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Full-Text Articles in Physical Sciences and Mathematics

Nnetfix: An Artificial Neural Network-Based Denoising Engine For Gravitational-Wave Signals, Kentaro Mogushi, Ryan Quitzow-James, Marco Cavaglià, Sumeet Kulkarni, Fergus Hayes Sep 2021

Nnetfix: An Artificial Neural Network-Based Denoising Engine For Gravitational-Wave Signals, Kentaro Mogushi, Ryan Quitzow-James, Marco Cavaglià, Sumeet Kulkarni, Fergus Hayes

Faculty and Student Publications

Instrumental and environmental transient noise bursts in gravitational-wave (GW) detectors, or glitches, may impair astrophysical observations by adversely affecting the sky localization and the parameter estimation of GW signals. Denoising of detector data is especially relevant during low-latency operations because electromagnetic follow-up of candidate detections requires accurate, rapid sky localization and inference of astrophysical sources. NNETFIX is a machine learning, artificial neural network-based algorithm designed to estimate the data containing a transient GW signal with an overlapping glitch as though the glitch was absent. The sky localization calculated from the denoised data may be significantly more accurate than the sky …

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Enhanced Detection Efficiencies And Reduced False Alarms In Searching For Gravitational Waves From Core Collapse Supernovae, Gaukhar Nurbek May 2021

Enhanced Detection Efficiencies And Reduced False Alarms In Searching For Gravitational Waves From Core Collapse Supernovae, Gaukhar Nurbek

Theses and Dissertations

A supernova is a star that flares up very suddenly and then slowly returns to its former luminosity or, explodes violently with energy $10^{52}$ erg. There are stars which are 10 times or more massive than the Sun, which usually end their lives going supernova. When there is no longer enough fuel for the fusion process in the core of the star and inward gravitational pull of the star’s great mass takes place, the star starts to explode. A series of nuclear reactions starts taking place after the star begins shrinking due to gravity. In the final phase of this …

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Fourier Transform Of The Continuous Gravitational Wave Signal, Sree Ram Valluri, V. Dergachev, X. Zhang, Farrukh Chishtie Jan 2021

Fourier Transform Of The Continuous Gravitational Wave Signal, Sree Ram Valluri, V. Dergachev, X. Zhang, Farrukh Chishtie

Physics and Astronomy Publications

The direct detection of continuous gravitational waves from pulsars is a much anticipated discovery in the emerging field of multimessenger gravitational wave (GW) astronomy. Because putative pulsar signals are exceedingly weak large amounts of data need to be integrated to achieve desired sensitivity. Contemporary searches use ingenious ad hoc methods to reduce computational complexity. In this paper we provide analytical expressions for the Fourier transform of realistic pulsar signals. This provides description of the manifold of pulsar signals in the Fourier domain, used by many search methods. We analyze the shape of the Fourier transform and provide explicit formulas for …

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Prospects For Observing And Localizing Gravitational-Wave Transients With Advanced Ligo, Advanced Virgo And Kagra, B. P. Abbott, R. Abbott, T. D. Abbott, M. R. Abernathy, F. Acernese, K. Ackley, C. Adams, T. Adams, P. Addesso, R. X. Adhikari, V. B. Adya, C. Affeldt, M. Agathos, K. Agatsuma, N. Aggarwal, O. D. Aguiar, L. Aiello, A. Ain, P. Ajith, T. Akutsu, B. Allen, A. Allocca, P. A. Altin, A. Ananyeva, S. B. Anderson, W. G. Anderson, M. Ando, S. Appert, K. Arai, A. Araya, Teviet Creighton, Mario C. Diaz, S. Mukherjee, V. Quetschke, Malik Rakhmanov, K. E. Ramirez, Satzhan Sitmukhambetov, Robert Stone, D. Tuyenbayev, W. H. Wang, A. K. Zadrozny Sep 2020

