Search Publications
Detection of visible lightning on Saturn
Kurth, W. S.; West, R. A.; Fischer, G. +4 more
Until now, evidence for lightning on Saturn has been indirect - through radio emissions and cloud morphology. Here we report the first visible detection of lightning, on the night side on August 17, 2009 at -36.4° ± 0.1° planetocentric latitude and 10.6° ± 0.9° west longitude. No other locations produced lightning detectable by either imaging or r…
Dust/gas correlations from Herschel observations
Bernard, J. -P.; Reach, W. T.; Okumura, K. +21 more
Context. Previous Spitzer and IRAS observations of the LMC suggest an excess of FIR emission with respect to the gas surface density traced by 12CO rotational emission lines and H i 21 cm emission. This so-called “FIR excess” is especially noticeable near molecular clouds in the LMC, and has usually been interpreted as indicating the pr…
Evidence for magnetic flux cancelation leading to an ejective solar eruption observed by Hinode, TRACE, STEREO, and SoHO/MDI
Young, P. R.; Mason, H. E.; Moore, R. L. +2 more
Aims: We study the onset of a solar eruption involving a filament ejection on 2007 May 20.
Methods: We observe the filament in Hα images from Hinode/SOT and in EUV with TRACE and STEREO/SECCHI/EUVI. Hinode/XRT images are used to study the eruption in soft X-rays. From spectroscopic data taken with Hinode/EIS we obtain bulk-flow velocitie…
X-ray Pulsations from the Radio-quiet Gamma-ray Pulsar in CTA 1
Caraveo, P. A.; Bignami, G. F.; Marelli, M. +4 more
Prompted by the Fermi-LAT discovery of a radio-quiet gamma-ray pulsar inside the CTA 1 supernova remnant, we obtained a 130 ks XMM-Newton observation to assess the timing behavior of this pulsar. Exploiting both the unprecedented photon harvest and the contemporary Fermi-LAT timing measurements, a 4.7σ single-peak pulsation is detected, making PSR…
On the Origin of the Solar Moreton Wave of 2006 December 6
Temmer, M.; Veronig, A. M.; Vršnak, B. +12 more
We analyzed ground- and space-based observations of the eruptive flare (3B/X6.5) and associated Moreton wave (~850 km s-1 ~270° azimuthal span) of 2006 December 6 to determine the wave driver—either flare pressure pulse (blast) or coronal mass ejection (CME). Kinematic analysis favors a CME driver of the wave, despite key gaps in corona…
On Calibrations Using the Crab Nebula and Models of the Nebular X-Ray Emission
Guainazzi, M.; O'Dell, S. L.; Weisskopf, M. C. +5 more
Motivated by a paper of Kirsch et al. on possible use of the Crab Nebula as a standard candle for calibrating X-ray response functions, we examine consequences of intrinsic departures from a single (absorbed) power law upon such calibrations. We limit our analyses to three more modern X-ray instruments—the ROSAT/PSPC, the RXTE/Proportional Counter…
V4332 Sagittarii: a circumstellar disc obscuring the main object
Schmidt, M.; Tylenda, R.; Kamiński, T.
Context. V4332 Sgr experienced an outburst in 1994 whose observational characteristics in many respects resemble those of the eruption of V838 Mon in 2002. It has been proposed that these objects erupted because of a stellar-merger event.
Aims: Our aim is to derive, from observational data, information on the present (10-15 yrs after the outb…
Elastic ice shells of synchronous moons: Implications for cracks on Europa and non-synchronous rotation of Titan
Goldreich, Peter M.; Mitchell, Jonathan L.
A number of synchronous moons are thought to harbor water oceans beneath their outer ice shells. A subsurface ocean frictionally decouples the shell from the interior. This has led to proposals that a weak tidal or atmospheric torque might cause the shell to rotate differentially with respect to the synchronously rotating interior. Applications al…
Outflows at the Edges of an Active Region in a Coronal Hole: A Signature of Active Region Expansion?
van Driel-Gesztelyi, L.; Baker, D.; Murray, M. J. +1 more
Outflows of plasma at the edges of active regions surrounded by quiet Sun are now a common observation with the Hinode satellite. While there is observational evidence to suggest that the outflows are originating in the magnetic field surrounding the active regions, there is no conclusive evidence that reveals how they are driven. Motivated by obs…
Temporal and Physical Connection Between Coronal Mass Ejections and Flares
Chen, James; Kunkel, Valbona
The physical connection between the eruption of coronal mass ejections (CMEs) and associated flare energy release is examined. The trajectories of five CMEs are determined using LASCO/SOHO or SECCHI/STEREO data, and the associated soft X-ray (SXR) light curves are obtained from GOES 1-8 Å data. As the theoretical description of CME physics, the ex…