Astrophysics and Astronomy Commons^™

Perfect Circles: A Study Of The Scattering Regions Of Wolf Rayet Binary Stars, Stella Yoos, Jennifer Hoffman, Andrew Fullard

DU Undergraduate Research Journal Archive

Although we have been able to develop an understanding of many aspects of stellar evolution and formation, a few key gaps remain. One is the fate of massive binary star systems composed of Wolf-Rayet (WR) and O-type stars. In these WR + O binaries, the stellar winds surrounding these stars collide, creating a complex interaction region in which light from the stars scatters and becomes polarized. To study these scattering regions, I employ a technique that allows me to map the polarization of the light emitted from these stars and track its variation over the binary orbit. I found that …

Polarization Measurements Of The Polluted White Dwarf G29-38, Ted Von Hippel, Daniel V. Cotton, Jeremy Bailey, J.E. Pringle, William B. Sparks, Jonathan P. Marshall

Publications

We have made high-precision polarimetric observations of the polluted white dwarf G29-38 with the HIgh Precision Polarimetric Instrument 2. The observations were made at two different observatories – using the 8.1-m Gemini North Telescope and the 3.9-m Anglo-Australian Telescope – and are consistent with each other. After allowing for a small amount of interstellar polarization, the intrinsic linear polarization of the system is found to be 275.3 ± 31.9 parts per million at a position angle of 90.8 ± 3.8◦ in the SDSS g

band. We compare the observed polarization with the predictions of circumstellar disc models. The measured polarization …

Supercritical Carbon Dioxide Based Heat Exchanger On The Martian, Sarah Guinn

Discovery Day - Prescott

The use of supercritical carbon dioxide (sCO2) in power cycles has been fairly new in the last decade. Due to this, there is a lack in research for both terrestrial and extraterrestrial applications. The purpose of this project is to utilize sCO2 as a working fluid and design and optimize a Brayton Cycle based heat exchanger on the Martian surface. Due to the lack of water on Mars, this research will provide a stronger analysis of planetary based drycooling processes in low atmospheric pressure and colder temperatures. We have been conducting an in-depth analysis of the heat exchanger by modeling …

The Sophie Search For Northern Extrasolar Planets Xvi. Hd 158259: A Compact Planetary System In A Near-3:2 Mean Motion Resonance Chain, Nathan Hara, François Bouchy, Manu Stalport, Isabelle Boisse, J. Rodrigues, Jean-Baptiste Delisle, Alexandre Santerne, Gregory W. Henry, Luc Arnold, Nicola Astudillo-Defru, Simon Borgniet, Xavier Bonfils, Vincent Bourrier, Bastien Brugger, B. Courcol, Shweta Dalal, Magali Deleuil, Xavier Delfosse, Olivier Demangeon, Rodrigo F. Díaz, Xavier Dumusque, Thierry Forveille, Guillaume Hébrard, Melissa J. Hobson, ‪Flavien Kiefer, Théodore Lopez, ‪Lucile Mignon, Olivier Mousis, Claire Moutou, Francesco Pepe, Javiera Rey, Nuno C. Santos, Damien Ségransan, Stéphane Udry, Paul Anthony Wilson

Information Systems and Engineering Management Research Publications

Aims. Since 2011, the SOPHIE spectrograph has been used to search for Neptunes and super-Earths in the northern hemisphere. As part of this observational program, 290 radial velocity measurements of the 6.4 V magnitude star HD 158259 were obtained. Additionally, TESS photometric measurements of this target are available. We present an analysis of the SOPHIE data and compare our results with the output of the TESS pipeline.