Prospects For Observing And Localizing Gravitational-Wave Transients With Advanced Ligo, Advanced Virgo And Kagra, B. P. Abbott, R. Abbott, T. D. Abbott, M. R. Abernathy, F. Acernese, K. Ackley, C. Adams, T. Adams, P. Addesso, R. X. Adhikari, V. B. Adya, C. Affeldt, M. Agathos, K. Agatsuma, N. Aggarwal, O. D. Aguiar, L. Aiello, A. Ain, P. Ajith, T. Akutsu, B. Allen, A. Allocca, P. A. Altin, A. Ananyeva, S. B. Anderson, W. G. Anderson, M. Ando, S. Appert, K. Arai, A. Araya, Teviet Creighton, Mario C. Diaz, S. Mukherjee, V. Quetschke, Malik Rakhmanov, K. E. Ramirez, Satzhan Sitmukhambetov, Robert Stone, D. Tuyenbayev, W. H. Wang, A. K. Zadrozny

Physics and Astronomy Faculty Publications and Presentations

We present our current best estimate of the plausible observing scenarios for the Advanced LIGO, Advanced Virgo and KAGRA gravitational-wave detectors over the next several years, with the intention of providing information to facilitate planning for multi-messenger astronomy with gravitational waves. We estimate the sensitivity of the network to transient gravitational-wave signals for the third (O3), fourth (O4) and fifth observing (O5) runs, including the planned upgrades of the Advanced LIGO and Advanced Virgo detectors. We study the capability of the network to determine the sky location of the source for gravitational-wave signals from the inspiral of binary systems of …

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A Guide To Ligo–Virgo Detector Noise And Extraction Of Transient Gravitational-Wave Signals, Tiffany Summerscales, Ligo Scientific Collaboration And The Virgo Collaboration Jan 2020

A Guide To Ligo–Virgo Detector Noise And Extraction Of Transient Gravitational-Wave Signals, Tiffany Summerscales, Ligo Scientific Collaboration And The Virgo Collaboration

Faculty Publications

The LIGO Scientific Collaboration and the Virgo Collaboration have cataloged eleven confidently detected gravitational-wave events during the first two observing runs of the advanced detector era. All eleven events were consistent with being from well-modeled mergers between compact stellarmass objects: black holes or neutron stars. The data around the time of each of these events have been made publicly available through the gravitationalwave open science center. The entirety of the gravitational-wave strain data from the first and second observing runs have also now been made publicly available. There is considerable interest among the broad scientific community in understanding the data …

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Automated Classification Of Stellar Spectra. Ii: Two-Dimensional Classification With Neural Networks And Principal Components Analysis, Ted Von Hippel, Coryn A.L. Bailer-Jones, Mike Irwin Aug 2019

Automated Classification Of Stellar Spectra. Ii: Two-Dimensional Classification With Neural Networks And Principal Components Analysis, Ted Von Hippel, Coryn A.L. Bailer-Jones, Mike Irwin

Ted von Hippel

We investigate the application of neural networks to the automation of MK spec- tral classification. The data set for this project consists of a set of over 5000 optical (3800–5200°A) spectra obtained from objective prism plates from the Michigan Spec- tral Survey. These spectra, along with their two-dimensional MK classifications listed in the Michigan Henry Draper Catalogue, were used to develop supervised neural network classifiers. We show that neural networks can give accurate spectral type classifications (68 = 0.82 subtypes, rms= 1.09 subtypes) across the full range of spectral types present in the data set (B2–M7). We show also that …

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Waveband Luminosity Correlations In Flux-Limited Multiwavelength Data, Jack Singal, V. Petrosian, Sami Malik, Jibran Haider Jan 2019

Waveband Luminosity Correlations In Flux-Limited Multiwavelength Data, Jack Singal, V. Petrosian, Sami Malik, Jibran Haider

Physics Faculty Publications

We explore the general question of correlations among different waveband luminosities in a flux-limited multiband observational data set. Such correlations, often observed for astronomical sources, may be either intrinsic or induced by the redshift evolution of the luminosities and the data truncation due to the flux limits. We first address this question analytically. We then use simulated flux-limited data with three different known intrinsic luminosity correlations and prescribed luminosity functions and evolution similar to the ones expected for quasars. We explore how the intrinsic nature of luminosity correlations can be deduced, including exploring the efficacy of partial correlation analysis with …

