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Comparison between KPVT/SPM and SoHO/MDI magnetograms with an application to solar irradiance reconstructions
Solanki, S. K.; Krivova, N. A.; Wenzler, T. +1 more
To be able to use both space- and ground-based solar magnetograms and construct long time series of derived parameters it is important to cross-calibrate them so that we can estimate their reliability and combine them. Using two different techniques, we compare magnetograms as well as continuum images recorded by the Spectropolarimeter (SPM) on Ki…
Monte Carlo simulations of the halo white dwarf population
Burkert, A.; Torres, S.; Isern, J. +1 more
The interpretation of microlensing results towards the Large Magellanic Cloud (LMC) still remains controversial. While white dwarfs have been proposed to explain these results and, hence, to contribute significantly to the mass budget of our Galaxy, there are also several constraints on the role played by white dwarfs. In this paper we analyze sel…
Kinetic parameters of interstellar neutral helium: updated results from the ULYSSES/GAS-instrument
Rosenbauer, H.; Witte, M.; Banaszkiewicz, M. +1 more
The GAS-instrument onboard the space probe ULYSSES (ULS) is designed to measure the local angular distribution of the flow of interstellar neutral He-atoms within ≈3 AU distance from the sun; it allows to infer the kinetic parameters (velocity vector, temperature and density) of these particles outside the heliosphere ("at infinity"). Around the s…
A Chandra View of the Morphological and Spectral Evolution of Supernova Remnant 1987A
Zhekov, Svetozar A.; Garmire, Gordon P.; Park, Sangwook +2 more
We present an update on the results of our monitoring observations of the X-ray remnant of supernova (SN) 1987A with Chandra. As of 2002 December, we have performed a total of seven observations of SN 1987A, which allows us to monitor the details of the earliest stage of the supernova remnant evolution in X-rays. The high angular resolution images…
Recycling of the Solar Corona's Magnetic Field
Longcope, D. W.; Priest, E. R.; Parnell, C. E. +1 more
Magnetic fields play a dominant role in the atmospheres of the Sun and other Sun-like stars. Outside sunspot regions, the photosphere of the so-called quiet Sun contains myriads of small-scale magnetic concentrations, with strengths ranging from the detection limit of ~1016 Mx up to ~3×1020 Mx. The tireless motion of these ma…
Unraveling the Helix Nebula: Its Structure and Knots
O'Dell, C. R.; Meixner, Margaret; McCullough, Peter R.
Through Hubble Space Telescope (HST) imaging of the inner part of the main ring of the Helix Nebula, together with CTIO 4 m images of the fainter outer parts, we have a view of unprecedented quality of the nearest bright planetary nebula. These images have allowed us to determine that the main ring of the nebula is composed of an inner disk of abo…
ESO 3060170: A Massive Fossil Galaxy Group with a Heated Gas Core?
Hornstrup, A.; Vikhlinin, A.; Forman, W. +3 more
We present a detailed study of the ESO 3060170 galaxy group, combining Chandra, XMM-Newton, and optical observations. The system is found to be a fossil galaxy group. The group X-ray emission is composed of a central, dense, cool core (10 kpc in radius) and an isothermal medium beyond the central 10 kpc. The region between 10 and 50 kpc (the cooli…
EUVE observations of the helium glow: Interstellar and solar parameters
Lallement, R.; Lemoine, M.; Vallerga, J. +2 more
We present new observations of the diffuse He I 58.4 nm background recorded in 1998 and 2000 by the Extreme Ultraviolet Explorer (EUVE). This emission is due to resonant scattering of the solar EUV radiation by interstellar and geocoronal helium. Depending on the geometry and relative velocity, a fraction of the interstellar helium glow can be abs…
Arrival time of halo coronal mass ejections in the vicinity of the Earth
Gopalswamy, N.; Lara, A.; Manoharan, P. K. +1 more
We describe an empirical model to predict the 1-AU arrival time of halo CMEs. This model is based on the effective acceleration described by Gopalswamy et al. (\cite{Gopalswamy00}a, Geophys. Res. Lett., 27, 145). We verify the Helios/Pioneer Venus Orbiter(PVO) estimation of the effective acceleration profile (Gopalswamy et al. \cite{Gopalswamy01}a…
Fe II/Mg II Emission-Line Ratios of QSOs. II. z > 6 Objects
Doi, Mamoru; Yoshii, Yuzuru; Motohara, Kentaro +4 more
Near-infrared spectra of four QSOs located at z>6 are obtained with the OH-airglow suppressor mounted on the Subaru telescope. The Fe II/Mg II emission-line ratios of these QSOs are examined by the same fitting algorithm as in our previous study of z<5.3 QSOs. The fitting results show that two out of the four z>6 QSOs have significant Fe …