Astrophysics and Astronomy Commons^™

Bridging The Gender Gap In Quantum Physics, Gordon Stecklein

Pomona Senior Theses

Why is it important to study the gender gap in physics? Despite entering the workforce in increasing numbers over the last fifty years, women remain severely underrepresented in science and technology-related careers, particularly in positions of authority. Simultaneously, numerous studies verify that women have the ability to perform as well as – or better than – males in physics, and, when presented in certain lights, as many women as men show an interest in physics. Changes must be made in order to strive for equality and, given the changing demographic of the workforce, increase our country’s diminishing scientific prowess.

Acoustical Measurement Of The Human Vocal Tract: Quantifying Speech & Throat-Singing, Bryant R. Foresman

Pomona Senior Theses

The field of biological acoustics has witnessed a steady increase in the research into overtone singing, or “throat-singing,” in which a singer utilizes resonance throughout the vocal tract to sing melodies with the overtones created by a vocal drone. Recent research has explored both how a singer vocalizes in order to obtain rich harmonics from a vocal drone, as well as how further manipulations of the vocal apparatus function to filter and amplify selected harmonics. In the field of phonetics, vowel production is quantified by measuring the frequencies of vocal tract resonances, or formants, which a speaker manipulates to voice …

The Extremely Rapid Rotational Braking Of The Magnetic Helium-Strong Star Hd 37776, Zdeněk Mikulášek, Jiří Krtička, Gregory W. Henry, Juraj Zverko, Jozef Žižňovský, David A. Bohlender, Iosif I. Romanyuk, Jan Janík, Hrvoje Božić, D. Korčáková, Miloslav Zejda, Ivan Kh. Iliev, Petr Škoda, Miroslav Šlechta, Tomáš Gráf, Martin Netolický, Michal Ceniga

Information Systems and Engineering Management Research Publications

Context. Light and spectrum variations of the magnetic chemically peculiar (mCP) stars are explained by the oblique rigid rotator model with a rotation period usually assumed to be stable on a long time scale. A few exceptions, such as CU Vir or 56 Ari, have been reported as displaying an increase in their rotation period. A possible increase in the period of light and spectrum variations has also been suggested from observations of the helium-strong mCP star HD 37776 (V901 Ori).

Aims. In this paper we attempt to confirm the possible period change of HD 37776 and discuss a possible …

Further Studies Of The Photometric Variability Of Bright Pulsating Red Giants, John R. Percy, Marina Mashintsova, Otilia Cristina Nasui, R. Palaniappan, R. Seneviratne, Gregory W. Henry

Information Systems and Engineering Management Research Publications

Long-term photoelectric V photometry of 13 pulsating red giants (TV Psc, EG And, RZ Ari, η Gem, V614 Mon, RS Cnc, VY UMa, FS Com, SW Vir, R Lyr, EU Del, V1070 Cyg, and W Cyg) from a robotic telescope (APT) and from the photoelectric photometry program of the American Association of Variable Star Observers has been merged to form data sets that are significantly longer and denser than the subsets, and have been analyzed using Fourier and self-correlation techniques. Improved values of the pulsation periods, and especially of the enigmatic long secondary periods (LSPs), have been determined. Most of …

The Effect Of 53 ΜM Ir Radiation On 18 Cm Oh Megamaser Emission, Philip Lockett, Moshe Elitzur

Physics and Astronomy Faculty Publications

OH megamasers (OHMs) emit primarily in the main lines at 1667 and 1665 MHz and differ from their Galactic counterparts due to their immense luminosities, large line widths, and 1667/1665 MHz flux ratios, which are always greater than 1. We find that these maser properties result from strong 53 μm radiative pumping combined with line overlap effects caused by turbulent line widths ~20 km s^-1 pumping calculations that do not include line overlap are unreliable. A minimum dust temperature of ~45 K is needed for inversion, and maximum maser efficiency occurs for dust temperatures ~80-140 K. We find …

Connections To The Cosmos: The Search For Life Beyond Earth, Shane L. Larson

Public Talks

No abstract provided.

The First Frontier: Harbor In Near Space, Shane L. Larson

Public Talks

No abstract provided.

