Astrophysics and Astronomy Commons^™

Transfer Entropy And Cumulant Based Cost As Measures Of Nonlinear Causal Relationships In Space Plasmas: Applications To D St., Jay R. Johnson, Simon Wing, Enrico Camporeale

Faculty Publications

It is well known that the magnetospheric response to the solar wind is nonlinear. Information theoretical tools such as mutual information, transfer entropy, and cumulant based analysis are able to characterize the nonlinearities in the system. Using cumulant based cost, we show that nonlinear significance of D st peaks at 3–12 hours lags that can be attributed to VBs which also exhibit similar behavior. However, the nonlinear significance that peaks at lags 25, 50, and 90 hours can be attributed to internal dynamics, which may be related to the relaxation of the ring current. These peaks are absent in the …

Gw170817: Observation Of Gravitational Waves From A Binary Neutron Star Inspiral, B. P. Abbott, K. Aultoneal, S. Gaudio, K. Gill, E. M. Gretarsson, B. Hughey, M. Muratore, J. W. W. Pratt, S. G. Schwalbe, K. Staats, M. J. Szczepańczyk, M. Zanolin, Et Al.

Publications

On August 17, 2017 at 12∶41:04 UTC the Advanced LIGO and Advanced Virgo gravitational-wave detectors made their first observation of a binary neutron star inspiral. The signal, GW170817, was detected with a combined signal-to-noise ratio of 32.4 and a false-alarm-rate estimate of less than one per 8.0 × 104 years. We infer the component masses of the binary to be between 0.86 and 2.26 M⊙, in agreement with masses of known neutron stars. Restricting the component spins to the range inferred in binary neutron stars, we find the component masses to be in the range 1.17–1.60 M⊙, with the total …

Absolute Ages And Distances Of 22 Gcs Using Monte Carlo Main-Sequence Fitting, Erin M. O'Malley, Christina Gilligan, Brian Chaboyer

Dartmouth Scholarship

The recent Gaia Data Release 1 of stellar parallaxes provides ample opportunity to find metal-poor main-sequence stars with precise parallaxes. We select 21 such stars with parallax uncertainties better than σ _π /π ≤ 0.10 and accurate abundance determinations suitable for testing metal-poor stellar evolution models and determining the distance to Galactic globular clusters (GCs). A Monte Carlo analysis was used, taking into account uncertainties in the model construction parameters, to generate stellar models and isochrones to fit to the calibration stars. The isochrones that fit the calibration stars best were then used to determine the distances and ages …

X-Ray And Optical Study Of The Gamma-Ray Source 3fgl J0838.8–2829: Identification Of A Candidate Millisecond Pulsar Binary And An Asynchronous Polar, Jules P. Halpern, Slavko Bogdanov, John R. Thorstensen

Dartmouth Scholarship

We observed the field of the Fermi source 3FGL J0838.8−2829 in optical and X-rays, initially motivated by the cataclysmic variable (CV) 1RXS J083842.1−282723 that lies within its error circle. Several X-ray sources first classified as CVs have turned out to be γ-ray emitting millisecond pulsars (MSPs). We find that 1RXS J083842.1−282723 is in fact an unusual CV, a stream-fed asynchronous polar in which accretion switches between magnetic poles (that are ≈120° apart) when the accretion rate is at minimum. High-amplitude X-ray modulation at periods of 94.8 ± 0.4 minutes and 14.7 ± 1.2 hr are seen. The former appears …

A Differential Abundance Analysis Of Very Metal-Poor Stars, Erin M. O'Malley, Andrew Mcwilliam, Brian Chaboyer, Ian Thompson

Dartmouth Scholarship

We have performed a differential line-by-line chemical abundance analysis, ultimately relative to the Sun, of nine very metal-poor main-sequence (MS) halo stars, near [Fe/H] = −2 dex. Our abundances range from dex with conservative uncertainties of 0.07 dex. We find an average [α/Fe] = 0.34 ± 0.09 dex, typical of the Milky Way. While our spectroscopic atmosphere parameters provide good agreement with Hubble Space Telescope parallaxes, there is significant disagreement with temperature and gravity parameters indicated by observed colors and theoretical isochrones. Although a systematic underestimate of the stellar temperature by a few hundred degrees could explain this …

The X-Ray And Mid-Infrared Luminosities In Luminous Type 1 Quasars, Chien-Ting J. Chen, Ryan C. Hickox, Andrew D. Goulding, Daniel Stern

