Mann, Ingrid
We apply recent in situ measurements of the mass density, mass distribution, and flux rate of dust particles that enter the solar system, i.e., the heliosphere, to study the properties and dynamics of the interstellar dust flux into the solar system. We show that depletion at the heliopause alters the flux for particles with mass, m<10-18<…
The morphology of extremely red objects
Cimatti, A.; Daddi, E.; Moriondo, G.
We present a quantitative study of the morphology of 41 Extremely Red Objects (EROs). The analysis is based on deep otical and near-infrared images from the Hubble Space Telescope public archive, and performed by fitting to each galaxy image a PSF-convolved bi-dimensional model brightness distribution. Relying both on the visual inspection of the …
Spectroscopic Abundances in Cool Pleiades Dwarfs and NGC 2264 Stars
Soderblom, David R.; King, Jeremy R.; Jones, Burton F. +1 more
We derive parameters and abundances of several elements in two cool Pleiades dwarfs, four cool NGC 2264 pre-main-sequence stars, and a probable NGC 2264 nonmember from high-resolution, moderate signal-to-noise ratio, Keck/HIRES spectra. Our Pleiades Fe abundance agrees with previous spectroscopic and photometric values of hotter stars and does not…
The Origin of a Chemically Enriched Lyα Absorption System at Z = 0.167
Chen, Hsiao-Wen; Prochaska, Jason X.
We present the first detailed analysis of the chemical abundances, ionization state, and origin of a partial Lyman limit system [N(H I)~1016 cm-2] at low redshift (z=0.167 toward PKS 0405-1219). Two galaxies at an ~70 h-1 kpc projected distance to the QSO have been identified at the absorber redshift. We analyze an…
On the origin of the fast solar wind in polar coronal funnels
Mann, G.; Marsch, E.; Hackenberg, P.
Funnels are open magnetic structures connecting the chromosphere with the solar corona ( \cite{Axf97,Mar97,Hac99}). We investigate the stationary plasma flow out of funnels with a flux-tube model. The funnel area function is derived from an analytical 2-D magnetic field model. Since the funnel height is only approximately 15 Mm, the area function …
Silicate Emission in T Tauri Stars: Evidence for Disk Atmospheres?
Meyer, Michael R.; Beckwith, Steven V. W.; Natta, Antonella
We present low-resolution mid-infrared spectra of nine classical T Tauri stars associated with the Chamaeleon I dark cloud. The data were obtained with the PHOT-S instrument on board the Infrared Space Observatory (ISO) in the two wavelength ranges 2.5-4.9 and 5.9-11.7 µm. All nine stars show evidence of silicate emission at 10 µm, whi…
A spectroscopic study of field BHB star candidates
Cacciari, C.; Bragaglia, A.; Castelli, F. +3 more
New spectroscopic observations are presented for a sample of thirty-one blue horizontal branch (BHB) star candidates that are sufficiently nearby to have reliable proper motions. Comments are given on a further twenty-five stars that have previously been suggested as BHB star candidates but which were not included in our sample. Moderately high-re…
The Very Red Afterglow of GRB 000418: Further Evidence for Dust Extinction in a Gamma-Ray Burst Host Galaxy
Pian, E.; Palazzi, E.; Greiner, J. +36 more
We report near-infrared and optical follow-up observations of the afterglow of the GRB 000418 starting 2.5 days after the occurrence of the burst and extending over nearly 7 weeks. GRB 000418 represents the second case for which the afterglow was initially identified by observations in the near-infrared. During the first 10 days its R-band aftergl…
Timescales of Disk Evolution and Planet Formation: HST, Adaptive Optics, and ISO Observations of Weak-Line and Post-T Tauri Stars
Brandner, Wolfgang; Alcalá, Juan M.; Covino, Elvira +7 more
We present high spatial resolution HST and ground-based adaptive optics observations and high-sensitivity ISO (ISOCAM & ISOPHOT) observations of a sample of X-ray selected weak-line (WTTS) and post- (PTTS) T Tauri stars located in the nearby Chamaeleon T and Scorpius-Centaurus OB associations. HST/NICMOS and adaptive optics observations aimed …