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Covariations Of Chromospheric And Photometric Variability Of The Young Sun Analogue Hd 30495: Evidence For And Interpretation Of Mid-Term Periodicities, Willie Soon, Victor M. Velasco Herrera, Rodolfo G. Cionco, S. Qiu, Sallie Baliunas, Ricky Egeland, Gregory W. Henry, Ivanka Charvátová Dec 2018

Covariations Of Chromospheric And Photometric Variability Of The Young Sun Analogue Hd 30495: Evidence For And Interpretation Of Mid-Term Periodicities, Willie Soon, Victor M. Velasco Herrera, Rodolfo G. Cionco, S. Qiu, Sallie Baliunas, Ricky Egeland, Gregory W. Henry, Ivanka Charvátová

Information Systems and Engineering Management Research Publications

This study reports the synchronization between the chromospheric and photometric variability at time-scale of about 1.6–1.8 yr as observed for the young, rapidly rotating solar analogue HD 30495. In addition, HD 30495 may be presenting evidence of surface differential rotation at time-scales of about 11 d and 21 d, as well as the sunspot-like decadal cycles at 11–12 yr or so. We apply a new gapped wavelet method of time–frequency analysis for studying the variability in a new composite of the chromospheric S-index (1967–2018) and the longest photometric Δ(b + y)/2 index (1993–2018). We discuss and interpret our results in …

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Detection Methods For Stochastic Gravitational-Wave Backgrounds: A Unified Treatment, Joseph D. Romano, Neil J. Cornish Apr 2017

Detection Methods For Stochastic Gravitational-Wave Backgrounds: A Unified Treatment, Joseph D. Romano, Neil J. Cornish

Physics and Astronomy Faculty Publications and Presentations

We review detection methods that are currently in use or have been proposed to search for a stochastic background of gravitational radiation. We consider both Bayesian and frequentist searches using ground-based and space-based laser interferometers, spacecraft Doppler tracking, and pulsar timing arrays; and we allow for anisotropy, non-Gaussianity, and non-standard polarization states. Our focus is on relevant data analysis issues, and not on the particular astrophysical or early Universe sources that might give rise to such backgrounds. We provide a unified treatment of these searches at the level of detector response functions, detection sensitivity curves, and, more generally, at the …

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A Multiwavelength Continuum Characterization Of High-Redshift Broad Absorption Line Quasars, D. Tuccillo, G. Bruni, M. A. Dipompeo, M. S. Brotherton Feb 2017

A Multiwavelength Continuum Characterization Of High-Redshift Broad Absorption Line Quasars, D. Tuccillo, G. Bruni, M. A. Dipompeo, M. S. Brotherton

Dartmouth Scholarship

We present the results of a multiwavelength study of a sample of high-redshift radio-loud (RL) broad absorption line (BAL) quasars. This way, we extend to higher redshift previous studies on the radio properties and broad-band optical colours of these objects. We have selected a sample of 22 RL BAL quasars with 3.6 ≤ z ≤ 4.8 cross-correlating the FIRST radio survey with the Sloan Digital Sky Survey (SDSS). Flux densities between 1.25 and 9.5 GHz have been collected with the Jansky Very Large Array and Effelsberg-100 m telescopes for 15 BAL and 14 non-BAL quasars used as a comparison sample. …

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The Data Reduction Pipeline For The Sdss-Iv Manga Ifu Galaxy Survey, David R. Law, Brian Cherinka, Renbin Yan, Brett H. Andrews, Matthew A. Bershady, Dmitry Bizyaev, Guillermo A. Blanc, Michael R. Blanton, Adam S. Bolton, Joel R. Brownstein, Kevin Bundy, Yanmei Chen, Niv Drory, Richard D'Souza, Hai Fu, Amy Jones, Guinevere Kauffmann, Nicholas Macdonald, Karen L. Masters, Jeffrey A. Newman, John K. Parejko, José R. Sánchez-Gallego, Sebastian F. Sánchez, David J. Schlegel, Daniel Thomas, David A. Wake, Anne-Marie Weijmans, Kyle B. Westfall, Kai Zhang Sep 2016

