Open Access. Powered by Scholars. Published by Universities.®

Astrophysics and Astronomy Commons™

Open Access. Powered by Scholars. Published by Universities.®

Discipline
Institution
Keyword
Publication Year
Publication
Publication Type
File Type

Articles 2851 - 2880 of 8856

Full-Text Articles in Astrophysics and Astronomy

Analysis Of Nucleus Properties Of The Enigmatic Comet 29p/Schwassmann-Wachmann 1, Charles Schambeau Aug 2018

Analysis Of Nucleus Properties Of The Enigmatic Comet 29p/Schwassmann-Wachmann 1, Charles Schambeau

Electronic Theses and Dissertations

We present results from a continuing effort to understand activity drivers for the enigmatic Comet 29P/Schwassmann-Wachmann 1 (SW1). SW1 has been of interest since its discovery almost 100 years ago because of its nearly continuous, quiescent activity beyond the water-sublimation line and its highly variable, outburst activity while receiving a nearly constant insolation due to its low eccentricity orbit. These characteristics make SW1 a useful target for investigating both distant cometary activity drivers and also cometary outburst behavior. We approach answering these questions through a detailed analysis of SW1; first by measuring nucleus properties required for a more accurate nucleus …

Go to article

Erratum: The Sluggs Survey: A Comparison Of Total-Mass Profiles Of Early-Type Galaxies From Observations And Cosmological Simulations, To ∼4 Effective Radii, Sabine Bellstedt, Duncan Forbes, Aaron Romanowsky, Rhea-Silvia Remus, Adam Stevens, Jean Brodie, Adriano Poci, Richard Mcdermid, Adebusola Alabi, Leonie Chevalier, Caitlin Adams, Anna Ferré-Mateu, Asher Wasserman, Viraj Pandya Aug 2018

Erratum: The Sluggs Survey: A Comparison Of Total-Mass Profiles Of Early-Type Galaxies From Observations And Cosmological Simulations, To ∼4 Effective Radii, Sabine Bellstedt, Duncan Forbes, Aaron Romanowsky, Rhea-Silvia Remus, Adam Stevens, Jean Brodie, Adriano Poci, Richard Mcdermid, Adebusola Alabi, Leonie Chevalier, Caitlin Adams, Anna Ferré-Mateu, Asher Wasserman, Viraj Pandya

Faculty Publications

This is an erratum to the paper “The SLUGGS Survey: A comparison of total-mass profiles of early-type galaxies from observations and cosmological simulations, to ∼4 effective radii” that was published in 2018, MNRAS, 476, 4543, which we refer to as the original paper.

Go to article

Cause Of Cambrian Explosion - Terrestrial Or Cosmic?, Edward J. Steele, Shirwan Al-Mufti, Kenneth A. Augustyn, Rohana Chandrajith, John P. Coghlan, S. G. Coulson, Et. Al. Aug 2018

Cause Of Cambrian Explosion - Terrestrial Or Cosmic?, Edward J. Steele, Shirwan Al-Mufti, Kenneth A. Augustyn, Rohana Chandrajith, John P. Coghlan, S. G. Coulson, Et. Al.

Michigan Tech Publications, Part 1

We review the salient evidence consistent with or predicted by the Hoyle-Wickramasinghe (H-W) thesis of Cometary (Cosmic) Biology. Much of this physical and biological evidence is multifactorial. One particular focus are the recent studies which date the emergence of the complex retroviruses of vertebrate lines at or just before the Cambrian Explosion of ∼500 Ma. Such viruses are known to be plausibly associated with major evolutionary genomic processes. We believe this coincidence is not fortuitous but is consistent with a key prediction of H-W theory whereby major extinction-diversification evolutionary boundaries coincide with virus-bearing cometary-bolide bombardment events. A second focus is …

Go to article

Force Multiplier Calculations For X-Ray Binaries And Active Galactic Nuclei, Randall Cody Dannen Aug 2018

Force Multiplier Calculations For X-Ray Binaries And Active Galactic Nuclei, Randall Cody Dannen

UNLV Theses, Dissertations, Professional Papers, and Capstones

Motivated by the work done to explore the winds from hot stars (Lamers & Cassinelli 1999), we develop a method for self consistently calculating force multipliers for Type 1 and Type 2 active galactic nuclei (AGN), soft and hard start X-ray binaries (XRBs) spectral energy distributions (SEDs). We find that the ampflication to the radiation force can be as large as 100 even when the gas is highly ionized due to Fe and O ions. We discuss future efforts to incorporate these findings in magnetohydrodynamic simulations.