Methods. The radial velocity data, ancillary spectroscopic indices, and ground-based photometric measurements were analyzed with classical and ℓ₁ periodograms. The stellar activity was modeled as a correlated Gaussian noise and its impact …

An Analysis Of The Debate Over Creation, Evolution, And The Timeline Of The Universe At An Ecumenical Christian University, Mason Pohlman

Honors Scholars Collaborative Projects

Throughout a significant portion of history and within modern culture, the fields of science and religion appear to be competing for the same holds in a person’s belief system. Universities are where academics and the sciences are the prevailing held truth, while in churches, the Bible reigns as supreme authority. However, in a Christian academic setting, the predominate school of thought in belief systems might turn into a little more of a melting pot. By analyzing gathered personal data (via surveys and interviews), one can begin to piece together the predominate thoughts on the apparent conflict between religion and science …

Response To Pitkanen’S Solar System Model: Towards Gross-Pitaevskiian Description Of Solar System And Galaxies And More Evidence Of Chiral Superfluid Vortices, Victor Christianto, Florentin Smarandache, Yunita Umniyati

Branch Mathematics and Statistics Faculty and Staff Publications

In a new paper in recent issue of this journal (PSTJ), Prof. M. Pitkanen describes a solar system model inspired by spiral galaxies. While we appreciate his new approach, we find it lacks substantial discussion on the nature of vortices and chirality in galaxy. Therefore we submit a viewpoint that Gross-Pitaevskii model can be a more complete description of both solar system and also spiral galaxies, especially taking into account the nature of chirality and vortices in galaxies. In this article, we also hope to bring out some correspondence among existing models, so we discuss shortly: the topological vortice approach, …

Optically Targeted Search For Gravitational Waves Emitted By Core-Collapse Supernovae During The First And Second Observing Runs Of Advanced Ligo And Advanced Virgo, B. P. Abbott, R. Abbott, Marco Cavaglia, For Full List Of Authors, Download The Pdf.

Physics Faculty Research & Creative Works

We present the results from a search for gravitational-wave transients associated with core-collapse supernovae observed within a source distance of approximately 20 Mpc during the first and second observing runs of Advanced LIGO and Advanced Virgo. No significant gravitational-wave candidate was detected. We report the detection efficiencies as a function of the distance for waveforms derived from multidimensional numerical simulations and phenomenological extreme emission models. The sources with neutrino-driven explosions are detectable at the distances approaching 5 kpc, and for magnetorotationally driven explosions the distances are up to 54 kpc. However, waveforms for extreme emission models are detectable up to …

Gravitational Wave Calibration Error For Supernovae Core Collapse, Brad Ratto

Discovery Day - Prescott

The existence of gravitational waves reveals yet another method in which information is transmitted across the cosmos, bringing with it further insight into the inner workings of our universe. In order to detect such phenomena, we use ground based Laser Interferometers to measure the microscopic deformations in space-time and explore a new frontier in gravitational astronomy. However, such instrumentation also induces distortions in the gravitational waves henceforth diminishing the ability to extract accurate physical information. Moreover, the ability to extract a coherent signal amongst the noise remains an issue that requires constant improvement. The aim of this study is to …

The Exotime Project: Signals In The O − C Diagrams Of The Rapidly Pulsating Subdwarfs Dw Lyn, V1636 Ori, Qq Vir, And V541 Hya, F. Mackebrandt, Terry Oswalt, S. Schuh, R. Silvotti, S. -L. Kim, D. Kilkenny, E. M. Green, R. Lutz, T. Nagel, J. L. Provencal, Tomomi Otani, S. Benatti, L. Lanteri, A. Bonanno, A. Frasca, R. Janulis, M. Paparó, L. Molnár, R. Claudi, R. H. Østensen

Publications

Aims. We aim to investigate variations in the arrival time of coherent stellar pulsations due to the light-travel time effect to test for the presence of sub-stellar companions. Those companions are the key to one possible formation scenario of apparently single sub-dwarf B stars. Methods. We made use of an extensive set of ground-based observations of the four large amplitude p-mode pulsators DW Lyn, V1636 Ori, QQ Vir, and V541 Hya. Observations of the TESS space telescope are available on two of the targets. The timing method compares the phase of sinusoidal fits to the full multi-epoch light curves with …

Orbital Refinement And Stellar Properties For The Hd 9446, Hd 43691, And Hd 179079 Planetary Systems, Michelle L. Hill, Teo Močnik, Stephen R. Kane, Gregory W. Henry, Joshua Pepper, Natalie R. Hinkel, Paul A. Dalba, Benjamin Fulton, Keivan Stassun, Lee J. Rosenthal, Andrew W. Howard, Steve B. Howell, Mark E. Everett, Tabetha S. Boyajian, Debra A. Fischer, Joseph E. Rodriguez, Thomas G. Beatty, David J. James