The Data Reduction Pipeline For The Sdss-Iv Manga Ifu Galaxy Survey, David R. Law, Brian Cherinka, Renbin Yan, Brett H. Andrews, Matthew A. Bershady, Dmitry Bizyaev, Guillermo A. Blanc, Michael R. Blanton, Adam S. Bolton, Joel R. Brownstein, Kevin Bundy, Yanmei Chen, Niv Drory, Richard D'Souza, Hai Fu, Amy Jones, Guinevere Kauffmann, Nicholas Macdonald, Karen L. Masters, Jeffrey A. Newman, John K. Parejko, José R. Sánchez-Gallego, Sebastian F. Sánchez, David J. Schlegel, Daniel Thomas, David A. Wake, Anne-Marie Weijmans, Kyle B. Westfall, Kai Zhang

Physics and Astronomy Faculty Publications

Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) is an optical fiber-bundle integral-field unit (IFU) spectroscopic survey that is one of three core programs in the fourth-generation Sloan Digital Sky Survey (SDSS-IV). With a spectral coverage of 3622–10354 Å and an average footprint of ~500 arcsec2 per IFU the scientific data products derived from MaNGA will permit exploration of the internal structure of a statistically large sample of 10,000 low-redshift galaxies in unprecedented detail. Comprising 174 individually pluggable science and calibration IFUs with a near-constant data stream, MaNGA is expected to obtain ~100 million raw-frame spectra and ~10 million …

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Modeling The Mass Function Of Stellar Clusters Using The Modified Lognormal Power-Law Probability Distribution Function, Deepakshi Madaan Aug 2016

Modeling The Mass Function Of Stellar Clusters Using The Modified Lognormal Power-Law Probability Distribution Function, Deepakshi Madaan

Electronic Thesis and Dissertation Repository

We use the Modified Lognormal Power-law (MLP) probability distribution function to model the behaviour of the mass function (MF) of young and populous stellar populations in different environments. We begin by modeling the MF of NGC1711, a simple stellar population (SSP) in the Large Magellanic Cloud as a pilot case. We then use model selection criterion to differentiate between candidate models. Using the MLP we find that the stellar catalogue of NGC1711 follows a pure power-law behaviour below the completeness limit with the slope α = 2.75 for dN/dlnm ∝ m^(−α+1) in the mass range 0.89 M⊙ to 7.75 M⊙. …

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Galaxy Zoo: Comparing The Demographics Of Spiral Arm Number And A New Method For Correcting Redshift Bias, Ross E. Hart, Steven P. Bamford, Kyle W. Willett, Karen L. Masters, Carolin Cardamone, Chris J. Lintott, Robert J. Mackay, Robert C. Nichol, Christopher K. Rosslowe, Brooke D. Simmons, Rebecca J. Smethurst Jul 2016

Galaxy Zoo: Comparing The Demographics Of Spiral Arm Number And A New Method For Correcting Redshift Bias, Ross E. Hart, Steven P. Bamford, Kyle W. Willett, Karen L. Masters, Carolin Cardamone, Chris J. Lintott, Robert J. Mackay, Robert C. Nichol, Christopher K. Rosslowe, Brooke D. Simmons, Rebecca J. Smethurst

Physics and Astronomy Faculty Publications

The majority of galaxies in the local Universe exhibit spiral structure with a variety of forms. Many galaxies possess two prominent spiral arms, some have more, while others display a many-armed flocculent appearance. Spiral arms are associated with enhanced gas content and star formation in the discs of low-redshift galaxies, so are important in the understanding of star formation in the local universe. As both the visual appearance of spiral structure, and the mechanisms responsible for it vary from galaxy to galaxy, a reliable method for defining spiral samples with different visual morphologies is required. In this paper, we develop …

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A Determination Of The Gamma-Ray Flux And Photon Spectral Index Distributions Of Blazars From The Fermi-Lat 3lac, Jack Singal Nov 2015