Go to article

Collisional Quenching Of Highly Excited H2 Due To H2 Collisions, Yier Wan, B. H. Yang, P. C. Stancil, Balakrishnan Naduvalath, Nikhil J. Parekh, R. C. Forrey Jul 2018

Collisional Quenching Of Highly Excited H2 Due To H2 Collisions, Yier Wan, B. H. Yang, P. C. Stancil, Balakrishnan Naduvalath, Nikhil J. Parekh, R. C. Forrey

Chemistry and Biochemistry Faculty Research

Rate coefficients for pure rotational quenching in H2(ν 1 = 0, j 1) + H2(ν 2 = 0, j 2) collisions from initial levels of j 1 = 2–31 (j 2 = 0 or 1) to all lower rotational levels are presented. We carried out extensive quantum mechanical close-coupling calculations based on a recently published H2–H2 potential energy surface (PES) developed by Patkowski et al. that has been demonstrated to be more reliable than previous work. Rotational transition cross sections with initial levels of j 1 = 2–14, 18, 19, 24, and 25 were computed for energies ranging from 10−6 …

Go to article

Space-Time In The Syk Model, Sumit R. Das, Aminik Ghosh, Antal Jevicki, Kenta Suzuki Jul 2018

Space-Time In The Syk Model, Sumit R. Das, Aminik Ghosh, Antal Jevicki, Kenta Suzuki

Physics and Astronomy Faculty Publications

We consider the question of identifying the bulk space-time of the SYK model. Focusing on the signature of emergent space-time of the (Euclidean) model, we explain the need for non-local (Radon-type) transformations on external legs of n-point Green’s functions. This results in a dual theory with Euclidean AdS signature with additional legfactors. We speculate that these factors incorporate the coupling of additional bulk states similar to the discrete states of 2d string theory.

Go to article

Gamma-Ray Burst/Supernova Associations: Energy Partition And The Case Of A Magnetar Central Engine, Hon-Jun Lü, Lin Lan, Bing Zhang, En-Wei Liang, David Alexander Kann, Shen-Shi Du, Jun Shen Jul 2018

Gamma-Ray Burst/Supernova Associations: Energy Partition And The Case Of A Magnetar Central Engine, Hon-Jun Lü, Lin Lan, Bing Zhang, En-Wei Liang, David Alexander Kann, Shen-Shi Du, Jun Shen

Physics & Astronomy Faculty Research

The favored progenitor model for Gamma-ray Bursts (GRBs) with Supernova (SN) association is the core collapse of massive stars. One possible outcome of such a collapse is a rapidly spinning, strongly magnetized neutron star ("magnetar"). We systematically analyze the multi-wavelength data of GRB/SN associations detected by several instruments before 2017 June. Twenty GRB/SN systems have been confirmed via direct spectroscopic evidence or a clear light curve bump, as well as some spectroscopic evidence resembling a GRB-SN. We derive/collect the basic physical parameters of the GRBs and the SNe, and look for correlations among these parameters. We find that the peak …

Go to article

Systematic Mischaracterization Of Exoplanetary System Dynamical Histories From A Model Degeneracy Near Mean-Motion Resonance, John H. Boisvert, Benjamin E. Nelson, Jason H. Steffen Jul 2018

Systematic Mischaracterization Of Exoplanetary System Dynamical Histories From A Model Degeneracy Near Mean-Motion Resonance, John H. Boisvert, Benjamin E. Nelson, Jason H. Steffen

