Search Publications
Synapses of active galactic nuclei:. Comparing X-ray and optical classifications using artificial neural networks
Papadakis, I. E.; Acosta-Pulido, J. A.; González-Martín, O. +5 more
Context. Many classes of active galactic nuclei (AGN) have been defined entirely through optical wavelengths, while the X-ray spectra have been very useful to investigate their inner regions. However, optical and X-ray results show many discrepancies that have not been fully understood yet.
Aims: The main purpose of the present paper is to st…
Crater detection via genetic search methods to reduce image features
Cohen, Joseph Paul; Ding, Wei
Recent approaches to crater detection have been inspired by face detection's use of gray-scale texture features. Using gray-scale texture features for supervised machine learning crater detection algorithms provides better classification of craters in planetary images than previous methods. When using Haar features it is typical to generate thousa…
On the identification of time interval threshold in the twin-CME scenario
Li, Gang; Ding, Liu-Guan; Jiang, Yong +3 more
Recently it has been suggested that the "twin-CME" scenario may be a very effective mechanism in causing extreme solar energetic particle (SEP) events and, in particular, ground level enhancement (GLE) events. Ding et al. (2013) performed a statistical examination of the twin-CME scenario with a total of 126 fast and wide western coronal mass ejec…
Observation of a retreating x line and magnetic islands poleward of the cusp during northward interplanetary magnetic field conditions
Fuselier, S. A.; Trattner, K. J.; Eriksson, S. +3 more
When the interplanetary magnetic field is northward, reconnection occurs in each hemisphere on lobe field lines, poleward of the cusp. We have identified a case where the Cluster spacecraft crossed the magnetopause and encountered a tailward retreating x line. The x line is identified by the encounter of both a tailward and sunward jet, as well as…
From Predicting Solar Activity to Forecasting Space Weather: Practical Examples of Research-to-Operations and Operations-to-Research
Biesecker, D. A.; Steenburgh, R. A.; Millward, G. H.
The successful transition of research to operations (R2O) and operations to research (O2R) requires, above all, interaction between the two communities. We explore the role that close interaction and ongoing communication played in the successful fielding of three separate developments: an observation platform, a numerical model, and a visualizati…
Fifty M31 Black Hole Candidates Identified by Chandra and XMM-Newton
Murray, S. S.; Garcia, M. R.; Barnard, R. +1 more
Over approximately the last five years, we have identified ~35 black hole candidates (BHCs) in M31 from their X-ray spectra. Our BHCs exhibited 0.3-10 keV spectra consistent with the X-ray binary (XB) hard state at luminosities that are above the upper limit for neutron star (NS) XBs. When our BHC spectra were modeled with a disk blackbody + black…
Oblique Alfvén Instabilities Driven by Compensated Currents
De Keyser, J.; Malovichko, P.; Voitenko, Y.
Compensated-current systems created by energetic ion beams are widespread in space and astrophysical plasmas. The well-known examples are foreshock regions in the solar wind and around supernova remnants. We found a new oblique Alfvénic instability driven by compensated currents flowing along the background magnetic field. Because of the vastly di…
Resolving different sources of fast X-ray variability of the dwarf nova RU Peg in quiescence
Ness, J. -U.; Dobrotka, A.; Mineshige, S.
We analysed an X-ray light curve of the dwarf nova RU Peg taken by XMM-Newton with a duration of 46300 s. The power density spectrum has a complicated shape with two red noise and two white noise components, indicating the presence of two turbulent regions. We developed a statistical `toy model' to study light curves with variability produced by a…
Heating and Dynamics of Two Flare Loop Systems Observed by AIA and EIS
Ding, M. D.; Li, Y.; Qiu, J.
We investigate heating and evolution of flare loops in a C4.7 two-ribbon flare on 2011 February 13. From Solar Dynamics Observatory/Atmospheric Imaging Assembly (AIA) imaging observations, we can identify two sets of loops. Hinode/EUV Imaging Spectrometer (EIS) spectroscopic observations reveal blueshifts at the feet of both sets of loops. The evo…
Scale-dependent hemispherical asymmetry from general initial state during inflation
Gong, Jinn-Ouk; Firouzjahi, Hassan; Namjoo, Mohammad Hossein
We consider a general initial state for inflation as the mechanism for generating scale-dependent hemispherical asymmetry. An observable scale-dependent non-Gaussianity is generated that leads to observable hemispherical asymmetry from the super-horizon long mode modulation. We show that the amplitude of dipole asymmetry falls off exponentially on…