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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 …
Blinker/macro-spicule activity in an off-limb polar region
Doyle, J. G.; Banerjee, D.; O'Shea, E.
Using measurements of O V 629.73 Å from the Coronal Diagnostic Spectrometer (CDS) on board SOHO we report on blinker activity in off-limb regions above the Northern pole of the Sun. The blinkers are found to be occurring above a region showing strong dynamic activity, with evidence for evacuation of plasma. The presence of blinkers is discussed in…
Thermal and Nonthermal Nature of the Soft Excess Emission from Sérsic 159-03 Observed with XMM-Newton
Kaastra, Jelle S.; Bonamente, Massimiliano; Lieu, Richard +2 more
Several nearby clusters exhibit an excess of soft X-ray radiation that cannot be attributed to the hot virialized intracluster medium. There is no consensus to date on the origin of the excess emission: it could be either of thermal origin or due to an inverse Compton scattering of the cosmic microwave background. Using high-resolution XMM-Newton …
Young Stars and Dust in AFGL 437: Hubble Space Telescope NICMOS Polarimetric Imaging of an Outflow Source
Hines, Dean C.; Meakin, Casey A.; Thompson, Roger I.
We present near-infrared broadband and polarimetric images of the compact star-forming cluster AFGL 437 obtained with the NICMOS instrument on board HST. Our high-resolution images reveal a well-collimated bipolar reflection nebulosity in the cluster and allow us to identify WK 34 as the illuminating source. The scattered light in the bipolar nebu…
Magnetic Twist of an Extreme-Ultraviolet Coronal Loop Inferred from Plasma Constriction
Moon, Yong-Jae; Chae, Jongchul
Magnetic twist is a very likely way of constricting coronal plasma into loops. An attempt is made to determine the magnetic twist that can explain the constriction of coronal loops indirectly from observations. We decompose the coronal magnetic field into a large-scale magnetic field and a small-scale magnetic field. The large-scale field is assum…