Search Publications
Proton temperature anisotropy in the magnetosheath: comparison of 3-D MHD modelling with Cluster data
Maksimovic, M.; Alexandrova, O.; Lacombe, C. +2 more
We study four intervals of Cluster data, lasting from five to eight hours, in the flanks of the magnetosheath. In a first part, we make numerical simulations of these magnetosheath crossings, using a three-dimensional double-adiabatic MHD model of the magnetosheath and assuming that the proton temperature anisotropy is bounded by the kinetic thres…
Evidence of Stellar-driven Outflows from the Classical T Tauri Star RY Tau
Gómez de Castro, Ana I.; Verdugo, Eva
RY Tau is a rapidly rotating classical T Tauri star observed close to edge-on. The combination of new HST/STIS observations obtained in 2001 with HST/GHRS archive data from 1993 has allowed us to get, for the first time, information on the thermal structure and velocity of the wind. The repeated observations of the Si III] and C III] lines show a …
Determining the Source of Coronal Helicity through Measurements of Braiding and Spin Helicity Fluxes in Active Regions
Barnes, G.; Longcope, D. W.; Ravindra, B.
Magnetic helicity has become a valuable tool for understanding the energetics and dynamics of coronal magnetic fields. Recently, long time sequences of magnetograms have been used to measure the flux of helicity into active region coronae. We demonstrate how this helicity flux can be usefully decomposed into contributions of differing origin, call…
Discovery of an Extended Debris Disk around the F2 V Star HD 15745
Kalas, Paul; Fitzgerald, Michael P.; Graham, James R. +1 more
Using the Advanced Camera for Surveys aboard the Hubble Space Telescope, we have discovered dust-scattered light from the debris disk surrounding the F2 V star HD 15745. The circumstellar disk is detected between 2.0" and 7.5" radius, corresponding to 128-480 AU radius. The circumstellar disk morphology is asymmetric about the star, resembling a f…
Determination of the Physical Conditions of the Knots in the Helix Nebula from Optical and Infrared Observations
O'Dell, C. R.; Henney, W. J.; Ferland, G. J.
We use new Hubble Space Telescope and archived images to clarify the nature of the ubiquitous knots in the Helix Nebula, which are variously estimated to contain a significant to majority fraction of the material ejected by its central star. We employ published far-infrared spectrophotometry and existing 2.12 µm images to establish that the …
The meridional phosphine distribution in Saturn's upper troposphere from Cassini/CIRS observations
Fletcher, L. N.; Irwin, P. G. J.; Teanby, N. A. +7 more
The Cassini Composite Infrared Spectrometer (CIRS) has been used to derive the vertical and meridional variation of temperature and phosphine (PH 3) abundance in Saturn's upper troposphere. PH 3 has a significant effect on the measured radiances in the thermal infrared and between May 2004 and September 2005 CIRS recorded tho…
The Remarkable X-Ray Spectrum of the Broad-Line Radio Galaxy 3C 445
Reeves, J. N.; Braito, V.; Sambruna, R. M.
We present the results of the analysis of an archival 15 ks XMM-Newton observation of the nearby (z=0.057) radio-loud source 3C 445, optically classified as a broad-line radio galaxy. While the RGS data are of insufficient quality to allow a meaningful analysis, the EPIC data show a remarkable X-ray spectrum. The 2-10 keV continuum is described by…
Mineralogical structure of the subsurface of Syrtis Major from OMEGA observations of lobate ejecta blankets
Bibring, J. -P.; Gendrin, A.; Pinet, P. +5 more
This paper focuses on the spectral characteristics of lobate ejecta across Syrtis Major volcano, a dark region of Mars presenting a mafic composition as revealed from the Observatoire pour la Minéralogie, l'Eau, les Glaces et l'Activité (OMEGA) instrument. Two spectrally distinct crater types are identified. Type I is enriched in high-calcium pyro…
Deep Chandra and Multicolor HST Observations of the Jets of 3C 371 and PKS 2201+044
Maraschi, L.; Cheung, C. C.; Tavecchio, F. +3 more
This paper presents multiwavelength imaging and broadband spectroscopy of the relativistic jets in the two nearby radio galaxies 3C 371 and PKS 2201+044, acquired with Chandra, HST, VLA, and MERLIN. Radio polarization is also presented for 3C 371. The two sources stand out as ``intermediate'' between FR I and FR II type galaxies; their cores are c…
Spectropolarimetric Observations of the Ca II λ8498 and λ8542 in the Quiet Sun
Pietarila, A.; Socas-Navarro, H.; Bogdan, T.
The Ca II infrared triplet is one of the few magnetically sensitive chromospheric lines available for ground-based observations. We present spectropolarimetric observations of the 8498 and 8542 Å lines in a quiet Sun region near a decaying active region and compare the results with a simulation of the lines in a high plasma-β regime. Cluster analy…