Information Systems and Engineering Management Research Publications

The Transit Ephemeris Refinement and Monitoring Survey is a project that aims to detect transits of intermediate-long period planets by refining orbital parameters of the known radial velocity planets using additional data from ground-based telescopes, calculating a revised transit ephemeris for the planet, then monitoring the planet host star during the predicted transit window. Here we present the results from three systems that had high probabilities of transiting planets: HD 9446 b and c, HD 43691 b, and HD 179079 b. We provide new radial velocity (RV) measurements that are then used to improve the orbital solution for the known …

Extended Gamma Analysis Of Snr G330.2 + 1.0, Abagael Barba, John W. Hewitt

Showcase of Osprey Advancements in Research and Scholarship (SOARS)

Analyzing gamma rays is an important aspect of modern astronomy and astrophysics, for they are the most powerful bands of energy on the electromagnetic spectrum. Comprehending gamma rays allows for deeper understanding of countless phenomena within our universe, such as cosmic rays. Cosmic rays are high energy particles thought to be formed via extremely violent explosions within our universe. These accelerated particles mirror conditions present in a supernova. A supernova is what occurs when a star at least 8 times as massive as our sun reaches the end of its lifespan and bursts. These explosions are the most powerful events …

Global 3d Radiation Magnetohydrodynamic Simulations For Fu Ori's Accretion Disc And Observational Signatures Of Magnetic Fields, Zhaohuan Zhu, Yan-Fei Jiang, James M. Stone

Physics & Astronomy Faculty Research

FU Ori is the prototype of FU Orionis systems that are outbursting protoplanetary discs. Magnetic fields in FU Ori’s accretion discs have previously been detected using spectropolarimetry observations for Zeeman effects. We carry out global radiation ideal MHD simulations to study FU Ori’s inner accretion disc. We find that (1) when the disc is threaded by vertical magnetic fields, most accretion occurs in the magnetically dominated atmosphere at z ∼ R, similar to the ‘surface accretion’ mechanism in previous locally isothermal MHD simulations. (2) A moderate disc wind is launched in the vertical field simulations with a terminal speed of …

Optically Targeted Search For Gravitational Waves Emitted By Core-Collapse Supernovae During The First And Second Observing Runs Of Advanced Ligo And Advanced Virgo, B. P. Abbott, R. Abbott, T. D. Abbott, S. Abra, F. Acernese, K. Ackley, C. Adams, V. B. Adya, Teviet Creighton, Mario C. Diaz

Physics & Astronomy Faculty Publications

We present the results from a search for gravitational-wave transients associated with core-collapse supernovae observed within a source distance of approximately 20 Mpc during the first and second observing runs of Advanced LIGO and Advanced Virgo. No significant gravitational-wave candidate was detected. We report the detection efficiencies as a function of the distance for waveforms derived from multidimensional numerical simulations and phenomenological extreme emission models. The sources with neutrino-driven explosions are detectable at the distances approaching 5 kpc, and for magnetorotationally driven explosions the distances are up to 54 kpc. However, waveforms for extreme emission models are detectable up to …

Optically Targeted Search For Gravitational Waves Emitted By Core-Collapse Supernovae During The First And Second Observing Runs Ff Advanced Ligo And Advanced Virgo, Tiffany Summerscales, Ligo Scientific Collaboration And The Virgo Collaboration, Asas=Sn Collaboration, Dlt40 Collaboration

Faculty Publications

We present the results from a search for gravitational-wave transients associated with core-collapse supernovae observed within a source distance of approximately 20 Mpc during the first and second observing runs of Advanced LIGO and Advanced Virgo. No significant gravitational-wave candidate was detected. We report the detection efficiencies as a function of the distance for waveforms derived from multidimensional numerical simulations and phenomenological extreme emission models. The sources with neutrino-driven explosions are detectable at the distances approaching 5 kpc, and for magnetorotationally driven explosions the distances are up to 54 kpc. However, waveforms for extreme emission models are detectable up to …

