Search Publications
Early SPI/INTEGRAL constraints on the morphology of the 511 keV line emission in the 4th galactic quadrant
Knödlseder, J.; Cordier, B.; Schönfelder, V. +11 more
We provide first constraints on the morphology of the 511 keV line emission from the galactic centre region on basis of data taken with the spectrometer SPI on the INTEGRAL gamma-ray observatory. The data suggest an azimuthally symmetric galactic bulge component with FWHM of ~ 9o with a 2sigma uncertainty range covering 6o-18…
Observations of Rotating Sunspots from TRACE
Schrijver, C. J.; Shine, R. A.; Title, A. M. +5 more
Recent observations from TRACE in the photospheric white-light channel have shown sunspots that rotate up to 200° about their umbral centre over a period of 3-5 days. The corresponding loops in the coronal fan are often seen to twist and can erupt as flares. In an ongoing study, seven cases of rotating sunspots have been identified, two of which c…
Latitude-dependent Effects in the Stellar Wind of η Carinae
Smith, Nathan; Hillier, D. John; Gull, Theodore R. +2 more
The Homunculus reflection nebula around η Carinae provides a rare opportunity to observe the spectrum of a star from more than one direction. In the case of η Car, the nebula's geometry is known well enough to infer how line profiles vary with latitude. We present Space Telescope Imaging Spectrograph (STIS) spectra of several positions in the Homu…
The Far Ultraviolet Spectroscopic Explorer Survey of O VI Absorption in and near the Galaxy
Kruk, J. W.; Savage, B. D.; Wakker, B. P. +18 more
We present Far Ultraviolet Spectroscopic Explorer (FUSE) observations of the O VI λλ1031.926, 1037.617 absorption lines associated with gas in and near the Milky Way, as detected in the spectra of a sample of 100 extragalactic targets and two distant halo stars. We combine data from several FUSE Science Team programs with guest observer data that …
Internal Dynamics, Structure, and Formation of Dwarf Elliptical Galaxies. II. Rotating versus Nonrotating Dwarfs
Geha, M.; van der Marel, R. P.; Guhathakurta, P.
We present spatially resolved internal kinematics and stellar chemical abundances for a sample of dwarf elliptical (dE) galaxies in the Virgo Cluster observed with the Keck telescope and Echelle Spectrograph and Imager. In combination with previous measurements, we find that four out of 17 dE's have major-axis rotation velocities consistent with r…
Toward a Self-Consistent Model of the Ionized Absorber in NGC 3783
Elvis, M.; Nicastro, F.; Krongold, Y. +3 more
We present a detailed model for the ionized absorbing gas evident in the 900 ks Chandra HETGS spectrum of NGC 3783. The analysis was carried out with PHASE, a new tool designed to model X-ray and UV absorption features in ionized plasmas. The 0.5-10 keV intrinsic continuum of the source is well represented by a single power law (Γ=1.53) and a soft…
The XMM-Newton EPIC background: Production of background maps and event files
Read, A. M.; Ponman, T. J.
XMM-Newton background maps for the 3 EPIC instruments in their different instrument/mode/filter combinations and in several energy bands have been constructed using a superposition of 72 pointed observations. Event datasets, with point sources excised, for the different instrument/mode/filter combinations have also been assembled, with longer expo…
Empirically Constrained Color-Temperature Relations. I. BV(RI)C
VandenBerg, Don A.; Clem, James L.
This investigation presents a set of transformations to Johnson B-V, Cousins V-R, and Cousins V-I, as well as bolometric corrections to V, for [Fe/H]=-3, -2, -1, -0.5, 0.0, and +0.3 and, in each case, values of logg from -0.5 to 5.0 for 3000 K<=Teff<=5500 K and from 2.0 to 5.0 for 6000 K<=Teff<=40,000 K. These tra…
Hα Spectroscopy of Galaxies at z > 2: Kinematics and Star Formation
Pettini, Max; Erb, Dawn K.; Shapley, Alice E. +5 more
We present near-infrared spectroscopy of Hα emission lines in a sample of 16 star-forming galaxies at redshifts 2.0<z<2.6. Our targets are drawn from a large sample of galaxies photometrically selected and spectroscopically confirmed to lie in this redshift range. We have obtained this large sample with an extension of the broadband Un<…
Theories of solar eruptions: a review
Lin, J.; Baliunas, S. L.; Soon, W.
This review highlights current theoretical research on eruptive phenomena in the solar atmosphere. We start by looking back upon the early theories and their development. Any theory and model of solar eruptions must explain two key aspects of eruption physics. The first aspect concerns the original cause of the eruption and the second pertains to …