Physical Sciences and Mathematics Commons^™

The June 2008 Flare Of Markarian 421 From Optical To Tev Energies, P. T. Reynolds, Et Al

Physical Sciences Publications

We present optical, X-ray, high-energy (30 GeV) and very high energy (100 GeV; VHE) observations of the high-frequency peaked blazar Mrk 421 taken between 2008 May 24 and June 23. A high-energy γ-ray signal was detected by AGILE with between June 9 and 15, with F(E>100 MeV) = 42+14 –12 × 10–8 photons cm–2 s–1. This flaring state is brighter than the average flux observed by EGRET by a factor of ~3, but still consistent with the highest EGRET flux. In hard X-rays (20-60 keV) SuperAGILE resolved a five-day flare (June 9-15) peaking at ~55 mCrab. SuperAGILE, …

Gravitational Wave Burst Source Direction Estimation Using Time And Amplitude Information, J. Markowitz, M. Zanolin, L. Cadonati, E. Katsavounidis

Publications

In this article we study two problems that arise when using timing and amplitude estimates from a network of interferometers (IFOs) to evaluate the direction of an incident gravitational wave burst (GWB). First, we discuss an angular bias in the least squares timing-based approach that becomes increasingly relevant for moderate to low signal-to-noise ratios. We show how estimates of the arrival time uncertainties in each detector can be used to correct this bias. We also introduce a stand alone parameter estimation algorithm that can improve the arrival time estimation and provide root-sum-squared strain amplitude (h(rss)) values for each site. In …

Gravitational Wave Burst Source Direction Estimation Using Time And Amplitude Information, J. Markowitz, M. Zanolin, L. Cadonati, E. Katsavounidis

Michele Zanolin

Discovery Of Very High-Energy Gamma-Ray Radiation From The Bl Lac 1es 0806+524, P. T. Reynolds, Et Al

Physical Sciences Publications

The high-frequency-peaked BL Lacertae object 1ES 0806+524, at redshift z = 0.138, was observed in the very high energy (VHE) gamma-ray regime by VERITAS between 2006 November and 2008 April. These data encompass the two- and three-telescope commissioning phases, as well as observations with the full four-telescope array. 1ES 0806+524 is detected with a statistical significance of 6.3 standard deviations from 245 excess events. Little or no measurable variability on monthly timescales is found. The photon spectrum for the period 2007 November to 2008 April can be characterized by a power law with photon index 3.6 ± 1.0stat ± 0.3sys …

The Acs Survey Of Galactic Globular Clusters. Vi. Ngc 6366: A Heavily Stripped Galactic Globular Cluster, Nathaniel E. Q. Paust, Antonio Aparicio, Giampaolo Piotto, I. Neill Reid, Jay Anderson, Ata Sarajedini, Luigi R. Bedin, Brian Chaboyer

Dartmouth Scholarship

We have used observations obtained as part of the Hubble Space Telescope/ACS Survey of Galactic globular clusters (GCs) to construct a color-magnitude diagram for the bulge cluster, NGC 6366. The luminosity function derived from those data extends to M _F606W ~ 9, or masses of ~0.3 M _☉. Unlike most GCs, the mass function peaks near the main-sequence turnoff with significantly fewer low-mass stars even after correction for completeness and mass segregation. Using a multimass King model, we extrapolate the global cluster behavior and find the global mass function to be poorly matched by a power law, with …

Rotational Quenching Rate Coefficients For H2 In Collisions With H2 From 2 To 10,000 K, T.-G. Lee, N. Balakrishnan, R. C. Forrey, P. C. Stancil, G. Shaw, D. R. Schultz, Gary J. Ferland

Physics and Astronomy Faculty Publications

Rate coefficients for rotational transitions in H₂ induced by H₂ impact are presented. Extensive quantum mechanical coupled-channel calculations based on a recently published (H₂)₂ potential energy surface were performed. The potential energy surface used here has been demonstrated to be more reliable than surfaces used in previous work. Rotational transition cross sections with initial levels of J≤8 were computed for collision energies ranging between 10^-4 and 2.5 eV, and the corresponding rate coefficients were calculated for the temperature range 2≤T≤10,000 K. In general, agreement with earlier calculations, which were limited to 100-6000 K, …

Direct Distance Measurement To The Dusty White Dwarf Gd 362, Mukremin Kilic, John R. Thorstensen, D. Koester

