Search Publications
Four-hundred Very Metal-poor Stars Studied with LAMOST and Subaru. I. Survey Design, Follow-up Program, and Binary Frequency
Shi, Jianrong; Zhao, Gang; Chen, Yuqin +11 more
The chemical abundances of very metal-poor stars provide important constraints on the nucleosynthesis of the first generation of stars and early chemical evolution of the Galaxy. We have obtained high-resolution spectra with the Subaru Telescope for candidates of very metal-poor stars selected with a large survey of Galactic stars carried out with…
Star Formation Suppression by Tidal Removal of Cold Molecular Gas from an Intermediate-redshift Massive Post-starburst Galaxy
Bezanson, Rachel; Kriek, Mariska; Greene, Jenny E. +7 more
Observations and simulations have demonstrated that star formation in galaxies must be actively suppressed to prevent the formation of overly massive galaxies. Galactic outflows driven by stellar feedback or supermassive black hole accretion are often invoked to regulate the amount of cold molecular gas available for future star formation but may …
METAL: The Metal Evolution, Transport, and Abundance in the Large Magellanic Cloud Hubble Program. IV. Calibration of Dust Depletions versus Abundance Ratios in the Milky Way and Magellanic Clouds and Application to Damped Lyα Systems
Jenkins, Edward B.; Yanchulova Merica-Jones, Petia; Gordon, Karl D. +9 more
The evolution of the metal content of the universe can be tracked through rest-frame UV spectroscopy of damped Lyα systems (DLAs). Gas-phase abundances in DLAs must be corrected for dust depletion effects, which can be accomplished by calibrating the relation between abundance ratios such as [Zn/Fe] and depletions (the fraction of metals in gas, a…
Coronal Mass Ejection Deformation at 0.1 au Observed by WISPR
Vourlidas, Angelos; Stenborg, Guillermo; Hess, Phillip +3 more
Although coronal mass ejections (CMEs) resembling flux ropes generally expand self-similarly, deformations along their fronts have been reported in observations and simulations. We present evidence of one CME becoming deformed after a period of self-similar expansion in the corona. The event was observed by multiple white-light imagers on 2021 Jan…
Near-Earth Sub-Alfvénic Solar Winds: Interplanetary Origins and Geomagnetic Impacts
Hajra, Rajkumar; Tsurutani, Bruce T.
The near-Earth solar wind is in general super-Alfvénic and supermagnetosonic. Using all available near-Earth solar wind measurements between 1973 and 2020, we identified 30 intervals with sub-Alfvénic solar winds. The majority (83%) of the events occurred within interplanetary coronal mass ejection magnetic clouds (MCs)/driver gases. These MC sub-…
Quasi-periodic Accelerations of Energetic Particles during a Solar Flare
Chen, Wei; Li, Dong
We report the observation of nonstationary quasi-periodic pulsations (QPPs) in high-energy particles during the impulsive phase of an X4.8 flare on 2002 July 23 (SOL2002-07-23T00:35). The X4.8 flare was simultaneously measured by the Reuven Ramaty High Energy Solar Spectroscopic Imager, Nobeyama Radio Polarimeters, and Nobeyama Radioheliograph. Th…
Chemodynamical Signatures of Bar Resonances in the Galactic Disk: Current Data and Future Prospects
Fragkoudi, Francesca; Wheeler, Adam; Ness, Melissa +2 more
The Galactic disk exhibits complex chemical and dynamical substructure thought to be induced by the bar, spiral arms, and satellites. Here, we explore the chemical signatures of bar resonances in action and velocity space, and characterize the differences between the signatures of corotation (CR) and higher-order resonances using test particle sim…
Binary Formation in the Orion Nebula Cluster: Exploring the Substellar Limit
Reiter, Megan; Meyer, Michael R.; De Furio, Matthew +3 more
We present results constraining the multiplicity of the very low mass stars and substellar objects in the Orion Nebula Cluster (ONC). Our sample covers primary masses 0.012-0.1 M ⊙ using archival Hubble Space Telescope data obtained with the Advanced Camera for Surveys using multiple filters. Studying the binary populations of clusters …
V606 Cen: A Newly Formed Massive Contact Binary in a Hierarchical Triple System
Zhang, J.; Qian, S. -B.; Liao, W. -P. +3 more
V606 Centauri (V606 Cen) is an early B-type close binary with an orbital period of 1.4950935 days, and its complete light curves are very difficult to observe on the ground. By analyzing the continuous light curve obtained by TESS, we found that it is a marginal contact binary with a very low fill-out factor of about 2%. The O - C diagram of V606 …
The HST Large Program on ω Centauri. V. Exploring the Ultracool Dwarf Population with Stellar Atmosphere and Evolutionary Modeling
Anderson, Jay; Salaris, Maurizio; Burgasser, Adam J. +5 more
Brown dwarfs can serve as both clocks and chemical tracers of the evolutionary history of the Milky Way due to their continuous cooling and high sensitivity of spectra to composition. We focus on brown dwarfs in globular clusters that host some of the oldest coeval populations in the galaxy. Currently, no brown dwarfs in globular clusters have bee…