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- Astronautics (2)
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- BASE-9 (1)
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- Galaxy: kinematics and dynamics (1)
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Articles 1 - 8 of 8
Full-Text Articles in Physical Sciences and Mathematics
A Deep Proper Motion Catalog Within The Sloan Digital Sky Survey Footprint, Jeffrey A. Munn, Hugh C. Harris, Ted Von Hippel, Mukremin Kilic, James W. Liebert, Kurtis A. Williams, Steven Degenarro, Elizabeth Jeffery, Trudy M. Tilleman
A Deep Proper Motion Catalog Within The Sloan Digital Sky Survey Footprint, Jeffrey A. Munn, Hugh C. Harris, Ted Von Hippel, Mukremin Kilic, James W. Liebert, Kurtis A. Williams, Steven Degenarro, Elizabeth Jeffery, Trudy M. Tilleman
Publications
A new proper motion catalog is presented, combining the Sloan Digital Sky Survey (SDSS) with second epoch observations in the r band within a portion of the SDSS imaging footprint. The new observations were obtained with the 90prime camera on the Steward Observatory Bok 90 inch telescope, and the Array Camera on the U.S. Naval Observatory, Flagstaff Station, 1.3 m telescope. The catalog covers 1098 square degrees to r = 22.0, an additional 1521 square degrees to r = 20.9, plus a further 488 square degrees of lesser quality data. Statistical errors in the proper motions range from 5 mas …
The Power Of Principled Bayesian Methods In The Study Of Stellar Evolution, Ted Von Hippel, David Van Dyk, David Stenning, Elliot Robinson, Elizabeth Jeffery, Nathan Stein, William Jefferys, Erin M. O'Malley
The Power Of Principled Bayesian Methods In The Study Of Stellar Evolution, Ted Von Hippel, David Van Dyk, David Stenning, Elliot Robinson, Elizabeth Jeffery, Nathan Stein, William Jefferys, Erin M. O'Malley
Publications
It takes years of effort employing the best telescopes and in- struments to obtain high-quality stellar photometry, astrometry, and spectroscopy. Stellar evolution models contain the experience of life- times of theoretical calculations and testing. Yet most astronomers fit these valuable models to these precious datasets by eye. We show that a principled Bayesian approach to fitting models to stellar data yields substantially more information over a range of stellar astrophysics. We highlight advances in determining the ages of star clusters, mass ratios of binary stars, limitations in the accuracy of stellar models, post-main-sequence mass loss, and the ages of individual …
Bayesian Analysis For Stellar Evolution With Nine Parameters (Base-9): User's Manual, Ted Von Hippel, Elliot Robinson, Elizabeth Jeffery, Rachel Wagner-Kaiser, Steven Degennaro, Nathan Stein, David Stenning, William H. Jefferys, David Van Dyk
Bayesian Analysis For Stellar Evolution With Nine Parameters (Base-9): User's Manual, Ted Von Hippel, Elliot Robinson, Elizabeth Jeffery, Rachel Wagner-Kaiser, Steven Degennaro, Nathan Stein, David Stenning, William H. Jefferys, David Van Dyk
Publications
BASE-9 is a Bayesian software suite that recovers star cluster and stellar parameters from photometry. BASE-9 is useful for analyzing single-age, single-metallicity star clusters, binaries, or single stars, and for simulating such systems. BASE-9 uses Markov chain Monte Carlo and brute-force numerical integration techniques to estimate the posterior probability distributions for the age, metallicity, helium abundance, distance modulus, and line-of-sight absorption for a cluster, and the mass, binary mass ratio, and cluster membership probability for every stellar object. BASE-9 is provided as open source code on a version-controlled web server. The executables are also available as Amazon Elastic Compute Cloud …