Physics & Astronomy Faculty Research

There is a degeneracy in the radial velocity exoplanet signal between a single planet on an eccentric orbit and a two-planet system with a period ratio of 2:1. This degeneracy could lead to misunderstandings of the dynamical histories of planetary systems as well as measurements of planetary abundances if the correct architecture is not established. We constrain the rate of mischaracterization by analysing a sample of 60 non-transiting, radial velocity systems orbiting main-sequence stars from the NASA Exoplanet Archive (NASA Archive) using a new Bayesian model comparison pipeline. We find that 15 systems (25 per cent of our sample) show …

Go to article

Globular Cluster Population Of The Hst Frontier Fields Galaxy J07173724+3744224, Nathan L. Carlson, Madina R. Sultanova, Sandanuwan P. Kalawila Vithanage, Wayne A. Barkhouse, Gihan L. Ipita Kaduwa Gamage, Cody M. Rude, Omar López-Cruz Jul 2018

Globular Cluster Population Of The Hst Frontier Fields Galaxy J07173724+3744224, Nathan L. Carlson, Madina R. Sultanova, Sandanuwan P. Kalawila Vithanage, Wayne A. Barkhouse, Gihan L. Ipita Kaduwa Gamage, Cody M. Rude, Omar López-Cruz

Physics Faculty Publications

We present the first measurement of the globular cluster (GC) population surrounding the elliptical galaxy J07173724+3744224 (⁠z" role="presentation" style="box-sizing: border-box; margin: 0px; padding: 0px; border: 0px; font-variant: inherit; font-stretch: inherit; line-height: normal; font-family: inherit; vertical-align: baseline; display: inline; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; position: relative;">zz = 0.1546). This galaxy is located in the foreground in the field-of-view of the Hubble Space Telescope (HST) Frontier Fields observations of galaxy cluster MACS J0717.5+3745 (⁠z" role="presentation" style="box-sizing: border-box; margin: 0px; padding: 0px; border: 0px; font-variant: inherit; font-stretch: …

Go to article

Asymmetric Free-Space Light Transport At Nonlinear Metasurfaces, Nir Shitrit, Jeongmin Kim, David S. Barth, Hamidreza Ramezani, Yuan Wang, Xiang Zhang Jul 2018

Asymmetric Free-Space Light Transport At Nonlinear Metasurfaces, Nir Shitrit, Jeongmin Kim, David S. Barth, Hamidreza Ramezani, Yuan Wang, Xiang Zhang

Physics & Astronomy Faculty Publications

Asymmetric light transport has significantly contributed to fundamental science and revolutionized advanced technology in various aspects such as unidirectional photonic devices, optical diodes, and isolators. While metasurfaces mold wave fronts at will with an ultrathin flat optical element, asymmetric transport of light cannot be fundamentally achieved by any linear system including linear metasurfaces. We report asymmetric transport of free-space light at nonlinear metasurfaces upon transmission and reflection. Moreover, we theoretically derive the nonlinear generalized Snell's laws that were experimentally confirmed by the anomalous nonlinear refraction and reflection. The asymmetric transport at optically thin nonlinear interfaces is revealed by the concept …

Go to article

Surf: Understanding And Predicting Urban Convection And Haze, X. Liang, S. Miao, J. Li, R. Bornstein, X. Zhang, Y. Gao, F. Chen, X. Cao, Z. Cheng, Craig Clements, W. Dabberdt, A. Ding, D. Ding, J. J. Dou, J.X. Dou, Y. Dou, C.S.B. Grimmond, J. E. González-Cruz, J. He, M. Huang, X. Huang, S. Ju, Q. Li, D. Niyogi, J. Quan, J. Sun, J.Z. Sun, M. Yu, J. Zhang, Y. Zhang, X. Zhao, Z. Zheng, M. Zhou Jul 2018

Surf: Understanding And Predicting Urban Convection And Haze, X. Liang, S. Miao, J. Li, R. Bornstein, X. Zhang, Y. Gao, F. Chen, X. Cao, Z. Cheng, Craig Clements, W. Dabberdt, A. Ding, D. Ding, J. J. Dou, J.X. Dou, Y. Dou, C.S.B. Grimmond, J. E. González-Cruz, J. He, M. Huang, X. Huang, S. Ju, Q. Li, D. Niyogi, J. Quan, J. Sun, J.Z. Sun, M. Yu, J. Zhang, Y. Zhang, X. Zhao, Z. Zheng, M. Zhou