Dartmouth Scholarship

We present trigonometric parallax observations of GD 362 obtained over seven epochs using the MDM 2.4m Hiltner Telescope. The existence of a dust disk around this possibly massive white dwarf makes it an interesting target for parallax observations. The measured parallax for GD 362 places it at a distance of 50.6 pc, which implies that its radius and mass are ~ 0.0106 Rsun and 0.71 Msun, respectively. GD 362 is not as massive as initially thought (1.2Msun). Our results are entirely consistent with the distance and mass estimates (52.2 pc and 0.73 Msun) by Zuckerman et al., who demonstrated that …

A Multizone Model For Simulating The High-Energy Variability Of Tev Blazars, Philip B. Graff, Markos Georganopoulos, Eric S. Perlman, Demosthenes Kazanas

Aerospace, Physics, and Space Science Faculty Publications

We present a time-dependent multizone code for simulating the variability of synchrotron self-Compton (SSC) sources. The code adopts a multizone pipe geometry for the emission region, appropriate for simulating emission from a standing or propagating shock in a collimated jet. Variations in the injection of relativistic electrons in the inlet propagate along the length of the pipe, cooling radiatively. Our code for the first time takes into account the nonlocal, time-retarded nature of SSC losses that are thought to be dominant in TeV blazars. The observed synchrotron and SSC emission is followed self-consistently, taking into account light-travel time delays. At …

Contamination Cannot Explain The Lack Of Large-Scale Power In The Cosmic Microwave Background Radiation, Emory F. Bunn, Austin Bourdon

Physics Faculty Publications

Several anomalies appear to be present in the large-angle cosmic microwave background (CMB) anisotropy maps of the Wilkinson Microwave Anisotropy Probe. One of these is a lack of large-scale power. Because the data otherwise match standard models extremely well, it is natural to consider perturbations of the standard model as possible explanations. We show that, as long as the source of the perturbation is statistically independent of the source of the primary CMB anisotropy, no such model can explain this large-scale power deficit. On the contrary, any such perturbation always reduces the probability of obtaining any given low value of …

Statistics Of Auroral Langmuir Waves, M. Samara, J. Labelle, I. H. Cairns

Dartmouth Scholarship

The Physics of Auroral Zone Electrons II (PHAZE II) sounding rocket was launched in February 1997 into active pre-midnight aurora. The resulting high frequency wave data are dominated by Langmuir waves. Consistent with many previous observations the Langmuir waves are sporadic, occurring in bursts lasting up to a few hundred ms. We compute statistics of the electric field amplitudes of these Langmuir waves, with two results. First, the shape of the distribution of running averages of the electric field amplitudes remains approximately stationary for a large range of widths of running average less than ~0.3 ms and for a large …

Simulation And Analysis Of Cadmium Sulfide Nanoparticles, Chad Everett Junkermeier

Theses and Dissertations

I used ab initio molecular dynamics calculations to model cadmium sulfide nanoparticles. The nanoparticles were originaly spherical, bulk-like zinc-blende structures. Constant temperature molecular dynamics calculations reveals that CdS nanoparticles that are about 2 nm in diameter and have unpassivated surfaces are in an amorphous structure with short range order. The nearest neighbor distance on the surface of the nanoparticles being near the wurtzite nearest neighbor distance. I wrote the program xyzSTATS and used its results in justifying the amorphous nanoparticles claim. I also estimated the band gap of the CdS nanoparticles with unpassivated dangling bonds.

A Three-Dimensional Pattern-Space Representation For Volumetric Arrays, William C. Barott, Paul G. Steffes

Publications

A three-dimensional pattern-space representation is presented for volumetric arrays. In this representation, the radiation pattern of an array is formed by the evaluation of the three-dimensional pattern-space on a spherical surface. The scan angle of the array determines the position of this surface within the pattern-space. This pattern-space representation is used in conjunction with a genetic algorithm to minimize the sidelobe levels exhibited by a thinned volumetric array during scanning.