Dartmouth Scholarship

Several recent studies have reported different intrinsic correlations between the AGN mid-IR luminosity (L_MIR) and the rest-frame 2-10 keV luminosity (L_X) for luminous quasars. To understand the origin of the difference in the observed L_X−L_MIR relations, we study a sample of 3,247 spectroscopically confirmed type 1 AGNs collected from Bo\"{o}tes, XMM-COSMOS, XMM-XXL-North, and the SDSS quasars in the Swift/XRT footprint spanning over four orders of magnitude in luminosity. We carefully examine how different observational constraints impact the observed L_X−L_MIR relations, including the inclusion of X-ray non-detected objects, possible X-ray absorption …

Testing Metal-Poor Stellar Models And Isochrones With Hst Parallaxes Of Metal-Poor Stars, B. Chaboyer, E. O'Malley, G. F. Benedict, G. A. Feiden

Dartmouth Scholarship

Hubble Space Telescope (HST) fine guidance sensor observations were used to obtain parallaxes of eight metal-poor ([Fe/H] < −1.4) stars. The parallaxes of these stars determined by the new Hipparcos reduction average 17% accuracy, in contrast to our new HST parallaxes, which average 1% accuracy and have errors on the individual parallaxes ranging from 85 to 144 μas. These parallax data were combined with HST Advanced Camera for Surveys photometry in the F606W and F814W filters to obtain the absolute magnitudes of the stars with an accuracy of 0.02–0.03 mag. Six of these stars are on the main sequence (MS) (with −2.7 < [Fe/H] < −1.8) and are suitable for testing metal-poor stellar evolution models and determining the distances to metal-poor globular clusters (GCs). Using the abundances obtained by O'Malley et al., we find that standard stellar models using the VandenBerg & Clem color transformation do a reasonable job of matching five of the MS stars, with HD 54639 ([Fe/H] = −2.5) being anomalous in its location in the color–magnitude diagram. Stellar models and isochrones were generated using a Monte Carlo analysis to take into account uncertainties in the models. Isochrones that fit the parallax stars were used to determine the distances and ages of nine GCs (with −2.4 ≤ [Fe/H] ≤ −1.9). Averaging together the age of all nine clusters led to an absolute age of the oldest, most metal-poor GCs of 12.7 ± 1.0 Gyr, where the quoted uncertainty takes into account the known uncertainties in the stellar models and isochrones, along with the uncertainty in the distance and reddening of the clusters.

Data Mining By Grid Computing In The Search For Extrasolar Planets, Oisin Creaner [Thesis]

Doctoral

A system is presented here to provide improved precision in ensemble differential photometry. This is achieved by using the power of grid computing to analyse astronomical catalogues. This produces new catalogues of optimised pointings for each star, which maximise the number and quality of reference stars available. Astronomical phenomena such as exoplanet transits and small-scale structure within quasars may be observed by means of millimagnitude photometric variability on the timescale of minutes to hours. Because of atmospheric distortion, ground-based observations of these phenomena require the use of differential photometry whereby the target is compared with one or more reference stars. …

Search For High-Energy Gamma Rays In The Northern Fermi Bubble Region With The Hawc Observatory, Hugo Alberto Ayala Solares

Dissertations, Master's Theses and Master's Reports

Gamma-ray astronomy is the study of very energetic photons, from E = m_ec² = 0.5x10⁶ eV to > 10²⁰eV. Due to the large span of the energy range, the field focuses on non-thermal processes that include the acceleration and propagation of relativistic particles, which can be found in extreme environments such as pulsars, supernova remnants, molecular clouds, black holes, etc.

The High Altitude Water Cherenkov (HAWC) observatory is an instrument designed for the study of gamma rays in the energy range of 100 GeV to 100 TeV. Using data from the HAWC observatory, a study …

Hubble Parameter Measurement Constraints On The Redshift Of The Deceleration-Acceleration Transition, Dynamical Dark Energy, And Space Curvature, Omer Farooq, Foram Ranjeet Madiyar, Sara Crandall, Bharat Ratra

Publications

We compile an updated list of 38 measurements of the Hubble parameter H(z) between redshifts 0.07 ≤ z ≤ 2.36 and use them to place constraints on model parameters of constant and time-varying dark energy cosmological models, both spatially flat and curved. We use five models to measure the redshift of the cosmological deceleration-acceleration transition, zda, from these H(z) data. Within the error bars, the measured zda are insensitive to the model used, depending only on the value assumed for the Hubble constant H0. The weighted mean of our measurements is zda = 0.72±0.05 (0.84±0.03) for H0 = 68 ± …