Faculty Publications, Meteorology and Climate Science

Urbanization modifies atmospheric energy and moisture balances, forming distinct features [e.g., urban heat islands (UHIs) and enhanced or decreased precipitation]. These produce significant challenges to science and society, including rapid and intense flooding, heat waves strengthened by UHIs, and air pollutant haze. The Study of Urban Impacts on Rainfall and Fog/Haze (SURF) has brought together international expertise on observations and modeling, meteorology and atmospheric chemistry, and research and operational forecasting. The SURF overall science objective is a better understanding of urban, terrain, convection, and aerosol interactions for improved forecast accuracy. Specific objectives include a) promoting cooperative international research to improve …

Go to article

Dust–Gas Scaling Relations And Oh Abundance In The Galactic Ism, Hiep Nguyen, J. R. Dawson, M. -A. Miville-Deschênes, Ningyu Tang, Di Li, Carl Heiles, Claire E. Murray, Snežana Stanimirović, Steven J. Gibson, N. M. Mcclure-Griffiths, Thomas Troland, L. Bronfman, R. Finger Jul 2018

Dust–Gas Scaling Relations And Oh Abundance In The Galactic Ism, Hiep Nguyen, J. R. Dawson, M. -A. Miville-Deschênes, Ningyu Tang, Di Li, Carl Heiles, Claire E. Murray, Snežana Stanimirović, Steven J. Gibson, N. M. Mcclure-Griffiths, Thomas Troland, L. Bronfman, R. Finger

Physics and Astronomy Faculty Publications

Observations of interstellar dust are often used as a proxy for total gas column density NH. By comparing Planck thermal dust data (Release 1.2) and new dust reddening maps from Pan-STARRS 1 and 2MASS, with accurate (opacity-corrected) H I column densities and newly published OH data from the Arecibo Millennium survey and 21-SPONGE, we confirm linear correlations between dust optical depth τ353, reddening E(B − V), and the total proton column density NH in the range (1–30) × 1020 cm−2, along sightlines with no molecular gas detections in emission. …

Go to article

The First Super-Earth Detection From The High Cadence And High Radial Velocity Precision Dharma Planet Survey, Bo Ma, Jian Ge, Matthew Muterspaugh, Michael A. Singer, Gregory W. Henry, Jonay I. González Hernández, Sirinrat Sithajan, Sarik Jeram, Michael H. Williamson, Keivan Stassun, Benjamin Kimock, Frank Varosi, Sidney Schofield, Jian Liu, Scott Powell, Anthony Cassette, Hali Jakeman, Louis Avner, Nolan Grieves, Rory Barnes, Bo Zhao, Sankalp Gilda, Jim Grantham, Greg Stafford, David Savage, Steve Bland, Brent Ealey Jul 2018

The First Super-Earth Detection From The High Cadence And High Radial Velocity Precision Dharma Planet Survey, Bo Ma, Jian Ge, Matthew Muterspaugh, Michael A. Singer, Gregory W. Henry, Jonay I. González Hernández, Sirinrat Sithajan, Sarik Jeram, Michael H. Williamson, Keivan Stassun, Benjamin Kimock, Frank Varosi, Sidney Schofield, Jian Liu, Scott Powell, Anthony Cassette, Hali Jakeman, Louis Avner, Nolan Grieves, Rory Barnes, Bo Zhao, Sankalp Gilda, Jim Grantham, Greg Stafford, David Savage, Steve Bland, Brent Ealey

Information Systems and Engineering Management Research Publications

The Dharma Planet Survey (DPS) aims to monitor about 150 nearby very bright FGKM dwarfs (within 50 pc) during 2016–2020 for low-mass planet detection and characterization using the TOU very high resolution optical spectrograph (⁠R≈100000⁠, 380–900 nm). TOU was initially mounted to the 2-m Automatic Spectroscopic Telescope at Fairborn Observatory in 2013–2015 to conduct a pilot survey, then moved to the dedicated 50-inch automatic telescope on Mt. Lemmon in 2016 to launch the survey. Here, we report the first planet detection from DPS, a super-Earth candidate orbiting a bright K dwarf star, HD 26965. It is the second brightest star …

