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Articles 241 - 270 of 609

Full-Text Articles in Cosmology, Relativity, and Gravity

Introduction To The Usu Library Of Solutions To The Einstein Field Equations, Ian M. Anderson, Charles G. Torre Dec 2017

Introduction To The Usu Library Of Solutions To The Einstein Field Equations, Ian M. Anderson, Charles G. Torre

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This is a Maple worksheet providing an introduction to the USU Library of Solutions to the Einstein Field Equations. The library is part of the DifferentialGeometry software project and is a collection of symbolic data and metadata describing solutions to the Einstein equations.

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Search For High-Energy Neutrinos From Binary Neutron Star Merger Gw170817 With Antares, Icecube, And The Pierre Auger Observatory, M. G. Aartsen, 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. Dec 2017

Search For High-Energy Neutrinos From Binary Neutron Star Merger Gw170817 With Antares, Icecube, And The Pierre Auger Observatory, M. G. Aartsen, 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

The Advanced LIGO and Advanced Virgo observatories recently discovered gravitational waves from a binary neutron star inspiral. A short gamma-ray burst (GRB) that followed the merger of this binary was also recorded by the Fermi Gamma-ray Burst Monitor (Fermi-GBM), and the Anti-Coincidence Shield for the Spectrometer for the International Gamma-Ray Astrophysics Laboratory (INTEGRAL), indicating particle acceleration by the source. The precise location of the event was determined by optical detections of emission following the merger. We searched for high-energy neutrinos from the merger in the GeV–EeV energy range using the ANTARES, IceCube, and Pierre Auger Observatories. No neutrinos directionally coincident …

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On The Progenitor Of Binary Neutron Star Merger Gw170817, 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. Dec 2017

On The Progenitor Of Binary Neutron Star Merger Gw170817, 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 2017 August 17 the merger of two compact objects with masses consistent with two neutron stars was discovered through gravitational-wave (GW170817), gamma-ray (GRB 170817A), and optical (SSS17a/AT 2017gfo) observations. The optical source was associated with the early-type galaxy NGC 4993 at a distance of just ~40 Mpc, consistent with the gravitational-wave measurement, and the merger was localized to be at a projected distance of ~2 kpc away from the galaxy's center. We use this minimal set of facts and the mass posteriors of the two neutron stars to derive the first constraints on the progenitor of GW170817 at the …

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Facing The Sun, Frank Prendergast, Muiris O'Sullivan, Ken Williams, Gabriel Cooney Dec 2017

Facing The Sun, Frank Prendergast, Muiris O'Sullivan, Ken Williams, Gabriel Cooney

Articles

December 2017 marked 50 years since archaeologist Michael J. O’Kelly first observed the solar illumination of the burial chamber in the Neolithic passage tomb at Newgrange during the period of the winter solstice. O’Kelly subsequently recorded direct sunlight entering Newgrange through the ‘especially contrived slit which lies under the roof-box at the outer end of the passage roof’ on 21 December 1969. The discovery of this historic phenomenon, dating back over 5,000 years, captured the public interest and imagination at that time and ever since. In this major article published in the Winter 2017 edition of Archaeology Ireland (date of …

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Estimating The Contribution Of Dynamical Ejecta In The Kilonova Associated With Gw170817, 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. Dec 2017

Estimating The Contribution Of Dynamical Ejecta In The Kilonova Associated With Gw170817, 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

The source of the gravitational-wave (GW) signal GW170817, very likely a binary neutron star merger, was also observed electromagnetically, providing the first multi-messenger observations of this type. The two-week-long electromagnetic (EM) counterpart had a signature indicative of an r-process-induced optical transient known as a kilonova. This Letter examines how the mass of the dynamical ejecta can be estimated without a direct electromagnetic observation of the kilonova, using GW measurements and a phenomenological model calibrated to numerical simulations of mergers with dynamical ejecta. Specifically, we apply the model to the binary masses inferred from the GW measurements, and use the resulting …

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On The Time Variation Of Dust Extinction And Gas Absorption For Type Ia Supernovae Observed Through A Nonuniform Interstellar Medium, Xiaosheng Huang, G Aldering, M. Biederman, B. Herger Nov 2017

On The Time Variation Of Dust Extinction And Gas Absorption For Type Ia Supernovae Observed Through A Nonuniform Interstellar Medium, Xiaosheng Huang, G Aldering, M. Biederman, B. Herger

