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

Astrophysics and Astronomy Commons

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

6,120 Full-Text Articles 14,546 Authors 373,058 Downloads 172 Institutions

All Articles in Astrophysics and Astronomy

Faceted Search

6,120 full-text articles. Page 1 of 184.

Real-Time Rfi Mitigation In Radio Astronomy, Emily Ramey, Nick Joslyn, Richard Prestage, Michael Lam, Luke Hawkins, Tim Blattner, Mark Whitehead 2019 Washington University in St. Louis

Real-Time Rfi Mitigation In Radio Astronomy, Emily Ramey, Nick Joslyn, Richard Prestage, Michael Lam, Luke Hawkins, Tim Blattner, Mark Whitehead

Senior Honors Papers / Undergraduate Theses

As the use of wireless technology has increased around the world, Radio Frequency Interference (RFI) has become more and more of a problem for radio astronomers. Preventative measures exist to limit the presence of RFI, and programs exist to remove it from saved data, but the use of algorithms to detect and remove RFI as an observation is occurring is much less common. Such a method would be incredibly useful for observations in which the data must undergo several rounds of processing before being saved, as in pulsar timing studies. Strategies for real-time mitigation have been discussed and tested with ...


Application Of Bradford’S Law Of Scattering On Research Publication In Astronomy & Astrophysics Of India, Satish Kumar, Senthilkumar R. 2018 Bharathiar University, Coimbatore & IIT(ISM) Dhanbad

Application Of Bradford’S Law Of Scattering On Research Publication In Astronomy & Astrophysics Of India, Satish Kumar, Senthilkumar R.

Library Philosophy and Practice (e-journal)

The present study is focused on examining the application of Bradford’s law of scattering on research articles published in the field of Astronomy & Astrophysics by Indian scientist during 1988-2017. The bibliographic data was retrieved from Web of Science (WoS) bibliographic data base for different period of time. Total 18,877 journal’s article have been published by Indian scientist in the field of Astronomy & Astrophysics during 1988-2017 which was further retrieved and analyzed separately for different blocks of 10 years as well as for 30 years consolidated too. The core journal of the field was identified. The Bradford law ...


Methanogens, Plausible Extraterrestrial Life Forms On Mars, And Their Tolerance To Increasing Concentrations Of Illite Clay, Chandler Kern 2018 University of Arkansas, Fayetteville

Methanogens, Plausible Extraterrestrial Life Forms On Mars, And Their Tolerance To Increasing Concentrations Of Illite Clay, Chandler Kern

Biological Sciences Undergraduate Honors Theses

Methanogens, some of Earth’s most primitive prokaryotic organisms, are candidates for possible life forms capable of inhabiting Mars. Specifically, four different species (Methanobacterium formicicum, Methanococcus maripaludis, Methanosarcina barkeri, Methanothermobacter wolfeii) were analyzed for their tolerance to the presence of illite clay. Illite is a crystalline mineral that has been identified from regions of Mars’s surface. Results indicated that all four species grew with some success in the illite at different concentrations. This experimentation with methanogens’ abilities to survive and reproduce in the presence of illite allows for a more accurate understanding of the potential capability of microbial growth ...


Magic, Matrimony, And The Moon: Medieval Lunar Symbolism In J.R.R. Tolkien’S “The Lay Of Aotrou And Itroun” And “The Fall Of Arthur”, Kristine Larsen 2018 Central Connecticut State University

Magic, Matrimony, And The Moon: Medieval Lunar Symbolism In J.R.R. Tolkien’S “The Lay Of Aotrou And Itroun” And “The Fall Of Arthur”, Kristine Larsen

Journal of Tolkien Research

This paper (originally delivered at the 2017 International Medieval Congress at the University of Leeds, UK) explores common lunar symbolism in "The Lay of Aotrou and Itroun" and "The Fall of Arthur."


Reason In Motion, Luke Francis 2018 Embry-Riddle Aeronautical University

Reason In Motion, Luke Francis

Student Works

This essay will explain the historical models of the solar system, which was the known universe for most of human history. There is far more to each model than simply positioning different celestial bodies at the center of the system, and the stories of the astronomers who derived the controversial theories are not discussed often enough. The creation of these theories is part of a much broader revolution in scientific thought and marked the start of a series of observational discoveries that would change the the philosophy of science for centuries to come.


Dance Of Two Supermassive Binary Black Holes, Karishma Bansal 2018 University of New Mexico

Dance Of Two Supermassive Binary Black Holes, Karishma Bansal

Shared Knowledge Conference

Black holes exist in a various range of masses ranging from stellar mass (~ 10 Solar Mass) to Supermassive black holes (SMBHs, million to billion Solar Mass). It is expected that as the separation between the black holes decreases, emission of gravitational waves will grow stronger, which makes binary black holes one of the most promising sources for gravitational radiation detection. Gravitational waves from merging stellar-mass black holes have recently been discovered by LIGO; however, we are yet to detect them from binary SMBHs. These massive black holes reside at the heart of most of the galaxies and when two such ...