Go to article

Bayesian Hierarchical Modelling Of Initial-Final Mass Relations Across Star Clusters, Shijing Si, David A. Van Dyk, Ted Von Hippel, Elliot Robinson, Elizabeth Jeffery, David C. Stenning Jul 2018

Bayesian Hierarchical Modelling Of Initial-Final Mass Relations Across Star Clusters, Shijing Si, David A. Van Dyk, Ted Von Hippel, Elliot Robinson, Elizabeth Jeffery, David C. Stenning

Publications

The initial-final mass relation (IFMR) of white dwarfs (WDs) plays an important role in stellar evolution. To derive precise estimates of IFMRs and explore how they may vary among star clusters, we propose a Bayesian hierarchical model that pools photometric data from multiple star clusters. After performing a simulation study to show the benefits of the Bayesian hierarchical model, we apply this model to five star clusters: the Hyades, M67, NGC 188, NGC 2168, and NGC 2477, leading to reasonable and consistent estimates of IFMRs for these clusters. We illustrate how a cluster-specific analysis of NGC 188 using its own …

Go to article

Radon Measurement For Neutrinoless Double Beta Decay, Xavier Carlos Quintana Jul 2018

Radon Measurement For Neutrinoless Double Beta Decay, Xavier Carlos Quintana

Physics & Astronomy ETDs

This thesis details the design and operation of a high-sensitivity radon detector for use in background radiation characterization and mitigation for the MAJORANA DEMONSTRATOR Neutrinoless Double Beta Decay Experiment and Large Enriched Germanium Experiment for Neutrinoless Double Beta Decay (LEGEND) Collaboration. Understanding and mitigating background radiation is especially important in searches for very rare nuclear processes, which utilize sensitive detectors. One such rare process is the yet-to-be-observed neutrinoless double beta decay. Observation of this process would imply that the neutrino is its own antiparticle, called a Majorana particle, violate lepton number, and provide experimental constraints on the masses and mixing …

Go to article

Gamma-Ray Burst Classification: New Insights From Mining Pulse Data, Stanley Mcafee, Jon Hakkila Jul 2018

Gamma-Ray Burst Classification: New Insights From Mining Pulse Data, Stanley Mcafee, Jon Hakkila

Journal of the South Carolina Academy of Science

Despite being the most energetic electromagnetic explosions in the universe, gamma-ray bursts (GRBs) are still poorly understood. The literature recognizes two potentially different types of GRB progenitors, although statistical data suggest the existence of three GRB classes. Reliable inference of GRB physics depends on the identification of appropriate classification attributes, as well as on the statistical classification techniques used. It has recently been shown that pulses are the basic unit of GRB emission. We use new data describing GRB pulse characteristics, in conjunction with data mining tools, to provide a more reliable gamma-ray burst classification system and place additional constraints …

Go to article

Path Integral Complexity For Perturbed Cfts, Arpan Bhattacharyya, Pawal Caputa, Sumit R. Das, Nilay Kundu, Masamichi Miyaji, Tadashi Takayanagi Jul 2018

Path Integral Complexity For Perturbed Cfts, Arpan Bhattacharyya, Pawal Caputa, Sumit R. Das, Nilay Kundu, Masamichi Miyaji, Tadashi Takayanagi

Physics and Astronomy Faculty Publications

In this work, we formulate a path-integral optimization for two dimensional conformal field theories perturbed by relevant operators. We present several evidences how this optimization mechanism works, based on calculations in free field theories as well as general arguments of RG flows in field theories. Our optimization is performed by minimizing the path-integral complexity functional that depends on the metric and also on the relevant couplings. Then, we compute the optimal metric perturbatively and find that it agrees with the time slice of the hyperbolic metric perturbed by a scalar field in the AdS/CFT correspondence. Last but not the least, …

Go to article

Table Of Contents Jul 2018

Table Of Contents

Journal of the South Carolina Academy of Science

No abstract provided.