Physics and Astronomy

For Type Ia supernovae (SNe Ia) observed through a nonuniform interstellar medium (ISM) in its host galaxy, we investigate whether the nonuniformity can cause observable time variations in dust extinction and in gas absorption due to the expansion of the SN photosphere with time. We show that, owing to the steep spectral index of the ISM density power spectrum, sizable density fluctuation amplitudes at the length scale of typical ISM structures () will translate to much smaller fluctuations on the scales of an SN photosphere. Therefore, the typical amplitude of time variation due to a nonuniform ISM, of absorption equivalent …

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Discovery Of Very-High-Energy Emission From Rgb J2243+203 And Derivation Of Its Redshift Upper Limit, P. T. Reynolds, Et Al Nov 2017

Discovery Of Very-High-Energy Emission From Rgb J2243+203 And Derivation Of Its Redshift Upper Limit, P. T. Reynolds, Et Al

Physical Sciences Publications

Very-high-energy (VHE; > 100 GeV) gamma-ray emission from the blazar RGB J2243+203 was discovered with the VERITAS Cherenkov telescope array, during the period between 2014 December 21 and 24. The VERITAS energy spectrum from this source can be fitted by a power law with a photon index of 4.6 ± 0.5, and a flux normalization at 0.15 TeV of . The integrated Fermi-LAT flux from 1 to 100 GeV during the VERITAS detection is , which is an order of magnitude larger than the four-year-averaged flux in the same energy range reported in the 3FGL catalog, (). The detection with …

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A Gravitational-Wave Standard Siren Measurement Of The Hubble Constant, B. P. Abbott, K. Aultoneal, S. Gaudio, K. Gill, E. M. Gretarrson, B. Hughey, M. Muratore, J. W. W. Pratt, S. G. Schwalde, K. Staats, M. J. Szczepańczyk, M. Zanolin, Et Al. Nov 2017

A Gravitational-Wave Standard Siren Measurement Of The Hubble Constant, B. P. Abbott, K. Aultoneal, S. Gaudio, K. Gill, E. M. Gretarrson, B. Hughey, M. Muratore, J. W. W. Pratt, S. G. Schwalde, K. Staats, M. J. Szczepańczyk, M. Zanolin, Et Al.

Publications

The detection of GW170817 (Abbott et al. 2017a) in both gravitational waves and electromagnetic waves heralds the age of gravitational-wave multi-messenger astronomy. On 17 August 2017 the Advanced Laser Interferometer Gravitational-wave Observatory (LIGO) (LIGO Scientific Collaboration et al. 2015) and Virgo (Acernese et al. 2015) detectors observed GW170817, a strong signal from the merger of a binary neutron-star system. Less than 2 seconds after the merger, a gamma-ray burst (GRB 170817A) was detected within a region of the sky consistent with the LIGO-Virgo-derived location of the gravitational-wave source (Abbott et al. 2017b; Goldstein et al. 2017; Savchenko et al. 2017). …

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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. Oct 2017

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 …

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Gravitational Waves And Gamma-Rays From A Binary Neutron Star Merger: Gw170817 And Grb 170817a, 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. Oct 2017

Gravitational Waves And Gamma-Rays From A Binary Neutron Star Merger: Gw170817 And Grb 170817a, 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 2017 August 17, the gravitational-wave event GW170817 was observed by the Advanced LIGO and Virgo detectors, and the gamma-ray burst (GRB) GRB 170817A was observed independently by the Fermi Gamma-ray Burst Monitor, and the Anti-Coincidence Shield for the Spectrometer for the International Gamma-Ray Astrophysics Laboratory. The probability of the near-simultaneous temporal and spatial observation of GRB 170817A and GW170817 occurring by chance is $5.0\times {10}^{-8}$. We therefore confirm binary neutron star mergers as a progenitor of short GRBs. The association of GW170817 and GRB 170817A provides new insight into fundamental physics and the origin of short GRBs. We use …

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Multi-Messenger Observations Of A Binary Neutron Star Merger, 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, Michele Zanolin, Et Al. Oct 2017

Multi-Messenger Observations Of A Binary Neutron Star Merger, 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, Michele Zanolin, Et Al.

