# Astrophysics and Astronomy Commons™

## All Articles in Astrophysics and Astronomy

7,350 full-text articles. Page 1 of 230.

Search For Gravitational Waves From Scorpius X-1 In The Second Advanced Ligo Observing Run With An Improved Hidden Markov Model, 2020 Andrews University

#### Search For Gravitational Waves From Scorpius X-1 In The Second Advanced Ligo Observing Run With An Improved Hidden Markov Model, Tiffany Summerscales, Ligo Scientific Collaboration And The Virgo Collaboration

##### Faculty Publications

We present results from a semicoherent search for continuous gravitational waves from the low-mass x-ray binary Scorpius X-1, using a hidden Markov model (HMM) to track spin wandering. This search improves on previous HMM-based searches of LIGO data by using an improved frequency domain matched filter, the J-statistic, and by analyzing data from Advanced LIGO’s second observing run. In the frequency range searched, from 60 to 650 Hz, we find no evidence of gravitational radiation. At 194.6 Hz, the most sensitive search frequency, we report an upper limit on gravitational wave strain (at 95% confidence) of h95%0 ...

Optical Study Of Pks B1322-110, The Intra-Hour Variable Radio Source, 2020 The University of Texas Rio Grande Valley

#### Optical Study Of Pks B1322-110, The Intra-Hour Variable Radio Source, Juan P. Madrid, Artem V. Tuntsov, Mischa Schirmer, Mark A. Walker, Carlos J. Donzelli, Keith W. Bannister, Hayley E. Bignall, Jamie Stevens, Cormac Reynolds, Simon Johnston

##### Physics and Astronomy Faculty Publications and Presentations

Observations with the Australia Telescope Compact Array revealed intra-hour variations in the radio source PKS B1322-110 (Bignall et al. 2019). As part of an optical follow-up, we obtained Gemini Hα and Hα continuum (HαC) images of the PKS B1322-110 field. A robust 19 σ detection of PKS B1322- 110 in the Hα−HαC image prompted us to obtain the first optical spectrum of PKS B1322-110. With the Gemini spectrum we determine that PKS B1322-110 is a flat-spectrum radio quasar at a redshift of z = 3.007 ± 0.002. The apparent flux detected in the Hα filter is likely to originate ...

Directional Limits On Persistent Gravitational Waves Using Data From Advanced Ligo’S First Two Observing Runs, 2020 Andrews University

#### Directional Limits On Persistent Gravitational Waves Using Data From Advanced Ligo’S First Two Observing Runs, Tiffany Summerscales, Ligo Scientific Collaboration And The Virgo Collaboration

##### Faculty Publications

We perform an unmodeled search for persistent, directional gravitational wave (GW) sources using data from the first and second observing runs of Advanced LIGO. We do not find evidence for any GW signals. We place limits on the broadband GW flux emitted at 25 Hz from point sources with a power law spectrum at Fα,Θ<(0.05–25)×10−8  erg cm−2 s−1 Hz−1 and the (normalized) energy density spectrum in GWs at 25 Hz from extended sources at Ωα(Θ)<(0.19–2.89)×10−8  sr−1 where α is the spectral index of the energy density spectrum. These represent improvements ...

Gw190521: A Binary Black Hole Merger With A Total Mass Of 150 M⊙, 2020 The University of Texas Rio Grande Valley

#### Gw190521: A Binary Black Hole Merger With A Total Mass Of 150 M⊙, R. Abbott, T. D. Abbott, A. Aich, G. Bissenbayeva, Teviet Creighton, Mario C. Diaz, Soma Mukherjee, Volker Quetschke, Malik Rakhmanov, K. E. Ramirez, P. K. Roy, W. H. Wang, A. K. Zadrozny

##### Physics and Astronomy Faculty Publications and Presentations

On May 21, 2019 at 03:02:29 UTC Advanced LIGO and Advanced Virgo observed a short duration gravitational-wave signal, GW190521, with a three-detector network signal-to-noise ratio of 14.7, and an estimated false-alarm rate of 1 in 4900 yr using a search sensitive to generic transients. If GW190521 is from a quasicircular binary inspiral, then the detected signal is consistent with the merger of two black holes with masses of 85+21−14  M⊙ and 66+17−18  M⊙ (90% credible intervals). We infer that the primary black hole mass lies within the gap produced by (pulsational) pair-instability supernova ...