A Trip To The Cataclysmic Binary Zoo: Detailed Follow-Up Of 35 Recently Discovered Systems, John R. Thorstensen, Erek H. Alper, Kathryn E. Weil

Dartmouth Scholarship

We report follow-up studies of 35 recently discovered cataclysmic variables (CVs), 32 of which were found in large, automated synoptic sky surveys. The objects were selected for observational tractability. For 34 of the objects, we present mean spectra and spectroscopic orbital periods, and for one more we give an eclipse-based period. Thirty-two of the period determinations are new, and three of these refine published estimates based on superhump periods. The remaining three of our determinations confirm previously published periods. Twenty of the stars are confirmed or suspected dwarf novae with periods shorter than 3 hr, but we also find three …

X-Ray Detected Active Galactic Nuclei In Dwarf Galaxies At 0 < Z < 1, K. Pardo, A. D. Goulding, J. E. Greene, R. S. Somerville, E. Gallo, R. C. Hickox

Dartmouth Scholarship

We present a sample of accreting supermassive black holes (SMBHs) in dwarf galaxies at z\lt 1. We identify dwarf galaxies in the NEWFIRM Medium Band Survey with stellar masses of {M}_\star \lt 3× {10}⁹ {M}_⊙ that have spectroscopic redshifts from the DEEP2 survey and lie within the region covered by deep (flux limit of ˜ 5× {10}^-17{--}6× {10}^-16 {erg} {{cm}}^-2 {{{s}}}^-1) archival Chandra X-ray data. From our sample of 605 dwarf galaxies, 10 exhibit X-ray emission consistent with that arising from active galactic nucleus (AGN) activity. If black-hole mass scales roughly …

Exoplanet Research: Differential Photometry For Kepler 6b, Garrett T. Benson, Charlotte Alexandra Olsen

IdeaFest: Interdisciplinary Journal of Creative Works and Research from Cal Poly Humboldt

No abstract provided.

Hubble Space Telescopeconstraints On The Winds And Astrospheres Of Red Giant Stars, Brian E. Wood, Hans-Reinhard Müller, Graham M. Harper

Dartmouth Scholarship

We report on an ultraviolet spectroscopic survey of red giants observed by the Hubble Space Telescope, focusing on spectra of the Mg ii h and k lines near 2800 Å in order to study stellar chromospheric emission, winds, and astrospheric absorption. We focus on spectral types between K2 III and M5 III, a spectral type range with stars that are noncoronal, but possessing strong, chromospheric winds. We find a very tight relation between Mg ii surface flux and photospheric temperature, supporting the notion that all K2-M5 III stars are emitting at a basal flux level. Wind velocities (V …

Gravitational Wave–Gauge Field Oscillations, R. R. Caldwell, C. Devulder, N. A. Maksimova

Dartmouth Scholarship

Gravitational waves propagating through a stationary gauge field transform into gauge field waves and back again. When multiple families of flavor-space locked gauge fields are present, the gravitational and gauge field waves exhibit novel dynamics. At high frequencies, the system behaves like coupled oscillators in which the gravitational wave is the central pacemaker. Due to energy conservation and exchange among the oscillators, the wave amplitudes lie on a multidimensional sphere, reminiscent of neutrino flavor oscillations. This phenomenon has implications for cosmological scenarios based on flavor-space locked gauge fields.

A Multi-Wavelength Analysis Of Cold Evolving Interstellar Clouds, Mary Spraggs

Mahurin Honors College Capstone Experience/Thesis Projects

The interstellar medium (ISM) is the dynamic system of gas and dust that fills the space between the stars within galaxies. Due to its integral role in star formation and ga-lactic structure, it is important to understand how the ISM itself evolves over time, in-cluding the process of cooling and condensing required to form new stars. This work aims to constrain and better understand the physical properties of the cold ISM with sev-eral different types of data, including large surveys of neutral atomic hydrogen (HI) 21cm spectral line emission and absorption, carbon monoxide (CO) 2.6mm line emission, and multi-band infrared …

Obscured Agns In Bulgeless Hosts Discovered By Wise : The Case Study Of Sdss J1224+5555, S. Satyapal, N. J. Secrest, B. Rothberg, J. A. O’Connor, S. L. Ellison, R. C. Hickox

