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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…
Interpreting the Statistical Properties of High-z Extragalactic Sources Detected by the South Pole Telescope Survey
Cai, Zhen-Yi; Negrello, Mattia; De Zotti, Gianfranco
The results of the recently published spectroscopically complete survey of dusty star-forming galaxies detected by the South Pole Telescope over 2500 deg2 proved to be challenging for galaxy formation models that generally underpredict the observed abundance of high-z galaxies. In this paper we interpret these results in the light of a …
The Color Gradients of the Globular Cluster Systems in M87 and M49
Liu, Chengze; Côté, Patrick; Peng, Eric W. +8 more
Combining data from the ACS Virgo Cluster Survey and the Next Generation Virgo cluster Survey, we extend previous studies of color gradients of the globular cluster (GC) systems of the two most massive galaxies in the Virgo cluster, M87 and M49, to radii of ~15 R e (~200 kpc for M87 and ~250 kpc for M49, where R e is the ef…
Follow-up of Young Stars Identified with BANYAN Σ: New Low-mass Members of Nearby Moving Groups
Johns-Krull, Christopher M.; Flagg, L.; Stahl, Asa G.
The characterization of moving groups offers a powerful means to identify large populations of young stars. In this paper, we present a sample of follow-up observations for 56 systems that have previously been proposed as members of young stellar associations through the application of the BANYAN Σ kinematic classification tool. Our measurements, …
Extremely Slow (V sw < 300 km s-1) Solar Winds (ESSWs) at 1 au: Causes of Extreme Geomagnetic Quiet at Earth
Hajra, Rajkumar; Tsurutani, Bruce T.
A search for extremely slow (V sw < 300 km s-1) solar winds (ESSWs) at 1 au has been conducted using hourly average solar wind data from 1963 through 2021. 297 ESSW events were identified with an average duration of ~2.0 ± 1.4 days. The lowest speed detected was 156 km s-1. Ten of the lowest-speed events were an…
Investigation of the Timing and Spectral Properties of an Ultraluminous X-Ray Pulsar NGC 7793 P13
Hu, Chin-Ping; Kong, A. K. H.; Hui, C. Y. +3 more
We perform both timing and spectral analyses using the archival X-ray data taken with Swift, XMM-Newton, NICER, and NuSTAR from 2016 to 2020 to study an ultraluminous pulsar, NGC 7793 P13, that showed a long period of super-Eddington accretion. We use the Rayleigh test to investigate the pulsation at different epochs, and confirm the variation of …
Sequential Star Formation in the Young SMC Region NGC 602: Insights from ALMA
Bolatto, Alberto D.; Meixner, Margaret; Sabbi, Elena +7 more
NGC 602 is a young, low-metallicity star cluster in the "Wing" of the Small Magellanic Cloud. We reveal the recent evolutionary past of the cluster through analysis of high-resolution (~0.4 pc) Atacama Large Millimeter/submillimeter Array observations of molecular gas in the associated H II region N90. We identify 110 molecular clumps (R < 0.8 …