Search Publications
A Sub-damped Lyα Absorber with Unusual Abundances: Evidence of Gas Recycling in a Low-redshift Galaxy Group
Frye, Brenda L.; Bowen, David V.; Tripp, Todd M. +3 more
Using Hubble Space Telescope/Space Telescope Imaging Spectrograph G140M spectroscopy, we investigate an absorption-line system at z = 0.07489 in the spectrum of the quasi-stellar object PG 1543+489 (z QSO = 0.401). The sightline passes within ρ = 66 kpc of an edge-on 2{L}* disk galaxy at a similar redshift, but the galaxy be…
The Enhancement of the Energetic Particle Intensities in ICMEs
Li, Gang; Wang, Yuming; Shen, Chenglong +5 more
The behavior of energetic particles in interplanetary coronal mass ejections (ICMEs) is of great interest. In general, due to the relatively closed magnetic structures of ICMEs, the energetic-particle intensities are usually depressed in them. However, previous studies have found some counterexamples. In this work, using protons with energies form…
Understanding the Plasma and Magnetic Field Evolution of a Filament Using Observations and Nonlinear Force-free Field Modeling
Savcheva, Antonia; van Driel-Gesztelyi, Lidia; Green, Lucie M. +4 more
We present observations and magnetic field models of an intermediate filament present on the Sun in 2012 August, associated with a polarity inversion line that extends from AR 11541 in the east into the quiet Sun at its western end. A combination of Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly, SDO/Helioseismic and Magnetic Imager…
Blue Straggler Stars beyond the Milky Way. IV. Radial Distributions and Dynamical Implications
Sills, Alison; Hong, Jongsuk; Deng, Licai +3 more
Blue straggler stars (BSSs) have been proposed as powerful indicators to measure the dynamical state of Galactic globular clusters (GCs). Here we examine for the first time whether this framework of BSSs as dynamical clocks, which was specifically developed for Galactic GCs, may also hold for younger GCs in the Large Magellanic Cloud (LMC). Using …
The Mass of the White Dwarf Companion in the Self-lensing Binary KOI-3278: Einstein versus Newton
Kruse, Ethan; Latham, David W.; Quinn, Samuel N. +10 more
KOI-3278 is a self-lensing stellar binary consisting of a white dwarf secondary orbiting a Sun-like primary star. Kruse & Agol noticed small periodic brightenings every 88.18 days in the Kepler photometry and interpreted these as the result of microlensing by a white dwarf with about 63% of the mass of the Sun. We obtained two sets of spectra …
A Chandra Study: Are Dwarf Carbon Stars Spun Up and Rejuvenated by Mass Transfer?
Roulston, Benjamin R.; Green, Paul J.; Anderson, Scott F. +9 more
Carbon stars (with C/O > 1) were long assumed to all be giants, because only asymptotic giant branch (AGB) stars dredge up significant carbon into their atmospheres. The case is nearly ironclad now that the formerly mysterious dwarf carbon (dC) stars are actually far more common than C giants and have accreted carbon-rich material from a former…
Are the Double-mode Bulge RR Lyrae Stars with Identical Period Ratios the Relic of a Disrupted Stellar System?
Rich, R. Michael; Kunder, Andrea; Johnson, Christian I. +6 more
Radial velocities of 15 double-mode bulge RR Lyrae (RR01) stars are presented, 6 of which belong to a compact group of RR01 stars in pulsation space, with the ratio of first-overtone period to fundamental mode period, P fo /P f ∼ 0.74, and P f ∼ 0.44. It has been suggested that these pulsationally clumped RR01…
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 …
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…
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…