Search Publications
SUMER observations of transition region fine structures
Mason, H. E.; Landini, M.; Lemaire, P. +1 more
The SUMER (Solar Ultraviolet Measurements of Emitted Radiation) instrument on SOHO (Solar and Heliospheric Observatory) provides an opportunity to observe and study the solar transition region with high spatial and spectral resolution. We present new evidence to confirm that the emission from the quiet Sun at 2x 105 K is dominated by co…
On measuring low-degree p-mode frequency splitting with full-disc integrated data
Appourchaux, T.; Gough, D. O.; Sekii, T. +1 more
The standard method of measuring rotational splitting from solar full-disc oscillation data, based on maximum-likelihood fitting of multi-Lorentzian profiles to oscillation power spectra, systematically overestimates the splitting. One of the reasons is that the maximum likelihood estimators (MLE) become unbiased only asymptotically as the number …
A Search for Broad Infrared Recombination Lines in NGC 1068
Lutz, D.; Genzel, R.; Sturm, E. +12 more
We report infrared spectroscopy of the prototypical Seyfert 2 galaxy NGC 1068, aiming at detection of broad components of hydrogen recombination lines that originate in the obscured broad-line region. Using the Short Wavelength Spectrometer on board the Infrared Space Observatory, we have observed for the first time the regions of Bβ 2.626 µ…
Wavelength measurements of heliumlike 1s2s 3S1-1s2p 3P0,2 transitions in Ne8+, Na9+, Mg10+, and Si12+ emitted by solar flare plasmas
Wilhelm, K.; Curdt, W.; Landi, E. +1 more
With the Solar Ultraviolet Measurements of Emitted Radiation instrument-a high-resolution normal-incidence telescope and spectrometer on board the Solar and Heliospheric Observatory-heliumlike 1s2s 3S1-1s2p 3P0,2 transitions in the highly ionized species Ne8+, Na9+, Mg10+…
An Erupting Active Region Filament: Three-Dimensional Trajectory and Hydrogen Column Density
Penn, M. J.
From 15:33 through 16:02 UT on 13 June 1998, observations of an erupting filament as it crossed solar disk center were obtained with the NSO/KPVT and SOHO/CDS instruments as part of the SOHO Joint Observing Program 70. Context observations show that this event was the eruption of the north-east section of a small active region filament associated …
Hydrogen temperature gradient in the transition region of a solar coronal hole
Wilhelm, K.; Tu, C. -Y.; Marsch, E.
The Lyman series of hydrogen was observed by SUMER on SOHO on the north polar limb of the Sun with a total exposure time of more than ten hours. The resulting line profiles have been analysed using the technique described by Marsch et al. (1999). The data analysis corroborates earlier findings on the Lyman lines, but also yields phenomena which ca…
A Study of Sunspots with Phase Time and Travel Time of P-Mode Waves in Acoustic Imaging
Chang, Hsiang-Kuang; Chou, Dean-Yi; Sun, Ming-Tsung
Solar acoustic signals constructed with the technique of acoustic imaging contain both intensity and phase information. The phase of constructed signals can be studied by computing the cross-correlation function between time series constructed with ingoing and outgoing waves. The envelope peak of the cross-correlation function provides information…
Wind-driven surface waves on Titan
Ghafoor, Nadeem A. -L.; Zarnecki, John C.; Challenor, Peter +1 more
The surface of Titan represents the largest surface area in the solar system essentially unexplored, although recent observations from Hubble Space Telescope and ground-based telescopes using adaptive optics have given perhaps the first low-resolution indications of its nature. Whilst early models citing global oceans have been all but abandoned, …
ISO Observations of Mars: An Estimate of the Water Vapor Vertical Distribution and the Surface Emissivity
de Graauw, Th.; Forget, F.; Lellouch, E. +9 more
Infrared spectra of Mars were taken with the two complementary spectrometers onboard the European Space Agency's Infrared Space Observatory (ISO), in both moderate- and high-resolution mode. From the strengths of the observed water lines we derived information about the vertical distribution of water vapor and on the emissivity of the dust/surface…
The Sombrero galaxy. III. Ionised gas and dust in the central 200 pc: a nuclear bar?
Emsellem, E.; Ferruit, P.
We present the results of new 3D TIGER spectroscopic observations and archived HST/WFPC2 and NICMOS images of the central region of M 104. The [N ii]+Hα images reveal the presence of a nuclear spiral structure, and the gaseous kinematics in the central arcsecond shows evidence for kinematical decoupling of the central peak. A straight nuclear dust…