Publications

On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of $\sim 1.7\,{\rm{s}}$ with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of ${40}_{-8}^{+8}$ Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to …

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Knotty Inflation And The Dimensionality Of Spacetime, Arjun Berera, Roman V. Buniy, Thomas W. Kephart, Heinrich Päs, João G. Rosa Oct 2017

Knotty Inflation And The Dimensionality Of Spacetime, Arjun Berera, Roman V. Buniy, Thomas W. Kephart, Heinrich Päs, João G. Rosa

Mathematics, Physics, and Computer Science Faculty Articles and Research

We suggest a structure for the vacuum comprised of a network of tightly knotted/linked flux tubes formed in a QCD-like cosmological phase transition and show that such a network can drive cosmological inflation. As the network can be topologically stable only in three space dimensions, this scenario provides a dynamical explanation for the existence of exactly three large spatial dimensions in our Universe.

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Almost-Bps Solutions In Multi-Center Taub-Nut, C. Rugina, A. Ludu Oct 2017

Almost-Bps Solutions In Multi-Center Taub-Nut, C. Rugina, A. Ludu

Publications

Microstates of multiple collinear black holes embedded in a non-collinear two-center Taub-NUT spacetime are sought in 4 dimensions. A set of coupled partial differential equations are obtained and solved for almost-BPS states, where some supersymmetry is preserved in the context of N = 2 supergravity in 4 dimensions. The regularity of solutions is carefully considered, and we ensure that no CTC (closed time-like curves) are present. The larger framework is that of 11-dimensional N = 2 supergravity, and the current theory is obtained by compactifying it down to 4 dimensions. This work is a generalization (to three non-collinear centers) of …

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Upper Limits On Gravitational Waves From Scorpius X-1 From A Model-Based Cross-Correlation Search In Advanced Ligo Data, B. P. Abbott, K. Aultoneal, S. Gaudio, K. Gill, B. Hughey, J. W. W. Pratt, E. Schmidt, S. G. Schwalbe, M. J. Szczepańczyk, M. Zanolin, Et Al. Sep 2017

Upper Limits On Gravitational Waves From Scorpius X-1 From A Model-Based Cross-Correlation Search In Advanced Ligo Data, B. P. Abbott, K. Aultoneal, S. Gaudio, K. Gill, B. Hughey, J. W. W. Pratt, E. Schmidt, S. G. Schwalbe, M. J. Szczepańczyk, M. Zanolin, Et Al.

Publications

We present the results of a semicoherent search for continuous gravitational waves from the low-mass X-ray binary Scorpius X-1, using data from the first Advanced LIGO observing run. The search method uses details of the modeled, parametrized continuous signal to combine coherently data separated by less than a specified coherence time, which can be adjusted to trade off sensitivity against computational cost. A search was conducted over the frequency range 25–$2000\,\mathrm{Hz}$, spanning the current observationally constrained range of binary orbital parameters. No significant detection candidates were found, and frequency-dependent upper limits were set using a combination of sensitivity estimates and …

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Full Band All-Sky Search For Periodic Gravitational Waves In The O1 Ligo Data, 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. Sep 2017

Full Band All-Sky Search For Periodic Gravitational Waves In The O1 Ligo Data, 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

We report on an all-sky search for periodic gravitational waves in the frequency band 20–475 Hz and with a frequency time derivative in the range of [−1.0,+0.1]×10−8  Hz/s. Such a signal could be produced by a nearby spinning and slightly nonaxisymmetric isolated neutron star in our galaxy. This search uses the data from Advanced LIGO’s first observational run, O1. No periodic gravitational wave signals were observed, and upper limits were placed on their strengths. The lowest upper limits on worst-case (linearly polarized) strain amplitude h0 are ∼4×10−25 near 170 Hz. For a circularly polarized source (most favorable orientation), the smallest …

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Magnetospherically-Trapped Dust And A Possible Model For The Unusual Transits At Wd1145+017, J. Farihi, Ted Von Hippel, J. E. Pringle Aug 2017

Magnetospherically-Trapped Dust And A Possible Model For The Unusual Transits At Wd1145+017, J. Farihi, Ted Von Hippel, J. E. Pringle

Publications

The rapidly evolving dust and gas extinction observed towardsWD1145+017 has opened a real-time window onto the mechanisms for destruction-accretion of planetary bodies onto white dwarf stars, and has served to underline the importance of considering the dynamics of dust particles around such objects. Here it is argued that the interaction between (charged) dust grains and the stellar magnetic field is an important ingredient in understanding the physical distribution of infrared emitting particles in the vicinity of such white dwarfs. These ideas are used to suggest a possible model for WD 1145+017 in which the unusual transit shapes are caused by …