Three Moving Groups Detected In The Lamost Dr1 Archive, Zhao J. K., Zhao G., Y. Q. Chen, T. D. Oswalt, K. F. Tan, Y. Zhang
Three Moving Groups Detected In The Lamost Dr1 Archive, Zhao J. K., Zhao G., Y. Q. Chen, T. D. Oswalt, K. F. Tan, Y. Zhang
Publications
We analyze the kinematics of thick disk and halo stars observed by the Large Sky Area Multi-Object Fiber Spectroscopic Telescope. We have constructed a sample of 7993 F, G, and K nearby main-sequence stars (d < 2 kpc) with estimates of position (x, y, z) and space velocity (U, V, W) based on color and proper motion from the Sloan Digital Sky Survey DR9 catalog. Three “phase-space overdensities” are identified in (V,√U2 + 2V 2) with significance levels of σ > 3. Two of them (the Hyades–Pleiades stream …
The White Dwarfs Within 25 Pc Of The Sun: Kinematics And Spectroscopic Subtypes, Edward M. Sion, J. B. Holberg, Terry D. Oswalt, George P. Mccook, Richard Wasatonic, Janine Myszka
The White Dwarfs Within 25 Pc Of The Sun: Kinematics And Spectroscopic Subtypes, Edward M. Sion, J. B. Holberg, Terry D. Oswalt, George P. Mccook, Richard Wasatonic, Janine Myszka
Publications
We present the fractional distribution of spectroscopic subtypes, range and distribution of surface temperatures, and kinematical properties of the white dwarfs (WDs) within 25 pc of the Sun. There is no convincing evidence of halo WDs in the total 25 pc sample of 224 WDs. There is also little to suggest the presence of genuine thick disk subcomponent members within 25 pc. It appears that the entire 25 pc sample likely belongs to the thin disk. We also find no significant kinematic differences with respect to spectroscopic subtypes. The total DA to non-DA ratio of the 25 pc sample is …
The Link Between Shocks, Turbulence And Magnetic Reconnection In Collisionless Plasmas, H. Karimabadi, V. Roytershteyn, H. X. Vu, Y. Omelchenko, J. Scudder, W. Daughton, A. Dimmock, Katariina (Heidi) Nykyri, Et Al.
The Link Between Shocks, Turbulence And Magnetic Reconnection In Collisionless Plasmas, H. Karimabadi, V. Roytershteyn, H. X. Vu, Y. Omelchenko, J. Scudder, W. Daughton, A. Dimmock, Katariina (Heidi) Nykyri, Et Al.
Publications
Global hybrid (electron fluid, kinetic ions) and fully kinetic simulations of the magnetosphere have been used to show surprising interconnection between shocks, turbulence and magnetic reconnection. In particular collisionless shocks with their reflected ions that can get upstream before retransmission can generate previously unforeseen phenomena in the post shocked flows: (i) formation of reconnecting current sheets and magnetic islands with sizes up to tens of ion inertial length. (ii) Generation of large scale low frequency electromagnetic waves that are compressed and amplified as they cross the shock. These 'wavefronts' maintain their integrity for tens of ion cyclotron times but eventually …
Book Review: Cosmic Dawn: The Search For The First Stars And Galaxies, T. D. Oswalt
Book Review: Cosmic Dawn: The Search For The First Stars And Galaxies, T. D. Oswalt
Publications
This document is Dr. Oswalt’s review of Cosmic Dawn : the Search for the First Stars and Galaxies by George Rhee, springer, 2013. 279p, 9781461478126 $39.99, 9781461478133 $29.99.
Book Review: The Observer's Guide To Planetary Motion: Explaining The Cycles Of The Night Sky, T. D. Oswalt
Book Review: The Observer's Guide To Planetary Motion: Explaining The Cycles Of The Night Sky, T. D. Oswalt
Publications
This document is Dr. Oswalt’s review of The Observer's Guide to Planetary Motion : Explaining the Cycles of the Night Sky by Dominic Ford. Springer, 2014 240p index afp, 9781493906284 $34.99.