Dartmouth Scholarship

There is mounting evidence that supermassive black holes form and grow in bulgeless galaxies. However, a robust determination of the fraction of AGNs in bulgeless galaxies, an important constraint to models of supermassive black hole seed formation and merger-free models of AGN fueling, is unknown, since optical studies have been shown to be incomplete for low mass AGNs. In a recent study using the Wide-field Infrared Survey Explorer, we discovered hundreds of bulgeless galaxies that display mid-infrared signatures of extremely hot dust suggestive of powerful accreting massive black holes, despite having no signatures of black hole activity at optical wavelengths. …

Flickering Analysis Of Ch Cygni Using Kepler Data, Thomas Holden Dingus

Undergraduate Honors Theses

Utilizing data from the Kepler Mission, we analyze a flickering phenomenon in the symbiotic variable star CH Cygni. We perform a spline interpolation of an averaged lightcurve and subtract the spline to acquire residual data. This allows us to analyze the deviations that are not caused by the Red Giant’s semi-regular periodic variations. We then histogram the residuals and perform moment calculations for variance, skewness, and kurtosis for the purpose of determining the nature of the flickering. Our analysis has shown that we see a much smaller scale flickering than observed in the previous literature. Our flickering scale is on …

Constraining The Age And Distance Of The Galactic Supernova Remnant G156.2+5.7 By H A Expansion Measurements, Satoru Katsuda, Masaomi Tanaka, Tomoki Morokuma, Robert Fesen, Dan Milisavljevic

Dartmouth Scholarship

We present deep Hα images of portions of the X-ray bright, but optically faint, Galactic supernova remnant G156.2+5.7, revealing numerous and delicately thin non-radiative filaments, which mark the location of the remnant's forward shock. These new images show that these filaments have a complex structure not visible on previous lower resolution optical images. By comparing Hα images taken in 2004 at the McDonald Observatory and in 2015–2016 at the Kiso Observatory, we set a stringent 1σ upper limit of expansion to be 0.06 arcsec/yr. This proper motion, combined with a shock speed of 500 km s^{−1 …}

The Intrinsic Eddington Ratio Distribution Of Active Galactic Nuclei In Star-Forming Galaxies From The Sloan Digital Sky Survey, Mackenzie L. Jones, Ryan C. Hickox, Christine S. Black, Kevin N. Hainline, Michael A. Dipompeo, Andy D. Goulding

Dartmouth Scholarship

An important question in extragalactic astronomy concerns the distribution of black hole accretion rates of active galactic nuclei (AGNs). Based on observations at X-ray wavelengths, the observed Eddington ratio distribution appears as a power law, while optical studies have often yielded a lognormal distribution. There is increasing evidence that these observed discrepancies may be due to contamination by star formation and other selection effects. Using a sample of galaxies from the Sloan Digital Sky Survey Data Release 7, we test whether or not an intrinsic Eddington ratio distribution that takes the form of a Schechter function is consistent with previous …

Population Properties Of Brown Dwarf Analogs To Exoplanets, Jacqueline K. Faherty, Adric R. Riedel, Kelle L. Cruz, Jonathan Gagne, Joseph C. Filippazzo, Erini Lambrides, Haley Fica, Alycia Weinberger, John R. Thorstensen

Dartmouth Scholarship

We present a kinematic analysis of 152 low surface gravity M7-L8 dwarfs by adding 18 new parallaxes (including 10 for comparative field objects), 38 new radial velocities, and 19 new proper motions. We also add low- or moderate-resolution near-infrared spectra for 43 sources confirming their low surface gravity features. Among the full sample, we find 39 objects to be high-likelihood or new bona fide members of nearby moving groups, 92 objects to be ambiguous members and 21 objects that are non-members. Using this age-calibrated sample, we investigate trends in gravity classification, photometric color, absolute magnitude, color–magnitude, luminosity, and effective temperature. …

A Tale Of Two Narrow-Line Regions: Ionization, Kinematics, And Spectral Energy Distributions For A Local Pair Of Merging Obscured Active Galaxies, Kevin N. Hainline, Ryan C. Hickox, Chien-Ting Chen, Christopher M. Carroll, Mackenzie L. Jones, Alexandros S. Zervos, Andrew D. Goulding