A Compton Telescope For Remote Location And Identification Of Radioactive Material, James M. Ryan, Justin Baker, John R. Macri, Mark L. Mcconnell, Richard Carande

Space Science Center

The spare detectors from NASA Compton Gamma-Ray Observatory COMPTEL instrument have been reconfigured to demonstrate the capability at ground level to remotely locate and identify sources of g radiation or the movement of material that might shield γ-ray sources. The Gamma-Ray Experimental Telescope Assembly (GRETA) employs two 28 cm diameter scintillation detectors separated by 81 cm: one 8.5 cm thick liquid scintillator detector and one 7.5 cm thick NaI(Tl) detector. The assembly electronics and real-time data acquisition system measures the energy deposits and time-of- flight for each coincident detection and compiles histograms of total energy and incident angle as computed …

Metallicity And Effective Temperature Of The Secondary Or Rs Ophicuhi, R. L. Pearson Iii, Ya. V. Pavlenko, A. Evans, T. Kerr, L. Yakovina, C. E. Woodward, D. Lynch, R. Rudy, R. W. Russell

Faculty Publications

Context. The recurrent nova RS Ophiuchi undergoes nova eruptions every 10-20 years as a result of thermonuclear runaway on the surface of a white dwarf close to the Chandrasekhar limit. Both the progress of the eruption and its aftermath depend on the (poorly known) composition of the red giant in the RS Oph system. Aims. Our aim is to understand better the effect of the giant secondary on the recurrent nova eruption. Methods. Synthetic spectra were computed for a grid of M-giant model atmospheres having a range of effective temperatures 3200 < Teff < 4400 K, gravities 0 < log g < 1 and abundances -4 < [Fe/H] < 0.5, and fit to infrared spectra of RS Oph as it returned to quiescence after its 2006 eruption. We have modelled the infrared spectrum in the range 1.4-2.5µm to determine metallicity and effective temperature of the red giant. Results. We find Teff= 4100 ±100 K, log g = 0.0 ±0.5, [Fe/H] = 0.0 ±0.5, [C/H] = -0.8 ±0.2, [N/H] = +0.6 ±0.3 in the atmosphere of the secondary, and demonstrate that inclusion of some dust "veiling" in the spectra cannot improve our fits.

Development And Performance Of The Fast Neutron Imaging Telescope For Snm Detection, James M. Ryan, U Bravar, E O. Fluckiger, John R. Macri, Mark L. Mcconnell, B Pirard, R S. Woolf

Space Science Center

FNIT (the Fast Neutron Imaging Telescope), a detector with both imaging and energy measurement capabilities, sensitive to neutrons in the range 0.8-20 MeV, was initially conceived to study solar neutrons as a candidate design for the Inner Heliosphere Sentinel (IHS) spacecraft of NASA's Solar Sentinels program and successively reconfigured to locate fission neutron sources. By accurately identifying the position of the source with imaging techniques and reconstructing the Watt spectrum of fission neutrons, FNIT can detect samples of special nuclear material (SNM), including heavily shielded and masked ones. The detection principle is based on multiple elastic neutron-proton scatterings in organic …

The Evolution Of Circumstellar Disks In Ophiuchus Binaries, J. Patience, R. L. Akeson, Eric L.N. Jensen

Physics & Astronomy Faculty Works

Four Ophiuchus binaries, two Class I systems and two Class II systems, with separations of similar to 450-1100 AU, were observed with the Owens Valley Radio Observatory (OVRO) millimeter interferometer. In each system, the 3 mm continuum maps show dust emission at the location of the primary star, but no emission at the position of the secondary. This result is different from observations of less evolved Class 0 binaries, in which dust emission is detected from both sources. The nondetection of secondary disks is, however, similar to the dust distribution seen in wide Class II Taurus binaries. The combined OVRO …

The Nature Of The Ultraluminous Oxygen‐Rich Supernova Remnant In Ngc 4449, Dan Milisavljevic, Robert A. Fesen

