Stars, Interstellar Medium and the Galaxy Commons^™

Searching For Supermassive Binary Black Holes And Their Gravitational Waves, Karishma Bansal

Physics & Astronomy ETDs

The recent discovery of gravitational waves (GWs) by the LIGO collaboration has opened a new observing window on the universe, but it is limited to the GWs in the frequency range of 10-1000 Hz. The main motivation of this thesis is to consider the possibility of detecting low frequency (nHz) GWs. In the pursuit of these waves, we need to understand their source of origin and build a detector with the required sensitivity. Low-frequency waves are expected as a result of coalescing binary supermassive black holes (SMBBHs). We hope to detect these waves in the near future using pulsar timing …

On Neutralization Of Charged Black Holes, Yi Gong, Zhoujian Cao, He Gao, Bing Zhang

Physics & Astronomy Faculty Research

For non-spinning, charged (Reissner–Nordström) black holes, the particles with an opposite sign of charge with respect to that of the black hole will be pulled into the black hole by the extra electromagnetic force. Such a hole will be quickly neutralized so that there should not exist significantly charged, non-spinning black holes in the universe. The case of spinning, charged (Kerr–Newmann, KN) black holes is more complicated. For a given initial position and initial velocity of the particle, an oppositely charged particle does not always more easily fall into the black hole than a neutral particle. The possible existence of …

New Constraints On Early-Type Galaxy Assembly From Spectroscopic Metallicities Of Globular Clusters In M87, Alexa Villaume, Aaron Romanowsky, Jean Brodie, Jay Strader

Faculty Publications

The observed characteristics of globular cluster (GC) systems, such as metallicity distributions, are commonly used to place constraints on galaxy formation models. However, obtaining reliable metallicity values is particularly difficult because of our limited means to obtain high quality spectroscopy of extragalactic GCs. Often, "color–metallicity relations" are invoked to convert easier-to-obtain photometric measurements into metallicities, but there is no consensus on what form these relations should take. In this paper we make use of multiple photometric data sets and iron metallicity values derived from applying full-spectrum stellar population synthesis models to deep Keck/LRIS spectra of 177 GCs centrally located around …

A Search For Analogs Of Kic 8462852 (Boyajian’S Star): A Proof Of Concept And The First Candidates, Edward G. Schmidt

Edward Schmidt Publications

The seemingly normal F dwarf, KIC 8462852 (a.k.a. Boyajian’s Star), has been observed to exhibit two types of behavior unique among known variable stars: infrequent episodes of small brightness dips and a long-term decline in brightness between the dips. No satisfactory mechanism has been found for this behavior, at least in part, because there is only one known example. To begin to rectify this, we have searched for other stars exhibiting similar dipping behavior using the Northern Sky Variability Survey and have used data from the All Sky Automated Survey for Supernovae to further investigate the behavior. Twenty-one stars are …

Methanol Masers In Star-Forming Regions, Nicolas Clarisse, Anuj P. Sarma

DePaul Discoveries

Methanol molecules in star-forming regions emit detectable microwave radiation. In particular, the rotational energy state transitions of methanol are responsible for two types of masers: Class I and Class II, found in the bipolar outflows and accretion disks of star-forming regions, respectively. Masers, being intense point-like sources in our sky, serve as an excellent source of information in further understanding the environment of high-mass star-forming regions due to their intense luminosities. High-mass star formation is still not entirely understood and remains an observational challenge. We have compiled a list of all the methanol maser transitions observed in the literature, in …

Cosmology-Independent Estimate Of The Fraction Of Baryon Mass In The Igm From Fast Radio Burst Observations, Zhengxiang Li, He Gao, Jun-Jie Wei, Yuan-Pei Yang, Bing Zhang, Zong-Hong Zhu

Physics & Astronomy Faculty Research

The excessive dispersion measure (DM) of fast radio bursts (FRBs) has been proposed to be a powerful tool to study intergalactic medium (IGM) and to perform cosmography. One issue is that the fraction of baryons in the IGM, f IGM, is not properly constrained. Here, we propose a method of estimating f IGM using a putative sample of FRBs with the measurements of both DM and luminosity distance d L. The latter can be obtained if the FRB is associated with a distance indicator (e.g., a gamma-ray burst or a gravitational-wave event), or the redshift z of the FRB is …

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 …

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. …

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 …

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 …

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 …

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 …

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 …

Gaia, White Dwarfs, And The Age Of The Galaxy, Ted Von Hippel, E.J. Jeffery, David Van Dyk, D.C. Stenning, E. Robinson, W.H. Jefferys

Publications

The Milky Way is composed of four major stellar populations: the thin disk, thick disk, bulge, and halo. At present, we do not know the age of any of these populations to better than one or two billion years. This lack of knowledge keeps us from answering fundamental questions about the Galaxy: When did the thin disk, thick disk, and halo form? Did they form over an extended period, and if so, how long? Was star formation continuous across these populations or instead occur in distinct episodes? The Gaia satellite is providing precise trigonometric parallaxes for a plethora of white …