Star Formation In Low-Redshift Cluster Dwarf Galaxies, Cody M. Rude, Madina R. Sultanova, Gihan L. Ipita Kaduwa Gamage, Wayne A. Barkhouse, Sandanuwan P. Kalawila Vithanage

Physics Faculty Publications

Evolution of galaxies in dense environments can be affected by close encounters with neighbouring galaxies and interactions with the intracluster medium. Dwarf galaxies (dGs) are important as their low mass makes them more susceptible to these effects than giant systems. Combined luminosity functions (LFs) in the r and u band of 15 galaxy clusters were constructed using archival data from the Canada–France–Hawaii Telescope. LFs were measured as a function of clustercentric radius from stacked cluster data. Marginal evidence was found for an increase in the faint-end slope of the u-band LF relative to the r-band with increasing clustercentric …

Towards A Real-Time Fully-Coherent All-Sky Search For Gravitational Waves From Compact Binary Coalescences Using Particle Swarm Optimization, Marc E. Normandin, Soumya Mohanty

Physics & Astronomy Faculty Publications

While a fully-coherent all-sky search is known to be optimal for detecting gravitational wave signals from compact binary coalescences, its high computational cost has limited current searches to less sensitive coincidence-based schemes. Following up on previous work that has demonstrated the effectiveness of particle swarm optimization (PSO) in reducing the computational cost of this search, we present an implementation that achieves near real-time computational speed. This is achieved by combining the search efficiency of PSO with a significantly revised and optimized numerical implementation of the underlying mathematical formalism along with additional multithreaded parallelization layers in a distributed computing framework. For …

In-Class Activities For Openstax Astronomy, Rosa Williams, Kimberly Shaw

Physics and Astronomy Ancillary Materials

This set of in-class activities in Microsoft Word format are intended to supplement OpenStax Astronomy. Topics include:

• Atmospheric Gas
• Celestial Sphere
• Dwarf Planets
• Earth Size
• Earth Impact
• Greenhouse Gases and Climate Change
• Jovian Planet
• Jovian Moon and Ring
• Mars Atmosphere and Climate
• Solar System Formation and Scale
• Sunspots
• Terrestrial Planet and Lunar Features
• Venus Atmosphere and Climate

Lhs 1815b: The First Thick-Disk Planet Detected By Tess, T. Gan, A. Shporer, J. H. Livingston, K. A. Collins, S. Mao, A. A. Trani, D. Gandolfi, T. Hirano, R. Luque, K. G. Stassun, C. Ziegler, S. B. Howell, C. Hellier, J. M. Irwin, J. G. Winters, D. R. Anderson, C. Briceño, N. Law, A. W. Mann, X. Bonfils, N. Astudillo-Defru, Eric L.N. Jensen, G. Anglada-Escudé, G. R. Ricker, R. Vanderspek, D. W. Latham, S. Seager, J. N. Winn, J. M. Jenkins, G. Furesz, N. M. Guerrero, E. Quintana, J. D. Twicken, D. A. Caldwell, P. Tenenbaum, C. X. Huang, P. Rowden, B. Rojas-Ayala

Physics & Astronomy Faculty Works

We report the first discovery of a thick-disk planet, LHS 1815b (TOI-704b, TIC 260004324), detected in the Transiting Exoplanet Survey Satellite (TESS) survey. LHS 1815b transits a bright (V = 12.19 mag, K = 7.99 mag) and quiet M dwarf located 29.87 ± 0.02 pc away with a mass of 0.502 ± 0.015 M _⊙ and a radius of 0.501 ± 0.030 R _⊙. We validate the planet by combining space- and ground-based photometry, spectroscopy, and imaging. The planet has a radius of 1.088 ± 0.064 R _⊕ with a 3σ mass upper limit of 8.7 M _⊕. …

Toros Optical Follow-Up Of The Advanced Ligo–Virgo O2 Second Observational Campaign, Rodolfo Artola, Martin Beroiz, Juan Cabral, R. Camuccio, Moises Castillo, Mario C. Diaz, Aldo Fonrouge, Alejandro F. Hinojosa, Andrea Hinojosa, Americo F. Hinojosa, Lucas M. Macri

