Search Publications
Solar hydrogen-Lyman continuum observations with SOHO/SUMER
Vial, J. -C.; Parenti, S.; Lemaire, P.
In this work we analyze the emission of the H Lyman continuum (HI LyC) in the Quiet Sun (QS) and a solar prominence, in order to derive information on the temperature of the emitting plasma. We used the spectral atlas obtained with SOHO/SUMER detector A in 1999 (Parenti et al. 2005, A&A, 443, 679). The high spectral resolution of this instrume…
Cluster and Double Star observations of dipolarization
Balogh, A.; Zhang, T. L.; Dandouras, I. +15 more
We studied two types of dipolarization events with different IMF conditions when Cluster and Double Star (TC-1) were located in the same local time sector: 7 August 2004, 18:00-24:00 UT, during a disturbed southward/northward IMF interval, and 14 August 2004, 21:00-24:00 UT, when the IMF was stably northward. Cluster observed dipolarization as wel…
A Study of the Near-Ultraviolet Spectrum of Vega
Hubeny, Ivan; Allende Prieto, Carlos; García López, Ramón J. +1 more
UV, optical, and near-IR spectra of Vega have been combined to test our understanding of stellar atmospheric opacities and to examine the possibility of constraining chemical abundances from low-resolution UV fluxes. We have carried out a detailed analysis assuming local thermodynamic equilibrium (LTE) to identify the most important contributors t…
Faint Blue Objects in the Hubble Deep Field-South Revealed: White Dwarfs, Subdwarfs, and Quasars
Winget, D. E.; Kilic, Mukremin; von Hippel, Ted +1 more
We explore the nature of the faint blue objects in the Hubble Deep Field-South. We have derived proper motions for the point sources in the Hubble Deep Field-South using a 3 yr baseline. Combining our proper-motion measurements with spectral energy distribution fitting enabled us to identify four quasars and 42 stars, including three white dwarf c…
Hα Stokes V/I Features Observed in a Solar Active Region
Hanaoka, Yoichiro
We carried out an imaging polarimetry observation of active region NOAA 10596 at 9-11 wavelengths around the Hα line with a ferroelectric liquid-crystal polarimeter during 2004 April 20-26. The latitude of the region was S8°, and it passed the central meridian on April 23. On the basis of this observation, the Stokes V/I features of the active reg…
85 Peg A: what age for a low-metallicity solar-like star?
Cardini, D.; D'Antona, F.; Montalbán, J. +3 more
We explore the possible evolutionary status of the primary component of the binary 85 Pegasi, listed as a target for asteroseismic observations by the MOST satellite. In spite of the assessed `subdwarf' status, and of the accurate distance determination from the Hipparcos data, the uncertainties in the metallicity and age, coupled with the uncerta…
Properties of a Sunspot Plume Observed With the Coronal Diagnostic Spectrometer Aboard the Solar and Heliospheric Observatory
Landi, Enrico; Brosius, Jeffrey W.
We used three instruments (CDS, EIT, MDI) aboard the Solar and Heliospheric Observatory spacecraft to observe the large sunspot in NOAA Active Region 8539 on 1999 May 9 and 13. The spot contained a bright plume, most easily seen in EUV emission lines formed at 5.2<~logT<~5.7 (where T is the temperature in K), in its umbra on both dates. The …
The FERRUM project: experimentally determined metastable lifetimes and transition probabilities for forbidden [TiII] lines observed in η Carinae
Lundberg, H.; Johansson, S.; Hartman, H. +7 more
In the spectrum of an emission-line region ejected from the massive star Eta Carinae, called the strontium filament (SrF), forbidden lines from many elements, in particular [SrII] and [TiII], are observed. These lines are strong in this specific region and valuable for plasma diagnostics. Forbidden lines are not easily produced in laboratory light…
The influence of internal magnetic layers on the frequencies of solar p-modes
Foullon, C.; Roberts, B.
Buried magnetic fields at the base of the convection zone and in the anchoring zones of sunspots are presumed to vary over the solar activity cycle. Their effect on p-mode oscillations is explored in detail, through theoretical modelling. The helioseismic signature from a "tachocline" or "shallow" horizontal layer of magnetic field, buried in a pl…
Line broadening of EUV lines across the Solar limb: A spicule contribution?
Doyle, J. G.; Madjarska, M. S.; Xia, L. D. +1 more
Spectral lines formed in the solar transition region show an increase in the line width, peaking at ≈10 000 km above the limb. Looking at a region off-limb with no obvious spicules, the non-spicule region has a significantly smaller line width above 6000 km compared those taken in a spicule region. We suggest that this increase in line broadening …