Stars, Interstellar Medium and the Galaxy Commons^™

The White Dwarf Luminosity Function, Enrique Garcia-Berro, Terry D. Oswalt

Publications

White dwarfs are the final remnants of low- and intermediate-mass stars. Their evolution is essentially a cooling process that lasts for ∼ 10 Gyr. Their observed properties provide information about the history of the Galaxy, its dark matter content and a host of other interesting astrophysical problems. Examples of these include an independent determination of the past history of the local star formation rate, identification of the objects responsible for the reported microlensing events, constraints on the rate of change of the gravitational constant, and upper limits to the mass of weakly interacting massive particles. To carry on these tasks …

Possible Evolution Of Supermassive Black Holes From Fri Quasars, Matthew I. Kim, Damian J. Christian, David Garofalo, Jaclyn D'Avanzo

Faculty Articles

We explore the question of the rapid buildup of black hole mass in the early universe employing a growing black hole mass-based determination of both jet and disc powers predicted in recent theoretical work on black hole accretion and jet formation. Despite simplified, even artificial assumptions about accretion and mergers, we identify an interesting low probability channel for the growth of one billion solar mass black holes within hundreds of millions of years of the big bang without appealing to super Eddington accretion. This result is made more compelling by the recognition of a connection between this channel and an …

Studying Solar Limb Darkening In H-Alpha With A Coronado Pst, Jessica N. Farrell, Jennifer Birriel

Celebration of Student Scholarship Poster Sessions Archive

No abstract provided.

Topics In The Detection Of Gravitational Waves From Compact Binary Inspirals, Shasvath Jagat Kapadia

Graduate Theses and Dissertations

Orbiting compact binaries - such as binary black holes, binary neutron stars and neutron star-black hole binaries - are among the most promising sources of gravitational waves observable by ground-based interferometric detectors. Despite numerous sophisticated engineering techniques, the gravitational wave signals will be buried deep within noise generated by various instrumental and environmental processes, and need to be extracted via a signal processing technique referred to as matched filtering.

Matched filtering requires large banks of signal templates that are faithful representations of the true gravitational waveforms produced by astrophysical binaries. The accurate and efficient production of templates is thus crucial …

Teaching Numerical Methods In The Context Of Galaxy Mergers, Maria Kourjanskaia

Physics

Methods of teaching numerical methods to solve ordinary differential equations in the context of galaxy mergers were explored. The research published in a paper by Toomre and Toomre in 1972 describing the formation of galactic tails and bridges from close tidal interactions was adapted into a project targeting undergraduate physics students. Typically undergraduate physics students only take one Computational Physics class in which various techniques and algorithms are taught. Although it is important to study computational physics techniques, it is just as important to apply this knowledge to a problem that is representative of what computational physics researchers are investigating …

Tev Gamma-Ray Observations Of The Galactic Center Ridge By Veritas, P. T. Reynolds, Et Al

Physical Sciences Publications

The Galactic Center ridge has been observed extensively in the past by both GeV and TeV gamma-ray instruments revealing a wealth of structure, including a diffuse component and the point sources G0.9+0.1 (a composite supernova remnant) and Sgr A* (believed to be associated with the supermassive black hole located at the center of our Galaxy). Previous very high energy (VHE) gamma-ray observations with the H.E.S.S. experiment have also detected an extended TeV gamma-ray component along the Galactic plane in the >300 GeV gamma-ray regime. Here we report on observations of the Galactic Center ridge from 2010 to 2014 by the …

X-Ray Observations Of Bow Shocks Around Runaway O Stars. The Case Of Ζ Oph And Bd+43°3654, Jesus Toala, Lidia M. Oskinova, A. González-Galán, M. A. Guerrero, Richard Ignace, M. Pohl

ETSU Faculty Works

Non-thermal radiation has been predicted within bow shocks around runaway stars by recent theoretical works. We present X-ray observations toward the runaway stars ζ Oph by Chandra and Suzaku and of BD+43°3654 by XMM-Newton to search for the presence of non-thermal X-ray emission. We found no evidence of non-thermal emission spatially coincident with the bow shocks; nonetheless, diffuse emission was detected in the vicinity of ζ Oph. After a careful analysis of its spectral characteristics, we conclude that this emission has a thermal nature with a plasma temperature of T ≈ 2 × 106 K. The cometary shape of this …

Peering Through The Dust: Nustar Observations Of Two First-2mass Red Quasars, Stephanie M. Lamassa, Angelo Ricarte, Eilat Glikman, C. Megan Urry, Daniel Stern, Tahir Yaqoob, George B. Lansbury, Francesca Civano

