Search Publications
Cosmic Alignment toward the Radio Einstein Ring PKS 1830-211?
Kneib, J. -P.; Lidman, C.; Meylan, G. +1 more
Optical and near-IR Hubble Space Telescope and Gemini North adaptive optics images, further improved through deconvolution, are used to explore the gravitationally lensed radio source PKS 1830-211. The line of sight to the quasar at z=2.507 appears to be very busy, with the presence, within 0.5" from the source, of (1) a possible galactic main-seq…
The Phoenix galaxy: UGC 4203 re-birth from its ashes?
Perola, G. C.; Fiore, F.; Guainazzi, M. +1 more
We report on a dramatic transition between a Compton-thick, reflection-dominated state and a Compton-thin state in the Seyfert 2 galaxy UGC 4203, discovered by comparing a recent (May 2001) XMM-Newton observation with ASCA observations performed about six years earlier. This transition can be explained either as a change in the column density of t…
Interplanetary radio emission due to interaction between two coronal mass ejections
Gopalswamy, Nat; Howard, Russell A.; Yashiro, Seiji +2 more
We report on the detection of a new class of nonthermal radio emission due to the interaction between two coronal mass ejections (CMEs). The radio emission was detected by the Radio and Plasma Wave Experiment (WAVES) on board the Wind satellite, while the CMEs were observed by the white-light coronagraphs of the Solar and Heliospheric Observatory …
Hubble Space Telescope/WFPC2 Images of the GG Tauri Circumbinary Disk
Krist, John E.; Stapelfeldt, Karl R.; Watson, Alan M.
We present the first visible wavelength images of the GG Tau circumbinary ring obtained with the Hubble Space Telescope's (HST) Wide Field and Planetary Camera 2. Scattered light from the ring is detected in both V- and I-band images. The images show that the ring is smooth, except for a small gap that could be a shadow caused by material between …
Energy Transformation Mechanism in the Solar Atmosphere Associated with Magnetofluid Coupling: Explosive and Eruptive Events
Ohsaki, Shuichi; Shatashvili, Nana L.; Yoshida, Zensho +1 more
By modeling the closed field structures in the solar atmosphere by ``slowly'' evolving double Beltrami two-fluid equilibria (created by the interaction of the magnetic and velocity fields), the conditions for catastrophic transformations of the original state are derived. The analysis for predicting sudden changes is carried out through a set of a…
The Next Geminga: Deep Multiwavelength Observations of a Neutron Star Identified with 3EG J1835+5918
Mirabal, N.; Camilo, F.; Gotthelf, E. V. +1 more
We describe Chandra, Hubble Space Telescope (HST), and radio observations that reveal a radio-quiet but magnetospherically active neutron star in the error circle of the high-energy γ-ray source 3EG J1835+5918, the brightest of the unidentified EGRET sources at high Galactic latitude. A Chandra ACIS-S spectrum of the ultrasoft X-ray source RX J183…
Interstellar Deuterium, Nitrogen, and Oxygen Abundances toward BD +28°4211: Results from the FUSE Mission
Tripp, Todd M.; Jenkins, Edward B.; Sembach, Kenneth R. +12 more
High-resolution far-UV spectra of the O-type subdwarf BD +28°4211 were obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE) to measure the interstellar deuterium, nitrogen, and oxygen abundances in this direction. The interstellar D I transitions are analyzed down to Lyι at 920.7 Å. The star was observed several times at different targe…
The Origin of Fe II and [Fe II] Emission Lines in the 4000-10000 Å Range in the BD Weigelt Blobs of η Carinae
Davidson, K.; Gull, T. R.; Bruhweiler, F. +3 more
We present numerical simulations that reproduce the salient features of the amazingly strong [Fe II] and Fe II emission spectra in the B and D Weigelt blobs of η Carinae. For our studies we have used spectra obtained during the 1998 epoch observations with the Hubble Space Telescope (HST). The spectrum of the B and D Weigelt blobs dominates in [Fe…
Radial Flows in Supergranules
Raymond, J.; Hathaway, D. H.; Han, S. +1 more
We determine the radial component of the supergranular flow velocity by examining the center-to-limb variation of the Doppler velocity signal. We acquire individual Doppler images obtained with the MDI instrument on the SOHO spacecraft and process them to remove the p-mode oscillation signal, the axisymmetric flows, the convective blueshift signal…
Discovery of complex narrow X-ray absorption features from the low-mass X-ray binary GX 13+1 with XMM-Newton
Parmar, A. N.; Sidoli, L.; Oosterbroek, T. +1 more
We report the detection of a complex of narrow X-ray absorption features from the low-mass X-ray binary GX 13+1 during 3 XMM-Newton observations in 2000 March and April. The features are consistent with being due to resonant scattering of the Kalpha and Kbeta lines of He- and H-like iron (Fe XXV and Fe XXVI) and H-like calcium (Ca XX) Kalpha . Onl…