Search Publications
Evidence of Superdiffusive Transport of Electrons Accelerated at Interplanetary Shocks
Perri, S.; Zimbardo, G.
We study the transport properties of energetic electrons accelerated at corotating interaction regions in the solar wind considering the possibility of anomalous diffusion. It is shown that the particle time decay has a power-law behavior when a non-Gaussian propagator, appropriate for superdiffusive transport, is assumed for particles accelerated…
The Post-Burst Awakening of the Anomalous X-Ray Pulsar in Westerlund 1
Campana, S.; Stella, L.; Israel, G. L. +4 more
On 2006 September 21, an intense (~1039 erg s-1) and short (20 ms) burst was detected by Swift BAT at a position consistent with that of the candidate anomalous X-ray pulsar (AXP) CXOU J164710.2-455216, discovered by Chandra in 2005. Swift follow-up observations began ~13 hr after the event and found the source at a 1-10 keV …
Mass Outflow from the Nucleus of the Seyfert 1 Galaxy NGC 4151
Kraemer, S. B.; Crenshaw, D. M.
We present an analysis of UV and optical spectra of NGC 4151 obtained at high spectral and angular resolutions with the Hubble Space Telescope Space Telescope Imaging Spectrograph (HST STIS). We identify a kinematic component of the emission lines that has a width of 1170 km s-1 (FWHM), intermediate between those from the broad and narr…
η Carinae across the 2003.5 Minimum: Spectroscopic Evidence for Massive Binary Interactions
Gull, T. R.; Nielsen, K. E.; Corcoran, M. F. +4 more
We have analyzed high spatial, moderate spectral resolution observations of η Carinae (η Car) obtained with the STIS from 1998.0 to 2004.3. The data were obtained at discrete times covering an entire 2024 day spectroscopic cycle, with focus on the X-ray/ionization low state that began in 2003 June. The spectra show prominent P Cygni lines in H I, …
Discovery of Extreme Asymmetry in the Debris Disk Surrounding HD 15115
Kalas, Paul; Fitzgerald, Michael P.; Graham, James R.
We report the first scattered light detection of a dusty debris disk surrounding the F2 V star HD 15115 using the Hubble Space Telescope in the optical and Keck adaptive optics in the near-infrared. The most remarkable property of the HD 15115 disk relative to other debris disks is its extreme length asymmetry. The east side of the disk is detecte…
Features and Properties of Coronal Mass Ejection/Flare Current Sheets
Raymond, J. C.; Ko, Y. -K.; Lin, J. +3 more
Solar eruptions occur when magnetic energy is suddenly converted into heat and kinetic energy by magnetic reconnection in a current sheet (CS). It is often assumed that CSs are too thin to be observable because the electric resistivity ηe in CSs is taken to be very small. In this work, we show the implications for the CS thickness d est…
Numerical Investigation of the Homologous Coronal Mass Ejection Events from Active Region 9236
Gombosi, T. I.; Tóth, G.; Lugaz, N. +2 more
We present a three-dimensional compressible magneto-hydrodynamics (MHD) simulation of the three coronal mass ejections (CMEs) of 2000 November 24, originating from NOAA active region 9236. These three ejections, with velocities around 1200 km s-1 and associated with X-class flares, erupted from the Sun in a period of about 16.5 hr. In o…
The Surface Density Profile of NGC 6388: A Good Candidate for Harboring an Intermediate-Mass Black Hole
Dalessandro, E.; Valenti, E.; Ferraro, F. R. +3 more
We have used a combination of HST high-resolution and ground-based wide-field observations of the Galactic globular cluster NGC 6388 to derive its center of gravity, projected density profile, and central surface brightness profile. While the overall projected profiles are well fit by a King model with an intermediate concentration (c=1.8) and a s…
A Panchromatic Study of the Globular Cluster NGC 1904. I. The Blue Straggler Population
Valenti, E.; Sanna, N.; Beccari, G. +6 more
By combining high-resolution (HST/WFPC2) and wide-field ground-based (2.2 m ESO/WFI) and space (GALEX) observations, we have collected a multiwavelength photometric database (ranging from the far-UV to the near infrared) of the galactic globular cluster NGC 1904 (M79). The sample covers the entire cluster extension, from the very central regions u…
X-Ray Spectral Variation of η Carinae through the 2003 X-Ray Minimum
Hamaguchi, Kenji; Corcoran, Michael F.; Hillier, D. John +7 more
We report the results of an observing campaign on η Car around the 2003 X-ray minimum, mainly using the XMM-Newton observatory. These are the first spatially resolved X-ray monitoring observations of the stellar X-ray spectrum during the minimum. The hard X-ray emission, associated with the wind-wind collision (WWC) in the binary system, varied st…