Search Publications
Solar Differential Rotation Influenced by Latitudinal Entropy Variations in the Tachocline
Toomre, Juri; Brun, Allan Sacha; Miesch, Mark S.
Three-dimensional simulations of solar convection in spherical shells are used to evaluate the differential rotation that results as thermal boundary conditions are varied. In some simulations a latitudinal entropy variation is imposed at the lower boundary in order to take into account the coupling between the convective envelope and the radiativ…
Discovery of Luminous Pulsed Hard X-Ray Emission from Anomalous X-Ray Pulsars 1RXS J1708-4009, 4U 0142+61, and 1E 2259+586 by INTEGRAL and RXTE
Kuiper, L.; Hermsen, W.; den Hartog, P. R. +1 more
We investigated the time-averaged high-energy spectral characteristics of the persistent anomalous X-ray pulsars (AXPs) 1RXS J1708-4009, 4U 0142+61, 1E 2259+586, and 1E 1048.1-5937, using RXTE PCA (2-60 keV), RXTE HEXTE (15-250 keV), and INTEGRAL IBIS ISGRI (20-300 keV) data. We discovered hard spectral tails for energies above 10 keV in the total…
A Spectroscopic Survey of Redshift 1.4<~z<~3.0 Galaxies in the GOODS-North Field: Survey Description, Catalogs, and Properties
Pettini, Max; Erb, Dawn K.; Shapley, Alice E. +2 more
We present the results of a spectroscopic survey with LRIS-B on Keck of more than 280 star-forming galaxies and AGNs at redshifts 1.4<~z<~3.0 in the GOODS-N field. Candidates are selected by their UnGR colors using the ``BM/BX'' criteria to target redshift 1.4<~z<~2.5 galaxies and the LBG criteria to target redshift z~3 gala…
Constraints on the Physics of Type Ia Supernovae from the X-Ray Spectrum of the Tycho Supernova Remnant
Hughes, John P.; Hwang, Una; Badenes, Carles +2 more
In this paper we use high-quality X-ray observations from XMM-Newton and Chandra to gain new insights into the explosion that originated Tycho's supernova 433 yr ago. We perform a detailed comparison between the ejecta emission from the spatially integrated X-ray spectrum of the supernova remnant and current models for Type Ia supernova explosions…
A Model for Spectral and Compositional Variability at High Energies in Large, Gradual Solar Particle Events
Lee, Martin A.; Tylka, Allan J.
Shocks driven by fast coronal mass ejections (CMEs) are generally believed to be the dominant accelerators in large, gradual solar energetic particle (SEP) events. A key challenge for this notion has been the highly variable spectral and compositional characteristics of these events above a few tens of MeV per nucleon. We have recently proposed th…
Nearby Debris Disk Systems with High Fractional Luminosity Reconsidered
Apai, D.; Derekas, A.; Ábrahám, P. +5 more
By searching the IRAS and ISO databases, we compiled a list of 60 debris disks that exhibit the highest fractional luminosity values (fd>10-4) in the vicinity of the Sun (d<120 pc). Eleven out of these 60 systems are new discoveries. Special care was taken to exclude bogus disks from the sample. We computed the fraction…
Fe II Emission in 14 Low-Redshift Quasars. I. Observations
Oyabu, Shinki; Tanabé, Toshihiko; Matsuoka, Yoshiki +3 more
We present the spectra of 14 quasars with a wide coverage of rest wavelengths from 1000 to 7300 Å. The redshift ranges from z=0.061 to 0.555 and the luminosity from MB=-22.69 to -26.32. These spectra of high quality result from combining Hubble Space Telescope spectra with those taken from ground-based telescopes. We describe the proced…
Stellar Populations in the Nuclei of Late-Type Spiral Galaxies
Ho, L. C.; Rix, H. -W.; Shields, J. C. +5 more
As part of an ongoing effort to study the stellar nuclei of very late type, bulge-less spirals, we present results from a high-resolution spectroscopic survey of nine such nuclear star clusters, undertaken with the VLT UVES. We fit the spectra with population synthesis models and measure Lick-type indices to determine mean luminosity-weighted ages…
Globular Cluster Systems in Brightest Cluster Galaxies: Bimodal Metallicity Distributions and the Nature of the High-Luminosity Clusters
Whitmore, Bradley C.; Kavelaars, J. J.; Baum, William A. +4 more
We present new (B, I) photometry for the globular cluster systems in eight brightest cluster galaxies (BCGs), obtained with the ACS/WFC camera on the Hubble Space Telescope. In the very rich cluster systems that reside within these giant galaxies, we find that all have strongly bimodal color distributions that are clearly resolved by the metallici…
Near-Infrared and Star-forming Properties of Local Luminous Infrared Galaxies
Pérez-González, Pablo G.; Ryder, Stuart D.; Colina, Luis +3 more
We use Hubble Space Telescope (HST) NICMOS continuum and Paα observations to study the near-infrared and star formation properties of a representative sample of 30 local (d~35-75 Mpc) luminous infrared galaxies (LIRGs, infrared [8-1000 µm] luminosities of logLIR=11-11.9 Lsolar). The data provide spatial resolutions of 2…