Search Publications
Discovery of 18 Stars with -3.10 < [Fe/H] < -1.45 in the Sagittarius Dwarf Galaxy
Frebel, Anna; Chiti, Anirudh; Hansen, Kylie Y.
Studies of the early chemical evolution of some larger dwarf galaxies (>107 M⊙) are limited by the small number of stars known at low metallicities in these systems. Here we present metallicities and carbon abundances for eighteen stars with metallicities between -3.08 ≤ [Fe/H] ≤ -1.47 in the Sagittarius dwarf spheroidal g…
The Streamer Blowout Origin of a Flux Rope and Energetic Particle Event Observed by Parker Solar Probe at 0.5 au
Luhmann, J. G.; Lario, D.; Arge, C. N. +18 more
The distribution of spacecraft in the inner heliosphere during 2019 March enabled comprehensive observations of an interplanetary coronal mass ejection (ICME) that encountered Parker Solar Probe (PSP) at 0.547 au from the Sun. This ICME originated as a slow (∼311 km s-1) streamer blowout (SBO) on the Sun as measured by the white-light c…
Detection of the Red Supergiant Wind from the Progenitor of Cassiopeia A
Chevalier, Roger A.; Raymond, John C.; Milisavljevic, Dan +4 more
Cassiopeia A (Cas A) is one of the best studied young Galactic supernova remnants. While it provides a rare opportunity to study in detail the remnant of a supernova (SN) type IIb, questions remain regarding the nature of its progenitor, its mass-loss history, and its pre-SN evolution. Here we present an optical investigation of the circumstellar …
The Warm Gas in the MW: A Kinematical Model
Bregman, Joel N.; Qu, Zhijie; Lindley, Ryan +2 more
We develop a kinematical model for the Milky Way Si IV-bearing gas to determine its density distribution and kinematics. This model is constrained by a column density line-shape sample extracted from the Hubble Space Telescope/Cosmic Origins Spectrograph archival data, which contains 186 active galactic nucleus sight lines. We find that the Si IV …
ZFIRE: Measuring Electron Density with [O II] as a Function of Environment at z = 1.62
Papovich, Casey; Kewley, Lisa J.; Harshan, Anishya +8 more
The global star formation rates (SFR) of galaxies at fixed stellar masses increase with redshift and are known to vary with environment up to z ∼ 2. We explore here whether the changes in the SFRs also apply to the electron densities of the interstellar medium by measuring the [O II] (λ 3726, λ 3729) ratio for cluster and field galaxies at z ∼ 2. …
On the Coronal Temperature in Solar Microflares
Testa, Paola; Reale, Fabio
We present a study of solar imaging and spectral observations of a microflare, focusing on the temperature diagnostics provided by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory, and the Extreme-Ultraviolet Imaging Spectrometer (EIS) on board Hinode. Our data analysis, in particular from the emission in the 131 and …
On the Relation between the Hard X-Ray Photon Index and Accretion Rate for Super-Eddington Accreting Quasars
Luo, Bin; Huang, Jian; Du, Pu +3 more
We investigate whether the correlation between the hard X-ray photon index ( ${\rm{\Gamma }}$ ) and accretion rate for super-Eddington accreting quasars is different from that for sub-Eddington accreting quasars. We construct a sample of 113 bright quasars from the Sloan Digital Sky Survey Data Release 14 quasar catalog, with 38 quasars as the sup…
Steady Wind-blown Cavities within Infalling Rotating Envelopes: Application to the Broad Velocity Component in Young Protostars
Johnstone, Doug; Cabrit, Sylvie; Kristensen, Lars E. +1 more
Wind-driven outflows are observed around a broad range of accreting objects throughout the universe, ranging from forming low-mass stars to supermassive black holes. We study the interaction between a central isotropic wind and an infalling, rotating envelope, which determines the steady-state cavity shape formed at their interface under the assum…
A Small-scale Filament Eruption Inducing a Moreton Wave, an EUV Wave, and a Coronal Mass Ejection
Xue, Zhike; Yan, Xiaoli; Wang, Jincheng +3 more
With the launch of the Solar Dynamic Observatory, many extreme ultraviolet (EUV) waves have been observed during solar eruptions. However, joint observations of Moreton and EUV waves are still relatively rare. We present an event in active region NOAA 12740 wherein a small-scale filament eruption simultaneously results in a Moreton wave, an EUV wa…
Statistical Analysis of the Relation between Coronal Mass Ejections and Solar Energetic Particles
Yashiro, Seiji; Nitta, Nariaki V.; Ichimoto, Kiyoshi +4 more
To improve the forecasting capability of impactful solar energetic particle (SEP) events, the relation between coronal mass ejections (CMEs) and SEP events needs to be better understood. Here we present a statistical study of SEP occurrences and timescales with respect to the CME source locations and speeds, considering all 257 fast (vCME