Astrophysics and Astronomy Commons^™

Recent Evolution Of The Eta Carinae Supernova Imposter System, Greta L. Helmel

Macalester Journal of Physics and Astronomy

The supernova imposter Eta Carinae and its surrounding Homunculus reflection nebula have been of great interest for the last several decades. As the most massive star known in our Galaxy, this object is of particular importance in understanding high mass loss episodes and final stages in the evolution of other similarly massive stars in the later stages of their lives. Observations using the STIS CCD Instrument have been taken over the past 20 years for both the central star and the Homunculus as part of the Hubble Space Telescope (HST) Treasury Program on Eta Carinae. Recent changes in …

The Neutral Hydrogen Kinematics Of The Dwarf Galaxy Merger Ngc 3239, Robert N. Ford

Macalester Journal of Physics and Astronomy

We present H I spectral line images of the nearby dwarf galaxy NGC 3239. The galaxy’s curious morphology suggests that it is a post-merger system. We propose that NGC 3239 is a merger because it has multiple tidal tails, an enhanced velocity dispersion throughout the disk, and widespread star formation. We have produced kinematic moment maps corresponding to the H I column density, radial velocity, and velocity dispersion. Further, position velocity (P-V) slices of the galaxy were taken and three-color images were made using the SDSS G, R, and I, filters for comparison with the moment maps. These slices illustrate …

Hst/Stis Analysis Of The First Main Sequence Pulsar Cu Virginis, Jiří Krtička, Zdeněk Mikulášek, Gregory W. Henry, Jan Janík, Oleg Kochukhov, Andrzej Pigulski, P. Leto, Corrado Trigilio, Iva Krtičková, Theresa Lüftinger, Milan Prvák, A. Tichý

Information Systems and Engineering Management Research Publications

Context. CU Vir has been the first main sequence star that showed regular radio pulses that persist for decades, resembling the radio lighthouse of pulsars and interpreted as auroral radio emission similar to that found in planets. The star belongs to a rare group of magnetic chemically peculiar stars with variable rotational period.

Aims. We study the ultraviolet (UV) spectrum of CU Vir obtained using STIS spectrograph onboard the Hubble Space Telescope (HST) to search for the source of radio emission and to test the model of the rotational period evolution.

Methods. We used our own far-UV and visual photometric …

Equation Of State Of A Magnetized Dense Neutron System, Efrain J. Ferrer, Aric Hackebill

Physics & Astronomy Faculty Publications

We discuss how a magnetic field can affect the equation of state of a many-particle neutron system. We show that, due to the anisotropy in the pressures, the pressure transverse to the magnetic field direction increases with the magnetic field, while the one along the field direction decreases. We also show that in this medium there exists a significant negative field-dependent contribution associated with the vacuum pressure. This negative pressure demands a neutron density sufficiently high (corresponding to a baryonic chemical potential of ��=2.25 GeV) to produce the necessary positive matter pressure that can compensate for the gravitational pull. The …

Machine Learning Pipeline For Exoplanet Classification, George Clayton Sturrock, Brychan Manry, Sohail Rafiqi

SMU Data Science Review

Planet identification has typically been a tasked performed exclusively by teams of astronomers and astrophysicists using methods and tools accessible only to those with years of academic education and training. NASA’s Exoplanet Exploration program has introduced modern satellites capable of capturing a vast array of data regarding celestial objects of interest to assist with researching these objects. The availability of satellite data has opened up the task of planet identification to individuals capable of writing and interpreting machine learning models. In this study, several classification models and datasets are utilized to assign a probability of an observation being an exoplanet. …

On The Time-Frequency Downward Drifting Of Repeating Fast Radio Bursts, Weiyang Wang, Bing Zhang, Xuelei Chen, Renxin Xu