Nonthermal Dark Matter From Early Matter Domination, Jacek Ksawery Osinski 2018 University of New Mexico

Nonthermal Dark Matter From Early Matter Domination, Jacek Ksawery Osinski

Shared Knowledge Conference

Dark matter (DM) production in the early universe traditionally assumes a standard thermal history where the universe is in a radiation-dominated phase after the end of inflation until matter-radiation equality. However, the presence of additional scalar fields (which is a generic prediction of explicit string constructions) can lead to an epoch of early matter domination (EMD) that ends before the onset of big bang nucleosynthesis. Such an EMD phase has important cosmological consequences and renders thermal production of DM irrelevant. We present three scenarios for DM production involving an era of EMD: evaporation of primordial black holes into DM, DM ...


5 - Irregularities In Young Stellar Models: Are Starspots To Blame?, Jessica Hamilton 2018 University of North Georgia

5 - Irregularities In Young Stellar Models: Are Starspots To Blame?, Jessica Hamilton

Georgia Undergraduate Research Conference (GURC)

Starspots are dark areas on a star’s surface formed by intense magnetic fields that actively suppress the flow of energy, causing the area to become cooler and darker than its surroundings. Starspots threaten a star’s equilibrium because they prevent energy from leaving the star, causing a buildup of pressure. The prevailing assumption is that increased pressure will cause the star to inflate, producing a cooler and larger star. For this reason, starspots have been proposed to explain why some stars appear cooler and larger than we expect. This requires energy blocked by a spot to be trapped deep ...


4 - A Flexible Model For Investigating The Properties Of Starspots: Comparison Of Model Predictions To Observed Data, Amanda Ash 2018 University of North Georgia

4 - A Flexible Model For Investigating The Properties Of Starspots: Comparison Of Model Predictions To Observed Data, Amanda Ash

Georgia Undergraduate Research Conference (GURC)

Accurate age estimates provide a wealth of information about the mechanisms of different astrophysical phenomenon. However, current methods of applying stellar evolution models to obtain these estimates has proven to be flawed, with models having little consistency. It has been speculated the source of this inconsistency may arise from deviations in stellar properties due to the presence of dark blemishes, starspots, present on young cool stars (Feiden, 2016). Using predictions of expected properties from the flexible starspot model to observed properties of various open clusters, we aim to define what starspot properties bring model predictions into agreement with observed data ...


P-43 Doing Astronomy With Gravitational Waves, Tiffany Summerscales 2018 Andrews University

P-43 Doing Astronomy With Gravitational Waves, Tiffany Summerscales

Celebration of Research and Creative Scholarship

With the first detection of gravitational waves on September 14, 2015, the new era of gravitational wave astronomy began. Gravitational wave detections, along with observations made by optical telescopes, have given us new information about the universe. This includes new estimates of the numbers of black holes in the universe and their properties, as well as confirming theories about the sources of some gamma ray bursts and how those sources produce heavy elements.


Observation Of High-Energy Gamma-Rays With The Calorimetric Electron Telescope (Calet) On-Board The International Space Station, Nicholas Wade Cannady 2018 Louisiana State University and Agricultural and Mechanical College

Observation Of High-Energy Gamma-Rays With The Calorimetric Electron Telescope (Calet) On-Board The International Space Station, Nicholas Wade Cannady

LSU Doctoral Dissertations

The CALorimetric Electron Telescope (CALET) is a multi-instrument high-energy astrophysics observatory deployed to the International Space Station (ISS) in August 2015. The primary instrument is the calorimeter (CAL), which is intended for measurement of the cosmic ray electron flux in the energy range 10 GeV - 20 TeV. The CAL is also sensitive to gamma-rays in the energy range 1 GeV - 10 TeV and protons and nuclei up to PeV energies. Also present on the CALET payload are an Advanced Stellar Compass (ASC) for the fine determination of the pointing direction and the CALET Gamma-ray Burst Monitor (CGBM) for the observation ...