Metallicity Analysis Of Macho Galactic Bulge Rr0 Lyrae Stars From Their Light Curves, Andrea Kunder, Brian Chaboyer

Dartmouth Scholarship

We present metallicities of 2690 RR0 Lyrae stars observed toward the MACHO Survey fields in the Galactic bulge. These [Fe/H] values are based upon an empirically-calibrated relationship that uses the Fourier coefficients of the light curve and are accurate to ±0.2 dex. The majority of the RR0 Lyrae stars in our sample are located in the Galactic bulge, but 255 RR0 stars are associated with the Sagittarius (Sgr) dwarf galaxy. We find that the RR0 Lyrae stars that belong to the Galactic bulge have average metallicities [Fe/H] = -1.25, with a broad metallicity range from [Fe/H] = -2.26 to -0.15. …

Magnetohydrodynamic Effects In Propagating Relativistic Jets: Reverse Shock And Magnetic Acceleration, Yosuke Mizuno, Bing Zhang, Bruno Giacomazzo, Ken-Ichi Nishikawa, Phillip E. Hardee, Shigehiro Nagataki, Dieter H. Hartmann

Publications

We solve the Riemann problem for the deceleration of an arbitrarily magne-tized relativistic flow injected into a static unmagnetized medium in one dimen-sion. We find that for the same initial Lorentz factor, the reverse shock becomes progressively weaker with increasing magnetization σ (the Poynting-to-kinetic energy flux ratio), and the shock becomes a rarefaction wave when σ exceeds a critical value, σc, defined by the balance between the magnetic pressure in the flow and the thermal pressure in the forward shock. In the rarefaction wave regime, we find that the rarefied region is accelerated to a Lorentz factor that is significantly …

Planetary Systems Around Close Binary Stars: The Case Of The Very Dusty, Sun-Like, Spectroscopic Binary Bd+20 307, Benjamin Zuckerman, Francis C. Fekel, Michael H. Williamson, Gregory W. Henry, Michael P. Muno

Information Systems and Engineering Management Research Publications

Field star BD+20 307 is the dustiest known main-sequence star, based on the fraction of its bolometric luminosity, ~4%, that is emitted at infrared wavelengths. The particles that carry this large infrared luminosity are unusually warm, comparable to the temperature of the zodiacal dust in the solar system, and their existence is likely to be a consequence of a fairly recent collision of large objects such as planets or planetary embryos. Thus, the age of BD+20 307 is potentially of interest in constraining the era of terrestrial planet formation. The present project was initiated with an attempt to derive this …

Multiwavelength Constraints On The Day–Night Circulation Patterns Of Hd 189733b, Heather Knutson, David Charbonneau, Nicolas B. Cowan, Jonathan J. Fortney, Adam P. Showman, Eric Agol, Gregory W. Henry, Mark E. Everett, Lori E. Allen

Information Systems and Engineering Management Research Publications

We present new Spitzer observations of the phase variation of the hot Jupiter HD 189733b in the MIPS 24 μm bandpass, spanning the same part of the planet's orbit as our previous observations in the IRAC 8 μm bandpass (Knutson et al. 2007). We find that the minimum hemisphere-averaged flux from the planet in this bandpass is 76% ± 3% of the maximum flux; this corresponds to minimum and maximum hemisphere-averaged brightness temperatures of 984 ± 48 K and 1220 ±  47 K, respectively. The planet reaches its maximum flux at an orbital phase of 0.396 ± 0.022, corresponding to …

An Aztec 1.1 Mm Survey Of The Goods-N Field - I. Maps, Catalogue And Source Statistics, T. A. Perera, E. L. Chapin, J. E. Austermann, K. S. Scott, G. W. Wilson, M. Halpern, A. Pope, D. Scott, M. S. Yun, James D. Lowenthal, G. Morrison, I. Aretxaga, J. J. Bock, K. Coppin, M. Crowe, L. Frey, D. H. Hughes, Y. Kang, S. Kim, P. D. Mauskopf

Astronomy: Faculty Publications

We have conducted a deep and uniform 1.1 mm survey of the Great Observatories Origins Deep Survey-North (GOODS-N) field with AzTEC on the James Clerk Maxwell Telescope. Here, we present the first results from this survey including maps, the source catalogue and 1.1 mm number counts. The results presented here were obtained from a 245 arcmin region with a near uniform coverage to a depth of 0.96-1.16 mJy beam . Our robust catalogue contains 28 source candidates detected with S/N ≥ 3.75, only ∼1- 2 of which are expected to be spurious detections. Of these source candidates, eight are also …

