Search Publications
Spectroscopic measurement of the plasma electron density and outflow velocity in a polar coronal hole
Giordano, S.; Antonucci, E.; Noci, G. +2 more
A new spectroscopic method, aimed to derive the plasma electron density and outflow velocity in expanding solar coronal regions, is discussed in this paper. The method is based on the analysis of a pair of coronal lines emitted via collisional and radiative excitation by the same ion, such as the O VI 1032, 1037 Å, doublet. The merit of this techn…
Effect of spatial resolution on estimating the Sun's magnetic flux
Solanki, S. K.; Krivova, N. A.
A critical question related to a possible secular trend in the Sun's total magnetic flux and consequently in solar irradiance is the total amount of magnetic flux present on the Sun and how it is distributed between active regions and the quiet Sun. NSO/Kitt Peak synoptic charts have in the past been used to estimate the total flux and the fractio…
The nuclear ring in the unbarred galaxy NGC 278: Result of a minor merger?
Knapen, J. H.; van der Hulst, J. M.; de Blok, W. J. G. +1 more
We present fully sampled high angular resolution two-dimensional kinematics in the Hα spectral line, optical and near-infrared imaging, as well as 21 cm atomic hydrogen data of the spiral galaxy NGC 278. This is a small non-barred galaxy, which has a bright star forming inner region of about 2 kpc in diameter, reminiscent of nuclear rings seen mai…
HST/STIS high resolution echelle spectra of α Centauri A (G2 V)
Pagano, I.; Linsky, J. L.; Valenti, J. +1 more
We describe and analyze HST/STIS observations of the G2 V star α Centauri A (
High-amplitude, long-term X-ray variability in the solar-type star HD 81809: The beginning of an X-ray activity cycle?
Schmitt, J. H. M. M.; Güdel, M.; Harnden, F. R., Jr. +5 more
We present the initial results from our XMM-Newton program aimed at searching for X-ray activity cycles in solar-type stars. HD 81809 is a G2-type star (somewhat more evolved than the Sun, and with a less massive companion) with a pronounced 8.2 yr chromospheric cycle, as evident from from the Mt. Wilson program data. We present here the results f…
Automatic detection of arcs and arclets formed by gravitational lensing
Schindler, S.; Lenzen, F.; Scherzer, O.
We present an algorithm developed particularly to detect gravitationally lensed arcs in clusters of galaxies. This algorithm is suited for automated surveys as well as individual arc detections. New methods are used for image smoothing and source detection. The smoothing is performed by so-called anisotropic diffusion, which maintains the shape of…
Dust and super star clusters in NGC 5253
Sauvage, M.; Vanzi, L.
We present new observations of the famous starburst galaxy NGC 5253 which owes its celebrity to possibly being the youngest and closest starburst galaxy known. Our observations in the infrared and millimeter contribute to shed light on the properties of this interesting object. We have used our new data along with data from the literature to study…
Detection of a companion to the pulsating sdB Feige 48
Heber, U.; Benjamin, R. A.; O'Toole, S. J.
We present the discovery of a binary companion to the pulsating sdB Feige 48. Using HST/STIS and archival FUSE spectra, we measure a period of 0.376±0.003 d and a velocity semi-amplitude of 28.0±0.2 km s-1. This implies that the companion star must either be of very low mass, or the orbit is at low inclination. Combining 2MASS fluxes, t…
A Chandra observation of the old open cluster M 67
Tagliaferri, G.; Belloni, T.; van den Berg, M. +1 more
We present the results of a 47-ks Chandra-ACIS observation of the old open cluster
Balltracking: An highly efficient method for tracking flow fields
Potts, H. E.; Barrett, R. K.; Diver, D. A.
We present a method for tracking solar photospheric flows that is highly efficient, and demonstrate it using high resolution MDI continuum images. The method involves making a surface from the photospheric granulation data, and allowing many small floating tracers or balls to be moved around by the evolving granulation pattern. The results are tes…