Gravity's Light In The Shadow Of The Moon, Andri Gretarsson, Preston Jones, Douglas Singleton 2018 Embry-Riddle Aeronautical University

Gravity's Light In The Shadow Of The Moon, Andri Gretarsson, Preston Jones, Douglas Singleton

Publications

In this essay we look at the possibility of vacuum production of very low frequency electromagnetic radiation from a gravitational wave background (i.e. gravity's light). We also propose that this counterpart electromagnetic radiation should be detectable by a lunar orbiting satellite which is periodically occulted by the Moon (i.e., in the shadow of the Moon). For concreteness we consider the possibility of detection of both the gravitational wave and hypothesized electromagnetic radiation counterpart from the supernova core collapse of Betelgeuse


Streaming Instability Of Multiple Particle Species In Protoplanetary Disks, Noemi Schaffer, Chao-Chin Yang, Anders Johansen 2018 Lund University

Streaming Instability Of Multiple Particle Species In Protoplanetary Disks, Noemi Schaffer, Chao-Chin Yang, Anders Johansen

Physics & Astronomy Faculty Publications

The radial drift and diffusion of dust particles in protoplanetary disks affect both the opacity and temperature of such disks, as well as the location and timing of planetesimal formation. In this paper, we present results of numerical simulations of particle-gas dynamics in protoplanetary disks that include dust grains with various size distributions. We have considered three scenarios in terms of particle size ranges, one where the Stokes number τs = 10−1−100, one where τs = 10−4−10−1, and finally one where τs= 10−3−100. Moreover, we considered both discrete and continuous distributions in particle size. In ...


A Bayesian Framework For Exoplanet Direct Detection And Non-Detection, Jean-Baptiste Ruffio, Dimitri Mawet, Ian Czekala, Bruce Macintosh, Robert J. De Rosa, Garreth Ruane, Michael Bottom, Laurent Pueyo, Jason J. Wang, Lea Hirsch, Zhaohuan Zhu, Eric L. Nielsen 2018 Stanford Univesity

A Bayesian Framework For Exoplanet Direct Detection And Non-Detection, Jean-Baptiste Ruffio, Dimitri Mawet, Ian Czekala, Bruce Macintosh, Robert J. De Rosa, Garreth Ruane, Michael Bottom, Laurent Pueyo, Jason J. Wang, Lea Hirsch, Zhaohuan Zhu, Eric L. Nielsen

Physics & Astronomy Faculty Publications

Rigorously quantifying the information in high-contrast imaging data is important for informing follow-up strategies to confirm the substellar nature of a point source, constraining theoretical models of planet–disk interactions, and deriving planet occurrence rates. However, within the exoplanet direct imaging community, non-detections have almost exclusively been defined using a frequentist detection threshold (i.e., contrast curve) and associated completeness. This can lead to conceptual inconsistencies when included in a Bayesian framework. A Bayesian upper limit is such that the true value of a parameter lies below this limit with a certain probability. The associated probability is the integral of ...


Expected And Achievable Accuracy In Estimating Parameters Of Standing Accretion Shock Instability (Sasi) Fluctuations From Neutrinos And Gravitational Wave Oscillations, Colter Richardson, Jonathan Westhouse 2018 Embry-Riddle Aeronautical University

Expected And Achievable Accuracy In Estimating Parameters Of Standing Accretion Shock Instability (Sasi) Fluctuations From Neutrinos And Gravitational Wave Oscillations, Colter Richardson, Jonathan Westhouse

Undergraduate Research Symposium - Prescott

Core collapse supernovae are one of the most interesting sources of gravitational waves. When the progenitor star is particularly massive, hydrodynamic instability called standing accretion shock instability can develop and it is characterized by deterministic oscillations in the gravitational wave signal as well as in the neutrino luminosity with frequencies of 100hz. In this talk we will review current efforts to extract physical information from the SASI components of the gravitational wave and enhance the detectability of gravitational waves with such components both using laser interferometers and neutrino detectors.


Modeling And Detectability Of Gravitational Wave Waveform Memory From Core Collapse Supernovae, Pedro Jesus Quinonez, Emily Grimes 2018 Embry-Riddle Aeronautical University

Modeling And Detectability Of Gravitational Wave Waveform Memory From Core Collapse Supernovae, Pedro Jesus Quinonez, Emily Grimes

Undergraduate Research Symposium - Prescott

Ever since the discovery of gravitational waves by LIGO, studying these waves have become of utmost importance. This is because gravitational waves have the potential to carry information that have remain unseen by physicist in the past. For example, take the case of a core collapse supernovae. Any information transferred through electromagnetic waves that attempts to escape the inner core of a dying star is blocked out by the intense radiation of its outer shell. For this reason, astronomers have been unable to truly study what goes in the core. However, this is not the case for gravitational waves, which ...