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 …

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The Impact Of Terrestrial Noise On The Detectability And Reconstruction Of Gravitational Wave Signals From Core-Collapse Supernovae, Jessica Mciver Nov 2015

The Impact Of Terrestrial Noise On The Detectability And Reconstruction Of Gravitational Wave Signals From Core-Collapse Supernovae, Jessica Mciver

Doctoral Dissertations

Among of the wide range of potentially interesting astrophysical sources for gravitational wave detectors Advanced LIGO and Advanced Virgo are galactic core-collapse supernovae. Although detectable core-collapse supernovae have a low expected rate (a few per century, or less) these signals would yield a wealth of new physics. Of particular interest is the insight into the explosion mechanism driving core-collapse supernovae that can be gleaned from the reconstructed gravitational wave signal. A well-reconstructed waveform will allow us to assess the likelihood of different explosion models, perform model selection, and potentially map unexpected features to new physics. This dissertation presents a series …

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Exonest: Bayesian Model Selection Applied To The Detection And Characterization Of Exoplanets Via Photometric Variations, Ben Placek, Kevin H. Knuth, Daniel Angerhausen Oct 2014

Exonest: Bayesian Model Selection Applied To The Detection And Characterization Of Exoplanets Via Photometric Variations, Ben Placek, Kevin H. Knuth, Daniel Angerhausen

Physics Faculty Scholarship

EXONEST is an algorithm dedicated to detecting and characterizing the photometric signatures of exoplanets, which include reflection and thermal emission, Doppler boosting, and ellipsoidal variations. Using Bayesian inference, we can test between competing models that describe the data as well as estimate model parameters. We demonstrate this approach by testing circular versus eccentric planetary orbital models, as well as testing for the presence or absence of four photometric effects. In addition to using Bayesian model selection, a unique aspect of EXONEST is the potential capability to distinguish between reflective and thermal contributions to the light curve. A case study is …

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Optical-Faint, Far-Infrared-Bright Herschel Sources In The Candels Fields: Ultra-Luminous Infrared Galaxies At Z > 1 And The Effect Of Source Blending, Haojing Yan, Mauro Stefanon, Zhiyuan Ma, S. P. Willner, Rachel Somerville, Matthew L.N. Ashby, Romeel Davé, Pablo G. Pérez-González, Antonio Cava, Tommy Wiklind, Dale D. Kocevski, Marc Rafelski, Jeyhan Kartaltepe, Asantha Cooray, Anton M. Koekemoer, Norman A. Grogin Jun 2014

Optical-Faint, Far-Infrared-Bright Herschel Sources In The Candels Fields: Ultra-Luminous Infrared Galaxies At Z > 1 And The Effect Of Source Blending, Haojing Yan, Mauro Stefanon, Zhiyuan Ma, S. P. Willner, Rachel Somerville, Matthew L.N. Ashby, Romeel Davé, Pablo G. Pérez-González, Antonio Cava, Tommy Wiklind, Dale D. Kocevski, Marc Rafelski, Jeyhan Kartaltepe, Asantha Cooray, Anton M. Koekemoer, Norman A. Grogin

Physics and Astronomy Faculty Publications

The Herschel very wide field surveys have charted hundreds of square degrees in multiple far-IR (FIR) bands. While the Sloan Digital Sky Survey (SDSS) is currently the best resource for optical counterpart identifications over such wide areas, it does not detect a large number of Herschel FIR sources and leaves their nature undetermined. As a test case, we studied seven "SDSS-invisible," very bright 250 μm sources (S 250 > 55 mJy) in the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey fields where we have a rich multi-wavelength data set. We took a new approach to decompose the FIR sources, using …

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The Allen Telescope Array Search For Electrostatic Discharges On Mars, Marin M. Anderson, Andrew P.V. Siemion, William C. Barott, Geoffery C. Bower, Gregory T. Delory, Imke De Pater, Dan Werthimer Mar 2014

The Allen Telescope Array Search For Electrostatic Discharges On Mars, Marin M. Anderson, Andrew P.V. Siemion, William C. Barott, Geoffery C. Bower, Gregory T. Delory, Imke De Pater, Dan Werthimer

