Search Publications
The effective temperatures of carbon-rich stars
Bergeat, J.; Knapik, A.; Rutily, B.
We evaluate effective temperatures of 390 carbon-rich stars. The interstellar extinction on their lines of sights was determined and circumstellar contributions derived. The intrinsic (dereddened) spectral energy distributions (SEDs) are classified into 14 photometric groups (HCi, CVj and SCV with i=0,5 and j=1,7). The new sc…
The Magnetic Structure and Generation of EUV Flare Ribbons
Fletcher, L.; Hudson, H.
The `ribbons' of two-ribbon flares show complicated patterns reflecting the linkages of coronal magnetic field lines through the lower solar atmosphere. We describe the morphology of the EUV ribbons of the July 14, 2000 flare, as seen in SOHO, TRACE, and Yohkoh data, from this point of view. A successful co-alignment of the TRACE, SOHO/MDI and Yoh…
Dynamical Friction in DE Globular Cluster Systems
Ferguson, Henry C.; Mack, Jennifer; Stiavelli, Massimo +3 more
The dynamical friction timescale for globular clusters to sink to the center of a dwarf elliptical galaxy (dE) is significantly less than a Hubble time if the halos have King-model or isothermal profiles and the globular clusters formed with the same radial density profile as the underlying stellar population. We examine the summed radial distribu…
Spectrophotometric Standards from the Far-Ultraviolet to the Near-Infrared: STIS and NICMOS Fluxes
Calzetti, D.; Dickinson, M. E.; Bohlin, R. C.
With photometric repeatability in the 0.2%-0.4% range and wavelength coverage from 1150 to 10,200 Å, the Space Telescope Imaging Spectrograph (STIS) low-dispersion spectrophotometry provides excellent absolute flux standards. STIS observations of 19 stars are used to update the database of Hubble Space Telescope standard stars with absolute fluxes…
Evidence for evolving spheroidals in the Hubble Deep Fields North and South
Menanteau, F.; Abraham, R. G.; Ellis, R. S.
We investigate the dispersion in the internal colours of faint spheroidals in the Hubble Deep Fields North and South. In high-redshift rapid-collapse scenarios, the dispersion in internal colours should be small at moderate redshift apart from a small metallicity induced reddening in the enriched cores. However, recently assembled spheroidals are …
Direct detection of a microlens in the Milky Way
Alcock, C.; Allsman, R. A.; Alves, D. R. +22 more
The nature of dark matter remains mysterious, with luminous material accounting for at most ~25 per cent of the baryons in the Universe. We accordingly undertook a survey looking for the microlensing of stars in the Large Magellanic Cloud (LMC) to determine the fraction of Galactic dark matter contained in massive compact halo objects (MACHOs). Th…
High-Resolution X-Ray and Ultraviolet Spectroscopy of the Complex Intrinsic Absorption in NGC 4051 with Chandra and the Hubble Space Telescope
Brandt, W. N.; Kaspi, Shai; Elvis, Martin +6 more
We present the results from simultaneous observations of the narrow-line Seyfert 1 galaxy NGC 4051 with the Chandra High Energy Transmission Grating Spectrometer and the Hubble Space Telescope Space Telescope Imaging Spectrograph. The X-ray grating spectrum reveals absorption and emission lines from hydrogen-like and helium-like ions of O, Ne, Mg,…
On OH line formation and oxygen abundances in metal-poor stars
Asplund, M.; García Pérez, A. E.
The formation of the UV OH spectral lines has been investigated for a range of stellar parameters in the light of 3D hydrodynamical model atmospheres. The low atmospheric temperatures encountered at low metallicities compared with the radiative equilibrium values enforced in classical 1D hydrostatic model atmospheres have a profound impact on the …
Chandra observations of the X-ray jet in 3C 66B
Hardcastle, M. J.; Birkinshaw, M.; Worrall, D. M.
Our Chandra observation of the FR I radio galaxy 3C 66B has resulted in the first detection of an X-ray counterpart to the previously known radio, infrared and optical jet. The X-ray jet is detected up to 7arcsec from the core and has a steep X-ray spectrum, α~1.3+/-0.1. The overall X-ray flux density and spectrum of the jet are consistent with a …
The Gaseous Extent of Galaxies and the Origin of Lyα Absorption Systems. V. Optical and Near-Infrared Photometry of Lyα-absorbing Galaxies at z<1
Chen, Hsiao-Wen; Lanzetta, Kenneth M.; Webb, John K. +1 more
We present results of a program to obtain and analyze HST WFPC2 images and ground-based images of galaxies identified in an imaging and spectroscopic survey of faint galaxies in fields of HST spectroscopic target QSOs. Considering a sample of physically correlated galaxy and absorber pairs with galaxy-absorber cross-correlation amplitude ξga<…