Physics & Astronomy Faculty Publications

We present themethods and results of the optical follow-up, conducted by the Transient Optical Robotic Observatory of the South Collaboration, of gravitational wave events detected during the Advanced LIGO–Virgo second observing run (2016 November–2017 August). Given the limited field of view (∼100 arcmin) of our observational instrumentation, we targeted galaxies within the area of high localization probability that were observable from our sites. We analysed the observations using difference imaging, followed by a random forest algorithm to discriminate between real and spurious transients. Our observations were conducted using telescopes at Estacion Astrofısica de Bosque Alegre, Cerro Tololo Inter-American Observatory, the …

Fast Radio Bursts As Strong Waves Interacting With The Ambient Medium, Yuan-Pei Yang, Bing Zhang

Physics & Astronomy Faculty Research

Fast radio bursts (FRBs) are mysterious radio transients whose physical origin is still unknown. Within a few astronomical units near an FRB source, the electric field of the electromagnetic wave is so large that the electron oscillation velocity becomes relativistic, which makes the classical Thomson scattering theory and the linear plasma theory invalid. We discuss FRBs as strong waves interacting with the ambient medium, in terms of both electron motion properties and plasma properties. Several novel features are identified. (1) The cross section of Thomson scattering is significantly enhanced for the scattering photons. (2) On the other hand, because of …

Toi-132 B: A Short-Period Planet In The Neptune Desert Transiting A V = 11.3 G-Type Star, M. R. Díaz, J. S. Jenkins, D. Gandolfi, E. D. Lopez, M. G. Soto, P. Cortés-Zuleta, Z. M. Berdiñas, K. G. Stassun, K. A. Collins, J. I. Vines, C. Ziegler, M. Fridlund, Eric L.N. Jensen, F. Murgas, A. Santerne, P. A. Wilson, M. Esposito, A. P. Hatzes, M. C. Johnson, K. W. F. Lam, J. H. Livingston, V. Van Eylen, N. Narita, C. Briceño, K. I. Collins, S. Csizmadia, M. Fausnaugh, T. Gan, R. A. García, I. Georgieva, A. Glidden, L. González-Cuesta, J. M. Jenkins, D. W. Latham, N. M. Law, A. W. Mann, S. Mathur, I. Mireles, R. Morris, E. Pallé, C. M. Persson, G. Ricker, S. Rinehart, M. E. Rose, S. Seager, J. C. Smith, T.-G. Tan, A. Tokovinin, A. Vanderburg, R. Vanderspek, J. N. Winn, D. A. Yahalomi

Physics & Astronomy Faculty Works

The Neptune desert is a feature seen in the radius-period plane, whereby a notable dearth of short period, Neptune-like planets is found. Here, we report the Transiting Exoplanet Survey Satellite (TESS) discovery of a new short-period planet in the Neptune desert, orbiting the G-type dwarf TYC 8003-1117-1 (TOI-132). TESS photometry shows transit-like dips at the level of ∼1400 ppm occurring every ∼2.11 d. High-precision radial velocity follow-up with High Accuracy Radial Velocity Planet Searcher confirmed the planetary nature of the transit signal and provided a semi-amplitude radial velocity variation of 11.38 +0.84−0.85 m s−1, which, when combined with the stellar …

On The Complexity Of Boson Sampling Using Atoms In Optical Lattices, Gopikrishnan Muraleedharan

Physics & Astronomy ETDs

The extended Church-Turing thesis says that any computation that can be done by a physically realizable model of computers can be efficiently computed by the simplest model of classical computer, a Turing machine. Since the introduction of the concept of quantum computers, a central goal has been to find instances where the extended Church- Turing thesis fails. In the current noisy intermediate-scale quantum devices era, one looks for such instances that can be simulated on modest devices of small scale in the presence of noise. In this thesis, we work with one such problem, namely the Boson Sampling problem. We …