Physics & Astronomy Faculty Research

The newly discovered second repeating fast radio burst (FRB) source, FRB 180814.J0422+73, was reported to exhibit a time–frequency downward drifting pattern, which is also seen in the first repeater FRB 121102. We propose a generic geometrical model to account for the observed downward drifting of sub-pulse frequency, within the framework of coherent curvature radiation by bunches of electron–positron pairs in the magnetosphere of a neutron star (NS). A sudden trigger event excites these coherent bunches of charged particles, which stream outward along open field lines. As the field lines sweep across the line of sight, the bunches seen later travel …

The Sophie Search For Northern Extrasolar Planets Xiv. A Temperate (Teq ~ 300 K) Super-Earth Around The Nearby Star Gliese 411, R. F. Díaz, Xavier Delfosse, Melissa J. Hobson, Isabelle Boisse, Nicola Astudillo-Defru, Xavier Bonfils, Gregory W. Henry, Luc Arnold, François Bouchy, Vincent Bourrier, Bastien Brugger, Shweta Dalal, Magali Deleuil, Olivier Demangeon, F. Dolon, Xavier Dumusque, Thierry Forveille, Nathan Hara, Guillaume Hébrard, ‪Flavien Kiefer, Théodore Lopez, ‪Lucile Mignon, F. Moreau, Olivier Mousis, C. Moutou, Francesco Pepe, S. Perruchot, Y. Richaud, Alexandre Santerne, Nuno Santos, R. Sottile, Manu Stalport, Damien Ségransan, Stéphane Udry, N. Unger, Paul A. Wilson

Information Systems and Engineering Management Research Publications

Periodic radial velocity variations in the nearby M-dwarf star Gl 411 are reported, based on measurements with the SOPHIE spectrograph. Current data do not allow us to distinguish between a 12.95-day period and its one-day alias at 1.08 days, but favour the former slightly. The velocity variation has an amplitude of 1.6 m s−1, making this the lowest-amplitude signal detected with SOPHIE up to now. We have performed a detailed analysis of the significance of the signal and its origin, including extensive simulations with both uncorrelated and correlated noise, representing the signal induced by stellar activity. The signal is significantly …

Absolute Dimensions Of The Early F-Type Eclipsing Binary V506 Ophiuchi, Guillermo Torres, Claud H. Sandberg Lacy, Francis C. Fekel, Matthew W. Muterspaugh

Information Systems and Engineering Management Research Publications

We report extensive differential V-band photometry and high-resolution spectroscopic observations of the early F-type, 1.06-day detached eclipsing binary V506 Oph. The observations, along with times of minimum light from the literature, are used to derive a very precise ephemeris and the physical properties for the components, with the absolute masses and radii being determined to 0.7% or better. The masses are 1.4153 ± 0.0100 M☉ and 1.4023 ± 0.0094 M☉ for the primary and secondary, the radii are 1.725 ± 0.010 R☉ and 1.692 ± 0.012 R☉, and the effective temperatures are 6840 ± 150 K and 6780 ± 110 …

Stability Of Binary Colloidal Crystals Immersed In A Cholesteric Liquid Crystal, Setarehalsadat Changizrezaei, Colin Denniston

Physics and Astronomy Publications

In this paper, we model a number of both closed-packed and non-closed-packed crystals inside a cholesteric liquid crystal (LC) with different pitch values and nematic LC through the Landau–de Gennes free-energy method. We used binary boundary conditions (normal and planar anchoring) applied on the surface of colloids as we are interested in investigating the stability of binary crystals. The results indicate that body-centered-cubic (BCC) crystals have a lower-energy lattice defect structure than the diamond crystal, and the most energetically favorable BCC lattice can be formed in a cholesteric liquid crystal with a pitch value commensurate with the lattice spacing. Furthermore, …

Studies On The Generation And Detection Of Orbital Angular Momentum Based On Beam-Shaping Techniques, Xijie Luo

Physics & Astronomy ETDs

Light carrying orbital angular momentum (OAM) has many applications ranging from optical manipulation, imaging and remote sensing, and optical communications, and can be used to perform fundamental studies in quantum mechanics and quantum information. Moreover, single photons with high-order OAM allow for increasing the amount of information carried per photon in quantum communication. This thesis describes the study of methods for the preparation and detection of OAM of light in high mode order by utilizing beam shaping techniques using spatial light modulators (SLMs). The quality of the generated high-order OAM mode is limited by optical aberrations which are induced by …

