Search Publications
The Faint Optical Stellar Luminosity Function in the Ursa Minor Dwarf Spheroidal Galaxy
Wyse, Rosemary F. G.; Gilmore, Gerard; Feltzing, Sofia
Analyses of their internal stellar kinematics imply that the dwarf spheroidal (dSph) companion galaxies to the Milky Way are among the most dark matter-dominated systems known. Should there be significant dark matter in the form of faint stars in these systems, the stellar luminosity function must be very different from that of a similar metallici…
The Misdirected Central Engine of the Hyperluminous Infrared Galaxy and Type 2 QSO IRAS P09104+4109
Hines, Dean C.; Schmidt, Gary D.; Smith, Paul S. +2 more
Hubble Space Telescope Wide-Field Planetary Camera 2 imaging polarimetry of the hyperluminous infrared galaxy (and misdirected QSO) IRAS P09104+4109 reveals a highly polarized (p~20%) giant (~5 kpc) bipolar reflection nebula centered on the nucleus. This, together with our previous detection of broad, polarized Mg II and newly detected broad, pola…
The Extended Blue Continuum and Line Emission around the Central Radio Galaxy in Abell 2597
Koekemoer, Anton M.; Baum, Stefi A.; O'Dea, Christopher P. +5 more
We present results from detailed imaging of the centrally dominant radio elliptical galaxy in the cooling-flow cluster Abell 2597, using data obtained with the Wide Field and Planetary Camera 2 (WFPC2) on the Hubble Space Telescope (HST). This object is one of the archetypal ``blue-lobed'' cooling-flow radio elliptical galaxies, also displaying a …
Parsec-Scale Radio Structures in the Nuclei of Four Seyfert Galaxies
Kukula, Marek J.; Ghosh, Tapasi; Pedlar, Alan +1 more
We present 18 cm radio maps of four Seyfert nuclei, Mrk 1, Mrk 3, Mrk 231, and Mrk 463E, made with the European VLBI Network (EVN). Linear radio structures are present in three out of four sources on scales of ~100 pc to ~1 kpc, and the 20 mas beam of the EVN enables us to resolve details within the radio structures on scales of less than 10 pc. M…
Transition-Region Network Boundaries in the Quiet Sun: Width Variation with Temperature as Observed with CDS on SOHO
Vial, J. -C.; Patsourakos, S.; Gabriel, A. H. +1 more
We report here the results of a study of the temperature variation of the network boundary thicknesses in the quiet-Sun transition region. A Fourier-based two-dimensional autocorrelation method has been applied to 240''×240'' rasters obtained in several transition-region lines by the CDS spectrometer on SOHO. The quantitative…
Large-Scale Flows in the Solar Interior: Effect of Asymmetry in Peak Profiles
Basu, Sarbani; Antia, H. M.
Ring diagram analysis can be used to study large-scale velocity fields in the outer part of the solar convection zone. All previous works assume that the peak profiles in the solar oscillation power spectrum are symmetrical. However, it has now been demonstrated that the peaks are not symmetrical. In this work we study how the explicit use of asym…
Sunspot Transition Region Oscillations in NOAA 8156
Wilhelm, K.; Kjeldseth-Moe, O.; Brynildsen, N. +2 more
Based on observations obtained with the Solar and Heliospheric Observatory joint observing program for velocity fields in sunspot regions, we have detected 3 minute transition region umbral oscillations in NOAA 8156. Simultaneous recordings of O V λ629 and N V λ1238, λ1242 with the SUMER instrument give the spatial distribution of power in the 3 m…
A 2.3 Day Periodic Variability in the Apparently Single Wolf-Rayet Star WR 134: Collapsed Companion or Rotational Modulation?
Moffat, Anthony F. J.; St-Louis, Nicole; Koenigsberger, Gloria +8 more
The apparently single WN 6 type star WR 134 (HD 191765) is distinguished among the Wolf-Rayet star population by its strong, presumably cyclical (\Pscr~2.3 day) spectral variations. A true periodicity--which is still very much debated--would render WR 134 a prime candidate for harboring either a collapsed companion or a rotating, large-scale, inho…
SUMER Observations of the Quiet-Sun Transition Region
Siegmund, O. H. W.; Fisher, G. H.; Griffiths, N. W. +1 more
We present new results from observations of the quiet Sun taken with the SUMER spectrograph on the SOHO spacecraft. This study includes line and continuum emission covering a wide range of temperatures, and the data have been used to create a number of intensity maps with a field of view of ~60''×300'' and a spatial resolutio…
Analysis of the HIPPARCOS Measurements of upsilon Andromedae: A Mass Estimate of Its Outermost Known Planetary Companion
Mazeh, Tsevi; van Leeuwen, Floor; Zucker, Shay +1 more
We present an analysis of Hipparcos astrometric measurements of υ Andromedae, a nearby main-sequence star around which three planet candidates have recently been discovered by means of radial velocity measurements. The stellar orbit associated with the outermost candidate has a period of 1269+/-9 days and a minimum semimajor axis of 0.6 mas. Using…