Search Publications
Electron and Proton Acceleration during the First Ground Level Enhancement Event of Solar Cycle 24
Li, C.; Sun, L. P.; Firoz, Kazi A. +1 more
High-energy particles were recorded by near-Earth spacecraft and ground-based neutron monitors (NMs) on 2012 May 17. This event was the first ground level enhancement (GLE) of solar cycle 24. In this study, we try to identify the acceleration source(s) of solar energetic particles by combining in situ particle measurements from the WIND/3DP, GOES …
A solar tornado triggered by flares?
Innes, D. E.; Low, B. C.; Tiwari, S. K. +1 more
Context. Solar tornados are dynamical, conspicuously helical magnetic structures that are mainly observed as a prominence activity.
Aims: We investigate and propose a triggering mechanism for the solar tornado observed in a prominence cavity by SDO/AIA on September 25, 2011.
Methods: High-cadence EUV images from the SDO/AIA and the Ahead…
Chromospheric Evaporation in Solar Flare Loop Strands Observed with the Extreme-ultraviolet Imaging Spectrometer on Board Hinode
Brosius, Jeffrey W.
The entire profile of the Fe XXIII line at 263.8 Å, formed at temperature ≈14 MK, was blueshifted by an upward velocity -122 ± 33 km s-1 when it was first detected by the Extreme-ultraviolet Imaging Spectrometer operating in rapid cadence (11.18 s) stare mode during a C1 solar flare. The entire profile became even more blueshifted over …
An Accretion Model for the Anomalous X-Ray Pulsar 4U 0142+61
Zezas, A.; Dennerl, K.; Trümper, J. E. +2 more
We propose that the quiescent emission of anomalous X-ray pulsars/soft gamma-ray repeaters (AXPs/SGRs) is powered by accretion from a fallback disk, requiring magnetic dipole fields in the range 1012-1013 G, and that the luminous hard tails of their X-ray spectra are produced by bulk-motion Comptonization in the radiative sho…
Curved Walls: Grain Growth, Settling, and Composition Patterns in T Tauri Disk Dust Sublimation Fronts
Hernández, J.; Watson, D. M.; Sargent, B. +6 more
The dust sublimation walls of disks around T Tauri stars represent a directly observable cross-section through the disk atmosphere and midplane. Their emission properties can probe the grain size distribution and composition of the innermost regions of the disk, where terrestrial planets form. Here we calculate the inner dust sublimation wall prop…
The virtual observatory service TheoSSA: Establishing a database of synthetic stellar flux standards. I. NLTE spectral analysis of the DA-type white dwarf G191-B2B
Rauch, T.; Werner, K.; Kruk, J. W. +1 more
Context. Hydrogen-rich, DA-type white dwarfs are particularly suited as primary standard stars for flux calibration. State-of-the-art NLTE models consider opacities of species up to trans-iron elements and provide reliable synthetic stellar-atmosphere spectra to compare with observations.
Aims: We will establish a database of theoretical spec…
The SLUGGS Survey: wide field imaging of the globular cluster system of NGC 4278
Spitler, Lee R.; Forbes, Duncan A.; Romanowsky, Aaron J. +4 more
We use multipointing Hubble Space Telescope Advanced Camera for Surveys and wide field Subaru Suprime-Cam imaging to study the globular cluster system of the L* elliptical galaxy NGC 4278. We have also obtained a handful of new globular cluster spectra with the Keck Deep Imaging Multi-Object Spectrograph. We determine the globular cluster surface …
Unveiling the nature of INTEGRAL objects through optical spectroscopy. X. A new multi-year, multi-observatory campaign
Palazzi, E.; Minniti, D.; Masetti, N. +18 more
Within the framework of our program (running since 2004) of identification of hard X-ray INTEGRAL sources through optical spectroscopy, we present the results concerning the nature of 33 high-energy objects. The data were acquired with the use of six telescopes of different sizes and from one on-line archive. The results indicate that the majority…
Distribution of Plasmoids in Post-coronal Mass Ejection Current Sheets
Huang, Y. -M.; Guo, L. -J.; Bhattacharjee, A.
Recently, the fragmentation of a current sheet in the high-Lundquist-number regime caused by the plasmoid instability has been proposed as a possible mechanism for fast reconnection. In this work, we investigate this scenario by comparing the distribution of plasmoids obtained from Large Angle and Spectrometric Coronagraph (LASCO) observational da…
Testing Diagnostics of Nuclear Activity and Star Formation in Galaxies at z > 1
Barro, Guillermo; Pérez-González, Pablo G.; Kocevski, Dale D. +9 more
We present some of the first science data with the new Keck/MOSFIRE instrument to test the effectiveness of different AGN/SF diagnostics at z ~ 1.5. MOSFIRE spectra were obtained in three H-band multi-slit masks in the GOODS-S field, resulting in 2 hr exposures of 36 emission-line galaxies. We compare X-ray data with the traditional emission-line …