First Measurement Of The Hubble Constant From A Dark Standard Siren Using The Dark Energy Survey Galaxies And The Ligo/Virgo Binary–Black-Hole Merger Gw170814, M. Soares-Santos, A. Palmese, Teviet Creighton, Mario C. Diaz, Soma Mukherjee, Volker Quetschke, Malik Rakhmanov, Karla E. Ramirez, Satzhan Sitmukhambetov, Robert Stone, D. Tuyenbayev, Wenhui Wang, Adam Zadrozny

Physics & Astronomy Faculty Publications

We present a multi-messenger measurement of the Hubble constant H0 using the binary–black-hole merger GW170814 as a standard siren, combined with a photometric redshift catalog from the Dark Energy Survey (DES). The luminosity distance is obtained from the gravitational wave signal detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO)/Virgo Collaboration (LVC) on 2017 August 14, and the redshift information is provided by the DES Year 3 data. Black hole mergers such as GW170814 are expected to lack bright electromagnetic emission to uniquely identify their host galaxies and build an object-by-object Hubble diagram. However, they are suitable for a statistical measurement, …

A Photometric Study Of The Eclipsing Binary V574 Lyrae, Abigail L.J. Rickards

Electronic Theses and Dissertations

Variable stars provide unparalleled insight into stellar evolution and eclipsing binary variables are particularly excellent laboratories for determining stellar physical parameters and behavior. These parameters, when taken with those of other stars, can be used to evaluate current theories on stellar evolution and stellar structure. With the view of contributing useful data to this cause, a photometric study of the eclipsing binary system V574 Lyrae (Lyr) was undertaken to determine the system's physical parameters and to create a model of the system. Data were collected with a 0.36 m Ritchey-Chr'etien telescope and the Sloan g', r', and i' filters and …

A 3+1 Decomposition Of The Minimal Standard-Model Extension Gravitational Sector, Nils A. Nilsson, Kellie O'Neal-Ault, Quentin G. Bailey

Publications

The 3+1 (ADM) formulation of General Relativity is used in, for example, canonical quantum gravity and numerical relativity. Here we present a 3+1 decomposition of the minimal Standard-Model Extension gravity Lagrangian. By choosing the leaves of foliation to lie along a timelike vector field we write the theory in a form which will allow for comparison and matching to other gravity models.

Morphometric Analysis And Application In Galaxy Evolution And High-Redshift Surveys., Samir Kusmic

College of Arts & Sciences Senior Theses

In this thesis, I will present my research work with statistical analysis towards a galaxy’s morphology and its morphometric. The first part would be with the galaxy morphometric and have heavy focus with one particular software: Source Extractor. Source Extractor was compared to GALFIT in order to see how accurate and precise we would expect the software to be with effective radii, scale length, inclination,position angle, and major and minor axes. This is towards preparation for future surveys with expectation of a large boom in galaxy discovery with the new observatories to be online (EUCLID, LSST, JWST, etc.). From our …

Variability In X-Ray Line Ratios In Helium-Like Ions Of Massive Stars: The Wind-Driven Case, Richard Ignace, Z. Damrau, K. T. Hole

ETSU Faculty Works

Context. High spectral resolution and long exposure times are providing unprecedented levels of data quality of massive stars at X-ray wavelengths.

Aims. A key diagnostic of the X-ray emitting plasma are the fir lines for He-like triplets. In particular, owing to radiative pumping effects, the forbidden-to-intercombination line luminosity ratio, R = f∕i, can be used to determine the proximity of the hot plasma to the UV-bright photospheres of massive stars. Moreover, the era of large observing programs additionally allows for investigation of line variability.

