Search Publications
New Constraints on the Continuum Emission Mechanism of Active Galactic Nuclei: Intensive Monitoring of NGC 7469 in the X-Ray and Ultraviolet
Malkan, M. A.; Nandra, K.; Clavel, J. +5 more
We have undertaken near-continuous monitoring of the Seyfert 1 galaxy NGC 7469 in the X-ray with RXTE over a ~30 day baseline. The source shows strong variability with a root mean square (rms) amplitude of ~16% and peak-to-peak variations of a factor of order 2. Simultaneous data over this period were obtained in the ultraviolet (UV) using IUE, ma…
Hubble Space Telescope Goddard High Resolution Spectrograph Observations of the Be + sdO Binary φ Persei
Gies, Douglas R.; Peters, Geraldine J.; Ferrara, Elizabeth C. +4 more
Mass transfer during the evolution of intermediate-mass stars in a close binary system can result in a rejuvenated and spun-up secondary star (which may appear as a rapidly rotating Be star) orbiting an unseen, stripped-down, remnant companion. One of the best candidates for such a system is the long-period (127 days) binary φ Per. Here we present…
Quantitative Morphology of Galaxies in the Hubble Deep Field
Simard, Luc; Marleau, Francine R.
We measure quantitative structural parameters of galaxies in the Hubble deep field (HDF) on the drizzled F814W images. Our structural parameters are based on a two-component surface brightness made up of a Sérsic profile and an exponential profile. We compare our results to the visual classification of van den Bergh et al. and the C-A classificati…
Broad P V Absorption in the QSO PG 1254+047: Column Densities, Ionizations, and Metal Abundances in Broad Absorption Line Winds
Hamann, Fred
This paper discusses the detection of P V λλ1118, 1128 and other broad absorption lines (BALs) in archival Hubble Space Telescope spectra of the low-redshift BAL QSO PG 1254+047. The P V identification is secured by excellent redshift and profile coincidences with the other BALs, such as C IV λλ1548, 1550 and Si IV λλ1393, 1403, and by photoioniza…
Exploring Cluster Elliptical Galaxies as Cosmological Standard Rods
Saglia, R. P.; Bender, Ralf; Greggio, Laura +4 more
We explore the possibility of calibrating massive cluster elliptical galaxies as cosmological standard rods using the fundamental plane relation combined with a correction for luminosity evolution. Although cluster ellipticals certainly formed in a complex way, their passive evolution out to redshifts of about 1 indicates that basically all major …
Multimodal Distributions along the Horizontal Branch
Ferraro, Francesco R.; Paltrinieri, Barbara; Fusi Pecci, Flavio +2 more
We report on the Hubble Space Telescope (HST) Wide Field Planetary Camera 2 (WFPC2) U, V, and far-ultraviolet observations of three galactic globular clusters (GGCs), NGC 5272 = M3, NGC 6205 = M13, and NGC 6093 = M80. Two of these clusters (namely, M13 and M80) have horizontal-branch (HB) tails that extend to the helium-burning main sequence, with…
An Infrared Einstein Ring in the Gravitational Lens PG 1115+080
Peng, C. Y.; Keeton, C. R.; Kochanek, C. S. +5 more
Hubble Space Telescope observations of the gravitational lens PG 1115+080 in the infrared show the known zl = 0.310 lens galaxy and reveal the zs = 1.722 quasar host galaxy. The main lens galaxy G is a nearly circular (ellipticity ɛ < 0.07) elliptical galaxy with a de Vaucouleurs profile and an effective radius of Re<…
NICMOS Imaging of the Nuclei of Arp 220
Scoville, N. Z.; Evans, A. S.; Schneider, G. +8 more
We report high-resolution imaging of the ultraluminous infrared galaxy Arp 220 at 1.1, 1.6, and 2.22 µm with the Near-Infrared Camera and Multiobject Spectrometer on the Hubble Space Telescope. The diffraction-limited images at 0.1"-0.2" resolution clearly resolve both nuclei of the merging galaxy system and reveal for the first time a numbe…
Asymmetry in Velocity and Intensity Helioseismic Spectra: A Solution to a Long-standing Puzzle
Kosovichev, A. G.; Scherrer, P. H.; Schou, J. +1 more
We give an explanation for the opposite sense of asymmetry of the solar acoustic mode lines in velocity and intensity oscillation power spectra, thereby solving the half-decade-old puzzle of Duvall and coworkers. The solution came after comparing the velocity and intensity oscillation data of medium angular degree l obtained from the Michelson Dop…
Photospheric Magnetic Field Changes Associated with Transition Region Explosive Events
Wang, Haimin; Chae, Jongchul; Schühle, Udo +2 more
From a comparison of the Solar and Heliospheric Observatory SUMER spectral data and a time series of Big Bear Solar Observatory magnetograms, we present observational clues to the physical origin of transition region explosive events. First, explosive events rarely occur in the interior of strong magnetic flux concentrations but rather are prefere…