Search Publications
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…
Hot Cores in Coronal Filament Cavities
Schwenn, R.; Hudson, H.
Filaments represent cold intrusions in the corona, embedded in magnetic configurations termed ``filament cavities.'' Such cavities may occur without actually containing prominence material. A cavity then may erupt, leading to a coronal mass ejection (CME). Studies of Yohkoh soft X-ray images have previously shown that such eruptions may contain el…
Another Search for Maia Variable Stars
Percy, John R.; Wilson, Joseph B.
We have used the Hipparcos epoch photometry database, and autocorrelation analysis, to search for the elusive Maia variables-short-period B7-A3 near-main-sequence pulsating variable stars. Of several hundred stars considered, and several dozen stars studied in detail, only a handful are possible variables: three are possible shallow eclipsing vari…
Helmet Streamers with Triple Structures: Simulations of resistive dynamics
Wiegelmann, Thomas; Schindler, Karl; Neukirch, Thomas
Recent observations of the solar corona with the LASCO coronagraph on board of the SOHO spacecraft have revealed the occurrence of triple helmet streamers even during solar minimum, which occasionally go unstable and give rise to large coronal mass ejections. There are also indications that the slow solar wind is either a combination of a quasi-st…
Optical Identification of Faint X-Ray Sources in the Core of ω Centauri
Cool, Adrienne M.; Grindlay, Jonathan E.; Carson, Jennifer E.
We present the results of a search for optical counterparts of three faint X-ray sources in the core of NGC 5139 (ω Cen) with the HST Wide Field Planetary Camera 2. Using images taken through the F656N (Hα), F675W, and F336W filters, we have identified two stars with strong Hα and UV excesses, one in each of two of the X-ray error circles, and a p…
DENIS and ISOGAL properties of variable star candidates in the Galactic Bulge
Alard, C.; Blommaert, J. A. D. L.; Ganesh, S. +9 more
Repeated DENIS observations (summer 1996 & 1998) in the J (1.25 mu m) and the KS (2.15 mu m) bands are used to look for variable stars. We present two catalogues of ~ 1000 probable variables in an area of ~ 4 deg2 of the inner galactic bulge. The first one contains ~ 720 variable star candidates which show variability in …
Optimizing ISOCAM data processing using spatial redundancy
Miville-Deschênes, M. -A.; Boulanger, F.; Abergel, A. +1 more
Several instrumental effects of the Long Wavelength channel of ISOCAM, the camera on board the Infrared Space Observatory, degrade the processed images. We present new data-processing techniques that correct these defects, taking advantage of the fact that a position in the sky has been observed by several pixels at different times. We use this re…
The age of globular clusters
Krauss, L. M.
I review here recent developments which have affected our understanding of both the absolute age of globular clusters and the uncertainties in this age estimate, and comment on the implications for cosmological models. This present estimate is in agreement with the range long advocated by David Schramm. The major uncertainty in determining ages of…
V1334 Cygni: A Triple System Containing a Classical Cepheid
Evans, Nancy Remage
We have observed the small-amplitude Cepheid V1334 Cyg A (pulsation period 3.3 days) for nearly 30 years. From these radial velocity data we have derived an orbit with a period of 5 years. From this orbit we have derived limits on the mass of the companion (V1334 Cyg C) of 3.1 to 4.4 Msolar. The system is also a marginally resolved visu…