Dartmouth Scholarship

Some reddened quasars appear to be transitional objects in the merger-induced black hole growth/galaxy evolution paradigm, where a heavily obscured nucleus starts to be unveiled by powerful quasar winds evacuating the surrounding cocoon of dust and gas. Hard X-ray observations are able to peer through this gas and dust, revealing the properties of circumnuclear obscuration. Here, we present NuSTAR and XMM-Newton/Chandra observations of FIRST-2MASS selected red quasars F2M 0830+3759 and F2M 1227+3214. We find that though F2M 0830+3759 is moderately obscured (N_H,Z=2.1±0.2×10²² cm⁻²) and F2M 1227+3214 is mildly absorbed (N_H,Z=3.4+0.8−0.7×10²¹ cm^{−2 …}

Activity Trends In Young Solar-Type Stars, Jyri J. Lehtinen, Lauri Jetsu, Thomas Hackman, Perttu Kajatkari, Gregory W. Henry

Information Systems and Engineering Management Research Publications

Aims. We study a sample of 21 young and active solar-type stars with spectral types ranging from late F to mid K and characterize the behaviour of their activity.

Methods. We apply the continuous period search (CPS) time series analysis method on Johnson B- and V-band photometry of the sample stars, collected over a period of 16 to 27 years. Using the CPS method, we estimate the surface differential rotation and determine the existence and behaviour of active longitudes and activity cycles on the stars. We supplement the time series results by calculating new log R'_HK = …

Probing The Fitting Accuracy Of Active Galaxy Spectra, Aaron T. Line

Physics

Prior to this study, Dr. Vardha N. Bennert and collaborators selected a sample of ~100 local active galaxies to study the relationships between black hole mass and host galaxy properties. The broad Hβ width is necessary to determine black hole mass. This value is determined using a spectral decomposition code was scripted in IDL by Dr. Daeseong Park. The script fit spectral features and collected data for properties such as width of emission lines and continuum contribution percentages. The results were logged for further analysis.

To probe the accuracy of the fitting process, artificial spectra were created and fitted to …

Scale Invariant Jet Suppression Across The Black Hole Mass Scale, David Garofalo, Chandra B. Singh

Faculty Articles

We provide a schematic framework for understanding observations of jet suppression in soft state black hole X-ray binaries based on the Blandford-Payne process and the net magnetic flux threading the black hole. Due to the geometrical thinness of soft state disks, mass-loading of field lines is ineffective compared to both geometrically thick disks as well as thin disks with greater black hole threading flux, a simple physical picture that allows us to understand the weakness of jets in radiatively efficient thin disks accreting in the prograde direction around high-spinning black holes. Despite a simplicity that forbids insights into the complexity …

A Search For Brief Optical Flashes Associated With The Seti Target Kic 8462852, P. T. Reynolds, Et Al

Physical Sciences Publications

The F-type star KIC 8462852 has recently been identified as an exceptional target for search for extraterrestrial intelligence (SETI) observations. We describe an analysis methodology for optical SETI, which we have used to analyze nine hours of serendipitous archival observations of KIC 8462852 made with the VERITAS gamma-ray observatory between 2009 and 2015. No evidence of pulsed optical beacons, above a pulse intensity at the Earth of approximately , is found. We also discuss the potential use of imaging atmospheric Cherenkov telescope arrays in searching for extremely short duration optical transients in general.

An Hst Survey Of The Highest-Velocity Ejecta In Cassiopeia A, Robert A. Fesen, Dan Milisavljevic

Dartmouth Scholarship

We present Hubble Space Telescope WFC3/IR images of the Cassiopeia A supernova remnant that survey its high-velocity, S-rich debris in the NE jet and SW counterjet regions through [S iii] λλ9069, 9531 and [S ii] λλ10,287–10,370 line emissions. We identify nearly 3400 sulfur emitting knots concentrated in ~120° wide opposing streams, almost triple the number previously known. The vast majority of these ejecta knots lie at projected distances well out ahead of the remnant's forward blast wave and main shell ejecta, extending to angular distance of to the NE and to the SW from the center of expansion. …

Reconciling Ag-Star Formation, The Soltan Argument, And Meier's Paradox, David Garofalo, Matthew I. Kim, Damian J. Christian, Emily Hollingworth

