Search Publications
Formation and Evolution of Blue Stragglers in 47 Tucanae
Heyl, Jeremy; Richer, Harvey; Kalirai, Jason +2 more
Blue stragglers (BSS) are stars whose position in the color-magnitude diagram (CMD) places them above the main sequence (MS) turn-off (TO) point of a star cluster. Using data from the core of 47 Tuc in the ultraviolet (UV), we have identified various stellar populations in the CMD, and used their radial distributions to study the evolution and ori…
Investigating the Conditions of the Formation of a Type II Radio Burst on 2014 January 8
Cheng, X.; Ding, M. D.; Chen, P. F. +3 more
It is believed that type II radio bursts are generated by shock waves. In order to understand the generation conditions of type II radio bursts, we analyze the physical parameters of a shock front. The type II radio burst we selected was observed by the Siberian Solar Radio Telescope (SSRT) and Learmonth radio station and was associated with a lim…
Multiwavelength observations of the blazar 1ES 1011+496 in Spring 2008
Maraschi, L.; Covino, S.; Antonelli, L. A. +157 more
The BL Lac object 1ES 1011+496 was discovered at very high energy (VHE, E > 100GeV) γ-rays by Major Atmospheric Gamma-ray Imaging Cherenkov (MAGIC) in Spring 2007. Before that the source was little studied in different wavelengths. Therefore, a multiwavelength (MWL) campaign was organized in Spring 2008. Along MAGIC, the MWL campaign included t…
Conjugate observations of quasiperiodic emissions by the Cluster, Van Allen Probes, and THEMIS spacecraft
Pickett, J. S.; Kurth, W. S.; Santolík, O. +3 more
We present results of a detailed analysis of two electromagnetic wave events observed in the inner magnetosphere at frequencies of a few kilohertz, which exhibit a quasiperiodic (QP) time modulation of the wave intensity. The events were observed by the Cluster and Van Allen Probes spacecraft and in one event also by the THEMIS E spacecraft. The s…
Field-aligned currents in Saturn's magnetosphere: Local time dependence of southern summer currents in the dawn sector between midnight and noon
Coates, A. J.; Dougherty, M. K.; Alexeev, I. I. +6 more
We examine and compare the magnetic field perturbations associated with field-aligned ionosphere-magnetosphere coupling currents at Saturn, observed by the Cassini spacecraft during two sequences of highly inclined orbits in 2006/2007 and 2008 under late southern summer conditions. These sequences explore the southern currents in the dawn-noon and…
DSMC simulation of Europa water vapor plumes
Trafton, L. M.; Berg, J. J.; Goldstein, D. B. +1 more
A computational investigation of the physics of water vapor plumes on Europa was performed with a focus on characteristics relevant to observation and spacecraft mission operations. The direct simulation Monte Carlo (DSMC) method was used to model the plume expansion assuming a supersonic vent source. The structure of the plume was determined, inc…
Lord of the Rings - Return of the King: Swift-XRT observations of dust scattering rings around V404 Cygni
Altamirano, D.; Motta, S. E.; Sivakoff, G. R. +5 more
On 2015 June 15, the black hole X-ray binary V404 Cygni went into outburst, exhibiting extreme X-ray variability which culminated in a final flare on June 26. Over the following days, the Swift-X-ray Telescope detected a series of bright rings, comprising five main components that expanded and faded with time, caused by X-rays scattered from the o…
Stability within Jupiter's polar auroral 'Swirl region' over moderate timescales
Clarke, John T.; O'Donoghue, James; Connerney, John E. P. +7 more
Jupiter's Swirl region, poleward of the main auroral emission, has been characterised in previous observations as having highly variable auroral emission, changing dramatically across the region on a two-minute timescale, the typical integration time for UV images. This variability has made comparisons with H3+ emission diffi…
Suzaku and XMM-Newton observations of the North Polar Spur: Charge exchange or ISM absorption?
Gu, Liyi; Kaastra, Jelle; Mao, Junjie +1 more
By revisiting the Suzaku and XMM-Newton data of the North Polar Spur, we discovered that the spectra are inconsistent with the traditional model consisting of pure thermal emission and neutral absorption. The most prominent discrepancies are the enhanced O vii and Ne ix forbidden-to-resonance ratios, and a high O viii Lyβ line relative to other Ly…
Flux rope proxies and fan-spine structures in active region NOAA 11897
Zhang, J.; Hou, Y. J.; Li, T.
Context. Flux ropes are composed of twisted magnetic fields and are closely connected with coronal mass ejections. The fan-spine magnetic topology is another type of complex magnetic fields. It has been reported by several authors, and is believed to be associated with null-point-type magnetic reconnection.
Aims: We try to determine the numbe…