Search Publications
M31's Heavy-Element Distribution and Outer Disk
MacArthur, Lauren A.; Courteau, Stéphane; Worthey, Guy +1 more
Hubble Space Telescope imaging of 11 fields in M31 were reduced to color-magnitude diagrams. The fields were chosen to sample all galactocentric radii to 50 kpc (~9 disk scale lengths, or >99.9% of the total light enclosed). The colors of the red giants at each pointing map to an abundance distribution with errors of order 0.1 dex in [M/H]. The…
First Soft X-Ray Observations of Global Coronal Waves with the GOES Solar X-Ray Imager
Mann, G.; Aurass, H.; Warmuth, A.
We present the first observations of global coronal waves obtained with the Solar X-Ray Imager (SXI) aboard the GOES-12 satellite. Focusing on six events, the basic morphological and kinematic characteristics of the waves observed in soft X-rays are derived. Taking advantage of SXI's high temporal cadence and comparing the wave signatures with ext…
Footpoint excitation of standing acoustic waves in coronal loops
Doyle, J. G.; Erdélyi, R.; Bradshaw, S. J. +1 more
A new theoretical model for the study of slow standing sausage mode oscillations in hot (T > 6 MK) active region coronal loops is presented. These oscillations are observed by the SUMER spectrometer on board the SoHO satellite. The model contains the transition region and the upper chromosphere which enables us to study the entire process of ho…
The X-Ray Spectral Properties and Variability of Luminous High-Redshift Active Galactic Nuclei
Brandt, W. N.; Strauss, Michael A.; Vignali, C. +4 more
We perform a detailed investigation of moderate- to high-quality X-ray spectra of 10 of the most luminous active galactic nuclei (AGNs) known at z>4 (up to z~6.28). This study includes five new XMM-Newton observations and five archived X-ray observations (four by XMM-Newton and one by Chandra). We find that the X-ray power-law photon indices of…
Slow wind and magnetic topology in the solar minimum corona in 1996-1997
Abbo, L.; Antonucci, E.; Dodero, M. A.
This study examines the physical conditions of the outer solar corona in order to identify the regions where the slow solar wind is accelerated and to investigate the latitudinal transition from slow to fast wind during the minimum of the solar cycle. The analysis is based on observations of six streamers obtained during the years of solar minimum…
Infall, the Butcher-Oemler Effect, and the Descendants of Blue Cluster Galaxies at z~0.6
Franx, Marijn; Illingworth, Garth D.; Tran, Kim-Vy H. +3 more
Using wide-field Hubble Space Telescope WFPC2 imaging and extensive Keck LRIS spectroscopy, we present a detailed study of the galaxy populations in MS 2053-04, a massive, X-ray-luminous cluster at z=0.5866+/-0.0011. Analysis of 149 confirmed cluster members shows that MS 2053 is composed of two structures that are gravitationally bound to each ot…
High-Resolution, Long-Slit Spectroscopy of VY Canis Majoris: The Evidence for Localized High Mass Loss Events
Humphreys, Roberta M.; Davidson, Kris; Wallerstein, George +1 more
High spatial and spectral resolution spectroscopy of the OH/IR supergiant VY CMa and its circumstellar ejecta reveals evidence for high mass loss events from localized regions on the star occurring over the past 1000 yr. The reflected absorption lines and the extremely strong K I emission lines show a complex pattern of velocities in the ejecta. W…
The mass loss of C-rich giants
Bergeat, J.; Chevallier, L.
The mass loss rates, expansion velocities and dust-to-gas density ratios from millimetric observations of 119 carbon-rich giants are compared, as functions of stellar parameters, to the predictions of recent hydrodynamical models. Distances and luminosities previously estimated from HIPPARCOS data, masses from pulsations and C/O abundance ratios f…
XMM-Newton EPIC Background Modeling for Extended Sources
Markevitch, M.; Lumb, D.; Nevalainen, J.
We use XMM-Newton blank-sky and closed-cover background data to explore background subtraction methods for large extended sources filling the EPIC field of view, such as nearby galaxy clusters, for which local background estimation is difficult. In particular, we investigate the uncertainties of the background modeling in the 0.8-7.0 keV band that…
Warm gas in the cold diffuse interstellar medium: Spectral signatures in the H2 pure rotational lines
Falgarone, E.; Hily-Blant, P.; Pineau Des Forêts, G. +1 more
We present ISO-SWS observations of five pure rotational lines of H2 along a line of sight through the Galaxy which avoids regions of massive star formation. It samples 30 mag of gas, half of it (i.e. 15 mag) being diffuse gas running from the solar neighbourhood to the molecular ring, up to the far side of the Galaxy. The intensities of…