Variability Of Active Galactic Nuclei From Differential Photometry, 2020 California Polytechnic State University, San Luis Obispo

#### Variability Of Active Galactic Nuclei From Differential Photometry, Nicholas Steven Yee

##### Physics

The Seoul AGN Monitoring Project, or SAMP for short, is an international project (PI Jonghak Woo from Korea) with the goal of measuring the masses of black holes residing in the center of massive active galactic nuclei (AGNs). AGNs are some of the brightest objects in the universe. Their light is attributed to the accretion of material onto the black hole. However, these objects are too distant to spatially resolve the gravitational sphere of influence of the black hole directly. Instead, we use a technique called reverberation mapping which observes the variability of the AGN power-law continuum emission and the ...

2020 The Graduate Center, City University of New York

#### An Accurate Solution Of The Self-Similar Orbit-Averaged Fokker-Planck Equation For Core-Collapsing Isotropic Globular Clusters: Properties And Application, Yuta Ito

##### Dissertations, Theses, and Capstone Projects

Hundreds of dense star clusters exist in almost all galaxies. Each cluster is composed of approximately ten thousand through ten million stars. The stars orbit in the clusters due to the clusters' self-gravity. Standard stellar dynamics expects that the clusters behave like collisionless self-gravitating systems on short time scales (~ million years) and the stars travel in smooth continuous orbits. Such clusters temporally settle to dynamically stable states or quasi-stationary states (QSS). Two fundamental QSS models are the isothermal- and polytropic- spheres since they have similar structures to the actual core (central part) and halo (outskirt) of the clusters. The two ...

2020 Purdue University - North Central Campus

#### Binary Neutron Star Mergers: Testing Ejecta Models For High Mass-Ratios, Allen Murray

##### The Journal of Purdue Undergraduate Research

Neutron stars are extremely dense stellar corpses which sometimes exist in orbiting pairs known as binary neutron star (BNS) systems. The mass ratio (q) of a BNS system is defined as the mass of the heavier neutron star divided by the mass of the lighter neutron star. Over time the neutron stars will inspiral toward one another and produce a merger event. Although rare, these events can be rich sources of observational data due to their many electromagnetic emissions as well as the gravitational waves they produce. The ability to extract physical information from such observations relies heavily on numerical ...

2020 Portland State University

#### Relativity Lite: A Pictorial Translation Of Einstein’S Theories Of Motion And Gravity, Jack C. Straton

##### PDXOpen: Open Educational Resources

Relativity Lite is designed for the General Astronomy sequence (PH 361-2U, SCI 315-6U) whose primary book glosses over Special Relativity and General Relativity while trying to explain the Cosmology that is based on those subjects. Relativity Lite translates the mathematical equations conventional relativity texts rely upon into pictures that are readily understood and contain within them the mathematical essentials. This book provides the comprehensive coverage needed to understand, in sufficient depth, these three linked areas of our reality.

Readers seeking this knowledge on their own, and those in other courses for nonscientists, may also find it helpful.

If ...

Kinds Of Science And Exploring The Past, 2020 Dordt University

#### Kinds Of Science And Exploring The Past, Channon Visscher

##### Faculty Work Comprehensive List

"Working alongside experimental and observational work, historical science helps us continue to learn the unfolding story of how a beautiful universe, created by a loving God, came to be as we see it today."