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Quantum Physics And Relativity In Lovecraft's Fiction, Garrison Mccammon Jul 2017

Quantum Physics And Relativity In Lovecraft's Fiction, Garrison Mccammon

English and Creative Writing Summer Fellows

The early twentieth century brought about some of the best and most influential horror or weird tales ever written in the English speaking world. The most impressive and most lauded author of the group composed of such figures as Algernon Blackwood, M. R. James, Arthur Machen, Clark A. Smith, and Robert E. Howard was H. P. Lovecraft. Posthumously declared the literary successor to Edgar Allan Poe, Lovecraft’s fiction and tales of terror have cast such a huge shadow that every significant author in weird writing since his passing has claimed him as a literary heir. Lovecraft’s works were a landmark …

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Magnetic Fields Threading Black Holes: Restrictions From General Relativity And Implications For Astrophysical Black Holes, David Garofalo Jun 2017

Magnetic Fields Threading Black Holes: Restrictions From General Relativity And Implications For Astrophysical Black Holes, David Garofalo

Faculty Articles

The idea that black hole spin is instrumental in the generation of powerful jets in active galactic nuclei and X-ray binaries is arguably the most contentious claim in black hole astrophysics. Because jets are thought to originate in the context of electromagnetism, and the modeling of Maxwell fields in curved spacetime around black holes is challenging, various approximations are made in numerical simulations that fall under the guise of ‘ideal magnetohydrodynamics’. But the simplifications of this framework may struggle to capture relevant details of real astrophysical environments near black holes. In this work, we highlight tension between analytic and numerical …

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Gw170104: Observation Of A 50-Solar-Mass Binary Black Hole Coalescence At Redshift 0.2, B. P. Abbott, K. Aultoneal, S. Gaudio, K. Gill, B. Hughey, J. W. W. Pratt, E. Schmidt, G. Schwalbe, M. J. Szczepańczyk, M. Zanolin, Et Al. Jun 2017

Gw170104: Observation Of A 50-Solar-Mass Binary Black Hole Coalescence At Redshift 0.2, B. P. Abbott, K. Aultoneal, S. Gaudio, K. Gill, B. Hughey, J. W. W. Pratt, E. Schmidt, G. Schwalbe, M. J. Szczepańczyk, M. Zanolin, Et Al.

Publications

We describe the observation of GW170104, a gravitational-wave signal produced by the coalescence of a pair of stellar-mass black holes. The signal was measured on January 4, 2017 at 10∶11:58.6 UTC by the twin advanced detectors of the Laser Interferometer Gravitational-Wave Observatory during their second observing run, with a network signal-to-noise ratio of 13 and a false alarm rate less than 1 in 70 000 years. The inferred component black hole masses are 31.2 þ8.4 −6.0M⊙ and 19.4 þ5.3 −5.9M⊙ (at the 90% credible level). The black hole spins are best constrained through measurement of the effective inspiral spin parameter, …

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Search For Gravitational Waves Associated With Gamma-Ray Bursts During The First Advanced Ligo Observing Run And Implications For The Origin Of Grb 150906b, B. P. Abbott, K. Gill, B. Hughey, J. W. W. Pratt, E. Rhoades, E. Schmidt, S. G. Schwalbe, M. J. Szczepańczyk, M. Zanolin, Et Al. Jun 2017

Search For Gravitational Waves Associated With Gamma-Ray Bursts During The First Advanced Ligo Observing Run And Implications For The Origin Of Grb 150906b, B. P. Abbott, K. Gill, B. Hughey, J. W. W. Pratt, E. Rhoades, E. Schmidt, S. G. Schwalbe, M. J. Szczepańczyk, M. Zanolin, Et Al.

Publications

We present the results of the search for gravitational waves (GWs) associated with γ-ray bursts detected during the first observing run of the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO). We find no evidence of a GW signal for any of the 41 γ-ray bursts for which LIGO data are available with sufficient duration. For all γ-ray bursts, we place lower bounds on the distance to the source using the optimistic assumption that GWs with an energy of ${10}^{-2}{M}_{\odot }{c}^{2}$ were emitted within the $16$–$500$ Hz band, and we find a median 90% confidence limit of 71 Mpc at 150 Hz. …

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Literature Review: Biomimetic And Conventional Aircraft Wing Tips, Naseeb Ahmed Siddiqui, Waqar Asrar, Erwin Sulaeman May 2017