Probing Grb Environments Through X-Ray Absorption, Hala Eid

All Theses

Although long-duration GRBs (LGRBs) are highly transient in nature, their early afterglow can in principle be detected to very high redshifts (Lamb & Reichart, 2000). This makes them potent probes of the chemical evolution and content of the high-redshift universe. In this work, we use photoelectric absorption observed in the XRT spectra of LGRBs to investigate the evolution of metallicities and hydrogen column densities of LGRB host galaxies. Using a high-quality sample of LGRBs indicates the presence of a weak anti-correlation between the abundances and redshift. We also find an evolution trend in intrinsic column density. To confirm these correlations, …

Physics Of Type Ia Supernovae, Ginger Bryngelson

All Theses

Type Ia supernovae (SNe Ia), the thermonuclear explosion of a white dwarf, were once considered standard candles. However, increased observations reveal inhomogeneities in chemical composition and luminosity behavior, roughly dividing SNe Ia into three luminosity classes; super-luminous, sub-luminous, and normally-luminous. After introducing the problem in the context of previous observations and modeling, this thesis explores the physical processes occurring in a SN Ia after explosion, and discusses observations of SN light curves.
A simple model of the expanding ejecta calculates the energy deposition from the decay of radioactive Ni56 as well as photon diffusion. It produces light curves that match …

The Adaptability Of Langmuir Probes To The Pico-Satellite Regime, Andrew Jay Auman

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The purpose of this thesis is to investigate whether it is feasible to use Langmuir probes on pico-satellites flying in low Earth orbit over mid- to low-latitude geographic regions. Following chapters on the expected ionospheric conditions and an overview of Langmuir probe theory, a chapter addressing the difficulties involved with pico-satellite Langmuir probes is presented. Also, the necessary satellite-to-probe surface area requirements in order to achieve confidence in pico-satellite Langmuir probe data, for the orbital regions of interest to this thesis, are stated.

An Aztec 1.1 Mm Survey Of The Goods-N Field – I. Maps, Catalogue And Source Statistics, Thushara Perera, E. Chapin, J. Austermann, K. Scott, G. Wilson, M. Halern, A. Pope, D. Scott, M. Yun, J. Lowenthal, G. Morrison, I. Aretxaga, J. Bock, K. Coppin, M. Crowe, L. Frey, D. Hughes, Y. Kang, S. Kim, P. Mauskopf

Thushara A. Perera

No abstract provided.

The Star Formation Law In Nearby Galaxies On Sub-Kpc Scales, F. Bigiel, A. Leroy, F. Walter, E. Brinks, W.J.G. De Blok, B. F. Madore, Michele D. Thornley

Michele Thornley

Tidal Heating Of Terrestrial Extrasolar Planets And Implications For Their Habitability, Brian Jackson, Rory Barnes, Richard Greenberg

Brian Jackson

The tidal heating of hypothetical rocky (or terrestrial) extrasolar planets spans a wide range of values depending on stellar masses and initial orbits. Tidal heating may be sufficiently large (in many cases, in excess of radiogenic heating) and long-lived to drive plate tectonics, similar to the Earth's, which may enhance the planet's habitability. In other cases, excessive tidal heating may result in Io-like planets with violent volcanism, probably rendering them unsuitable for life. On water-rich planets, tidal heating may generate subsurface oceans analogous to Europa's with similar prospects for habitability. Tidal heating may enhance the outgassing of volatiles, contributing to …

Search For Gravitational-Wave Bursts From Soft Gamma Repeaters, B. Abbott, R. Abbott, R. Adhikari, P. Ajith, B. Allen, G. Allen, R. S. Amin, S. B. Anderson, W. G. Anderson, M. A. Arain, M. Araya, H. Armandula, P. Armor, Y. Aso, S. Aston, P. Aufmuth, C. Aulbert, S. Babak, S. Ballmer, H. Bantilan, B. C. Barish, C. Barker, D. Barker, B. Barr, P. Barriga, M. A. Barton, I. Bartos, M. Bastarrika, K. Bayer, J. Betzwieser, P. T. Beyersdorf, Tiffany Z. Summerscales

Faculty Publications

We present a LIGO search for short-duration gravitational waves (GWs) associated with soft gamma ray repeater (SGR) bursts. This is the first search sensitive to neutron star f modes, usually considered the most efficient GW emitting modes. We find no evidence of GWs associated with any SGR burst in a sample consisting of the 27 Dec. 2004 giant flare from SGR 1806-20 and 190 lesser events from SGR 1806-20 and SGR 1900+14. The unprecedented sensitivity of the detectors allows us to set the most stringent limits on transient GW amplitudes published to date. We find upper limit estimates on the …

