Search Publications
Dynamical Characteristics of Small-Scale Hα Upflow Events on the Quiet Sun
Wang, Haimin; Chae, Jongchul; Lee, Chik-Yin
Studies of small-scale dynamical features on the quiet Sun are crucial for understanding the energetics and mass supply in the chromosphere and corona. Recent works by Wang and coworkers revealed the existence of numerous short-lived upflow events in Hα on the quiet Sun. In this paper we examine in detail the dynamical characteristics of these Hα …
Numerical Simulations of Oscillation Modes of the Solar Convection Zone
Kosovichev, A. G.; Georgobiani, D.; Nigam, R. +2 more
We use the three-dimensional hydrodynamic code of Stein & Nordlund to realistically simulate the upper layers of the solar convection zone in order to study physical characteristics of solar oscillations. Our first result is that the properties of oscillation modes in the simulation closely match the observed properties. Recent observations fr…
A Multiwavelength Campaign on γ Cassiopeiae. IV. The Case for Illuminated Disk-enhanced Wind Streams
Smith, Myron A.; Cranmer, Steven R.; Robinson, Richard D.
On 1996 March 14-15 we conducted a campaign with the Hubble Space Telescope GHRS to observe the Si IV λλ1394, 1403 lines of the B0.5e star γ Cas at high temporal and spectral resolution. As a part of this ~22 hr campaign, the Rossi X-Ray Timing Explorer (RXTE) was also used to monitor this star's copious and variable X-ray emission. In this fourth…
Hubble Space Telescope Observations of the Luminous Blue Variable/W-R Eclipsing Binary System HD 5980
Walborn, Nolan R.; Morrell, Nidia; Niemela, Virpi S. +5 more
We report the results of Hubble Space Telescope STIS observations of the intriguing luminous blue variable/Wolf-Rayet binary system HD 5980 in the Small Magellanic Cloud. Although its spectral characteristics (WN6) are currently very similar to those observed in 1995 in the FUV, some of the line fluxes continue with the increasing trend observed s…
ASCA Observation of the Quiescent X-Ray Counterpart to SGR 1627-41
Hurley, K.; Sugizaki, M.; Kouveliotou, C. +9 more
We present a 2-10 keV ASCA observation of the field around the soft gamma repeater SGR 1627-41. A quiescent X-ray source, whose position is consistent both with that of a recently discovered BeppoSAX X-ray source and with the Interplanetary Network localization for this soft gamma repeater, was detected in this observation. In 2-10 keV X-rays, the…
High-Resolution Study of Associated C IV Absorption Systems in NGC 5548
Srianand, R.
We present the results of a careful analysis of associated absorption systems toward NGC 5548. Most of the well-resolved narrow components in the associated system, defined by the Lyα, C IV, and N V profiles, show velocity separation similar (to within 10 km s-1) to the C IV doublet splitting. We estimate the chance probability of the o…
A Search for Broad Infrared Recombination Lines in NGC 1068
Lutz, D.; Genzel, R.; Sturm, E. +12 more
We report infrared spectroscopy of the prototypical Seyfert 2 galaxy NGC 1068, aiming at detection of broad components of hydrogen recombination lines that originate in the obscured broad-line region. Using the Short Wavelength Spectrometer on board the Infrared Space Observatory, we have observed for the first time the regions of Bβ 2.626 µ…
A Study of Sunspots with Phase Time and Travel Time of P-Mode Waves in Acoustic Imaging
Chang, Hsiang-Kuang; Chou, Dean-Yi; Sun, Ming-Tsung
Solar acoustic signals constructed with the technique of acoustic imaging contain both intensity and phase information. The phase of constructed signals can be studied by computing the cross-correlation function between time series constructed with ingoing and outgoing waves. The envelope peak of the cross-correlation function provides information…
Mid-Infrared Infrared Space Observatory Spectroscopy of the Prototypical LINER NGC 1052: Shocks Reconsidered
Sugai, H.; Malkan, M. A.
We have observed the prototypical LINER NGC 1052 with the Infrared Space Observatory Short-Wavelength Spectrometer. While we have detected the [Ne II] 12.8 µm line, we have obtained a strict upper limit for the [Ne III] 15.6 µm line. A large [Ne II]/[Ne III] line ratio and small [Ne III]/[O III] λ5007 and [Ne II]/[OIII] line ratios are…
The Mg II and Lyα Lines of Nearby K Dwarfs: Interstellar Medium Components and Flux Measurements
Brown, Alexander; Wood, Brian E.; Linsky, Jeffrey L. +1 more
We analyze local interstellar medium (LISM) absorption observed in the Lyα and Mg II h and k lines of six nearby K dwarf stars, using UV spectra of these stars obtained with the Goddard High Resolution Spectrograph on the Hubble Space Telescope. For four of the six stars, we detect an absorption component with a velocity and column density consist…