Literature Review: Biomimetic And Conventional Aircraft Wing Tips, Naseeb Ahmed Siddiqui, Waqar Asrar, Erwin Sulaeman

International Journal of Aviation, Aeronautics, and Aerospace

This paper is an attempt to summarize the effect of wing tip devices employed by birds, as well as aeronautical engineers in the past to improve the performance characteristics of aircraft. The focus is on reduction of the induced drag or drag due to lift also known as inviscid drag. This paper will provide an insight on both biomimetic and conventional wing tip approaches to reduce the induced drag. Prior analysis and experiments on the aerodynamics of airplane performance due to both these separate studies have been discussed. The needs of the industry and their past inventions have been described …

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Fermi-Lat Daily Monitoring Observations Of The Microquasar Cygnus X-1, Austin P. Waldron, Stephen R. Hood, Arash Bodaghee Apr 2017

Fermi-Lat Daily Monitoring Observations Of The Microquasar Cygnus X-1, Austin P. Waldron, Stephen R. Hood, Arash Bodaghee

Georgia College Student Research Events

Detection of gamma-ray emission from microquasars is important for understanding particle acceleration in the jet, and for constraining leptonic/hadronic emission models. We present a continuation of a 1-d likelihood analysis on gamma-ray observations by Fermi-LAT (0.1-10 GeV) of the accreting black hole candidate Cygnus X-1. Combining this gamma-ray data with available X-ray monitoring data from Swift and MAXI allowed us to reveal over a dozen days (in 2008-2016) during which Cyg X-1 displayed low-significance (3-4 sigma) excesses, many of which were contemporaneous with apparent transitions in the X-rays.

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Lorentz-Symmetry Test At Planck-Scale Suppression With Nucleons In A Spin-Polarized 133 Cs Cold Atom Clock, H. Pihan-Le Bars, C. Guerlin, R.-D. Lasseri, J.-P. Ebran, Q. G. Bailey, S. Bize, E. Khan, P. Wolf Apr 2017

Lorentz-Symmetry Test At Planck-Scale Suppression With Nucleons In A Spin-Polarized 133 Cs Cold Atom Clock, H. Pihan-Le Bars, C. Guerlin, R.-D. Lasseri, J.-P. Ebran, Q. G. Bailey, S. Bize, E. Khan, P. Wolf

Publications

The authors introduce an improved model that links the frequency of the 133 Cs hyperfine Zeeman transitions.

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The Ages Of The Thin Disk, Thick Disk, And The Halo From Nearby White Dwarfs, Mukremin Kilic, Ted Von Hippel, Jeffrey A. Munn, Hugh C. Harris, James W. Liebert, Et Al. Feb 2017

The Ages Of The Thin Disk, Thick Disk, And The Halo From Nearby White Dwarfs, Mukremin Kilic, Ted Von Hippel, Jeffrey A. Munn, Hugh C. Harris, James W. Liebert, Et Al.

Publications

We present a detailed analysis of the white dwarf luminosity functions derived from the local 40 pc sample and the deep proper motion catalog of Munn et al. (2014, 2017). Many of the previous studies ignored the contribution of thick disk white dwarfs to the Galactic disk luminosity function, which results in an erronous age measurement. We demonstrate that the ratio of thick/thin disk white dwarfs is roughly 20% in the local sample. Simultaneously fitting for both disk components, we derive ages of 6.8-7.0 Gyr for the thin disk and 8.7 ± 0.1 Gyr for the thick disk from the …

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Sensitivity To A Frequency-Dependent Circular Polarization In An Isotropic Stochastic Gravitational Wave Background, Tristan L. Smith, Robert Caldwell Feb 2017

Sensitivity To A Frequency-Dependent Circular Polarization In An Isotropic Stochastic Gravitational Wave Background, Tristan L. Smith, Robert Caldwell

Dartmouth Scholarship

We calculate the sensitivity to a circular polarization of an isotropic stochastic gravitational wave background (ISGWB) as a function of frequency for ground- and space-based interferometers and observations of the cosmic microwave background. The origin of a circularly polarized ISGWB may be due to exotic primordial physics (i.e., parity violation in the early universe) and may be strongly frequency dependent. We present calculations within a coherent framework which clarifies the basic requirements for sensitivity to circular polarization, in distinction from previous work which focused on each of these techniques separately. We find that the addition of an interferometer with the …