Research In Optics For Gravitational Wave Detection, Britney Biltz, Noura Ibrahim, Brennan Moore 2018 Embry-Riddle Aeronautical University

Research In Optics For Gravitational Wave Detection, Britney Biltz, Noura Ibrahim, Brennan Moore

Undergraduate Research Symposium - Prescott

B.Biltz uses a horizontal “Zollner style” pendulum to monitor changes in the local gravitational field. The pendulum is attracted to the moon and the Sun and so, as the Earth turns, the pendulum’s equilibrium point shifts within a 24-hour period. This is an experiment designed to test the limits of such a pendulum. This sort of system may be useful as a method of monitoring and correcting for gravity gradient noise in future gravitational wave detectors.

N.Ibrahim characterizes thermo-optic noise in high-performance mirror coatings of the type used in Advanced LIGO. To characterize thermo-optic noise, she measures ...


Multicolor Blackbody Emission In Grb 081221, Shu-Jin Hou, Bin-Bin Zhang, Yan-Zhi Meng, Xue-Feng Wu, En-Wei Liang, Hou-Jun Lü, Tong Liu, Yun-Feng Liang, Lin Lin, Rui-jing Lu, Jin-Shu Huang, Bing Zhang 2018 Nanyang Normal University; Chinese Academy of Sciences; Guangxi University

Multicolor Blackbody Emission In Grb 081221, Shu-Jin Hou, Bin-Bin Zhang, Yan-Zhi Meng, Xue-Feng Wu, En-Wei Liang, Hou-Jun Lü, Tong Liu, Yun-Feng Liang, Lin Lin, Rui-Jing Lu, Jin-Shu Huang, Bing Zhang

Physics & Astronomy Faculty Publications

The radiation mechanism of the prompt emission of gamma-ray bursts (GRBs) remains an open question. Although their spectra are usually well fitted with the empirical Band function, which is widely believed to be fully nonthermal and interpreted as an optically thin synchrotron emission, accumulating evidence shows that a thermal component actually exists. In this paper, a multicolor blackbody (mBB) model is proposed for the time-integrated spectrum of GRB 081221 by assuming a power-law distribution of the thermal luminosities with temperature, which manifests photospheric emissions from a different radius and/or angle. The effects of the minimum temperature kT min, the ...


A Comprehensive Analysis Of Fermi Gamma-Ray Burst Data. Iv. Spectral Lag And Its Relation To E P Evolution, Rui-Jing Lu, Yun-Feng Liang, Da-Bin Lin, Jing Lü, Xiang-Gao Wang, Hou-Jun Lü, Hong-Bang Liu, En-Wei Liang, Bing Zhang 2018 Guangxi University

A Comprehensive Analysis Of Fermi Gamma-Ray Burst Data. Iv. Spectral Lag And Its Relation To E P Evolution, Rui-Jing Lu, Yun-Feng Liang, Da-Bin Lin, Jing Lü, Xiang-Gao Wang, Hou-Jun Lü, Hong-Bang Liu, En-Wei Liang, Bing Zhang

Physics & Astronomy Faculty Publications

The spectral evolution and spectral lag behavior of 92 bright pulses from 84 gamma-ray bursts observed by the Fermi Gamma-ray Burst Monitor (GBM) telescope are studied. These pulses can be classified into hard-to-soft pulses (H2S; 64/92), H2S-dominated-tracking pulses (21/92), and other tracking pulses (7/92). We focus on the relationship between spectral evolution and spectral lags of H2S and H2S-dominated-tracking pulses. The main trend of spectral evolution (lag behavior) is estimated with ( ), where E p is the peak photon energy in the radiation spectrum, t + t 0 is the observer time relative to the beginning of pulse −t ...


Chromodynamical Analysis Of Lenticular Galaxies Using Globular Clusters And Planetary Nebulae, Emilio Zanatta, Arianna Cortesi, Ana Chies-Santos, Duncan Forbes, Aaron Romanowsky, Adebusola Alabi, Lodovico Coccato, Claudia Mendes de Oliveira, Jean Brodie, Michael Merrifield 2018 Universidade Federal do Rio Grande do Sul

Chromodynamical Analysis Of Lenticular Galaxies Using Globular Clusters And Planetary Nebulae, Emilio Zanatta, Arianna Cortesi, Ana Chies-Santos, Duncan Forbes, Aaron Romanowsky, Adebusola Alabi, Lodovico Coccato, Claudia Mendes De Oliveira, Jean Brodie, Michael Merrifield

Faculty Publications

Recovering the origins of lenticular galaxies can shed light on the understanding of galaxy and compare them with the kinematics of planetary nebulae (PNe). The PNe and GC data come from the Planetary Nebulae Spectrograph and the SLUGGS Surveys. Through photometric spheroid-disc decomposition and PNe kinematics. we find the probability for a given GC to belong to either the spheroid or the disc of its host galaxy or be rejected from the model. We find that there is no correlation between the components that the GCs are likely to belong to and their colours. Particularly, for NGC 2768, we find ...


Digital Commons powered by bepress