Search Publications
Echelle Long-Slit Optical Spectroscopy of Evolved Stars
Sahai, R.; Sánchez Contreras, C.; Gil de Paz, A. +1 more
We present echelle long-slit optical spectra of a sample of objects evolving off the asymptotic giant branch (AGB), most of them in the preplanetary nebula (PPN) phase, obtained with the ESI and MIKE spectrographs at the 10 m Keck II and 6.5 m Magellan-I telescopes, respectively. The total wavelength range covered with ESI (MIKE) is ~3900-10900 Å …
What is the best method to calculate the solar wind propagation delay?
Haaland, S.; Mailyan, B.; Munteanu, C.
We present a statistical study of propagation times of solar wind discontinuities between Advanced Composition Explorer (ACE) spacecraft orbiting the L1 libration point and the Cluster quartet of spacecraft near the Earth's magnetopause. The propagation times for almost 200 events are compared with the predicted times from four different models. T…
The XRS microcalorimeter spectrometer at the Livermore electron beam ion trap
Boyce, K. R.; Kilbourne, C. A.; Porter, F. S. +9 more
NASAs X-ray spectrometer (XRS) microcalorimeter instrument has been operating at the electron beam ion trap (EBIT) facility at Lawrence Livermore National Laboratory since July of 2000. The spectrometer is currently undergoing its third major upgrade to become an easy to use and extremely high-performance instrument for a broad range of EBIT exper…
Large-scale structure of Saturn's E-ring
Morfill, Gregor E.; Horányi, Mihály; Juhász, Antal
Geysers on the recently discovered, geologically active south-polar region of the moon Enceladus are now recognized as the dominant source of material in Saturn's E ring. The ring was traditionally thought to span the region between 3 to 8 R S , where R S is the radius of Saturn. However, new in situ dust measurements indi…
Discovery of a Very Highly Extinguished Supernova in a Luminous Infrared Galaxy
Colina, L.; Kankare, E.; Efstathiou, A. +9 more
We report the discovery of a confirmed supernova (SN) and a supernova candidate in near-infrared images from the ALTAIR/NIRI adaptive optics system on the Gemini-North Telescope and NICMOS on the Hubble Space Telescope. The Gemini images were obtained as part of a near-infrared K-band search for highly obscured SNe in the nuclear regions of lumino…
Structure and Evolution of Supergranulation from Local Helioseismology
Hirzberger, Johann; Solanki, Sami K.; Gizon, Laurent +1 more
Supergranulation is visible at the solar surface as a cellular pattern of horizontal outflows. Although it does not show a distinct intensity pattern, it manifests itself indirectly in, for example, the chromospheric network. Previous studies have reported significant differences in the inferred basic parameters of the supergranulation phenomenon.…
The Extragalactic Distance Scale without Cepheids
Sakai, Shoko; Mould, Jeremy
Distances of galaxies in the Hubble Space Telescope Key Project are based on the Cepheid period-luminosity relation. An alternative basis is the tip of the red giant branch. Using archival HST data, we calibrate the infrared Tully-Fisher relation using 14 galaxies with tip of the red giant branch measurements. Compared with the Key Project, a high…
Distribution of the O2 infrared nightglow observed with VIRTIS on board Venus Express
Hueso, R.; Sánchez-Lavega, A.; Erard, S. +5 more
We present characteristics of the statistical horizontal distribution of the O2 infrared nightglow over most of the southern hemisphere observed with the VIRTIS instrument over a period spanning nearly 11 months of low solar activity. We show that the distribution is inhomogeneous with the regions of brightest emission reaching ~3 MegaR…
Solar flare forecasting model supported with artificial neural network techniques
Li, R.; Wang, H. N.; Cui, Y. M. +2 more
Nowadays operational models for solar activity forecasting are still based on the statistical relationship between solar activity and solar magnetic field evolution. In order to set up this relationship, many parameters have been proposed to be the measures. Conventional measures are based on the sunspot group classification which provides limited…
Novae as a Class of Transient X-Ray Sources
Mukai, K.; Della Valle, M.; Orio, M.
Motivated by the recently discovered class of faint (1034-1035 ergs s-1) X-ray transients in the Galactic center region, we investigate the 2-10 keV properties of classical and recurrent novae. Existing data are consistent with the idea that all classical novae are transient X-ray sources with durations of months t…