Tess Spots A Hot Jupiter With An Inner Transiting Neptune, C. X. Huang, S. N. Quinn, A. Vanderburg, J. Becker, J. E. Rodriguez, F. J. Pozuelos, D. Gandolfi, G. Zhou, A. W. Mann, K. A. Collins, I. Crossfield, K. Barkaoui, K. I. Collins, M. Fridlund, M. Gillon, E. J. Gonzales, M. N. Günther, T. J. Henry, S. B. Howell, H.-S. James, W.-C. Jao, E. Jehin, Eric L.N. Jensen, S. R. Kane, J. J. Lissauer, E. Matthews, R. A. Matson, L. A. Paredes, J. E. Schlieder, K. G. Stassun, A. Shporer, L. Sha, T.-G. Tan, I. Georgieva, S. Mathur, E. Palle, C. M. Persson, V. Van Eylen, G. R. Ricker, R. K. Vanderspek, D. W. Latham, J. N. Winn, S. Seager, J. M. Jenkins, C. J. Burke, R. F. Goeke, S. Rinehart, M. E. Rose, E. B. Ting, G. Torres, I. Wong

Physics & Astronomy Faculty Works

Hot Jupiters are rarely accompanied by other planets within a factor of a few in orbital distance. Previously, only two such systems have been found. Here, we report the discovery of a third system using data from the Transiting Exoplanet Survey Satellite (TESS). The host star, TOI-1130, is an eleventh magnitude K-dwarf in Gaia G-band. It has two transiting planets: a Neptune-sized planet (3.65 ± 0.10 ${R}_{\oplus }$) with a 4.1 days period, and a hot Jupiter (${1.50}_{-0.22}^{+0.27}$ ${R}_{{\rm{J}}}$) with an 8.4 days period. Precise radial-velocity observations show that the mass of the hot Jupiter is ${0.974}_{-0.044}^{+0.043}$ ${M}_{{\rm{J}}}$. For the …

Gw190425: Observation Of A Compact Binary Coalescence With Total Mass ∼ 3.4 M O, B. P. Abbott, R. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

On 2019 April 25, the LIGO Livingston detector observed a compact binary coalescence with signal-to-noise ratio 12.9. The Virgo detector was also taking data that did not contribute to detection due to a low signal-to-noise ratio, but were used for subsequent parameter estimation. The 90% credible intervals for the component masses range from to if we restrict the dimensionless component spin magnitudes to be smaller than 0.05). These mass parameters are consistent with the individual binary components being neutron stars. However, both the source-frame chirp mass and the total mass of this system are significantly larger than those of any …

Gw190425: Observation Of A Compact Binary Coalescence With Total Mass ∼ 3.4 M⊙, B. P. Abbott, R. Abbott, T. D. Abbott, Teviet Creighton, Mario C. Diaz, Soma Mukherjee, Volker Quetschke, Malik Rakhmanov, Satzhan Sitmukhambetov, Wenhui Wang

Physics & Astronomy Faculty Publications

On 2019 April 25, the LIGO Livingston detector observed a compact binary coalescence with signal-to-noise ratio 12.9. The Virgo detector was also taking data that did not contribute to detection due to a low signal-to-noise ratio, but were used for subsequent parameter estimation. The 90% credible intervals for the component masses range from to (– if we restrict the dimensionless component spin magnitudes to be smaller than 0.05). These mass parameters are consistent with the individual binary components being neutron stars. However, both the source-frame chirp mass and the total mass of this system are significantly larger than those of …

Gw190425: Observation Of A Compact Binary Coalescence With Total Mass ∼ 3.4 M O, B. P. Abbott, R. Abbott, T. D. Abbott, S. Abraham, F. Acernese, K. Ackley, C. Adams, R. X. Adhikari, V. B. Adya, C. Affeldt, M. Agathos, K. Agatsuma, N. Aggarwal, O. D. Aguiar, L. Aiello, A. Ain, P. Ajith, G. Allen, A. Allocca, M. A. Aloy, P. A. Altin, A. Amato, S. Anand, A. Ananyeva, S. B. Anderson, W. G. Anderson, S. V. Angelova, S. Antier, S. Appert, K. Arai, M. C. Araya, Tiffany Z. Summerscales