Dartmouth Scholarship

Optical images and spectra, both ground based and taken by Hubble Space Telescope (HST), of the young, luminous O-rich supernova remnant in the irregular galaxy NGC 4449 are presented. HST images of the remnant and its local region were obtained with the ACS/WFC using filters F435W, F555W, F814W (B, V, and I, respectively), F502N ([O III]), F658N (Hα + [N II]), F660N ([N II]), and F550M (line-free continuum). These images show an unresolved remnant (FWHM < 0.05'') located within a rich cluster of OB stars which itself is enclosed by a nearly complete interstellar shell seen best in Hα + [N II] emission approximately 8'' × 6'' (150 pc × 110 pc ) in size. The remnant and its associated OB cluster are isolated …

Investigating The Nature Of Absorption Lines In The Chandra X-Ray Spectra Of The Neutron Star Binary 4u 1820-30, E. M. Cackett, J. M. Miller, J. Raymond, J. Homan, M. Van Der Klis, M. Méndez, D. Steeghs, R. Wijnands

Physics and Astronomy Faculty Research Publications

We use four Chandra gratings spectra of the neutron star low-mass X-ray binary 4U 1820-30 to better understand the nature of certain X-ray absorption lines in X-ray binaries, including the Ne II, Ne III, Ne IX, O VII, and O VIII lines. The equivalent widths of the lines are generally consistent between the observations, as expected if these lines originate in the hot interstellar medium. No evidence was found that the lines were blueshifted, again supporting the interstellar medium origin, although this may be due to poor statistics. There is apparent variability in the O VIII Lyα line equivalent width …

Implications Of The Hall Effect For Turbulent Molecular Clouds, Turlough Downes, Stephen O'Sullivan

Conference papers

No abstract provided.

Numerical Modeling Of Weakly Ionized Plasmas, Stephen O'Sullivan, Turlough Downes

Conference papers

No abstract provided.

Resonance Scattering In The X-Ray Emission Lines Profiles Of Ζ Puppis, M. A. Leutenegger, David H. Cohen, S. M. Kahn, S. P. Owocki, F. B.S. Paerels

Physics & Astronomy Faculty Works

We present XMM-Newton Reflection Grating Spectrometer observations of pairs of X-ray emission line profiles from the O star ζ Pup that originate from the same He-like ion. The two profiles in each pair have different shapes and cannot both be consistently fit by models assuming the same wind parameters. We show that the differences in profile shape can be accounted for in a model including the effects of resonance scattering, which affects the resonance line in the pair but not the intercombination line. This implies that resonance scattering is also important in single resonance lines, where its effect is difficult …

Quantitative Analysis Of Resolved X-Ray Emission Line Profiles Of O Stars, David H. Cohen, M. A. Leutenegger, R. H.D. Townsend

Physics & Astronomy Faculty Works

By quantitatively fitting simple emission line profile models that include both atomic opacity and porosity to the Chandra X-ray spectrum of ζ Pup, we are able to explore the trade-offs between reduced mass-loss rates and wind porosity. We find that reducing the mass-loss rate of ζ Pup by roughly a factor of four, to 1.5 \times 10^{-6} M_sun/yr, enables simple non-porous wind models to provide good fits to the data. If, on the other hand, we take the literature mass-loss rate of 6 \times 10^{-6} M_sun/yr, then to produce X-ray line profiles that fit the data, extreme porosity lengths -- …

A New Look At The Local White Dwarf Population, Jay B. Holberg, Edward M. Sion, Terry D. Oswalt, George P. Mccook, S Foran, John P. Subasavage

Aerospace, Physics, and Space Science Faculty Publications

We have conducted a detailed new survey of the local population of white dwarfs lying within 20 pc of the Sun. A new revised catalog of local white dwarfs containing 122 entries (126 individual degenerate stars) is presented. This list contains 27 white dwarfs not included in a previous list from 2002, as well as new and recently published trigonometric parallaxes. In several cases new members of the local white dwarf population have come to light through accurate photometric distance estimates. In addition, a suspected new double degenerate system (WD 0423+120) has been identified. The 20 pc sample is currently …

Comparing Various Multi-Component Global Heliosphere Models, H.-R. Müller, V. Florinski, J. Heerikhuisen, V. V. Izmodenov

Dartmouth Scholarship

Modeling of the global heliosphere seeks to investigate the interaction of the solar wind with the partially ionized local interstellar medium. Models that treat neutr al hydrogen self-consistently and in great detail, together with the plasma, but that neglect magnetic fields, constitute a sub-category within global heliospheric models. There are several different modeling strategies used for this sub-category in the literature. Differences and commonalities in the modeling results from different strategies are pointed out.