Methods. This contribution is the second to explore how variability in the line …

Luminomagnetic Nd3+ Doped Fluorapatite Coated Fe3o4 Nanostructures For Biomedical Applications, Sekar Karthi, Raji Govindan, Ajithkumar Gangadharan, Gamage Chamath Dannangoda, Karen S. Martirosyan, Dhiraj K. Sardar, Santhosh Chidangil, Girija Easwaradas Kreedapathy

Physics & Astronomy Faculty Publications

Luminomagnetic nanostructured Nd3+ doped fluorapatite (FAP) coated Fe3O4 nanoparticles were produced by hydrothermal method. X-ray diffraction analysis indicates that the prepared nanoparticles contain both FAP and Fe3O4 phases. Electron microscope analysis shows the formation of nanoparticles of Fe3O4 encased in rod shaped FAP nanoparticles of average length 40 nm. Magnetic measurements confirm the room temperature superparamagnetic nature of the nanoparticles with saturation magnetization value up to 7.8 emu/g. The prepared nanoparticles display strong near infrared (NIR) emission at 1060 nm under 800 nm excitation. Cell viability studies for 72 hour demonstrate the survival rate of over 84% with 500 μg/mL …

Recent Developments In Spacetime-Symmetry Tests In Gravity, Q. G. Bailey

Publications

Motivated by potentially detectable but minuscule signatures from Planckscale or other new physics, there has been a substantial increase in tests of spacetime symmetry in gravity in recent years. Some novel hypothetical effects that break local Lorentz symmetry and CPT symmetry in gravitational experiments as well as solar system and astrophysical observations have been studied in recent works. Much of this work uses the effective field theory framework, the Standard-Model Extension (SME), that includes gravitational couplings. In other cases, the parameters in specific hypothetical models of Lorentz violation in gravity have been tested.

Deep Space Radiation Shelter Through Magnetic Shielding, Lauren Elizabeth Eastberg Persons

Theses and Dissertations

As human space exploration begins to reach beyond Earth for the first time in 50 years, we must prepare for the eventuality of long-duration missions outside the protection of Earth's magnetic field. In interplanetary space astronauts are exposed to highly energetic galactic cosmic radiation, most commonly in the range of 1-GeV protons. Present day shielding technologies are not sufficient to protect astronauts against such particles; as such, the following paper proposes an alternate method of creating deep space radiation shelters through the use of magnetic shielding. Using a series of circular superconducting loops arranged in the shape of a shell, …

Induced Magnetic Dipole On Jupiter’S Moon Europa, Luke Francis, Michele Zanolin

Student Works

Physics can have some of the most unique and extraordinary applications of basic principles applied on a larger scale. This paper will explore the properties of induced magnetic dipoles and will examine this phenomenon directly from Jupiter's moon, Europa. These properties will be used to determine if there is liquid water beneath its icy surface and how this conclusion was verified. This will be accomplished using the concepts of magnetic dipoles and induced currents. Recent missions have also revealed estimates of the depth of Europa's subsurface ocean. There have been many measurements taken of Europa's magnetic field, and they are …

Cloud Coalescence: A Dynamical Instability Affecting Multiphase Environments, Tim Waters, Daniel Proga

Physics & Astronomy Faculty Research

Mass and size distributions are the key characteristics of any astrophysical object, including the densest clumps comprising the cold phase of multiphase environments. In our recent papers, we showed how individual clouds of various sizes form and evolve in active galactic nuclei. In particular, we showed that large clouds undergo damped oscillations as a response to their formation process. Here we follow up this investigation, addressing how different size clouds interact. We find that smaller clouds become trapped in the advective flows generated by larger clouds. The explanation for this behavior leads to a rather remarkable conclusion: even in the …

Non-Isobaric Thermal Instability, Tim Waters, Daniel Proga

Physics & Astronomy Faculty Research

Multiphase media have very complex structure and evolution. Accurate numerical simulations are necessary to make advances in our understanding of this rich physics. Because simulations can capture both the linear and nonlinear evolution of perturbations with a relatively wide range of sizes, it is important to thoroughly understand the stability of condensation and acoustic modes between the two extreme wavelength limits of isobaric and isochoric instability as identified by Field. Partially motivated by a recent suggestion that large non-isobaric clouds can "shatter" into tiny cloudlets, we revisit the linear theory to survey all possible regimes of thermal instability. We uncover …