Go to article

A 3.5 Million Solar Masses Black Hole In The Centre Of The Ultracompact Dwarf Galaxy Fornax Ucd3, Anton Afanasiev, Igor Chilingarian, Steffen Mieske, Karina Voggel, Arianna Picotti, Michael Hilker, Anil Seth, Nadine Neumayer, Matthias Frank, Aaron Romanowsky, George Hau, Holger Baumgardt, Christopher Ahn, Jay Strader, Mark Den Brok, Richard Mcdermid, Lee Spitler, Jean Brodie, Jonelle Walsh Jul 2018

A 3.5 Million Solar Masses Black Hole In The Centre Of The Ultracompact Dwarf Galaxy Fornax Ucd3, Anton Afanasiev, Igor Chilingarian, Steffen Mieske, Karina Voggel, Arianna Picotti, Michael Hilker, Anil Seth, Nadine Neumayer, Matthias Frank, Aaron Romanowsky, George Hau, Holger Baumgardt, Christopher Ahn, Jay Strader, Mark Den Brok, Richard Mcdermid, Lee Spitler, Jean Brodie, Jonelle Walsh

Faculty Publications

The origin of ultracompact dwarfs (UCDs), a class of compact stellar systems discovered two decades ago, still remains a matter of debate. Recent discoveries of central supermassive black holes in UCDs likely inherited from their massive progenitor galaxies provide support for the tidal stripping hypothesis. At the same time, on statistical grounds, some massive UCDs might be representatives of the high luminosity tail of the globular cluster luminosity function. Here we present a detection of a 3.3+1.4−1.2×106M⊙ black hole (1σ uncertainty) in the centre of the UCD3 galaxy in the Fornax cluster, which corresponds to 4 per cent of its …

Go to article

Hst Follow-Up Observations Of Two Bright Z ∼ 8 Candidate Galaxies From The Borg Pure-Parallel Survey, R. C. Livermore, M. Trenti, L. D. Bradley, S. R. Bernard, Benne W. Holwerda, C. A. Mason, T. Treu Jul 2018

Hst Follow-Up Observations Of Two Bright Z ∼ 8 Candidate Galaxies From The Borg Pure-Parallel Survey, R. C. Livermore, M. Trenti, L. D. Bradley, S. R. Bernard, Benne W. Holwerda, C. A. Mason, T. Treu

Faculty and Staff Scholarship

We present follow-up imaging of two bright (L > L∗) galaxy candidates at z ≳ 8 from the Brightest of Reionizing Galaxies (BoRG) survey with the F098M filter on the Hubble Space Telescope/Wide Field Camera 3 (HST/WFC3). The F098M filter provides an additional constraint on the flux blueward of the spectral break, and the observations are designed to discriminate between low- and high-z photometric redshift solutions for these galaxies. Our results confirm one galaxy, BoRG-0116+1425-747, as a highly probable z ∼ 8 source, but reveal that BoRG-0116+1425-630 - previously the brightest known z > 8 candidate (m AB = 24.5) - is …

Go to article

Fermi-Bounce Cosmology And Scale-Invariant Power Spectrum, Stephon Alexander, Cosimo Bambi, Antonino Marcianò, Leonardo Modesto Jul 2018

Fermi-Bounce Cosmology And Scale-Invariant Power Spectrum, Stephon Alexander, Cosimo Bambi, Antonino Marcianò, Leonardo Modesto

Dartmouth Scholarship

We develop a non-singular bouncing cosmology using a non-trivial coupling of general relativity to fermionic fields. The usual Big Bang singularity is avoided thanks to a negative energy density contribution from the fermions. Our theory is ghost-free since the fermionic operator that generates the bounce is equivalent to torsion, which has no kinetic terms. The physical system consists of standard general relativity plus a topological sector for gravity, and fermionic matter described by Dirac fields with a non-minimal coupling. We show that a scale invariant power-spectrum generated in the contracting phase can be recovered by suitable choice s of fermion …

