Search Publications
Temporal evolution of two auroral arcs as measured by the Cluster satellite and coordinated ground-based instruments
Buchert, S.; Vaivads, A.; Dunlop, M. +7 more
The four Cluster s/c passed over Northern Scandinavia on 6 February 2001 from south-east to north-west at a radial distance of about 4.4 RE in the post-midnight sector. When mapped along geomagnetic field lines, the separation of the spacecraft in the ionosphere was confined to within 110km in latitude and 50km in longitude. This constellation all…
Probing the Evolution of the Galaxy Interaction/Merger Rate Using Collisional Ring Galaxies
Charmandaris, Vassilis; Lavery, Russell J.; Remijan, Anthony +2 more
We present the results from our program to determine the evolution of the galaxy interaction/merger rate with redshift using the unique star-forming characteristics of collisional ring galaxies. We have identified 25 distant collisional ring galaxy candidates (CRGCs) in a total of 162 deep Hubble Space Telescope (HST) Wide Field Planetary Camera 2…
Terminal Velocities of Luminous, Early-Type Stars in the Small Magellanic Cloud
Lennon, D. J.; Evans, C. J.; Heap, S. R. +2 more
Ultraviolet spectra from the Space Telescope Imaging Spectrograph (STIS) are used to determine terminal velocities for 11 O and B-type giants and supergiants in the Small Magellanic Cloud (SMC) from the Si IV and C IV resonance lines. Using archival data from observations with the Goddard High-Resolution Spectrograph and the International Ultravio…
On the Measurement of Elemental Abundance Ratios in Inner Galaxy H II Regions
Rubin, Robert H.; Haas, Michael R.; Colgan, Sean W. J. +2 more
Although variations in elemental abundance ratios in the Milky Way certainly exist, details remain uncertain, particularly in the inner Galaxy, where stars and H II regions in the Galactic plane are obscured optically. In this paper we revisit two previously studied, inner Galaxy H II regions: G333.6-0.2 and W43. We observed three new positions in…
INTEGRAL and XMM-Newton Spectral Studies of NGC 4388
Gehrels, N.; Petrucci, P. -O.; Walter, R. +4 more
We present INTEGRAL and XMM-Newton observations of a Seyfert galaxy, the type 2 active galactic nucleus (AGN) NGC 4388. Several INTEGRAL observations performed in 2003 allow us to study the spectrum in the 20-300 keV range. In addition, two XMM-Newton observations give detailed insight into the 0.2-10 keV emission. The measurements presented here …
On the Relationship between the Rotational Velocity and the Field Strength of Solar Magnetic Elements
Zhao, Junwei; Kosovichev, Alexander G.; Duvall, Thomas L., Jr.
By tracking various solar surface tracers, previous studies have found that magnetic structures, such as plages and sunspots, rotate faster than the quiet solar regions. We investigate how the rotational speed of these magnetic features is related to their magnetic field strength. By use of near-surface horizontal velocities inferred from time-dis…
Hubble Space Telescope Advanced Camera for Surveys Imaging of ω Centauri: Optical Counterpart for the Quiescent Low-Mass X-Ray Binary
Anderson, Jay; Heinke, Craig O.; Bailyn, Charles D. +5 more
We report the discovery of an optical counterpart to a quiescent neutron star in the globular cluster ω Centauri (NGC 5139). The star was found as part of our wide-field imaging study of ω Cen using the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope. Its magnitude and color (R625=25.2, B435-R625=1.…
The Visible and Near-Infrared Dust Opacity Law in the HH 30 Circumstellar Disk
Stapelfeldt, Karl R.; Watson, Alan M.
We present new images of the scattered-light disk around HH 30 at 0.44 and 0.81 µm. We model these images and an existing 2.04 µm image by using a multiple-scattering code, varying and fitting for the disk parameters and the dust opacity ratios at these wavelengths. A wide range of different disk geometries provide adequate fits to the…
Inner Polar Rings in Regular Lenticular Galaxies
Sil'chenko, O. K.; Afanasiev, V. L.
We have investigated a sample of S0 galaxies, mostly with circumnuclear dust lanes orthogonal to their major axes, chosen from Hubble Space Telescope Wide Field Planetary Camera 2 images. Two-dimensional spectroscopy undertaken with the Multipupil Fiber Spectrograph of the 6 m telescope of the Special Astrophysical Observatory of the Russian Acade…
Circumstellar interaction of the type Ia supernova 2002ic
Lundqvist, P.; Chevalier, R. A.; Chugai, N. N.
We propose a model to account for the bolometric light curve, the quasi-continuum and the CaII emission features of the peculiar type Ia supernova (SN) 2002ic, which exploded in a dense circumstellar envelope. The model suggests that the SN Ia had the maximum possible kinetic energy and that the ejecta expand in an approximately spherically symmet…