Search Publications
Dwarf spheroidal galaxies in the M81 group imaged with WFPC2
Sarajedini, A.; Dolphin, A. E.; Grebel, E. K. +7 more
We obtained HST/WFPC2 images of the dwarf spheroidal (dSph) galaxies K61, K63, K64, DDO78, BK6N, and kk77 in the M81 group. Our color-magnitude diagrams show red giant branches with tips (TRGB) falling within the range of I = [23.8 -24.0] mag. The derived true distance moduli (DM) of the 6 dSphs ranging from 27.71 to 27.93 mag are consistent with …
Rossby waves on the Sun as revealed by solar `hills'
Kuhn, J. R.; Bush, R. I.; Scherrer, P. +1 more
It is a long-standing puzzle that the Sun's photosphere-its visible surface-rotates differentially, with the equatorial regions rotating faster than the poles. It has been suggested that waves analogous to terrestrial Rossby waves, and known as r-mode oscillations, could explain the Sun's differential rotation: Rossby waves are seen in the oceans …
The Hubble Space Telescope Quasar Absorption Line Key Project. XV. Milky Way Absorption Lines
Schneider, Donald P.; Savage, Blair D.; Sargent, W. L. W. +10 more
This paper presents the results of an analysis of the Milky Way absorption lines found in the Hubble Space Telescope (HST) Quasar Absorption Line Key Project database for 83 QSOs observed with the Faint Object Spectrograph G190H and G270H gratings, of which 16 QSOs are also observed with the G130H grating. The HST Key Project observations are supp…
Pluto's Non-isothermal Surface
Lellouch, E.; Crovisier, J.; Coustenis, A. +4 more
We report on repeated far-infrared photometric observations of the Pluto-Charon system conducted in 1997 with the Infrared Space Observatory (ISO). These observations have led to the first detection of the system at 150 and 200 µm and to the first clear detection of its thermal lightcurve at 60 µm (and more marginally at 100 µm).…
Rings in the Planetesimal Disk of β Pictoris
Schultz, A.; Kalas, P.; Larwood, J. +1 more
The nearby main-sequence star β Pictoris is surrounded by an edge-on disk of dust produced by the collisional erosion of larger planetesimals. Here we report the discovery of substructure within the northeast extension of the disk midplane that may represent an asymmetric ring system around β Pic. We present a dynamical model showing that a close …
The Extreme-Ultraviolet Solar Irradiance Spectrum Observed with the Coronal Diagnostic Spectrometer (CDS) on SOHO
Brekke, P.; Thompson, W. T.; Woods, T. N. +1 more
We present a calibrated solar EUV irradiance spectrum in the ranges 307-380 Å and 515-632 Å. The ``Sun as a star'' spectrum was recorded by the Coronal Diagnostic Spectrometer (CDS) on SOHO on 1997 May 15 using the normal incidence spectrometer (NIS) with a spectral resolution between 0.3 and 0.6 Å. The relatively high spectral resolution allows t…
Analysis of a Solar Active Region Extreme-Ultraviolet Spectrum from SERTS-97
Landi, Enrico; Brosius, Jeffrey W.; Thomas, Roger J. +1 more
Goddard Space Flight Center's Solar EUV Research Telescope and Spectrograph was flown on 1997 November 18, carrying an intensified CCD detector and a multilayer-coated toroidal diffraction grating with enhanced sensitivity over that of a standard gold-coated grating throughout the instrument's 299-353 Å spectral bandpass. Spectra and spectroheliog…
Adding More Mysteries to the DA White Dwarf GD 394
Vennes, Stéphane; Christian, Damian J.; Chayer, Pierre +2 more
We present spectroscopic and timing analyses of the hot DA white dwarf GD 394 showing abundance inhomogeneities across its surface. Lick Hamilton echelle, International Ultraviolet Explorer (IUE), HST GHRS, and Hopkins Ultraviolet Telescope (HUT) spectra show dominant Si III and Si IV features, while Extreme Ultraviolet Explorer (EUVE) spectra sho…
ISO observations of a sample of Compact Steep Spectrum and GHz Peaked Spectrum radio galaxies
Pozzi, F.; Bremer, M.; Dallacasa, D. +13 more
We present results from observations obtained with ISOPHOT, on board the ISO satellite, of a representative sample of seventeen CSS/GPS radio galaxies and of a control sample of sixteen extended radio galaxies spanning similar ranges in redshift (0.2 <= z <= 0.8) and radio luminosity (P_{2.7 GHz} >= 1026 W/Hz). The observations…
The coupling of solar convection and rotation - (Invited Review)
Miesch, Mark S.
In recent years, helioseismology has provided an unprecedented look at the dynamics of the solar interior. These new insights have been accompanied by tremendous advances in high-performance computing technology, prompting increasingly sophisticated and realistic numerical models of solar convection. Among the most important helioseismic constrain…