Still Missing Dark Matter: Kcwi High-Resolution Stellar Kinematics Of Ngc1052-Df2, Shany Danieli, Pieter Van Dokkum, Charlie Conroy, Roberto Abraham, Aaron Romanowsky

Faculty Publications

The velocity dispersion of the ultra diffuse galaxy NGC1052-DF2 was found to be σgc = 7.8 +5.2/-2.2 km s−1, much lower than expected from the stellar mass–halo mass relation and nearly identical to the expected value from the stellar mass alone. This result was based on the radial velocities of 10 luminous globular clusters that were assumed to be associated with the galaxy. A more precise measurement is possible from high-resolution spectroscopy of the diffuse stellar light. Here we present an integrated spectrum of the diffuse light of NGC1052-DF2 obtained with the Keck Cosmic Web Imager (KCWI), with an instrumental …

Extreme Chemical Abundance Ratio Suggesting An Exotic Origin For An Ultradiffuse Galaxy, Ignacio Martín-Navarro, Aaron Romanowsky, Jean Brodie, Anna Ferr´E-Mateu, Adebusola Alabi, Duncan Forbes, Margarita Sharina, Alexa Villaume, Viraj Pandya, David Martinez-Delgado

Faculty Publications

Ultradiffuse galaxies (UDGs) are a population of extended galaxies but with relatively low luminosities. The origin of these objects remains unclear, largely due to the observational challenges of the low surface brightness Universe. We present here a detailed stellar population analysis of a relatively isolated UDG, DGSAT I, based on spectroscopic data from the Keck Cosmic Web Imager integral field unit. The star formation history of DGSAT I seems to be extended, with a mean luminosity-weighted age of ∼3 Gyr, in agreement with previous photometric studies. However, we find a very high [Mg/Fe] abundance ratio, which is extreme even in …

Veritas And Fermi-Lat Observations Of Tev Gamma-Ray Sources Discovered By Hawc In The 2hwc Catalog, John Hewitt

Showcase of Faculty Scholarly & Creative Activity

The High Altitude Water Cherenkov (HAWC) collaboration recently published their 2HWC catalog, listing 39 very high energy (VHE; >100 GeV) gamma-ray sources based on 507 days of observation. Among these, 19 sources are not associated with previously known teraelectronvolt (TeV) gamma-ray sources. We have studied 14 of these sources without known counterparts with VERITAS and Fermi-LAT. VERITAS detected weak gamma-ray emission in the 1 TeV–30 TeV band in the region of DA 495, a pulsar wind nebula coinciding with 2HWC J1953+294, confirming the discovery of the source by HAWC. We did not find any counterpart for the selected 14 new …

Magic And Fermi-Lat Gamma-Ray Results On Unassociated Hawc Sources, John Hewitt

Showcase of Faculty Scholarly & Creative Activity

The HAWC Collaboration released the 2HWC catalogue of TeV sources, in which 19 show no association with any known high-energy (HE; E>10 GeV) or very-high-energy (VHE; E>300 GeV) sources. This catalogue motivated follow-up studies by both the Major Atmospheric Gamma-ray Imaging Cherenkov (MAGIC) and Fermi-LAT (Large Area Telescope) observatories with the aim of investigating gamma-ray emission over a broad energy band. In this paper, we report the results from the first joint work between High Altitude Water Cherenkov (HAWC), MAGIC, and Fermi-LAT on three unassociated HAWC sources: 2HWC J2006+341, 2HWC J1907+084*, and 2HWC J1852+013*. Although no significant detection …

A Second Galaxy Missing Dark Matter In The Ngc 1052 Group, Pieter Van Dokkum, Shany Danieli, Roberto Abraham, Charlie Conroy, Aaron Romanowsky

Faculty Publications

The ultra-diffuse galaxy NGC1052-DF2 has a very low velocity dispersion, indicating that it has little or no dark matter. Here we report the discovery of a second galaxy in this class, residing in the same group. NGC1052-DF4closely resembles NGC1052-DF2 in terms of its size, surface brightness, and morphology; has a similar distance of Dsbf = 19.9 +/- 2.8 Mpc; and also has a population of luminous globular clusters extending out to >7 kpc from the center of the galaxy. Accurate radial velocities of the diffuse galaxy light and seven of the globular clusters were obtained with the Low Resolution Imaging …

Long-Period Giant Companions To Three Compact, Multiplanet Systems, Sean M. Mills, Andrew W. Howard, Lauren M. Weiss, Jason H. Steffen, Howard Isaacson, Benjamin Fulton, Erik A. Petigura, Molly R. Kosiarek, Lea A. Hirsch, John H. Boisvert

Physics & Astronomy Faculty Research

Understanding the relationship between long-period giant planets and multiple smaller short-period planets is critical for formulating a complete picture of planet formation. This work characterizes three such systems. We present Kepler-65, a system with an eccentric (e = 0.28 ± 0.07) giant planet companion discovered via radial velocities (RVs) exterior to a compact, multiply transiting system of sub-Neptune planets. We also use precision RVs to improve mass and radius constraints on two other systems with similar architectures, Kepler-25 and Kepler-68. In Kepler-68 we propose a second exterior giant planet candidate. Finally, we consider the implications of these systems for planet …

