Search Publications
Missions
Journals
Publication Years
Sensitivity of spectral lines to temperature, velocity, and magnetic field
Bellot Rubio, L. R.; del Toro Iniesta, J. C.; Cabrera Solana, D.
We present an analytical and numerical study of the sensitivity of weak solar photospheric lines to temperature, velocity, and magnetic fields. Our investigation is based on the concept of response functions (Landi degl'Innocenti & Landi degl'Innocenti 1977; Ruiz Cobo & del Toro Iniesta 1994). Lines commonly used in solar spectropolarimetr…
An old quasar in a young dark energy-dominated universe?
Friaça, A. C. S.; Alcaniz, J. S.; Lima, J. A. S.
Dark energy is the invisible fuel that seems to drive the current acceleration of the Universe. Its presence, which is inferred from an impressive convergence of high-quality observational results along with some apparently successful theoretical predictions, is also supported by the current estimates of the age of the Universe from dating of loca…
Solar Convection-Zone Dynamics, 1995-2004
Thompson, M. J.; Howe, R.; Komm, R. +3 more
The nine-year span of medium-degree helioseismic data from the Global Oscillation Network Group (GONG) and the Michelson Doppler Imager (MDI) allows us to study the evolving zonal flows in the solar convection zone over the rising phase, maximum, and early declining phase of solar cycle 23. Using two independent two-dimensional rotation inversion …
Feeding the Monster: The Nucleus of NGC 1097 at Subarcsecond Scales in the Infrared with the Very Large Telescope
Reunanen, Juha; Prieto, M. Almudena; Maciejewski, Witold
Near-IR images of the prototype LINER/Seyfert type 1 galaxy NGC 1097 observed with the Very Large Telescope using adaptive optics disclose with unprecedented detail a complex central network of filamentary structure spiraling down to the center of the galaxy. The structure, consisting of several spiral arms, some almost completing a revolution abo…
Asphericity and clumpiness in the winds of Luminous Blue Variables
Vink, Jorick S.; Davies, Ben; Oudmaijer, René D.
We present the first systematic spectropolarimetric study of Luminous Blue Variables (LBVs) in the Galaxy and the Magellanic Clouds, in order to investigate the geometries of their winds. We find that at least half of our sample show changes in polarization across the strong Hα emission line, indicating that the light from the stars is intrinsical…
Propagation of whistler-mode chorus to low altitudes: divergent ray trajectories and ground accessibility
Santolík, O.; Chum, J.
We investigate the ray trajectories of nonductedly propagating lower-band chorus waves with respect to their initial angle θ0, between the wave vector and ambient magnetic field. Although we consider a wide range of initial angles θ0, in order to be consistent with recent satellite observations, we pay special attention to th…
XMM-Newton Observations of Ultraluminous X-Ray Sources in Nearby Galaxies
Feng, Hua; Kaaret, Philip
We examined X-ray spectral and timing properties of ultraluminous X-ray sources (ULXs) in nearby galaxies in XMM-Newton archival data. There appear to be three distinct classes of spectra. One class shows emission from hot, diffuse plasma. This thermal emission is similar to that seen from recent supernovae; the temperatures are in the range 0.6-0…
Fe K emission in the ultraluminous infrared galaxy Arp 220
Sanders, D. B.; Iwasawa, K.; Miniutti, G. +3 more
Prominent Fe Kα line emission is detected in the XMM-Newton spectrum of the ultraluminous infrared galaxy Arp 220. The centroid of the line is found at an energy of 6.7 keV and the equivalent width of the line is EW ~ 1.9 keV (at 3.5σ significance). A few other spectral features are found at various degrees of significance in the lower energy rang…
Initial results of a survey of equatorial noise emissions observed by the Cluster spacecraft
de Conchy, Y.; Santolík, O.; Němec, F. +3 more
Initial results of a survey of equatorial noise emissions are presented. These plasma wave emissions are observed in the inner magnetosphere close to the geomagnetic equator at frequencies below the local lower hybrid frequency. We use the data recorded by the four Cluster spacecraft during the first 24 months of measurements. The data set was pro…
Highly Ionized High-Velocity Clouds: Hot Intergalactic Medium or Galactic Halo?
Shull, J. Michael; Giroux, Mark L.; Collins, Joseph A.
We use spectroscopic data from the Hubble Space Telescope (HST) and Far Ultraviolet Spectroscopic Explorer (FUSE) to study the wide range of ionization states of the ``highly ionized high-velocity clouds'' (HVCs). Studied extensively in O VI absorption, these clouds are usually assumed to be infalling gas in the Galactic halo at distances less tha…