Search Publications
Role of Sunspot and Sunspot-Group Rotation in Driving Sigmoidal Active Region Eruptions
Alexander, David; Tian, Lirong
We study active region NOAA 9684 (N06L285) which produced an X1.0/3B flare on November 4, 2001 associated with a fast CME (1810 km s−1) and the largest proton event (31 700 pfu) in cycle 23. SOHO/MDI continuum image data show that a large leading sunspot rotated counter-clockwise around its umbral center for at least 4 days prior to the…
The Jet-Disk Connection in AGNs: Chandra and XMM-Newton Observations of Three Powerful Radio-Loud Quasars
Maraschi, L.; Tavecchio, F.; Gliozzi, Mario +2 more
The connection between the accretion process that powers AGNs and the formation of jets is still poorly understood. Here we tackle this issue using new, deep Chandra and XMM-Newton observations of the cores of three powerful radio-loud quasars, 1136-135, 1150+497 (Chandra), and 0723+679 (XMM-Newton), in the redshift range z=0.3-0.8. These sources …
The OB binary HD152219: a detached, double-lined, eclipsing system
Gosset, E.; Rauw, G.; Sana, H.
We present the results of an optical spectroscopic campaign on the massive binary HD152219 located near the core of the NGC6231 cluster. Though the primary to secondary optical brightness ratio is probably about 10, we clearly detect the secondary spectral signature and we derive the first reliable SB2 orbital solution for the system. The orbital …
Multiplicity of very low-mass objects in the Upper Scorpius OB association: a possible wide binary population
Béjar, V. J. S.; Schirmer, M.; Ghez, A. M. +5 more
Aims.Properties of multiplicity, such as the multiplicity frequency, the distribution of mass ratios and periods, provide important informations on the formation processes at work. Studying these properties in different environments and at different ages allows us to constrain the models of formation and to understand the influence of the environm…
A Method for Deriving Accurate Gas-Phase Abundances for the Multiphase Interstellar Galactic Halo
Sembach, Kenneth R.; Savage, Blair D.; Howk, J. Christopher
We describe a new method for accurately determining total gas-phase abundances for the Galactic halo interstellar medium with minimal ionization uncertainties. For sight lines toward globular clusters containing both ultraviolet-bright stars and radio pulsars, it is possible to measure column densities of H I and several ionization states of selec…
26Al in the inner Galaxy. Large-scale spectral characteristics derived with SPI/INTEGRAL
Wang, W.; Strong, A. W.; Knödlseder, J. +12 more
Aims.We performed a spectroscopic study of the 1809 keV gamma-ray line from 26Al decay in the Galaxy using the SPI imaging spectrometer with its high-resolution Ge detector camera on the INTEGRAL observatory. Methods.We analyzed observations of the first two mission years, fitting spectra from all 7130 telescope pointings in narrow ener…
Observations in the Saturn system during approach and orbital insertion, with Cassini's visual and infrared mapping spectrometer (VIMS)
Sotin, C.; Brown, R. H.; Baines, K. H. +23 more
The Visual and Infrared Mapping Spectrometer observed Phoebe, Iapetus, Titan and Saturn's rings during Cassini's approach and orbital insertion. Phoebe's surface contains water ice, CO{2}, and ferrous iron. Iapetus contains CO{2} and organic materials. Titan's atmosphere shows methane fluorescence, and night-side atmospheric emission that may be C…
Infrared Observations of the Helix Planetary Nebula
Smith, Howard A.; Marengo, Massimo; Hora, Joseph L. +1 more
We have mapped the Helix (NGC 7293) planetary nebula (PN) with the IRAC instrument on the Spitzer Space Telescope. The Helix is one of the closest bright PNs and therefore provides an opportunity to resolve the small-scale structure in the nebula. The emission from this PN in the 5.8 and 8 µm IRAC bands is dominated by the pure rotational li…
Numerical interpretation of high-altitude photoelectron observations
Coates, A. J.; Kallio, E.; Fedorov, A. +47 more
The Electron Spectrometer (ELS) instrument of the ASPERA-3 package on the Mars Express satellite has recorded photoelectron energy spectra up to apoapsis ( ∼10,000 km altitude). The characteristic photoelectron shape of the spectrum is sometimes seen well above the ionosphere in the evening sector across a wide range of near-equatorial latitudes. …
New developments in SOLAR2000 for space research and operations
Tobiska, W. Kent; Bouwer, S. Dave
The SOLAR2000 (S2K) project provides solar spectral irradiances and integrated solar irradiance proxies for space researchers as well as ground- and space-based operational users. The S2K model currently represents empirical solar irradiances and integrated irradiance proxies covering the spectral range from the X-rays through the far infrared and…