Galactic Preservation And Beyond: A Framework For Protecting Cultural, Natural, And Scientific Heritage In Space, Matthew Rosendahl

William & Mary Environmental Law and Policy Review

In July 2017, Moon Express, a private spaceflight company, announced plans to build an outpost on the South Pole of the Moon by 2020. The goal? To mine the Moon for minerals and water that could then be sold for profit. Indeed, the Moon has been found to possess resources with lucrative uses, both in space and here on Earth. The potential for huge rewards has incentivized several private and governmental actors to launch planned expeditions to the Moon, with China becoming the third nation to land a spacecraft there in 2013. Both China and India have since announced plans …

Charged Compact Binary Coalescence Signal And Electromagnetic Counterpart Of Plunging Black Hole–Neutron Star Mergers, Bing Zhang

Physics & Astronomy Faculty Research

If at least one of the members of a compact binary coalescence is charged, the inspiral of the two members would generate a Poynting flux with an increasing power, giving rise to a brief electromagnetic counterpart temporally associated with the chirp signal of the merger (with possibly a small temporal offset), which we term as the charged compact binary coalescence (cCBC) signal. We develop a general theory of cCBC for any mass and amount of charge for each member. Neutron stars (NSs), as spinning magnets, are guaranteed to be charged, so the cCBC signal should accompany all NS mergers. The …

Coordinated Uv And X-Ray Spectroscopic Observations Of The O-Type Giant Ξ Per: The Connection Between X-Rays And Large-Scale Wind Structure, Derek Massa, Lidi Oskinova, Raman Prinja, Richard Ignace

ETSU Faculty Works

We present new, contemporaneous Hubble Space Telescope STIS and XMM-Newton observations of the O7 III(n)((f)) star ξ Per. We supplement the new data with archival IUE spectra, to analyze the variability of the wind lines and X-ray flux of ξ Per. The variable wind of this star is known to have a 2.086-day periodicity. We use a simple, heuristic spot model that fits the low-velocity (near-surface) IUE wind line variability very well, to demonstrate that the low-velocity absorption in the new STIS spectra of N iv λ1718 and Si iv λ1402 vary with the same 2.086-day period. It …

Book Review: Exoplanets : Hidden Worlds And The Quest For Extraterrestrial Life, T. D. Oswalt

Publications

This document is Dr. Oswalt’s review of Exoplanets : Hidden Worlds and the Quest for Extraterrestrial Life. Harvard, 2018. 254p bibl index, 9780674976900 $24.95, 9780674988897

Long-Term Spot Monitoring Of The Young Solar Analogue V889 Herculis, Teemu Willamo, Thomas Hackman, Jyri J. Lehtinen, Maarit J. Käpylä, Ilya Ilyin, Gregory W. Henry, Lauri Jetsu, Oleg Kochukhov, Nikolai Piskunov

Information Systems and Engineering Management Research Publications

Context. Starspots are important manifestations of stellar magnetic activity. By studying their behaviour in young solar analogues, we can unravel the properties of their magnetic cycles. This gives crucial information of the underlying dynamo process. Comparisons with the solar cycle enable us to infer knowledge about how the solar dynamo has evolved during the Sun’s lifetime.

Aims. Here we study the correlation between photometric brightness variations, spottedness, and mean temperature in V889 Her, a young solar analogue. Our data covers 18 years of spectroscopic and 25 years of photometric observations.

Methods. We use Doppler imaging to derive …

Infrared Spectroscopy Of Symbiotic Stars. Xii. The Neutron Star Syxb System 4u 1700+24 = V934 Herculis, Kenneth H. Hinkle, Francis C. Fekel, Richard Joyce, Joanna Mikołajewska, Cezary Gałan, Thomas Lebzelter

Information Systems and Engineering Management Research Publications

The X-ray symbiotic (SyXB) V934 Her = 4U 1700+24 is an M giant–neutron star (NS) binary system. Employing optical and infrared radial velocities spanning 29 yr combined with the extensive velocities in the literature, we compute the spectroscopic orbit of the M giant in that system. We determine an orbital period of 4391 days, or 12.0 yr, the longest for any SyXB and far longer than the 404 day orbit commonly cited for this system in the literature. In addition to the 12.0 yr orbital period, we find a shorter period of 420 days, similar to the one previously found. …

Astronomy For Educators, Daniel E. Barth

Open Educational Resources

Astronomy for Educators provides new and accomplished K-12 instructors with concepts and projects for low-cost, high-impact STEM classroom instruction that is built around the National Academies National Research Council's K-12 Framework for Science Education.

Gemini, Michael Dalton

Natural Sciences Student Research Presentations

This poster for the Natural Sciences Poster Session at Parkland College features the constellation Gemini, including a calculation of the change in rise time to determine the length of a year, determining the life span of the major stars in the constellation, identifying Messier objects within the region as well as the mythology behind the name of the constellation.