Searches For Continuous Gravitational Waves From 15 Supernova Remnants And Fomalhaut B With Advanced Ligo, 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, A. Ananyeva, S. B. Anderson, W. G. Anderson, S. V. Angelova, S. Antier, S. Appert, K. Arai, M. C. Araya, J. S. Areeda, Tiffany Z. Summerscales

Faculty Publications

© 2019. The American Astronomical Society. All rights reserved. We describe directed searches for continuous gravitational waves (GWs) from 16 well-localized candidate neutron stars, assuming none of the stars has a binary companion. The searches were directed toward 15 supernova remnants and Fomalhaut b, a directly imaged extrasolar planet candidate that has been suggested to be a nearby old neutron star. Each search covered a broad band of frequencies and first and second time derivatives. After coherently integrating spans of data from the first Advanced LIGO observing run of 3.5-53.7 days per search, applying data-based vetoes, and discounting known instrumental …

Low-Latency Gravitational-Wave Alerts For Multimessenger Astronomy During The Second Advanced Ligo And Virgo Observing Run, B. P. Abbott, R. Abbott, Teviet Creighton, Mario C. Diaz, Soma Mukherjee, Volker Quetschke, Malik Rakhmanov, Satzhan Sitmukhambetov, Robert Stone, Darkhan Tuyenbayev, Wenhui Wang, Adam Zadrozny

Physics & Astronomy Faculty Publications

Advanced LIGO's second observing run (O2), conducted from 2016 November 30 to 2017 August 25, combined with Advanced Virgo's first observations in 2017 August, witnessed the birth of gravitational-wave multimessenger astronomy. The first ever gravitational-wave detection from the coalescence of two neutron stars, GW170817, and its gamma-ray counterpart, GRB 170817A, led to an electromagnetic follow-up of the event at an unprecedented scale. Several teams from across the world searched for EM/neutrino counterparts to GW170817, paving the way for the discovery of optical, X-ray, and radio counterparts. In this article, we describe the online identification of gravitational-wave transients and the distribution …

Nature Of Faint Radio Sources In Goods-North And Goods-South Fields – I. Spectral Index And Radio-Fir Correlation, Hansung B. Gim, Min S. Yun, Frazer N. Owen, Emmanuel Momjian, Neal A. Miller, Mauro Giavalisco, Grant Wilson, James Lowenthal, Itziar Aretxaga, David H. Hughes, Glenn E. Morrison, Ryohei Kawabe

Astronomy: Faculty Publications

We present the first results from the deep and wide 5 GHz radio observations of the Great Observatories Origins Deep Survey (GOODS)-North (σ = 3.5 μJy beam−1, synthesized beam size θ = 147 × 142, and 52 sources over 109 arcmin2) and GOODS-South (σ = 3.0 μJy beam−1, θ = 098 × 045, and 88 sources over 190 arcmin2) fields using the Karl G. Jansky Very Large Array. We derive radio spectral indices α between 1.4 and 5 GHz using the beam-matched images and show that the overall spectral index distribution is broad even when the …

Second Repeating Frb 180814.J0422+73: Ten-Year Fermi-Lat Upper Limits And Implications, Yu-Han Yang, Bin-Bin Zhang, Bing Zhang

Physics & Astronomy Faculty Research

The second repeating fast radio burst source, FRB 180814.J0422+73, was detected recently by the CHIME collaboration. We use the ten-year Fermi Large Area Telescope archival data to place a flux upper limit in the energy range of 100 MeV−10 GeV at the position of the source, which is ~1.1 × 10−11 erg cm−2 s−1 for a six-month time bin on average, and ~2.4 × 10−12 erg cm−2 s−1 for the entire ten-year time span. For the maximum redshift of z = 0.11, the ten-year upper limit of luminosity is ~7.3 × 1043 erg s−1. We utilize these upper limits to …