Faculty Publications

© 2020. The Author(s). Published by the American Astronomical Society.. On 2019 April 25, the LIGO Livingston detector observed a compact binary coalescence with signal-to-noise ratio 12.9. The Virgo detector was also taking data that did not contribute to detection due to a low signal-to-noise ratio, but were used for subsequent parameter estimation. The 90% credible intervals for the component masses range from to if we restrict the dimensionless component spin magnitudes to be smaller than 0.05). These mass parameters are consistent with the individual binary components being neutron stars. However, both the source-frame chirp mass and the total mass …

Loop-Closure Kinetics Reveal A Stable, Right-Handed Dna Intermediate In Cre Recombination, Massa J. Shoura, Stefan M. Giovan, Alexandre A. Vetcher, Riccardo Ziraldo, Andreas Hanke, Stephen D. Levene

Physics & Astronomy Faculty Publications

In Cre site-specific recombination, the synaptic intermediate is a recombinase homotetramer containing a pair of loxP DNA target sites. The enzyme system's strand-exchange mechanism proceeds via a Holliday-junction (HJ) intermediate; however, the geometry of DNA segments in the synapse has remained highly controversial. In particular, all crystallographic structures are consistent with an achiral, planar Holliday-junction (HJ) structure, whereas topological assays based on Cre-mediated knotting of plasmid DNAs are consistent with a right-handed chiral junction. We use the kinetics of loop closure involving closely spaced (131–151 bp) loxP sites to investigate the in-aqueo ensemble of conformations for the longest-lived looped DNA …

On The Frb Luminosity Function – – Ii. Event Rate Density, Rui Luo, Yunpeng Men, Kejia Lee, Weiyang Wang, D. R. Lorimer, Bing Zhang

Physics & Astronomy Faculty Research

The luminosity function of Fast Radio Bursts (FRBs), defined as the event rate per unit cosmic co-moving volume per unit luminosity, may help to reveal the possible origins of FRBs and design the optimal searching strategy. With the Bayesian modelling, we measure the FRB luminosity function using 46 known FRBs. Our Bayesian framework self-consistently models the selection effects, including the survey sensitivity, the telescope beam response, and the electron distributions from Milky Way/ the host galaxy/ local environment of FRBs. Different from the previous companion paper, we pay attention to the FRB event rate density and model the event counts …

Testing The Hypothesis Of Compact-Binary-Coalescence Origin Of Fast Radio Bursts Using A Multimessenger Approach, Min-Hao Wang, Shun-Ke Ai, Zheng-Xiang Li, Nan Xing, He Gao, Bing Zhang

Physics & Astronomy Faculty Research

In the literature, compact binary coalescences (CBCs) have been proposed as one of the main scenarios to explain the origin of some non-repeating fast radio bursts (FRBs). The large discrepancy between the FRB and CBC event rate densities suggests that their associations, if any, should only apply at most for a small fraction of FRBs. Through a Bayesian estimation method, we show how a statistical analysis of the coincident associations of FRBs with CBC gravitational wave (GW) events may test the hypothesis of these associations. We show that during the operation period of the advanced Laser Interferometer Gravitational-Wave Observatory (aLIGO), …

A Comprehensive Catalog Of Dark Matter Halo Models For Sparc Galaxies, Pengfei Li, Stacy S. Mcgaugh

Faculty Scholarship

We present rotation curve fits to 175 late-type galaxies from the Spitzer Photometry and Accurate Rotation Curves database using seven dark matter (DM) halo profiles: pseudo-isothermal, Burkert, Navarro-Frenk-White (NFW), Einasto, Di Cintio et al. (2014, hereafter DC14), cored-NFW, and a new semi-empirical profile named Lucky13. We marginalize over the stellar mass-to-light ratio, galaxy distance, disk inclination, halo concentration, and halo mass (and an additional shape parameter for Einasto) using a Markov Chain Monte Carlo method. We find that cored halo models, such as the DC14 and Burkert profiles, generally provide better fits to rotation curves than the cuspy NFW profile. …