Go to article

White Dwarf Pollution By Asteroids From Secular Resonances, Jeremy L. Smallwood, Rebecca G. Martin, Mario Livio, Stephen H. Lubow Jul 2018

White Dwarf Pollution By Asteroids From Secular Resonances, Jeremy L. Smallwood, Rebecca G. Martin, Mario Livio, Stephen H. Lubow

Physics & Astronomy Faculty Research

In the past few decades, observations have revealed signatures of metals polluting the atmospheres of white dwarfs. The diffusion time-scale for metals to sink from the atmosphere of a white dwarf is of the order of days for a hydrogen-dominated atmosphere. Thus, there must be a continuous supply of metal-rich material accreting onto these white dwarfs. We investigate the role of secular resonances that excite the eccentricity of asteroids allowing them to reach star-grazing orbits leading them to tidal disruption and the formation of a debris disc. Changes in the planetary system during the evolution of the star lead to …

Go to article

What Powered The Optical Transient At2017gfo Associated With Gw170817?, Shao-Ze Li, Liang-Duan Liu, Yun-Wei Yu, Bing Zhang Jul 2018

What Powered The Optical Transient At2017gfo Associated With Gw170817?, Shao-Ze Li, Liang-Duan Liu, Yun-Wei Yu, Bing Zhang

Physics & Astronomy Faculty Research

The groundbreaking discovery of the optical transient AT2017gfo associated with GW170817 opens a unique opportunity to study the physics of double neutron star (NS) mergers. We argue that the standard interpretation of AT2017gfo as being powered by radioactive decay of r-process elements faces the challenge of simultaneously accounting for the peak luminosity and peak time of the event, as it is not easy to achieve the required high mass, and especially the low opacity of the ejecta required to fit the data. A plausible solution would be to invoke an additional energy source, which is probably provided by the merger …

Go to article

Bayesian Analysis Of Two Stellar Populations In Galactic Globular Clusters I: Statistical And Computational Methods, David Stenning, Ted Von Hippel, Rachel Wagner-Kaiser, Elliot Robinson, David Van Dyk, Ata Sarajedini, Nathan Stein Jul 2018

Bayesian Analysis Of Two Stellar Populations In Galactic Globular Clusters I: Statistical And Computational Methods, David Stenning, Ted Von Hippel, Rachel Wagner-Kaiser, Elliot Robinson, David Van Dyk, Ata Sarajedini, Nathan Stein

Publications

We develop a Bayesian model for globular clusters composed of multiple stellar populations, extend- ing earlier statistical models for open clusters composed of simple (single) stellar populations (e.g., van Dyk et al. 2009; Stein et al. 2013). Specifically, we model globular clusters with two populations that differ in helium abundance. Our model assumes a hierarchical structuring of the parameters in which physical properties|age, metallicity, helium abundance, distance, absorption, and initial mass|are common to (i) the cluster as a whole or to (ii) individual populations within a cluster, or are unique to (iii) individual stars. An adaptive Markov chain Monte Carlo …

Go to article

Fitting The Radial Acceleration Relation To Individual Sparc Galaxies, Pengfei Li, Stacy Mcgaugh Jul 2018

Fitting The Radial Acceleration Relation To Individual Sparc Galaxies, Pengfei Li, Stacy Mcgaugh

Faculty Scholarship

Galaxies follow a tight radial acceleration relation (RAR): the acceleration observed at every radius correlates with that expected from the distribution of baryons. We use the Markov chain Monte Carlo method to fit the mean RAR to 175 individual galaxies in the SPARC database, marginalizing over stellar mass-to-light ratio (γ ∗), galaxy distance, and disk inclination. Acceptable fits with astrophysically reasonable parameters are found for the vast majority of galaxies. The residuals around these fits have an rms scatter of only 0.057 dex (~13%). This is in agreement with the predictions of modified Newtonian dynamics (MOND). We further consider a …

Go to article

Characterization Of Eight Potentially Hazardous Near Earth Asteroids: Rotation Period Analysis And Structure Modeling Via Light Curve Inversion Techniques, Stacy Jo Hicks Jul 2018