William Barott

The Allen Telescope Array was used to monitor Mars between 2010 March 9 and June 2, over a total of approximately 30 hr, for radio emission indicative of electrostatic discharge. The search was motivated by the report from Ruf et al. of the detection of non-thermal microwave radiation from Mars characterized by peaks in the power spectrum of the kurtosis, or kurtstrum, at 10 Hz, coinciding with a large dust storm event on 2006 June 8. For these observations, we developed a wideband signal processor at the Center for Astronomy Signal Processing and Electronics Research. This 1024 channel spectrometer calculates …

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Calculating Time Lags From Unevenly Sampled Light Curves, A. Zoghbi, C. Reynolds, E. M. Cackett Nov 2013

Calculating Time Lags From Unevenly Sampled Light Curves, A. Zoghbi, C. Reynolds, E. M. Cackett

Physics and Astronomy Faculty Research Publications

Timing techniques are powerful tools to study dynamical astrophysical phenomena. In the X-ray band, they offer the potential of probing accretion physics down to the event horizon. Recent work has used frequency- and energy-dependent time lags as tools for studying relativistic reverberation around the black holes in several Seyfert galaxies. This was achieved due to the evenly sampled light curves obtained using XMM-Newton. Continuously sampled data are, however, not always available and standard Fourier techniques are not applicable. Here, building on the work of Miller et al., we discuss and use a maximum likelihood method to obtain frequency-dependent lags that …

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Characterization Of Samples For Optimization Of Infrared Stray Light Coatings, Carey L. Baxter, Rebecca Salvemini, Zaheer A. Ali, Patrick Waddell, Greg Perryman, Bob Thompson Aug 2013

Characterization Of Samples For Optimization Of Infrared Stray Light Coatings, Carey L. Baxter, Rebecca Salvemini, Zaheer A. Ali, Patrick Waddell, Greg Perryman, Bob Thompson

STAR Program Research Presentations

NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA) is a converted 747SP that houses a 2.5 m telescope that observes the sky through an opening in the side of the aircraft. Because it flies at altitudes up to 45,000 feet, SOFIA gets 99.99% transmission in the infrared. Multiple science instruments mount one at a time on the telescope to interpret infrared and visible light from target sources. Ball Infrared Black (BIRB) currently coats everything that the optics sees inside the telescope assembly (TA) cavity in order to eliminate noise from the glow of background sky, aircraft exhaust, and other sources. A …

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Distribution Of Plasmoids In Post-Coronal Mass Ejection Current Sheets, L.-J. Guo, A. Bhattacharjee, Y.-M. Huang Jul 2013

Distribution Of Plasmoids In Post-Coronal Mass Ejection Current Sheets, L.-J. Guo, A. Bhattacharjee, Y.-M. Huang

Dartmouth Scholarship

Recently, the fragmentation of a current sheet in the high-Lundquist-number regime caused by the plasmoid instability has been proposed as a possible mechanism for fast reconnection. In this work, we investigate this scenario by comparing the distribution of plasmoids obtained from Large Angle and Spectrometric Coronagraph (LASCO) observational data of a coronal mass ejection event with a resistive magnetohydrodynamic simulation of a similar event. The LASCO/C2 data are analyzed using visual inspection, whereas the numerical data are analyzed using both visual inspection and a more precise topological method. Contrasting the observational data with numerical data analyzed with both methods, we …

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Flux And Photon Spectral Index Distributions Of Fermi-Lat Blazars And Contribution To The Extragalactic Gamma-Ray Background, Jack Singal, V. Petrosian, M. Ajello Jun 2012

Flux And Photon Spectral Index Distributions Of Fermi-Lat Blazars And Contribution To The Extragalactic Gamma-Ray Background, Jack Singal, V. Petrosian, M. Ajello

