Search Publications
A Comparison of the Chemical Composition of Main-sequence and Giant Stars in the Open Cluster NCC 752
Lum, Michael G.; Boesgaard, Ann Merchant
The chemical composition of stars in open clusters provides the best information on the chemical evolution of stars via comparison of main-sequence stars with evolved giants. This is a case study of the abundances in the dwarfs and giants in the old open cluster NGC 752. It is also a pilot program for automated abundance determinations, including …
Exploring the role of X-ray reprocessing and irradiation in the anomalous bright optical outbursts of A0538-66
Mereghetti, S.; Santangelo, A.; Ducci, L. +2 more
Context. In 1981, the Be/X-ray binary A0538-66 showed outbursts characterized by high peak luminosities in the X-ray (Lx ≈ 1039 erg s-1) and optical (Lopt ≈ 3 × 1038 erg s-1) bands. The bright optical outbursts were qualitatively explained as X-ray reprocessing in a gas cloud surrou…
Global Energetics of Solar Flares. VII. Aerodynamic Drag in Coronal Mass Ejections
Gopalswamy, Nat; Aschwanden, Markus J.
The free energy that is dissipated in a magnetic reconnection process of a solar flare, generally accompanied by a coronal mass ejection (CME), has been considered as the ultimate energy source of the global energy budget of solar flares in previous statistical studies. Here we explore the effects of the aerodynamic drag force on CMEs, which suppl…
Deflections of ultra-high energy cosmic rays by the Milky Way magnetic field: how well can they be corrected?
Pavlidou, V.; Magkos, G.
Locating the sources of ultra-high energy cosmic rays (UHECRs) still remains a difficult puzzle for modern astrophysics. A major hurdle in the search for the sources is the fact that UHECRs are deflected by the Galactic magnetic field (GMF). Current knowledge of the GMF is limited, as most experimental measurements track line-of-sight-integrated q…
Degradation of Endeavour Crater Based on Orbital and Rover-Based Observations in Combination With Landscape Evolution Modeling
Arvidson, R. E.; Grant, J. A.; Wilson, S. A. +3 more
Exploration of Endeavour crater's Shoemaker formation rim rocks by the Opportunity rover, combined with extensive observations from the Mars Express and Mars Reconnaissance Orbiters, provides unique and quantitative insights into the processes that have degraded this 22-km diameter Noachian age impact crater. These insights are informed by compari…
Magnetic Field Observations on Cassini's Proximal Periapsis Passes: Planetary Period Oscillations and Mean Residual Fields
Dougherty, M. K.; Cowley, S. W. H.; Bunce, E. J. +4 more
We analyze periapsis pass magnetic field data from the final 23 orbits of the Cassini spacecraft at Saturn, uniquely encompassing auroral, subauroral, ring region, and intra-ring field lines, to determine the planetary period oscillations (PPOs) and mean residual fields in these regions. Dual modulation by northern and southern PPO systems is foun…
Reconstruction of Local Magnetic Structures by a Modified Radial Basis Function Method
Semenov, V. S.; Tsyganenko, N. A.; Andreeva, V. A. +2 more
Local magnetic structures in space environments, in particular, those in the diffusion region such as magnetic nulls or separators, are very difficult to identify by satellite measurements but important for understanding of magnetic reconnection. Multi-spacecraft missions such as Cluster or MMS, however, provide an opportunity to reconstruct the f…
Direct Observation of the Broad Line Region in X-Rays during the Low State of NGC 4051
Miller, Jon M.; Behar, Ehud; Peretz, Uria
NGC 4051 is one of the most variable and X-ray bright Seyfert galaxies. During 2009, NGC 4051 was caught at its lowest state ever observed by XMM-Newton. The low source continuum emission allows a clear measurement of the He-like emission lines of {{{N}}}+5 and O+6. The exceptionally high intercombination line flux is a direc…
Efficacy of Electric Field Models in Reproducing Observed Ring Current Ion Spectra During Two Geomagnetic Storms
Kistler, L. M.; Mouikis, C. G.; Matsui, H. +4 more
We use the UNH-IMEF, Weimer 1996, https://doi.org/10.1029/96GL02255 and Volland-Stern electric field models along with a dipole magnetic field to calculate drift paths for particles that reach the Van Allen Probes' orbit for two inbound passes during two large geomagnetic storms. We compare the parti…
Deep X-ray view of the Class I YSO Elias 29 with XMM-Newton and NuSTAR
Micela, G.; Reale, F.; Sciortino, S. +4 more
X-ray emission is a characteristic feature of young stellar objects (YSOs) and the result of the interplay between rotation, magnetism, and accretion. For this reason high energy phenomena are key elements to understand the process of star formation, the evolution of their circumstellar disks, and eventually the formation of planets. We investigat…