Search Publications
Why the Shock-ICME Complex Structure Is Important: Learning from the Early 2017 September CMEs
Wang, Yuming; Shen, Chenglong; Luo, Bingxian +2 more
In the early days of 2017 September, an exceptionally energetic solar active region AR 12673 aroused great interest in the solar physics community. It produced four X class flares, more than 20 coronal mass ejections (CMEs), and an intense geomagnetic storm, for which the peak value of the Dst index reached up to -142 nT at 2017 September 8 02:00 …
SN 2017ein and the Possible First Identification of a Type Ic Supernova Progenitor
Van Dyk, Schuyler D.; Filippenko, Alexei V.; Kelly, Patrick L. +11 more
We have identified a progenitor candidate in archival Hubble Space Telescope (HST) images for the Type Ic supernova (SN Ic) SN 2017ein in NGC 3938, pinpointing the candidate’s location via HST Target of Opportunity imaging of the SN itself. This would be the first identification of a stellar-like object as a progenitor candidate for any SN Ic to d…
The Black Hole in the Most Massive Ultracompact Dwarf Galaxy M59-UCD3
Romanowsky, Aaron J.; Pechetti, Renuka; Krajnović, Davor +19 more
We examine the internal properties of the most massive ultracompact dwarf galaxy (UCD), M59-UCD3, by combining adaptive-optics-assisted near-IR integral field spectroscopy from Gemini/NIFS and Hubble Space Telescope (HST) imaging. We use the multiband HST imaging to create a mass model that suggests and accounts for the presence of multiple stella…
Electron Acceleration by Dipolarization Fronts and Magnetic Reconnection: A Quantitative Comparison
Xu, Y.; Fu, H. S.; Liu, C. M. +1 more
Suprathermal electrons with energy from tens to hundreds of keV are frequently observed in the Earth's magnetotail. The generation of such electrons is typically attributed to magnetic reconnection, dipolarization fronts (DFs), or flux transport. However, which of these contributes more to this generation remains unclear. In this study, we quantit…
The R-Process Alliance: A Comprehensive Abundance Analysis of HD 222925, a Metal-poor Star with an Extreme R-process Enhancement of [Eu/H] = -0.14
Beers, Timothy C.; Placco, Vinicius M.; Hansen, Terese T. +4 more
We present a detailed abundance analysis of the bright (V = 9.02), metal-poor ([Fe/H] = -1.47 ± 0.08) field red horizontal-branch star HD 222925, which was observed as part of an ongoing survey by the R-Process Alliance. We calculate stellar parameters and derive abundances for 46 elements based on 901 lines examined in a high-resolution optical s…
Characteristics of Late-phase >100 MeV Gamma-Ray Emission in Solar Eruptive Events
White, S. M.; Dennis, B. R.; Murphy, R. J. +5 more
We characterize and catalog 30 solar eruptive events observed by the Fermi Large Area Telescope (LAT) having late-phase >100 MeV γ-ray emission (LPGRE), identified 30 yr ago in what were called long-duration gamma-ray flares. We show that LPGRE is temporally and spectrally distinct from impulsive phase emission in these events. The spectra are …
BANYAN. XII. New Members of Nearby Young Associations from GAIA-Tycho Data
Faherty, Jacqueline K.; Gagné, Jonathan; Doyon, René +2 more
We present a search for stellar members of young associations within 150 pc of the Sun, based on TGAS and an updated version of the BANYAN Σ software to determine Bayesian membership probabilities that includes Gaia-2MASS color-magnitude diagrams. We identify 32 new F0-M3-type bona fide members of the 10-200 Myr old Sco-Cen, Carina, Tucana-Horolog…
The Redshift Evolution of Rest-UV Spectroscopic Properties in Lyman-break Galaxies at z ∼ 2-4
Pettini, Max; Erb, Dawn K.; Shapley, Alice E. +8 more
We present the first comprehensive evolutionary analysis of the rest-frame UV spectroscopic properties of star-forming galaxies at z ∼ 2-4. We match samples at different redshifts in UV luminosity and stellar mass, and perform systematic measurements of spectral features and stellar population modeling. By creating composite spectra grouped accord…
The Distance of the Dark Matter Deficient Galaxy NGC 1052-DF2
van Dokkum, Pieter; Romanowsky, Aaron J.; Conroy, Charlie +2 more
We recently inferred that the galaxy NGC 1052-DF2 has little or no dark matter and a rich system of unusual globular clusters. We assumed that the galaxy is a satellite of the luminous elliptical galaxy NGC 1052 at ≈20 Mpc, on the basis of its surface brightness fluctuations (SBFs) distance of 19.0 ± 1.7 Mpc, its radial velocity of ≈1800 km s…
Detecting Black Hole Binaries by Gaia
Bulik, Tomasz; Piran, Tsvi; Kawanaka, Norita +1 more
We study the prospects of the Gaia satellite to identify black hole (BH) binary systems by detecting the orbital motion of the companion stars. Taking into account the initial mass function, mass transfer, common envelope phase, interstellar absorption, and identifiability of the systems, we estimate the number of BH binaries that can be detected …