Do R_{Aa} And R_{Cp} Quantify Nuclear Medium Effects?, Robert Adrian Zaballa

Physics and Astronomy Dissertations

With the use of an incoherent binary nucleon-nucleon collision model of heavy ion collisions for simulating particle production, it is demonstrated that the nuclear modification factors, R_{AA} and R_{CP}, are less than unity for hard scattering in the absence of any nuclear modification effects. The nuclear modification factor R_{dAu} is also shown to approach or exceed unity only if p_T broadening is taken into account. With a simple phenomenological parameter, the mean nucleon energy loss fraction, this model yields particle distributions that are comparable to those of experiment. The nuclear geometry is described by the Glauber model, and particle production …

The Separated Fringe Packet Survey: Updating Multiplicity Of Solar-Type Stars Within 22 Parsecs, Christopher Donald Farrington

Physics and Astronomy Dissertations

Over the past half century, multiplicity studies have provided a foundation for the theories of stellar formation and evolution through understanding how likely it is that stars form alone or with companions. If spectroscopic orbits are combined with techniques that can determine visual orbits, we can access the most fundamental parameter of stellar evolution, stellar mass. This dissertation is composed of two main sections. The first involves the investigation of the seminal multiplicity study of Duquennoy & Mayor (1991b) which has been the ``gold standard" for solar-type stars for nearly 20 years. Improvements in technology in the intervening years have …

Theory Of Electronic And Optical Properties Of Nanostructures, Prabath Hewageegana

Physics and Astronomy Dissertations

"There is plenty of room at the bottom." This bold and prophetic statement from Nobel laureate Richard Feynman back in 1950s at Cal Tech launched the Nano Age and predicted, quite accurately, the explosion in nanoscience and nanotechnology. Now this is a fast developing area in both science and technology. Many think this would bring the greatest technological revolution in the history of mankind. To understand electronic and optical properties of nanostructures, the following problems have been studied. In particular, intensity of mid-infrared light transmitted through a metallic diffraction grating has been theoretically studied. It has been shown that for …

Short-Wave Infrared Diffuse Reflectance Of Textile Materials, Terence Haran

Physics and Astronomy Theses

This thesis analyzes the reflectance behavior of textiles in the short-wave infrared (SWIR) band (1 – 2 microns) in order to identify/design potential diagnostic tools that allow the remote detection of human presence in a scene. Analyzing the spectral response of fabrics in the SWIR band has gained significant interest in the remote sensing community since it provides a potential path to discriminate camouflaged clothing from backgrounds that appear similar to the object of interest in the visible band. Existing research, originating primarily from the textiles community, has thoroughly documented the behavior of clothing fabrics in the visible band. Other …

Antiphase Ordering And Surface Phases In Lithium Aluminate, Richard R. Vanfleet, J. A. Simmons, D. W. Hill, M. M. C. Chou, B. H. Chai

Faculty Publications

Antiphase domains are seen in single crystal gamma lithium aluminate (gamma-LiAlO2) with 16.7 nm periodicity in the <110> direction. Alternate domains have a (1/2) [001] shift. Beta phase lithium aluminate (beta-LiAlO2) is seen to form on the surface of the as-received wafers with an epitaxial strain limited relationship with the bulk gamma phase. The orthorhombic beta phase aligns with the a and b axes (0.528 and 0.630 nm) matching with the tetragonal gamma phase's a and c axes (0.5168 and 0.6268 nm). The gamma and beta phases are seen to have different etch rates. The beta phase converts back to the …

Redshifted Absorption At He I Λ10830 As A Probe Of The Accretion Geometry Of T Tauri Stars, William Fischer, John Kwan, Suzan Edwards, Lynne A. Hillenbrand

Astronomy: Faculty Publications

We probe the geometry of magnetospheric accretion in classical T Tauri stars (CTTSs) by modeling red absorption at He I λ10830 via scattering of the stellar and veiling continua. Under the assumptions that the accretion flow is an azimuthally symmetric dipole and helium is sufficiently optically thick that all incident 1 μm radiation is scattered, we illustrate the sensitivity of He I λ10830 red absorption to both the size of the magnetosphere and the filling factor of the hot accretion shock. We compare model profiles to those observed in 21 CTTSs with subcontinuum redshifted absorption at He I λ10830 and …