Posting about scientific methods from In All Things - an online journal for critical reflection on faith, culture, art, and every ordinary-yet-graced square inch of God’s creation.

https://inallthings.org/kinds-of-science-and-exploring-the-past/

Adaptive Spline Fitting With Particle Swarm Optimization, 2020 The University of Texas Rio Grande Valley

#### Adaptive Spline Fitting With Particle Swarm Optimization, Soumya Mohanty, Ethan Fahnestock

##### Physics and Astronomy Faculty Publications and Presentations

In fitting data with a spline, finding the optimal placement of knots can significantly improve the quality of the fit. However, the challenging high-dimensional and non-convex optimization problem associated with completely free knot placement has been a major roadblock in using this approach. We present a method that uses particle swarm optimization (PSO) combined with model selection to address this challenge. The problem of overfitting due to knot clustering that accompanies free knot placement is mitigated in this method by explicit regularization, resulting in a significantly improved performance on highly noisy data. The principal design choices available in the method ...

Diffuse Spectra Model Of Photoluminescence In Carbon Quantum Dots, 2020 The University of Texas Rio Grande Valley

#### Diffuse Spectra Model Of Photoluminescence In Carbon Quantum Dots, S. E. Kumekov, N. K. Saitova, Karen S. Martirosyan

##### Physics and Astronomy Faculty Publications and Presentations

The attractive aspect of excitation related to fluorescence nature in carbon quantum dots (CQD) has guided to several assumptions correlated with clusters size distribution, shapes as well as presence of different emissive states. In this study, a dimer–excimer model of photoluminescence (PL) in CQD describing discrete multiple electronic states for the excitation-dependent emission is described. The functional dependence of the characteristic width of the diffuse spectra of PL on the size of a quantum dots are calculated. The effective width of PL spectrum can be tuned from 0.1 to 1 eV.

2020 The University of Texas MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences

#### Active Magnetic Radiation Shielding For Long-Duration Human Spaceflight, Kristine Ferrone

##### The University of Texas MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences Dissertations and Theses (Open Access)

Exploration of interplanetary space presents dramatic hazards to human survival.

Space radiation hazards outside the protection of the Earth’s magnetosphere can

produce both acute and chronic health risks and thus become limiting factors for

NASA’s planned mission to Mars by the 2030s. Radiation exposure on a Mars mission

is delivered primarily by high energy ions from galactic cosmic rays and moderate

energy protons from solar particle events. The chronic radiation dose due to galactic

cosmic rays on a typical Mars mission is on the order of 1 Sv, and additional acute

radiation dose from solar flares can reach ...

Galileo's Verse, 2020 Claremont Colleges

#### Galileo's Verse, Bruce F. Mcguffin

##### Journal of Humanistic Mathematics

A response to Thomas Hardy's statement "If Galileo had said in verse that the world moved, the inquisition might have let him alone."

All-Sky Search For Short Gravitational-Wave Bursts In The Second Advanced Ligo And Advanced Virgo Run, 2020 Andrews University

#### All-Sky Search For Short Gravitational-Wave Bursts In The Second Advanced Ligo And Advanced Virgo Run, Tiffany Summerscales, Ligo Scientific Collaboration And The Virgo Collaboration

##### Faculty Publications

We present the results of a search for short-duration gravitational-wave transients in the data from the second observing run of Advanced LIGO and Advanced Virgo. We search for gravitational-wave transients with a duration of milliseconds to approximately one second in the 32–4096 Hz frequency band with minimal assumptions about the signal properties, thus targeting a wide variety of sources. We also perform a matched-filter search for gravitational-wave transients from cosmic string cusps for which the waveform is well modeled. The unmodeled search detected gravitational waves from several binary black hole mergers which have been identified by previous analyses. No ...

Earth-Like Planet In A Binary Star System, 2020 University of Minnesota Morris

#### Earth-Like Planet In A Binary Star System, Melissa Kamrowski

##### Scholarly Horizons: University of Minnesota, Morris Undergraduate Journal

This paper was written as a final lab report for a computer modeling class. It uses dynamical simulations to investigate the behavior of a planet with the mass and velocity magnitude of the Earth placed in a low mass binary star system, which was loosely based on the Sirius binary. The simulations are completed using gravitational force properties along with the Verlet algorithm, then the results were observed through a modeling program, in which each set was set as an animation to determine behavior. Results came from 40 strategic starting points, which were chosen to cover a large spread of ...