Coherent Radio Emission From A Twisted Magnetosphere After A Magnetar-Quake, Weiyang Wang, Bing Zhang, Xuelei Chen, Renxin Xu

Physics & Astronomy Faculty Research

Magnetars are a class of highly magnetized, slowly rotating neutron stars, only a small fraction of which exhibit radio emission. We propose that the coherent radio curvature emission is generated by net charge fluctuations from a twist-current-carrying bundle (the j-bundle) in the scenario of magnetar-quake. Two-photon pair production is triggered, which requires a threshold voltage not too much higher than 109 V in the current-carrying bundle, and which can be regarded as the "open field lines" of a magnetar. Continued untwisting of the magnetosphere maintains change fluctuations, and hence coherent radio emission, in the progressively shrinking j-bundle, which lasts for …

Testing The Gravitational Weak Equivalence Principle In The Standard-Model Extension With Binary Pulsars, Lijing Shao, Quentin G. Bailey

Publications

The standard model extension provides a framework to systematically investigate possible violation of the Lorentz symmetry. Concerning gravity, the linearized version was extensively examined. We here cast the first set of experimental bounds on the nonlinear terms in the field equation from the anisotropic cubic curvature couplings. These terms introduce body-dependent accelerations for self-gravitating objects, thus violating the gravitational weak equivalence principle (GWEP). Novel phenomena, which are absent in the linearized gravity, remain experimentally unexplored. We constrain them with precise binary-orbit measurements from pulsar timing, wherein the high density and large compactness of neutron stars are crucial for the test. …

Alignment Of A Circumbinary Disc Around An Eccentric Binary With Application To Kh 15d, Jeremy L. Smallwood, Stephen H. Lubow, Alessia Franchini, Rebecca G. Martin

Physics & Astronomy Faculty Research

We analyse the evolution of a mildly inclined circumbinary disc that orbits an eccentric orbit binary by means of smoothed particle hydrodynamics (SPH) simulations and linear theory. We show that the alignment process of an initially misaligned circumbinary disc around an eccentric orbit binary is significantly different than around a circular orbit binary and involves tilt oscillations. The more eccentric the binary, the larger the tilt oscillations and the longer it takes to damp these oscillations. A circumbinary disc that is only mildly inclined may increase its inclination by a factor of a few before it moves towards alignment. The …

Is Theistic Belief Rational In A Scientific Age? (Research Materials), Holy Cross Libraries

Library Resources for Campus Events

A bibliography of resources available through the Holy Cross Libraries which provide additional information related to "Is Theistic Belief Rational in a Scientific Age," a dialogue between William Lane Craig and Jeff Hester on theism, atheism and science. Craig is research professor of philosophy at Talbot School of Theology and professor of philosophy at Houston Baptist University. Hester is an astrophysicist known for his work with the Hubble Space Telescope and professor emeritus in the School of Earth and Space Exploration at Arizona State University.

This event was one of the Deitchman Family Lectures on Religion and Modernity held at …

An Analytic Study Of The Wiedemann-Franz Law And The Thermoelectric Figure Of Merit, Aakash Yadav, Pc Deshmukh, Ken Roberts, Nm Jisrawi, Sree Ram Valluri

Physics and Astronomy Publications

Advances in optimizing thermoelectric material efficiency have seen a parallel activity in theoretical and computational advances. In the current work, it is shown that the calculation of exact Fermi-Dirac integrals enables the generalization of the Wiedemann-Franz law (WF) to optimize the dimensionless thermoelectric figure of merit ZT. This is done by optimizing the Seebeck coefficient, the electrical conductivity and the thermal conductivity. In the calculation of the thermal conductivity, both electronic and phononic contributions are included. The solutions provide insight into the relevant parameter space including the physical significance of complex solutions and their dependence on the scattering parameter r …