Physics Faculty Publications

We present a determination of the distributions of the photon spectral index and gamma-ray flux—the so-called log N–log S relation—for the 352 blazars detected with a greater than approximately 7σ detection threshold and located above ±20◦ Galactic latitude by the Large Area Telescope of the Fermi Gamma-ray Space Telescope in its first year catalog. Because the flux detection threshold depends on the photon index, the observed raw distributions do not provide the true log N–log S counts or the true distribution of the photon index. We use the non-parametric methods developed by Efron and Petrosian to reconstruct the intrinsic distributions …

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The Allen Telescope Array Search For Electrostatic Discharges On Mars, Marin M. Anderson, Andrew P.V. Siemion, William C. Barott, Geoffery C. Bower, Gregory T. Delory, Imke De Pater, Dan Werthimer Jan 2012

The Allen Telescope Array Search For Electrostatic Discharges On Mars, Marin M. Anderson, Andrew P.V. Siemion, William C. Barott, Geoffery C. Bower, Gregory T. Delory, Imke De Pater, Dan Werthimer

Department of Electrical Engineering and Computer Science - Daytona Beach

The Allen Telescope Array was used to monitor Mars between 2010 March 9 and June 2, over a total of approximately 30 hr, for radio emission indicative of electrostatic discharge. The search was motivated by the report from Ruf et al. of the detection of non-thermal microwave radiation from Mars characterized by peaks in the power spectrum of the kurtosis, or kurtstrum, at 10 Hz, coinciding with a large dust storm event on 2006 June 8. For these observations, we developed a wideband signal processor at the Center for Astronomy Signal Processing and Electronics Research. This 1024 channel spectrometer calculates …

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New Methods For Exafs Analysis In Structural Genomics, Grant Bunker, N. Dimakis, Gocha Kelashvili Jan 2004

New Methods For Exafs Analysis In Structural Genomics, Grant Bunker, N. Dimakis, Gocha Kelashvili

Physics and Astronomy Faculty Publications and Presentations

Data analysis is one of the remaining bottlenecks in high-throughput EXAFS for structural genomics. Here some recent developments in methodology are described that offer the potential for rapid and automated XAS analysis of metalloproteins.

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The Warps Survey - Iv. The X-Ray Luminosity-Temperature Relation Of High-Redshift Galaxy Clusters, B. W. Fairley, L. R. Jones, C. Scharf, H. Ebeling, E. Perlman, D. Horner, G. Wegner, M. Malkan Jul 2000

The Warps Survey - Iv. The X-Ray Luminosity-Temperature Relation Of High-Redshift Galaxy Clusters, B. W. Fairley, L. R. Jones, C. Scharf, H. Ebeling, E. Perlman, D. Horner, G. Wegner, M. Malkan

Dartmouth Scholarship

We present a measurement of the cluster X-ray luminosity-temperature (L-T) relation out to high redshift (z∼0.8). Combined ROSAT PSPC spectra of 91 galaxy clusters detected in the Wide Angle ROSAT Pointed Survey (WARPS) are simultaneously fitted in redshift and luminosity bins. The resulting temperature and luminosity measurements of these bins, which occupy a region of the high-redshift L-T relation not previously sampled, are compared with existing measurements at low redshift in order to constrain the evolution of the L-T relation. We find the best fit to low-redshift (z<0.2) cluster data, at T …

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Automated Classification Of Stellar Spectra. Ii: Two-Dimensional Classification With Neural Networks And Principal Components Analysis, Ted Von Hippel, Coryn A.L. Bailer-Jones, Mike Irwin Oct 1997

Automated Classification Of Stellar Spectra. Ii: Two-Dimensional Classification With Neural Networks And Principal Components Analysis, Ted Von Hippel, Coryn A.L. Bailer-Jones, Mike Irwin

Publications

We investigate the application of neural networks to the automation of MK spec- tral classification. The data set for this project consists of a set of over 5000 optical (3800–5200°A) spectra obtained from objective prism plates from the Michigan Spec- tral Survey. These spectra, along with their two-dimensional MK classifications listed in the Michigan Henry Draper Catalogue, were used to develop supervised neural network classifiers. We show that neural networks can give accurate spectral type classifications (68 = 0.82 subtypes, rms= 1.09 subtypes) across the full range of spectral types present in the data set (B2–M7). We show also that …

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