Spatially Resolved Spectroscopy Of Coma Cluster Early‐Type Galaxies. Iv. Completing The Data Set, E. M. Corsini, G. Wegner, R. P. Saglia, J. Thomas

Dartmouth Scholarship

The long-slit spectra obtained along the minor axis, offset major axis, and diagonal axis are presented for 12 E and S0 galaxies of the Coma Cluster drawn from a magnitude-limited sample studied before. The rotation curves, velocity dispersion profiles, and the H₃ and H₄ coefficients of the Hermite decomposition of the line-of-sight velocity distribution are derived. The radial profiles of the Hβ, Mg, and Fe line strength indices are measured too. In addition, the surface photometry of the central regions of a subsample of four galaxies recently obtained with the Hubble Space Telescope is presented. The data will …

Book Review: The Road To Galaxy Formation 2nd Ed, T. D. Oswalt

Publications

This document is Dr. Oswalt’s review of The road to galaxy formation 2nd ed by William C. Keel. Springer/Praxis, 2007 262p, 9783540725343 $99.00.

A New Look At The Local White Dwarf Population, J. B. Holberg, E. M. Sion, Terry D. Oswalt, G. P. Mccook, S. Foran, John P. Subasavage

Publications

We have conducted a detailed new survey of the local population of white dwarfs lying within 20 pc of the Sun. A new revised catalog of local white dwarfs containing 122 entries (126 individual degenerate stars) is presented. This list contains 27 white dwarfs not included in a previous list from 2002, as well as new and recently published trigonometric parallaxes. In several cases new members of the local white dwarf population have come to light through accurate photometric distance estimates. In addition, a suspected new double degenerate system (WD 0423+120) has been identified. The 20 pc sample is currently …

Mass Models For Low Surface Brightness Galaxies With High-Resolution Optical Velocity Fields, Stacy S. Mcgaugh

Faculty Scholarship

We present high-resolution optical velocity fields from DensePak integral field spectroscopy, along with derived rotation curves, for a sample of low surface brightness galaxies. In the limit of no baryons, we fit the NFW and pseudoisothermal halo models to the data and find the rotation curve shapes and halo central densities to be better described by the isothermal halo. For those galaxies with photometry, we present halo fits for three assumptions of the stellar mass-to-light ratio, Υ*. We find that the velocity contribution from the baryons is significant enough in the maximum disk case that maximum disk and the NFW …

Comparison Of Birkeland Current Observations During Two Magnetic Cloud Events With Mhd Simulations, H Korth, B J. Anderson, J G. Lyon, M Wiltberger

Dartmouth Scholarship

Low altitude field-aligned current densities ob-

tained from global magnetospheric simulations are compared

with two-dimensional distributions of Birkeland currents at

the topside ionosphere derived from magnetic field observa-

tions by the constellation of Iridium satellites. We present the

analysis of two magnetic cloud events, 17–19 August 2003

and 19–21 March 2001, where the interplanetary magnetic

field (IMF) rotates slowly (∼10◦/h) to avoid time-aliasing in

the magnetic perturbations used to calculate the Birkeland

currents. In the August 2003 event the IMF rotates from

southward to northward while maintaining a negative IMF

By during much of the interval. During the March 2001 …

Excited-State Oh Masers And Supernova Remnants, Ylva M. Pihlström, Vincent L. Fish, Loránt O. Sjouwerman, Laura K. Zschaechner, Philip B. Lockett, Moshe Elitzur

Physics and Astronomy Faculty Publications

The collisionally pumped, ground-state 1720 MHz maser line of OH is widely recognized as a tracer for shocked regions and observed in star-forming regions and supernova remnants. Whereas some lines of excited states of OH have been detected and studied in star-forming regions, the subject of excited-state OH in supernova remnants-where high collision rates are to be expected-is only recently being addressed. Modeling of collisional excitation of OH demonstrates that 1720, 4765, and 6049 MHz masers can occur under similar conditions in regions of shocked gas. In particular, the 6049 and 4765 MHz masers become more significant at increased OH …

