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Improved oscillator strengths and wavelengths in Hf II, with applications to stellar elemental abundances

Nilsson, H.; Leckrone, D. S.; Lundberg, H. +4 more

Aims. We present new and improved radiative lifetimes for eight levels in Hf I and 18 levels in Hf II, along with oscillator strengths and wavelengths for 195 transitions in Hf II. With these data we determine the abundance of hafnium in two chemically peculiar stars: the hot-Am star HR 3383 and the HgMn star χ Lupi, and discuss the implications o…

Magnetic structure of the solar transition region as observed in various ultraviolet lines emitted at different temperatures

Tu, C. -Y.; Marsch, E.; He, J. -S. +1 more

Aims.The structure of the solar transition region (TR) in a polar coronal hole of the Sun is studied. In particular, the detailed association of the coronal magnetic field (carpet) with the radiance patterns of the TR, when seen in various far ultraviolet (FUV) emission lines, is investigated.
Methods: .A detailed comparison is made of the cor…

Near-infrared adaptive optics dissection of the core of NGC 1068 with NAOS-CONICA

Rouan, D.; Gendron, E.; Fusco, T. +4 more

We present an update analysis of recent near-infrared adaptive optics observations of NGC 1068 obtained with NAOS-CONICA at VLT/UT4. Ks, L' and M' bands images were deconvolved using MISTRAL, a regularized algorithm based on a maximum a posteriori estimation of the object. Two regularization methods, one including a new maximum …

A short hard X-ray flare from the blazar NRAO 530 observed by INTEGRAL

Maraschi, L.; Ghisellini, G.; Pian, E. +6 more

We report about a short flare from the blazar NRAO 530 occurred on 17 February 2004 and detected serendipitously by the IBIS/ISGRI detector on board INTEGRAL. In the 20-40 keV energy range, the source, that is otherwise below the detection limit, is detected at a level of ≈2 × 10^-10 erg cm^-2 s^-1 during a time inter…

Large-scale horizontal flows in the solar photosphere. I. Method and tests on synthetic data

Švanda, M.; Sobotka, M.; Klvaňa, M.

We propose a useful method for mapping large-scale velocity fields in the solar photosphere. It is based on the local

correlation tracking algorithm when tracing supergranules in full-disc dopplergrams. The method was developed using synthetic data.

The data are transformed during the data processing into a suitable coordinate system, th…

Tests of stellar model atmospheres by optical interferometry. III. NPOI and VINCI interferometry of the M0 giant γ Sagittae covering 0.5-2.2 µm

Wittkowski, M.; Hummel, C. A.; Roccatagliata, V. +1 more

Context: .Optical interferometry allows a measurement of the intensity profile across a stellar disc, leading to a direct test and calibration of theoretical model atmospheres as well as to a precise determination of fundamental stellar parameters.
Aims: .We present a comparison of the visual and near-infrared intensity profile of the M0 giant…

Sensitivity of solar off-limb line profiles to electron density stratification and the velocity distribution anisotropy

Solanki, S. K.; Raouafi, N. -E.

The effect of the electron density stratification on the intensity profiles of the H I Ly-α line and the O VI and Mg X doublets formed in solar coronal holes is investigated. We employ an analytical 2-D model of the large scale coronal magnetic field that provides a good representation of the corona at the minimum of solar activity. We use the mas…

Spectral line width decrease in the solar corona: resonant energy conversion from Alfvén to acoustic waves

Oliver, R.; Zaqarashvili, T. V.; Ballester, J. L.

Context: .Observations reveal an increase with height of the line width of several coronal spectral lines probably caused by outwardly propagating Alfvén waves. However, the spectral line width sometimes shows a sudden decrease at a height ~0.1-0.2 R_⊙, where the ratio of sound to Alfvén speeds may approach unity.
Aims: .To explain t…

Study of an extended EUV filament using SoHO/SUMER observations of the hydrogen Lyman lines

Heinzel, P.; Anzer, U.; Schmieder, B. +1 more

Context: .In previous work we determined the 3D structure of an EUV extension of the filament observed by SoHO/CDS on 15 October 1999. The determination of the 3D structure depends on the optical thickness τ₉₁₂ at the hydrogen Lyman-continuum edge at 912 Å. The τ₉₁₂ value was unknown, therefore it was taken as a free paramete…

The faint 2005 hard state outburst of Aquila X-1 seen by INTEGRAL and RXTE

Rodriguez, J.; Corbel, S.; Shaw, S. E.

We report on the spectral analysis of RXTE and INTEGRAL data of the 2005 April outburst of the transient Atoll source Aql X-1. Although this outburst is one of the faintest ever detected for this source in the soft X-rays (RXTE/ASM), one of our INTEGRAL observations, taken close to the soft X-ray peak, shows that the source flux was quite high, wi…