Search Publications
COol Companions ON Ultrawide orbiTS (COCONUTS). III. A Very Red L6 Benchmark Brown Dwarf around a Young M5 Dwarf
Magnier, Eugene A.; Shappee, Benjamin J.; Morley, Caroline V. +5 more
We present the third discovery from the COol Companions ON Ultrawide orbiTS (COCONUTS) program, the COCONUTS-3 system, composed of the young M5 primary star UCAC4 374-046899 and the very red L6 dwarf WISEA J081322.19-152203.2. These two objects have a projected separation of $61^{\prime\prime} $ (1891 au) and are physically associated given their …
The Star Formation-Gas Density Relation in Four Galactic GMCs: Effects of Stellar Feedback
Bieging, John H.; Kong, Shuo
We present maps of four Galactic giant molecular clouds (GMCs) in the J = 2-1 emission of both CO and 13CO. We use an LTE analysis to derive maps of the CO excitation temperature and column density and the distribution of total molecular gas column density, Σgas. The depletion of CO by freeze-out onto cold dust grains is acco…
Constraining Global Solar Models through Helioseismic Analysis
Kosovichev, Alexander G.; Stejko, Andrey M.; Guerrero, Gustavo +4 more
Global hydrodynamic simulations of internal solar dynamics have focused on replicating the conditions for solar-like (equator rotating faster than the poles) differential rotation and meridional circulation using the results of helioseismic inversions as a constraint. Inferences of meridional circulation, however, have provided controversial resul…
The Mysterious Affair of the H2 in AU Mic
France, Kevin; Youngblood, Allison; Johns-Krull, Christopher M. +8 more
Molecular hydrogen is the most abundant molecule in the galaxy and plays important roles in planets, their circumstellar environments, and many of their host stars. We have confirmed the presence of molecular hydrogen in the AU Mic system using high-resolution FUV spectra from HST-STIS during both quiescence and a flare. AU Mic is a ~23 Myr M dwar…
Multipoint Analysis of the Interaction between a Shock and an ICME-like Structure around 2011 March 22
Wang, Yuming; Shen, Chenglong; Xu, Mengjiao +3 more
This work reports on the interaction between a fast forward shock and an interplanetary coronal-mass-ejection-like structure (ICMELS) as observed by in situ observations of radially aligned spacecraft. Around 2011 March 22, the Venus EXpress (VEX) and Solar TErrestrial RElations Observatory-A (STEREO-A) were nearly at the same longitude, providing…
Spectroscopic Line Modeling of the Fastest Rotating O-type Stars
Gies, Douglas R.; Shepard, Katherine; Kaper, Lex +1 more
We present a spectroscopic analysis of the most rapidly rotating stars currently known, VFTS 102 ( ${v}_{e}\sin i=649\pm 52$ km s-1; O9: Vnnne+) and VFTS 285 ( ${v}_{e}\sin i=610\pm 41$ km s-1; O7.5: Vnnn), both members of the 30 Dor complex in the Large Magellanic Cloud. This study is based on high-resolution ultraviolet spe…
The Orbits and Dynamical Masses of the Castor System
Torres, Guillermo; Klement, Robert; Monnier, John D. +12 more
Castor is a system of six stars in which the two brighter objects, Castor A and B, revolve around each other every ~450 yr and are both short-period spectroscopic binaries. They are attended by the more distant Castor C, which is also a binary. Here we report interferometric observations with the Center for High Angular Resolution Astronomy (CHARA…
At What Mass Are Stars Braked? The Implication from the Turnoff Morphology of NGC 6819
Huang, Yang; Li, Chengyuan; Yang, Yong +1 more
Extended main-sequence turnoffs (eMSTOs) apparent in most young and intermediate-age clusters (younger than ~2 Gyr) are known features caused by fast rotating early-type (earlier than F-type) stars. Late-type stars are not fast rotators because their initial angular momenta have been quickly dispersed due to magnetic braking. However, the mass lim…
Additions to the Spectrum of Fe IX in the 110-200 Å Region
Young, Peter R.; Ryabtsev, Alexander N.; Kononov, Edward Y.
The spectrum of eight-times ionized iron, Fe IX, was studied in the 110-200 Å region. A low inductance vacuum spark and a 3 m grazing incidence spectrograph were used for the excitation and recording of the spectrum. Previous analyses of Fe IX have been greatly extended and partly revised. The number of known lines in the 3p 53d-3p
Very Metal-poor Stars in the Solar Vicinity: Age Determination
Villanova, Sandro; Carraro, Giovanni; Plotnikova, Anastasiia +1 more
The ages of the oldest and most metal-poor stars in the Milky Way bear important information on the age of the universe and its standard model. We analyze a sample of 28 extremely metal-poor field stars in the solar vicinity culled from the literature and carefully determine their ages. To this aim, we critically make use of Gaia data to derive th…