Characterization Of Eight Potentially Hazardous Near Earth Asteroids: Rotation Period Analysis And Structure Modeling Via Light Curve Inversion Techniques, Stacy Jo Hicks

Masters Theses & Specialist Projects

The term “homeland security”, seems to have become synonymous with terrorism in the minds of the general public. However, there are other threats to the security of the United States homeland that can be just as, if not more, devastating than terrorism. Included among these other threats is the potential of an asteroid collision with Earth. Historically, asteroid impact events have been responsible for the devastation of our planet and many of the mass extinction events encountered throughout the geologic record. Knowledge of physical parameters such as structure and rotational dynamics of the asteroid are critical parameters in developing interception …

Go to article

Molpop-Cep: An Exact, Fast Code For Multi-Level Systems, Andrés Asensio Ramos, Moshe Elitzur Jul 2018

Molpop-Cep: An Exact, Fast Code For Multi-Level Systems, Andrés Asensio Ramos, Moshe Elitzur

Physics and Astronomy Faculty Publications

We present MOLPOP-CEP, a universal line transfer code that allows the exact calculation of multi-level line emission from a slab with variable physical conditions for any arbitrary atom or molecule for which atomic data exist. The code includes error control to achieve any desired level of accuracy, providing full confidence in its results. Publicly available, MOLPOP-CEP employs our recently developed coupled escape probability (CEP) technique, whose performance exceeds other exact methods by orders of magnitude. The program also offers the option of an approximate solution with different variants of the familiar escape probability method. As an illustration of the MOLPOP-CEP …

Go to article

Ion Friction At Small Values Of The Coulomb Logarithm, Robert Tucker Sprenkle Jul 2018

Ion Friction At Small Values Of The Coulomb Logarithm, Robert Tucker Sprenkle

Theses and Dissertations

We create a dual-species ultracold neutral plasma (UNP) by photo-ionizing Yb and Ca atoms in a dual-species magneto-optical trap. Unlike single-species UNP expansion, these plasmas are well outside of the collisionless (Vlasov) approximation. We observe the mutual interaction of the Yb and Ca ions by measuring the velocity distribution for each ion species separately. We model the expansion using a fluid code including ion-ion friction and compare with experimental results to obtain a value of the Coulomb logarithm of Λ= 0.04.

Go to article

Finite-Volume Effects Due To Spatially Nonlocal Operators, Raúl A. Briceño, Juan V. Guerrero, Maxwell T. Hansen, Christopher J. Monahan Jul 2018

Finite-Volume Effects Due To Spatially Nonlocal Operators, Raúl A. Briceño, Juan V. Guerrero, Maxwell T. Hansen, Christopher J. Monahan

Physics Faculty Publications

Spatially nonlocal matrix elements are useful lattice-QCD observables in a variety of contexts, for example in determining hadron structure. To quote credible estimates of the systematic uncertainties in these calculations, one must understand, among other things, the size of the finite-volume effects when such matrix elements are extracted from numerical lattice calculations. In this work, we estimate finite- volume effects for matrix elements of nonlocal operators, composed of two currents displaced in a spatial direction by a distance ξ. We find that the finite-volume corrections depend on the details of the matrix element. If the external state is the lightest …

Go to article

One-Loop Evolution Of Parton Pseudo-Distribution Functions On The Lattice, Anatoly Radyushkin Jul 2018

One-Loop Evolution Of Parton Pseudo-Distribution Functions On The Lattice, Anatoly Radyushkin

Physics Faculty Publications

We incorporate recent calculations of one-loop corrections for the reduced Ioffe-time pseudo-distribution m(v, z(3)(2) thorn to extend the leading-logarithm analysis of lattice data obtained by Orginos et al. We observe that the one-loop corrections contain a large term reflecting the fact that effective distances involved in the most important diagrams are much smaller than the nominal distance z(3). The large correction in this case may be absorbed into the evolution term, and the perturbative expansion used for extraction of parton densities at the μ ≈ 2 GeV scale is under control. The extracted parton distribution is rather close to global …

Go to article

First Prev Next Last