Search Publications
Machine Learning Applied to Star-Galaxy-QSO Classification and Stellar Effective Temperature Regression
Bai, Yu; Wang, Song; Yang, Fan +1 more
In modern astrophysics, machine learning has increasingly gained popularity with its incredibly powerful ability to make predictions or calculated suggestions for large amounts of data. We describe an application of the supervised machine-learning algorithm, random forests (RF), to the star/galaxy/QSO classification and the stellar effective tempe…
Li Evolution and the Open Cluster NGC 6819: A Correlation between Li Depletion and Spindown in Dwarfs More Massive Than the F-Dwarf Li-Dip
Twarog, Bruce A.; Anthony-Twarog, Barbara J.; Deliyannis, Constantine P. +1 more
Spectroscopy of 333 NGC 6819 stars and Gaia astrometry are used to map Li evolution from the giant branch tip to 0.5 mag below the Li dip. Isochrone comparison with [Fe/H] = -0.04, based upon neural network spectroscopic analysis, produces an age of 2.25 (2.4) Gyr for E(B - V) = 0.16 (0.14) and (m - M) = 12.40 (12.29). Despite originating outside …
The Physics of the Accelerating Universe Camera
Carretero, Jorge; Castander, Francisco J.; Eriksen, Martin +30 more
The Physics of the Accelerating Universe (PAU) Survey goal is to obtain photometric redshifts (photo-z) and spectral energy distributions (SEDs) of astronomical objects with a resolution roughly one order of magnitude better than current broadband (BB) photometric surveys. To accomplish this, a new large field-of-view (FoV) camera (PAUCam) has bee…
Cloud Atlas: Hubble Space Telescope Near-infrared Spectral Library of Brown Dwarfs, Planetary-mass Companions, and Hot Jupiters
Schneider, Glenn; Apai, Dániel; Burgasser, Adam J. +12 more
Bayesian atmospheric retrieval tools can place constraints on the properties of brown dwarfs' and hot Jupiters' atmospheres. To fully exploit these methods, high signal-to-noise spectral libraries with well-understood uncertainties are essential. We present a high signal-to-noise spectral library (1.10-1.69 µm) of the thermal emission of 76 …
Stellar Proper Motions in the Orion Nebula Cluster
Lu, Jessica R.; Anderson, Jay; Morris, Mark R. +5 more
The Orion Nebula Cluster (ONC) is the nearest site of ongoing massive star formation, which allows us to study the kinematics and dynamics of the region in detail and constrain star formation theories. Using HST ACS/WFPC2/WFC3IR and Keck II NIRC2 data, we have measured the proper motions of 701 stars within an ∼6‧ × 6‧ field of view around the cen…
Long-term Variations of Venus’s 365 nm Albedo Observed by Venus Express, Akatsuki, MESSENGER, and the Hubble Space Telescope
Marcq, Emmanuel; Imamura, Takeshi; Titov, Dmitrij V. +16 more
An unknown absorber near the cloud-top level of Venus generates a broad absorption feature from the ultraviolet (UV) to visible, peaking around 360 nm, and therefore plays a critical role in the solar energy absorption. We present a quantitative study of the variability of the cloud albedo at 365 nm and its impact on Venus’s solar heating rates ba…
Kinematics of the Palomar 5 Stellar Stream from RR Lyrae Stars
Price-Whelan, Adrian M.; Belokurov, Vasily; Bonaca, Ana +3 more
Thin stellar streams, formed from the tidal disruption of globular clusters, are important gravitational tools, sensitive to both global and small-scale properties of dark matter. The Palomar 5 stellar stream (Pal 5) is an exemplar stream within the Milky Way: its ∼20° tidal tails connect back to the progenitor cluster, and the stream has been use…
The Role of Cluster Mass in the Multiple Populations of Galactic and Extragalactic Globular Clusters
Milone, Antonino P.; Tailo, Marco; Lagioia, Edoardo P. +2 more
Studies based on Hubble Space Telescope (HST) photometry in F275W, F336W, and F438W have shown that the incidence and complexity of multiple populations (MPs) in globular clusters (GCs) depend on cluster mass. This result, however, is based on nearby, low-reddening Galactic GCs, for which we can obtain accurate F275W photometry. In this work, we e…
Extreme Debris Disk Variability: Exploring the Diverse Outcomes of Large Asteroid Impacts During the Era of Terrestrial Planet Formation
Reichart, D. E.; Rujopakarn, W.; Dong, Ruobing +14 more
The most dramatic phases of terrestrial planet formation are thought to be oligarchic and chaotic growth, on timescales of up to 100-200 Myr, when violent impacts occur between large planetesimals of sizes up to protoplanets. Such events are marked by the production of large amounts of debris, as has been observed in some exceptionally bright and …
Speckle Interferometry at SOAR in 2018
Tokovinin, Andrei; Briceño, Cesar; Horch, Elliott P. +2 more
The results of speckle interferometric observations at the 4.1 m Southern Astrophysical Research Telescope (SOAR) in 2018 are given, totaling 3097 measurements of 2427 resolved pairs with separations from 11 mas to 5.″9 (median 0.″15, magnitude difference up to 7 mag) and nonresolutions of 624 targets. This work continues our long-term speckle pro…