Faculty Articles

We provide a theoretical context for understanding the recent work of Kalfountzou et al. showing that star formation is enhanced at lower optical luminosity in radio-loud quasars. Our proposal for coupling the assumption of collimated FRII quasar-jet-induced star formation with lower accretion optical luminosity also explains the observed jet power peak in active galaxies at higher redshift compared to the peak in accretion power, doing so in a way that predicts the existence of a family of radio-quiet active galactic nuclei associated with rapidly spinning supermassive black holes at low redshift, as mounting observations suggest. The relevance of this work …

Comparative Analysis Of Sn 2012dn Optical Spectra:Days −14 To +114, J. T. Parrent, D. A. Howell, R. A. Fesen, S. Parker

Dartmouth Scholarship

SN 2012dn is a super-Chandrasekhar mass candidate in a purportedly normal spiral (SAcd) galaxy, and poses a challenge for theories of type Ia supernova diversity. Here we utilize the fast and highly parametrized spectrum synthesis tool, SYNAPPS, to estimate relative expansion velocities of species inferred from optical spectra obtained with six facilities. As with previous studies of normal SN Ia, we find that both unburned carbon and intermediate-mass elements are spatially coincident within the ejecta near and below 14 000 km s⁻¹. Although the upper limit on SN 2012dn's peak luminosity is comparable to some of the most …

The Spectroscopic Orbits Of Five Γ Doradus Stars, Francis C. Fekel, Gregory W. Henry, Dimitri Pourbaix

Information Systems and Engineering Management Research Publications

We have determined the spectroscopic orbits of five γ Dor variables, HD 776, HD 6568, HD 17310, HD 19684, and HD 62196. Their orbital periods range from 27.8 to 1163 days and their eccentricities from 0.01 to 0.65. Of the five systems, only HD 19684 shows lines of its binary companion, but those lines are always so weak and blended with the lines of the primary that we were unable to measure them satisfactorily. The velocity residuals of the orbital fits were searched for periodicities associated with pulsation. No clear, convincing case for velocity periodicities in the residuals was found …

Exceptionally Bright Tev Flares From The Binary Ls I+61 Degrees 303, P. T. Reynolds, Et Al

Physical Sciences Publications

The TeV binary system LS I +61° 303 is known for its regular, non-thermal emission pattern that traces the orbital period of the compact object in its 26.5 day orbit around its B0 Ve star companion. The system typically presents elevated TeV emission around apastron passage with flux levels between 5% and 15% of the steady flux from the Crab Nebula (>300 GeV). In this article, VERITAS observations of LS I +61° 303 taken in late 2014 are presented, during which bright TeV flares around apastron at flux levels peaking above 30% of the Crab Nebula flux were detected. …

Modeling Extrasolar Trojan Asteroids In Gravitational Potentials Of Migrating Jovian-Like Planets To Inform Future Observations, Austin Hinkel

Lewis Honors College Capstone Collection

In this paper, I construct a program to map the evolution of the potential in a planet-star system where a planet with a few Jupiter masses migrates inward. Given a trojan asteroid librating around the fourth or fifth Lagrange point, the asteroid follows the evolving equipotential lines of the slowly changing potential map. As the planet and its trojan asteroids migrate inward towards the host star, the trojan asteroid librations become tighter, providing a denser “cloud” of trojan asteroids. Such a change in the density of trojan asteroids is examined with the intent to deduce the likelihood of detection via …

Planetary Nebula Associations With Star Clusters In The Andromeda Galaxy, Yasmine Kahvaz

Theses, Dissertations and Capstones

The objective of this research is to find planetary nebulae (PNe) and star cluster associations in the Andromeda galaxy (M31). To identify PNe in M31, a red-green-blue image is obtained using 3 emission line filters of H↵, 5007˚A [OIII], and 6717, 6731˚A [SII], using images from the Local Group Survey. By completing a visual search of the RGB images, 477 PN candidates are identified. In order to find star clusters associated with the PN candidates, an RGB image is made using the Panchromatic Hubble Andromeda Treasury survey. Filter F814W is used as red and filter F475W is used as both …

Probing Physical Conditions In The Crab Nebula With Emission Line Analysis, Xiang Wang

Theses and Dissertations--Physics and Astronomy

We present a range of steady-state photoionization simulations, corresponding to different assumed shell geometries and compositions, of the unseen postulated rapidly expanding outer shell to the Crab Nebula. The properties of the shell are constrained by the mass that must lie within it, and by limits to the intensities of hydrogen recombination lines. In all cases the photoionization models predict very strong emission from high ionization lines that will not be emitted by the Crab’s filaments, alleviating problems with detecting these lines in the presence of light scattered from brighter parts of the Crab. The NIR [Ne VI] λ 7.652 …