Search Publications
Missions
Journals
Publication Years
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…
The Spectral Evolution of Transient Anomalous X-Ray Pulsar XTE J1810-197
Gotthelf, E. V.; Halpern, J. P.
We present a multiepoch spectral study of the transient anomalous X-ray pulsar XTE J1810-197 obtained with the X-Ray Multi-Mirror Mission (XMM-Newton). Four observations taken over the course of a year reveal strong spectral evolution as the source fades from outburst. The origin of this is traced to the individual decay rates of the pulsar's spec…
The ACS Virgo Cluster Survey. IV. Data Reduction Procedures for Surface Brightness Fluctuation Measurements with the Advanced Camera for Surveys
Jordán, Andrés; Tonry, John L.; Côté, Patrick +7 more
The Advanced Camera for Surveys (ACS) Virgo Cluster Survey is a large program to image 100 early-type Virgo galaxies using the F475W and F850LP bandpasses of the Wide Field Channel of the ACS instrument on the Hubble Space Telescope (HST). The scientific goals of this survey include an exploration of the three-dimensional structure of the Virgo Cl…
The Core of NGC 6240 from Keck Adaptive Optics and Hubble Space Telescope NICMOS Observations
Antonucci, R.; Schneider, G.; Canalizo, G. +4 more
We present results of near-infrared imaging of the disk-galaxy merger NGC 6240 using adaptive optics on the Keck II telescope and reprocessed archival data from NICMOS on the Hubble Space Telescope. Both the northern and southern nuclei of NGC 6240 are clearly elongated, with considerable substructure within each nucleus. In K' band there are at l…
A Near-Solar Metallicity, Nitrogen-deficient Lyman Limit Absorber Associated with Two S0 Galaxies
Bowen, David V.; Tripp, Todd M.; Jenkins, Edward B. +1 more
The UV spectrum of the bright quasar PHL 1811 at zem=0.192 reveals a foreground gas system at z=0.080923 with logN(HI)=17.98+/-0.05. We have determined the abundances of various atomic species in this system from a spectrum covering the wavelength range 1160-1730 Å recorded at 7 km s-1 resolution by the E140M grating of the S…