Search Publications
Neon Abundances of B Stars in the Solar Neighborhood
Zhao, Gang; Alexeeva, Sofya; Sadakane, Kozo +4 more
We constructed a comprehensive model atom for Ne I-Ne II using the most-up-to-date atomic data available and evaluated the nonlocal thermodynamic equilibrium (NLTE) line formation for Ne I and Ne II in classical 1D models representing the atmospheres of B-type stars. We find that the large NLTE strengthening of the Ne I lines corresponding to the …
Hi-C 2.1 Observations of Small-scale Miniature-filament-eruption-like Cool Ejections in an Active Region Plage
Winebarger, Amy R.; Panesar, Navdeep K.; Moore, Ronald L. +5 more
We examine 172 Å ultra-high-resolution images of a solar plage region from the High-Resolution Coronal Imager, version 2.1 (Hi-C 2.1, or Hi-C) rocket flight of 2018 May 29. Over its five minute flight, Hi-C resolved a plethora of small-scale dynamic features that appear near noise level in concurrent Solar Dynamics Observatory (SDO) Atmospheric Im…
A Study of the Observational Properties of Coronal Mass Ejection Flux Ropes near the Sun
Gopalswamy, N.; Sindhuja, G.
We present the observational properties of coronal mass ejection (CME) flux ropes (FRs) near the Sun based on a set of 35 events from solar cycle 24 (2010-2017). We derived the CME FR properties using the Flux Rope from Eruption Data technique. According to this technique, the geometrical properties are obtained from a flux-rope fit to CMEs and th…
Search for Alignment of Disk Orientations in Nearby Star-forming Regions: Lupus, Taurus, Upper Scorpius, ρ Ophiuchi, and Orion
Suto, Yasushi; Aizawa, Masataka; Nakazato, Takeshi +2 more
Spatial correlations among protoplanetary disk orientations carry unique information on physics of multiple-star formation processes. We select five nearby star-forming regions that comprise a number of protoplanetary disks with spatially resolved images with ALMA and Hubble Space Telescope, and we search for the mutual alignment of the disk axes.…
Oversized Gas Clumps in an Extremely Metal-poor Molecular Cloud Revealed by ALMA's Parsec-scale Maps
Qiu, Keping; Chen, Yanmei; Zhang, Qizhou +8 more
Metals are thought to have profound effects on the internal structures of the molecular clouds in which stars are born. The absence of metals is expected to prevent gas from efficient cooling and fragmentation in theory. However, this effect has not yet been observed in low-metallicity environments, such as in the early universe and local dwarf ga…
Connecting the Local Stellar Halo and Its Dark Matter Density to Dwarf Galaxies via Blue Stragglers
Casagrande, Luca
The Gaia H-R diagram shows the presence of apparently young stars at high tangential velocities. Using a simple analytical model, I show that these stars are likely to be blue stragglers. Once normalized to red giant stars, the fraction of nearby halo blue stragglers is of order 20%, and remarkably close to that measured in dwarf galaxies. Motivat…
Paβ, Hα, and Attenuation in NGC 5194 and NGC 6946
Murphy, Eric; Schinnerer, Eva; Wong, Tony +5 more
We combine Hubble Space Telescope Paschen β (Paβ) imaging with ground-based, previously published Hα maps to estimate the attenuation affecting Hα, A(Hα), across the nearby, face-on galaxies NGC 5194 and NGC 6946. We estimate A(Hα) in ∼2000 independent 2″ ∼ 75 pc diameter apertures in each galaxy, spanning out to a galactocentric radius of almost …
Applying Noether's Theorem to Matter in the Milky Way: Evidence for External Perturbations and Non-steady-state Effects from Gaia Data Release 2
Yanny, Brian; Gardner, Susan; Hinkel, Austin
We apply Noether's theorem to observations of main-sequence stars from the Gaia Data Release 2 archive to probe the matter distribution function of the Galaxy. That is, we examine the axial symmetry of stars at vertical heights z, $0.2\leqslant | z| \leqslant 3\,\mathrm{kpc}$ , to probe the quality of the angular momentum Lz as an integ…
Assessing Spectroscopic Binary Multiplicity Properties Using Robo-AO Imaging
Stassun, Keivan G.; Mathieu, Robert D.; Laos, Emily
We present higher-order multiplicity results for 60 solar-type spectroscopic binaries based on 0.75 µm imaging data taken by the robotic adaptive optics (Robo-AO) system at the Kitt Peak 2.1 m telescope. Our contrast curves show sensitivity up to ∼5 mag at ∼1″ separation; at very small separations, we identify candidate companions from image…
Carbon- and Oxygen-rich Asymptotic Giant Branch (AGB) Stars in the Bulge Asymmetries and Dynamical Evolution (BAaDE) Survey
Morris, Mark R.; Stroh, Michael C.; Sjouwerman, Loránt O. +3 more
Detections of SiO masers from the Bulge Asymmetries and Dynamical Evolution (BAaDE) survey more tightly define the region where Oxygen-rich (O) Asymptotic Giant Branch (AGB) stars reside in multiple infrared (IR) color-color diagrams. Using Midcourse Space eXperiment (MSX) and Two Micron All Sky Survey (2MASS) data along with radio spectra from th…