2020 Swarthmore College

#### Toi-1235 B: A Keystone Super-Earth For Testing Radius Valley Emergence Models Around Early M Dwarfs, Eric L.N. Jensen

##### Physics & Astronomy Faculty Works

Small planets on close-in orbits tend to exhibit envelope mass fractions of either effectively zero or up to a few percent depending on their size and orbital period. Models of thermally driven atmospheric mass loss and of terrestrial planet formation in a gas-poor environment make distinct predictions regarding the location of this rocky/nonrocky transition in period–radius space. Here we present the confirmation of TOI-1235 b (P = 3.44 days, ${r}_{{\rm{p}}}={1.738}_{-0.076}^{+0.087}$ ${R}_{\oplus }$), a planet whose size and period are intermediate between the competing model predictions, thus making ...

A Remnant Planetary Core In The Hot-Neptune Desert, 2020 Swarthmore College

#### A Remnant Planetary Core In The Hot-Neptune Desert, Eric L.N. Jensen

##### Physics & Astronomy Faculty Works

The interiors of giant planets remain poorly understood. Even for the planets in the Solar System, difficulties in observation lead to large uncertainties in the properties of planetary cores. Exoplanets that have undergone rare evolutionary processes provide a route to understanding planetary interiors. Planets found in and near the typically barren hot-Neptune ‘desert’1,2 (a region in mass–radius space that contains few planets) have proved to be particularly valuable in this regard. These planets include HD149026b3, which is thought to have an unusually massive core, and recent discoveries such as LTT9779b4 and NGTS-4b5, on which photoevaporation has removed ...

2020 Swarthmore College

#### A Pair Of Tess Planets Spanning The Radius Valley Around The Nearby Mid-M Dwarf Ltt 3780, Eric L.N. Jensen

##### Physics & Astronomy Faculty Works

We present the confirmation of two new planets transiting the nearby mid-M dwarf LTT 3780 (TIC 36724087, TOI-732, V = 13.07, K s = 8.204, R s = 0.374 R ⊙, M s = 0.401 M ⊙, d = 22 pc). The two planet candidates are identified in a single Transiting Exoplanet Survey Satellite sector and validated with reconnaissance spectroscopy, ground-based photometric follow-up, and high-resolution imaging. With measured orbital periods of P b = 0.77, P c = 12.25 days and sizes r p,b = 1.33 ± 0.07, r p,c = 2.30 ± 0.16 R ⊕, the two planets span the radius ...

2020 Swarthmore College

#### Precise Mass And Radius Of A Transiting Super-Earth Planet Orbiting The M Dwarf Toi-1235: A Planet In The Radius Gap?, Eric L.N. Jensen

##### Physics & Astronomy Faculty Works

We report the confirmation of a transiting planet around the bright weakly active M0.5 V star TOI-1235 (TYC 4384–1735–1, V ≈ 11.5 mag), whose transit signal was detected in the photometric time series of sectors 14, 20, and 21 of the TESS space mission. We confirm the planetary nature of the transit signal, which has a period of 3.44 d, by using precise RV measurements with the CARMENES, HARPS-N, and iSHELL spectrographs, supplemented by high-resolution imaging and ground-based photometry. A comparison of the properties derived for TOI-1235 b with theoretical models reveals that the planet has ...

Topics In Gravitational Wave Physics, 2020 University of Arkansas, Fayetteville

#### Topics In Gravitational Wave Physics, Aaron David Johnson

##### Theses and Dissertations

We begin with a brief introduction to gravitational waves. Next we look into the origin of the Chandrasekhar transformations between the different equations found by perturbing a Schwarzschild black hole. Some of the relationships turn out to be Darboux transformations. Then we turn to GW150914, the first detected black hole binary system, to see if the nonlinear memory might be detectable by current and future detectors. Finally, we develop an updated code for computing equatorial extreme mass ratio inspirals which will be open sourced as soon as it has been generalized for arbitrary inclinations.