Search For Gravitational Waves Associated With 39 Gamma-Ray Bursts Using Data From The Second, Third, And Fourth Ligo Runs, B. Abbott, R. Abbott, R. Adhikari, J. Agresti, P. Ajith, B. Allen, R. Amin, S. B. Anderson, W. G. Anderson, M. Arain, M. Araya, H. Armandula, M. Ashley, 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, K. Bayer, K. Belczynski, S. J. Berukoff, J. Betzwieser, P. T. Beyersdorf, B. Bhawal, Tiffany Z. Summerscales

Faculty Publications

We present the results of a search for short-duration gravitational-wave bursts associated with 39 gamma-ray bursts (GRBs) detected by gamma-ray satellite experiments during LIGO's S2, S3, and S4 science runs. The search involves calculating the crosscorrelation between two interferometer data streams surrounding the GRB trigger time. We search for associated gravitational radiation from single GRBs, and also apply statistical tests to search for a gravitational-wave signature associated with the whole sample. For the sample examined, we find no evidence for the association of gravitational radiation with GRBs, either on a single-GRB basis or on a statistical basis. Simulating gravitational-wave bursts …

Error Sensor Strategies For Active Noise Control And Active Acoustic Equalization In A Free Field, Ryan T. Chester

Theses and Dissertations

Several measurements may be used as error signals to determine how to appropriately control a sound field. These include pressure, particle velocity, energy density and intensity. In this thesis, numerical models are used to show which signals perform best in is free-field active noise control (ANC) using error sensors located in the near field of the sound sources. The second is equalization in a free field and a semi-free field. Minimized energy density total power output (MEDToPO) plots are developed; these indicate the maximum achievable attenuation for a chosen error sensor as a function of location. A global listening area …

Improving Performance Of The Filtered-X Least Mean Square Algorithm For Active Control Of Noise Contatining Multiple Quasi-Stationary Tones, Stephan P. Lovstedt

Theses and Dissertations

The Filtered-X Least-Mean-Square (FXLMS) algorithm is widely used in active noise control due to its robustness, simplicity, and ability to be implemented in real time. In a feedforward implementation of the FXLMS algorithm, a reference signal that is highly correlated with the noise to be controlled is filtered with an estimate of the transfer function of the secondary path. The convergence characteristics of the FXLMS algorithm have been well studied. A convergence parameter is used to optimize the convergence of the algorithm. However, the optimal value for the convergence parameter is frequency dependent. Thus for noise containing multiple tones at …

Five New Transits Of The Super-Neptune Hd 149026b, Joshua N. Winn, Gregory W. Henry, Guillermo Torres, Matthew J. Holman

Information Systems and Engineering Management Research Publications

We present new photometry of HD 149026 spanning five transits of its "super-Neptune" planet. In combination with previous data, we improve on the determination of the planet-to-star radius ratio: Rp/R⋆ = 0.0491+ 0.0018−0.0005. We find the planetary radius to be 0.71 ± 0.05 RJup, in accordance with previous theoretical models invoking a high metal abundance for the planet. The limiting error is the uncertainty in the stellar radius. Although we find agreement among four different ways of estimating the stellar radius, the uncertainty remains at 7%. We also present a refined transit ephemeris and a constraint on the orbital eccentricity …

Orbital Parameters And Chemical Composition Of Four White Dwarfs In Post-Common-Envelope Binaries, Adéla Kawka, Stéphane Vennes, Jean François Dupuis, Pierre Chayer, Thierry M. Lanz

Aerospace, Physics, and Space Science Faculty Publications

We present FUSE observations of the hot white dwarfs in the post-common-envelope binaries Feige 24, EUVE J0720-317, BPM 6502, and EUVE J2013+400. The spectra show numerous photospheric absorption lines, which trace the white dwarf orbital motion. We report the detection of C III, O VI, P V, and Si IV in the spectra of Feige 24, EUVE J0720-317, and EUVE J2013+400 and the detection of C III, N II, Si III, Si IV, and Fe III in the spectra of BPM 6502. Abundance measurements support the possibility that white dwarfs in post-common-envelope binaries accrete material from the secondary star wind. …