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Far Ultraviolet Spectroscopic Explorer 900-1200 Å Spectroscopy of AM Herculis
Hutchings, J. B.; Fullerton, A. W.; Cowley, A. P. +1 more
Spectra of the magnetic white dwarf binary AM Herculis were obtained with the Far Ultraviolet Spectroscopic Explorer during three consecutive spacecraft orbits. These observations were split into 19 spectra of about 5 minutes' duration (0.025P binary phase) partially covering the binary orbit. We report the phase-related changes in the far-ultravi…
Coronal Loops Heated by Magnetohydrodynamic Turbulence. I. A Model of Isobaric Quiet-Sun Loops with Constant Cross Sections
Chae, Jongchul; Aschwanden, Markus J.; Poland, Arthur I.
Several recent papers have presented new observational results indicating that many coronal loops in active regions are nearly isothermal. It is expected that quiet-Sun loops may have similar thermal structures, since quiet-Sun differential emission measures look similar to those in active regions. In the quiet Sun, it is well known from observati…
A morphological comparison between the central region in AGN and normal galaxies using HST data
Papadakis, I. E.; Xilouris, E. M.
We study the morphology of the central region of a sample of Active Galactic Nuclei (AGN) and a ``control'' sample of normal galaxies using archival observations of the WFPC2 instrument onboard the Hubble Space Telescope (HST). We use the ellipse fitting technique in order to get a good description of the inner ``smooth'' light distribution of the…
Precision and accuracy of the orbital parameters derived from 2D & 1D space observations of visual or astrometric binaries
Pourbaix, D.
Recent investigations (e.g. Han et al. \cite{Han-2001:a}) have shown that fitting the Hipparcos observations with an orbital model when the astrometric wobble caused by the companion is below the noise level can have rather unexpected consequences. With new astrometric missions coming out within the next ten years, it is worth investigating the or…
Diagnosis of coronal magnetic field with data of Nobeyama Radio Heliograph
Nakajima, Hiroshi; Huang, Guang-Li
The expression is derived for the coronal magnetic field strength from the observations of brightness, temperature, peak frequency, spectral index, and polarization degree of solar microwave bursts. One example of solar burst on November 28, 1998 is given for the calculation of coronal magnetic field from the data of Nobeyama Radio Heliograph (NoR…
No Hexagonal Wave around Saturn's Southern Pole
Sánchez-Lavega, A.; Pérez-Hoyos, S.; French, R. G. +1 more
Hubble Space Telescope (HST) images (1997-2002) do not show a hexagonal wave in the south pole that is a counterpart of the northern one (D. A. Godfrey 1988, Icarus76, 335-356). However, a polar jet similar to that in which the north polar hexagonal wave is embedded has been discovered in the southern hemisphere. The HST images also reveal the exi…
On the source of the flaring activity in AB Doradus: the UV spectral signatures
Gómez de Castro, Ana I.
AB Dor is a young, 30-Myr-old, low-mass star with a short rotation period and strong flaring activity. In this work, a detailed analysis of the flaring activity is carried out based on ultraviolet spectral tracers of hot (T ~105 ) plasma, namely HST /GHRS profiles of the Civ[uv1] and Siiv[uv1] lines. The quiescent component has been sub…
The Interpretation of the Emission Spectra of the Seyfert 2 Galaxy NGC 7130: Determination of the Active Galactic Nucleus and Starburst Contributions
Rafanelli, P.; Radovich, M.; Contini, M. +1 more
Detailed modeling of the different regions of NGC 7130 is presented, accounting for its composite nature of an active galactic nucleus (AGN) and a starburst galaxy. Shock waves, created by stellar winds from hot massive stars and by supernova ejecta, are evident in the continuum and line spectra emitted from the clouds. Therefore, the SUMA code, w…
The signature of high-velocity gas in the spectra of NGC 4151
Prieto, M. A.; Contini, M.; Viegas, S. M.
The multiwavelength emission spectrum and associated velocity field of the Seyfert prototype NGC 4151 is modeled. Since the thirties NGC 4151 has been the subject of extensive modeling, nuclear photoionization being the basic approach considered by all authors. HST data has impressively revealed the existence of a large range of velocities (100-15…
Mrk 1014: an AGN-dominated ultraluminous infrared galaxy
Lutz, D.; Sturm, E.; Boller, Th. +1 more
In this paper we report on an XMM-Newton observation of the ultraluminous infrared QSO Mrk 1014. The X-ray observation reveals a power-law-dominated (Γ~ 2.2) spectrum with a slight excess in the soft energy range. Active galactic nucleus (AGN) and starburst emission models fit the soft excess emission equally well, however, the most plausible expl…