ORCID Profile
0000-0001-6072-9344
Current Organisation
University of Arizona
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Publisher: American Astronomical Society
Date: 08-03-2022
Abstract: We train a convolutional neural network, APOGEE Net, to predict T eff , log g , and, for some stars, [Fe/H], based on the APOGEE spectra. This is the first pipeline adapted for these data that is capable of estimating these parameters in a self-consistent manner not only for low-mass stars, (such as main-sequence dwarfs, pre-main-sequence stars, and red giants), but also high-mass stars with T eff in excess of 50,000 K, including hot dwarfs and blue supergiants. The catalog of ∼650,000 stars presented in this paper allows for a detailed investigation of the star-forming history of not just the Milky Way, but also of the Magellanic clouds, as different type of objects tracing different parts of these galaxies can be more cleanly selected through their distinct placement in T eff – log g parameter space than in previous APOGEE catalogs produced through different pipelines.
Publisher: American Astronomical Society
Date: 11-01-2023
Abstract: The Sloan Digital Sky Survey IV APOGEE-2 primary science goal was to observe red giant stars throughout the Galaxy to study its dynamics, morphology, and chemical evolution. The APOGEE instrument, a high-resolution 300-fiber H -band (1.55–1.71 μ m) spectrograph, is also ideal to study other stellar populations in the Galaxy, among which are a number of star-forming regions and young open clusters. We present the results of the determination of six stellar properties ( T eff , log g , [Fe/H], L / L ⊙ , M / M ⊙ , and age) for a s le that is composed of 3360 young stars, of subsolar to supersolar types, in 16 Galactic star formation and young open cluster regions. Those sources were selected by using a clustering method that removes most of the field contamination. S les were also refined by removing targets affected by various systematic effects of the parameter determination. The final s les are presented in a comprehensive catalog that includes all six estimated parameters. This overview study also includes parameter spatial distribution maps for all regions and Hertzsprung–Russell ( log L / L ⊙ vs. T eff ) diagrams. This study serves as a guide for detailed studies on in idual regions and paves the way for the future studies on the global properties of stars in the pre-main-sequence phase of stellar evolution using more robust s les.
Publisher: American Astronomical Society
Date: 02-2022
Abstract: Understanding the origin of accretion and dispersal of protoplanetary disks is fundamental for investigating planet formation. Recent numerical simulations show that launching winds are unavoidable when disks undergo magnetically driven accretion and/or are exposed to external UV radiation. Observations also hint that disk winds are common. We explore how the resulting wind mass loss rate can be used as a probe of both disk accretion and dispersal. As a proof-of-concept study, we focus on magnetocentrifugal winds, magnetorotational instability turbulence, and external photoevapotaion. By developing a simple yet physically motivated disk model and coupling it with simulation results available in the literature, we compute the wind mass loss rate as a function of external UV flux for each mechanism. We find that different mechanisms lead to different levels of mass loss rate, indicating that the origin of disk accretion and dispersal can be determined, by observing the wind mass loss rate resulting from each mechanism. This determination provides important implications for planet formation. This work thus shows that the ongoing and future observations of the wind mass loss rate for protoplanetary disks are paramount to reliably constrain how protoplanetary disks evolve with time and how planet formation takes place in the disks.
Publisher: American Astronomical Society
Date: 29-04-2019
No related grants have been discovered for Jinyoung Serena Kim.