Search Publications
Revealing the X-ray source in IRAS 13224-3809 through flux-dependent reverberation lags
Fabian, A. C.; Miniutti, G.; Uttley, P. +2 more
IRAS 13224-3809 was observed in 2011 for 500 ks with the XMM-Newton observatory. We detect highly significant X-ray lags between soft (0.3-1 keV) and hard (1.2-5 keV) energies. The hard band lags the soft at low frequencies (i.e. hard lag), while the opposite (i.e. soft lag) is observed at high frequencies. In this paper, we study the lag during f…
Dust in active galactic nuclei. Mid-infrared T-ReCS/Gemini spectra using the new RedCan pipeline
Esquej, P.; Telesco, C.; Díaz-Santos, T. +6 more
Context. The unified model of active galactic nuclei (AGN) claims that the properties of AGN depend on the viewing angle of the observer with respect to a toroidal distribution of dust surrounding the nucleus. Both the mid-infrared (MIR) attenuation and continuum luminosity are expected to be related to dust associated with the torus. Therefore, i…
Magnetic signatures of Kelvin-Helmholtz vortices on Saturn's magnetopause: Global survey
Wilson, R. J.; Delamere, P. A.; Bagenal, F. +1 more
Saturn's rapid rotation combined with relatively weak magnetic fields in the outer magnetosphere and sheath lead to conditions that are favorable for the Kelvin-Helmholtz (KH) instability. A Kelvin-Helmholtz unstable magnetopause boundary has important consequences for Saturn's interaction with the solar wind due to mass, momentum, and energy tran…
Simulation of the 23 July 2012 extreme space weather event: What if this extremely rare CME was Earth directed?
Galvin, A. B.; Zheng, Yihua; Pulkkinen, Antti +7 more
Extreme space weather events are known to cause adverse impacts on critical modern day technological infrastructure such as high-voltage electric power transmission grids. On 23 July 2012, NASA's Solar Terrestrial Relations Observatory-Ahead (STEREO-A) spacecraft observed in situ an extremely fast coronal mass ejection (CME) that traveled 0.96 ast…
A High-resolution Spectroscopic Search for the Remaining Donor for Tycho's Supernova
Anderson, Jay; Filippenko, Alexei V.; Foley, Ryan J. +12 more
In this paper, we report on our analysis using Hubble Space Telescope astrometry and Keck-I HIRES spectroscopy of the central six stars of Tycho's supernova remnant (SN 1572). With these data, we measured the proper motions, radial velocities, rotational velocities, and chemical abundances of these objects. Regarding the chemical abundances, we do…
The Extraordinary Multi-tailed Main-belt Comet P/2013 P5
Mutchler, Max; Jewitt, David; Agarwal, Jessica +2 more
Hubble Space Telescope observations of main-belt comet P/2013 P5 reveal an extraordinary system of six dust tails that distinguish this object from any other. Observations two weeks apart show dramatic morphological change in the tails while providing no evidence for secular fading of the object as a whole. Each tail is associated with a unique ej…
Quantitative comparison of methods for predicting the arrival of coronal mass ejections at Earth based on multiview imaging
Vourlidas, A.; Colaninno, R. C.; Wu, C. C.
We investigate the performance of six methods for predicting the coronal mass ejection (CME) time of arrival (ToA) and velocity at Earth using a sample of nine Earth-impacting CMEs between March 2010 and June 2011. The CMEs were tracked continuously from the Sun to near Earth in multiviewpoint imaging data from STEREO Sun-Earth Connection Coronal …
Origins of Rolling, Twisting, and Non-radial Propagation of Eruptive Solar Events
Vourlidas, Angelos; Velli, Marco; Panasenco, Olga +1 more
We demonstrate that major asymmetries in erupting filaments and CMEs, namely major twists and non-radial motions are typically related to the larger-scale ambient environment around eruptive events. Our analysis of prominence eruptions observed by the STEREO, SDO, and SOHO spacecraft shows that prominence spines retain, during the initial phases, …
The Firm Redshift Lower Limit of the Most Distant TeV-detected Blazar PKS 1424+240
Filippenko, A. V.; Furniss, A.; Williams, D. A. +7 more
We present the redshift lower limit of z >= 0.6035 for the very high energy (VHE; E >= 100 GeV) emitting blazar PKS 1424+240 (PG 1424+240). This limit is inferred from Lyβ and Lyγ absorption observed in the far-ultraviolet spectra from the Hubble Space Telescope/Cosmic Origins Spectrograph. No VHE-detected blazar has shown solid spectroscopi…
Thermodynamics of the Coma Cluster Outskirts
Simionescu, A.; Fabian, A. C.; Allen, S. W. +10 more
We present results from a large mosaic of Suzaku observations of the Coma Cluster, the nearest and X-ray brightest hot (~8 keV), dynamically active, non-cool core system, focusing on the thermodynamic properties of the intracluster medium on large scales. For azimuths not aligned with an infalling subcluster toward the southwest, our measured temp…