Search Publications
Atmospheric Electricity at Saturn
Dyudina, Ulyana A.; Gurnett, Donald A.; Fischer, Georg +5 more
The Cassini mission provides a great opportunity to enlarge our knowledge of atmospheric electricity at the gas giant Saturn. Following Voyager studies, the RPWS (Radio and Plasma Wave Science) instrument has measured again the so-called SEDs (Saturn Electrostatic Discharges) which are the radio signature of lightning flashes. Observations by Cass…
Mg II h+k emission lines as stellar activity indicators of main sequence F-K stars
Buccino, A. P.; Mauas, P. J. D.
Context: The largest dataset of stellar activity measurements available at present is the one obtained at the Mount Wilson Observatory, where high-precision Ca II H+K fluxes have been measured from 1966 for about 2200 stars. Since the Mg II h and k lines at λ2800 Å are formed in a similar way to the Ca II H+K emission lines, they are also good ind…
XMM-Newton X-ray study of early type stars in the Carina OB1 association
van der Hucht, K. A.; Rauw, G.; Vreux, J. -M. +2 more
Aims:X-ray properties of the stellar population in the Carina OB1 association are examined with special emphasis on early-type stars. Their spectral characteristics provide some clues to understanding the nature of X-ray formation mechanisms in the winds of single and binary early-type stars.
Methods: A timing and spectral analysis of five obs…
Disk-dominated States of 4U 1957+11: Chandra, XMM-Newton, and RXTE Observations of Ostensibly the Most Rapidly Spinning Galactic Black Hole
Homan, Jeroen; Wilms, Jörn; Canizares, Claude R. +4 more
We present simultaneous Chandra High-Energy Transmission Gratings (HETG) and Rossi X-ray Timing Explorer (RXTE) observations of a "soft state" of the black hole candidate 4U 1957+11. These spectra, having limited hard X-ray excess, are an excellent test of disk atmosphere models that include effects of black hole spin. The HETG data show, by model…
Electron properties of high-speed solar wind from polar coronal holes obtained by Ulysses thermal noise spectroscopy: Not so dense, not so hot
McComas, D. J.; Issautier, K.; MacDowall, R. J. +4 more
We present radio observations of Ulysses' third fast latitude scan near the 2007 solar activity minimum of cycle 23. We deduce in situ measurements of the electron density and temperature using the method of quasi-thermal noise spectroscopy. We study the large-scale properties of the fast solar wind coming from polar coronal holes and compare our …
Radiation transport of heliospheric Lyman-α from combined Cassini and Voyager data sets
Quemerais, E.; Möbius, E.; Bzowski, M. +15 more
Aims: Heliospheric neutral hydrogen scatters solar Lyman-α radiation from the Sun with “27-day” intensity modulations observed near Earth due to the Sun's rotation combined with Earth's orbital motion. These modulations are increasingly damped in amplitude at larger distances from the Sun due to multiple scattering in the heliosphere, providing a …
Flattened current sheet and its evolution in substorms
Malova, H. V.; Escoubet, C. P.; Lucek, E. +10 more
In this research, the properties of a tail current sheet, which has a flattened geometry, and its evolution during substorm activity have been investigated. The geometrical configuration of the magnetic field and the spatial distribution of the current density in a flattened current sheet have been revealed with certainty for the first time. It is…
Multiple stellar populations in Galactic GCs: observational evidence
Piotto, Giampaolo
An increasing number of photometric observations of multiple stellar populations in Galactic globular clusters is seriously challenging the paradigm of GCs hosting single, simple stellar populations. These multiple populations manifest themselves in a split of some evolutionary sequences of the cluster color-magnitude diagrams. In this paper we wi…
The Horizontal Branch of NGC 1851: Constraints on the Cluster Subpopulations
Salaris, M.; Pietrinferni, A.; Cassisi, S.
We investigate the distribution of stars along the horizontal branch of the Galactic globular cluster NGC 1851, to shed light on the progeny of the two distinct subgiant-branch populations harbored by this cluster. On the basis of detailed synthetic horizontal-branch modeling, we conclude that the two subpopulations are distributed in different re…
High-excitation OH and H2O Lines in Markarian 231: The Molecular Signatures of Compact Far-infrared Continuum Sources
Smith, Howard A.; Ashby, Matthew L. N.; González-Alfonso, Eduardo +3 more
The ISO LWS far-infrared spectrum of the ultraluminous galaxy Mrk 231 shows OH and H2O lines in absorption from energy levels up to 300 K above the ground state, and emission in the [O I] 63 µm and [C II] 158 µm lines. Our analysis shows that OH and H2O are radiatively pumped by the far-infrared continuum emission…