Search Publications
The Diverse Morphologies and Structures of Dwarf Galaxies Hosting Optically Selected Active Massive Black Holes
Greene, Jenny E.; Geha, Marla; Schutte, Zachary +2 more
We present a study of 41 dwarf galaxies hosting active massive black holes (BHs) using Hubble Space Telescope observations. The host galaxies have stellar masses in the range of M⋆ ∼ 108.5-109.5 M⊙ and were selected to host active galactic nuclei (AGNs) based on narrow emission line ratios derived from S…
Discovery of Double-ring Structure in the Supernova Remnant N103B: Evidence for Bipolar Winds from a Type Ia Supernova Progenitor
Acero, Fabio; Yamaguchi, Hiroya; Chu, You-Hua +1 more
The geometric structure of supernova remnants (SNR) provides a clue to unveiling the pre-explosion evolution of their progenitors. Here we present an X-ray study of N103B (0509-68.7), a Type Ia SNR in the Large Magellanic Cloud, that is known to be interacting with dense circumstellar matter (CSM). Applying our novel method for feature extraction …
Estimating the Contribution of Foreground Halos to the FRB 180924 Dispersion Measure
Simha, Sunil; Prochaska, J. Xavier; Ryder, Stuart D. +6 more
Fast radio burst (FRB) dispersion measures (DMs) record the presence of ionized baryons that are otherwise invisible to other techniques enabling resolution of the matter distribution in the cosmic web. In this work, we aim to estimate the contribution to FRB 180924 DM from foreground galactic halos. Localized by ASKAP to a massive galaxy, this si…
An Atacama Large Millimeter/submillimeter Array Survey of Chemistry in Disks around M4-M5 Stars
Pascucci, Ilaria; Wilner, David J.; Cleeves, L. Ilsedore +10 more
M-stars are the most common hosts of planetary systems in the Galaxy. Protoplanetary disks around M-stars thus offer a prime opportunity to study the chemistry of planet-forming environments. We present an Atacama Large Millimeter/submillimeter Array survey of molecular line emission toward a sample of five protoplanetary disks around M4-M5 stars …
Highly Structured Inner Planetary System Debris around the Intermediate Age Sun-like Star TYC 8830 410 1
Weinberger, Alycia J.; Song, Inseok; Olofsson, Johan +4 more
We present a detailed characterization of the extremely dusty main-sequence star TYC 8830 410 1. This system hosts inner planetary system dust (T dust ≈ 300 K) with a fractional infrared luminosity of ~1%. Mid-infrared spectroscopy reveals a strong, mildly crystalline solid-state emission feature. TYC 8830 410 1 (spectral type G9 V) has…
APOGEE-2 Discovery of a Large Population of Relatively High-metallicity Globular Cluster Debris
Bizyaev, Dmitry; Pan, Kaike; Majewski, Steven R. +13 more
We report the discovery of a new, chemically distinct population of relatively high-metallicity ([Fe/H] > -0.7) red giant stars with super-solar [N/Fe] (≳+0.75) identified within the bulge, disk, and halo of the Milky Way. This sample of stars was observed during the second phase of the Apache Point Observatory Galactic Evolution Experiment (AP…
Direct Measurements of Giant Star Effective Temperatures and Linear Radii: Calibration against Spectral Types and V - K Color
Ciardi, David R.; Clark, Catherine A.; van Belle, Gerard T. +8 more
We calculate directly determined values for effective temperature (T eff) and radius (R) for 191 giant stars based upon high-resolution angular size measurements from optical interferometry at the Palomar Testbed Interferometer. Narrow- to wideband photometry data for the giants are used to establish bolometric fluxes and luminosities t…
Random Walk and Trapping of Interplanetary Magnetic Field Lines: Global Simulation, Magnetic Connectivity, and Implications for Solar Energetic Particles
Matthaeus, William H.; Goldstein, Melvyn L.; Usmanov, Arcadi V. +4 more
The random walk of magnetic field lines is an important ingredient in understanding how the connectivity of the magnetic field affects the spatial transport and diffusion of charged particles. As solar energetic particles propagate away from near-solar sources, they interact with the fluctuating magnetic field, which modifies their distributions. …
Probing Current Sheet Instabilities from Flare Ribbon Dynamics
Matthews, Sarah A.; French, Ryan J.; Jonathan Rae, I. +1 more
The presence of current sheet instabilities, such as the tearing mode instability, are needed to account for the observed rate of energy release in solar flares. Insights into these current sheet dynamics can be revealed by the behavior of flare ribbon substructure, as magnetic reconnection accelerates particles down newly reconnected field lines …
On the Issue of the Origin of Type II Solar Radio Bursts
Chernov, Gennady; Fomichev, Valery
Type II solar radio bursts are among the most powerful events in the solar radio emission in the meter wavelength range. It is generally accepted that the agents generating type II radio bursts are magnetohydrodynamic shock waves. But the relationship between the shock waves and the other manifestations of the large-scale disturbances in the solar…