Dartmouth Scholarship

We explore the gas ionization and kinematics, as well as the optical-IR spectral energy distributions for UGC 11185, a nearby pair of merging galaxies hosting obscured active galactic nuclei (AGNs), also known as SDSS J181611.72+423941.6 and J181609.37+423923.0 (J1816NE and J1816SW, z ≈ 0.04). Due to the wide separation between these interacting galaxies (~23 kpc), observations of these objects provide a rare glimpse of the concurrent growth of supermassive black holes at an early merger stage. We use BPT line diagnostics to show that the full extent of the narrow-line emission in both galaxies is photoionized by an AGN, and confirm …

Gravitational-Wave Cosmology Across 29 Decades In Frequency, Paul D. Lasky, Chiara `. Mingarelli, Tristan L. Smith, John T. Giblin, Eric Thrane, Daniel J. Reardon, Robert Caldwell

Dartmouth Scholarship

Quantum fluctuations of the gravitational field in the early Universe, amplified by inflation, produce a primordial gravitational-wave background across a broad frequency band. We derive constraints on the spectrum of this gravitational radiation, and hence on theories of the early Universe, by combining experiments that cover 29 orders of magnitude in frequency. These include Planck observations of cosmic microwave background temperature and polarization power spectra and lensing, together with baryon acoustic oscillations and big bang nucleosynthesis measurements, as well as new pulsar timing array and ground-based interferometer limits. While individual experiments constrain the gravitational-wave energy density in specific frequency bands, …

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 …

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 …

Investigating The Consistency Of Stellar Evolution Models With Globular Cluster Observations Via The Red Giant Branch Bump, M. Joyce, B. Chaboyer

Dartmouth Scholarship

Synthetic Red Giant Branch Bump (RGBB) magnitudes are generated with the most recent theoretical stellar evolution models computed with the Dartmouth Stellar Evolution Program (DSEP) code. They are compared to the observational work of Nataf et al., who present RGBB magnitudes for 72 globular clusters. A DSEP model using a chemical composition with enhanced α capture [α/Fe] = +0.4 and an age of 13 Gyr shows agreement with observations over metallicities ranging from [Fe/H] = 0 to [Fe/H] ≈ −1.5, with discrepancy emerging at lower metallicities.

A Determination Of The Gamma-Ray Flux And Photon Spectral Index Distributions Of Blazars From The Fermi-Lat 3lac, Jack Singal

Physics Faculty Publications

We present a determination of the distributions of gamma-ray photon flux – the so-called LogN–LogS relation – and photon spectral index for blazars, based on the third extragalactic source catalogue of the Fermi Gamma-ray Space Telescope's Large Area Telescope, and considering the photon energy range from 100 MeV to 100 GeV. The data set consists of the 774 blazars in the so-called Clean sample detected with a greater than approximately 7σ detection threshold and located above ±20° Galactic latitude. We use non-parametric methods verified in previous works to reconstruct the intrinsic distributions from the observed ones …

Optical Studies Of 13 Hard X-Ray Selected Cataclysmic Binaries From The Swift-Bat Survey, Jules P. Halpern, John R. Thorstensen

Dartmouth Scholarship

From a set of 13 cataclysmic binaries that were discovered in the Swift Burst Alert Telescope (BAT) survey, we conducted time-resolved optical spectroscopy and/or time-series photometry of 11, with the goal of measuring their orbital periods and searching for spin periods. Seven of the objects in this study are new optical identifications. Orbital periods are found for seven targets, ranging from 81 minutes to 20.4 hr. PBC J0706.7+0327 is an AM Herculis star (polar) based on its emission-line variations and large amplitude photometric modulation on the same period. Swift J2341.0+7645 may be a polar, although the evidence here is less …

Discovery Of An Apparent High Latitude Galactic Supernova Remnant, Robert A. Fesen, Jack M. M. Neustadt, Christine S. Black, Ari H. D. Koeppel

Dartmouth Scholarship

Deep Hα images of a faint emission complex 4.0 x 5.5 degrees in angular extent and located far off the Galactic plane at l = 70.0 degrees, b=-21.5 degrees reveal numerous thin filaments suggestive of a supernova remnant's shock emission. Low dispersion optical spectra covering the wavelength range 4500 - 7500 A show only Balmer line emissions for one filament while three others show a Balmer dominated spectrum along with weak [N I] 5198, 5200 A, [O I] 6300, 6364 A, [N II] 6583 A, [S II] 6716, 6731 A and in one case [O III] 5007 A line emission. …

Astr 224: Astronomy And Astrophysics Laboratory, Zachary Smith

Department of Physics and Astronomy: Syllabi

Syllabus for ASTR 224 Astronomy and Astrophysics Laboratory for Fall 2015.