Search Publications
First Optical Images of Circumstellar Dust Surrounding the Debris Disk Candidate HD 32297
Kalas, Paul
Near-infrared imaging with the Hubble Space Telescope recently revealed a circumstellar dust disk around the A star HD 32297. Dust-scattered light is detected as far as 400 AU radius, and the linear morphology is consistent with a disk ~10° away from an edge-on orientation. Here we present the first optical images that show the dust-scattered ligh…
A bar signature and central disc in the gaseous and stellar velocity fields of NGC 5448
Emsellem, Eric; van de Ven, Glenn; Peletier, Reynier F. +4 more
We analyse Spectrographic Areal Unit for Research on Optical Nebulae (SAURON) kinematic maps of the inner kiloparsec of the early-type (Sa) barred spiral galaxy NGC 5448. The observed morphology and kinematics of the emission-line gas is patchy and perturbed, indicating clear departures from circular motion. The kinematics of the stars is more reg…
Non-LTE Model Atmosphere Analysis of the Large Magellanic Cloud Supersoft X-Ray Source CAL 83
Rasmussen, Andrew P.; Paerels, Frits; Hubeny, Ivan +3 more
We present a non-LTE (NLTE) model atmosphere analysis of Chandra High Resolution Camera (HRC-S) and Low Energy Transmission Grating (LETG) and XMM-Newton Reflection Grating Spectrometer (RGS) spectroscopy of the prototypical supersoft source CAL 83 in the Large Magellanic Cloud. Taken with a 16 month interval, the Chandra and XMM-Newton spectra ar…
Star Cluster Survival in Star Cluster Complexes under Extreme Residual Gas Expulsion
Kroupa, P.; Fellhauer, M.
After the stars of a new, embedded star cluster have formed, they blow the remaining gas out of the cluster. Especially winds of massive stars and definitely the onset of the first supernovae can remove the residual gas from a cluster. This leads to a very violent mass loss and leaves the cluster out of dynamical equilibrium. Standard models predi…
Spherical harmonic decomposition of solar magnetic fields
Stenflo, J. O.; Knaack, R.
We have investigated the temporal evolution of large-scale magnetic fields in the solar photosphere during the time interval 1966-2004 by means of spherical harmonic decomposition and subsequent time series analysis. Two data sets of daily magnetograms recorded at the Mt. Wilson and Kitt Peak observatories were used to calculate the spherical harm…
Detailed comparison of downflows seen both in EIT 30.4 nm and Big Bear Hα movies
Berghmans, D.; Poedts, S.; de Groof, A. +2 more
An EIT shutterless campaign was conducted on 11 July 2001 and provided 120 high-cadence (68 s) 30.4 nm images of the north-eastern quarter of the Sun. Systematic intensity variations are seen which appear to propagate along an off-disk loop-like structure. In this paper we study the nature of these intensity variations by confronting the EIT obser…
Weak-line T Tauri stars: circumstellar disks and companions. I. Spectral energy distributions and infrared excesses
Ray, T. P.; Gras-Velázquez, À.
We have analysed new infrared photometric data taken by the Infrared Space Observatory, in combination with 2MASS data where available, of 12 weak-line T Tauri stars (WTTS), belonging to different molecular clouds. A control study of 6 classical T Tauri stars (CTTS) for comparison with IRAS data has also been made. WTTS traditionally are not expec…
Color-Magnitude Diagrams and Luminosity Functions Down to the Hydrogen-Burning Limit. III. A Preliminary Hubble Space Telescope Study of NGC 6791
Anderson, Jay; Bedin, Luigi R.; Piotto, Giampaolo +2 more
Using Hubble Space Telescope Advanced Camera for Surveys Wide Field Channel images, we derive the color-magnitude diagram of the old, metal-rich open cluster NGC 6791 to nearly 29th magnitude in V, which is the neighborhood of the hydrogen-burning limit. Comparison with isochrones leads to a discussion of the distance modulus, the reddening, and t…
The inner magnetosphere of Saturn: Cassini RPWS cold plasma results from the first encounter
Gurnett, D. A.; Persoon, A. M.; Hospodarsky, G. B. +12 more
We present new results from the inner magnetosphere of Saturn obtained by the Radio and Plasma Wave Science (RPWS) investigation onboard Cassini around the period of the Saturn orbit injection (July 1, 2004). Plasma wave electric field emissions, voltage sweeps by the Langmuir probe (LP) and radio sounder data were used to infer the cold plasma (&…
An XMM-Newton observation of Mkn 3 - a Seyfert galaxy just over the edge
Page, K. L.; Pounds, K. A.
A 100-ks XMM-Newton observation of the nearby Seyfert 2 galaxy Mkn 3 offers a unique opportunity to explore the complexity of its X-ray spectrum. We find the ~3-8 keV continuum to be dominated by reflection from cold matter, with fluorescent K-shell lines detected from Ni, Fe, Ca, Ar, S, Si and Mg. At higher energies an intrinsic power-law continu…