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The Extinction Properties Of And Distance To The Highly Reddened Type Ia Supernova Sn 2012cu, Xiaosheng Huang, Z. Raha, G. Aldering, P. Antilogus, S. Bailey, C. Baltay, K. Barbary, D. Baugh, K. Boone, S. Bongard, C. Buton, J. Chen, N. Chotard, Y. Copin, P. Fagrelius, H. K. Fakhouri, U. Feindt, D. Fouchez, E. Gangler, B. Hayden, W. Hillebrandt, A. G. Kim, M. Kowalski, P. F. Leget, S. Lombardo, J. Nordin, R. Pain, E. Pecontal, R. Pereira, S. Perlmutter, D. Rabinowitz, M. Rigault, D. Rubin, K. Runge, C. Saunders, G. Smadja, C. Sofiatti, A. Stocker, N. Suzuki, S. Taubenberger, C. Tao, R. C. Thomas Feb 2017

The Extinction Properties Of And Distance To The Highly Reddened Type Ia Supernova Sn 2012cu, Xiaosheng Huang, Z. Raha, G. Aldering, P. Antilogus, S. Bailey, C. Baltay, K. Barbary, D. Baugh, K. Boone, S. Bongard, C. Buton, J. Chen, N. Chotard, Y. Copin, P. Fagrelius, H. K. Fakhouri, U. Feindt, D. Fouchez, E. Gangler, B. Hayden, W. Hillebrandt, A. G. Kim, M. Kowalski, P. F. Leget, S. Lombardo, J. Nordin, R. Pain, E. Pecontal, R. Pereira, S. Perlmutter, D. Rabinowitz, M. Rigault, D. Rubin, K. Runge, C. Saunders, G. Smadja, C. Sofiatti, A. Stocker, N. Suzuki, S. Taubenberger, C. Tao, R. C. Thomas

Physics and Astronomy

Correcting Type Ia Supernova brightnesses for extinction by dust has proven to be a vexing problem. Here we study the dust foreground to the highly reddened SN 2012cu, which is projected onto a dust lane in the galaxy NGC 4772. The analysis is based on multi-epoch, spectrophotometric observations spanning from 3300–9200 Å, obtained by the Nearby Supernova Factory. Phase-matched comparison of the spectroscopically twinned SN 2012cu and SN 2011fe across 10 epochs results in the best-fit color excess of (, RMS) = (1.00, 0.03) and total-to-selective extinction ratio of (R V , RMS) = (2.95, 0.08) toward SN 2012cu …

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Testing Atomic Collision Theory With The Two-Photon Continuum Of Astrophysical Nebulae, Francisco Guzmán, N. R. Badnell, Marios Chatzikos, P. A. M. Van Hoof, R. J. R. Williams, Gary J. Ferland Feb 2017

Testing Atomic Collision Theory With The Two-Photon Continuum Of Astrophysical Nebulae, Francisco Guzmán, N. R. Badnell, Marios Chatzikos, P. A. M. Van Hoof, R. J. R. Williams, Gary J. Ferland

Physics and Astronomy Faculty Publications

Accurate rates for energy-degenerate l-changing collisions are needed to determine cosmological abundances and recombination. There are now several competing theories for the treatment of this process, and it is not possible to test these experimentally. We show that the H i two-photon continuum produced by astrophysical nebulae is strongly affected by l-changing collisions. We perform an analysis of the different underlying atomic processes and simulate the recombination and two-photon spectrum of a nebula containing H and He. We provide an extended set of effective recombination coefficients and updated l-changing 2s − 2p transition rates using …

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Edgar Allan Poe’S Cosmology And Natural Theology: A Constructive Postmodern Appreciation, Theodore Walker Jan 2017

Edgar Allan Poe’S Cosmology And Natural Theology: A Constructive Postmodern Appreciation, Theodore Walker

Perkins Faculty Research and Special Events

Contrary to some literary classifications, Edgar Allan Poe’s book-length prose poem Eureka is not intended to be fiction. In Eureka Poe was seriously attempting to advance ‘truth’ about the universe. Poe was doing natural science and poetry in the tradition of Samuel Taylor Coleridge and other natural philosophers. Poe’s prose poem is natural scientific astronomy and cosmology, plus natural theology, not science fiction.

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Hubble Parameter Measurement Constraints On The Redshift Of The Deceleration-Acceleration Transition, Dynamical Dark Energy, And Space Curvature, Muhammad O. Farooq, Foram R. Madiyar, Sara Crandall, Bharat Ratra Jan 2017

Hubble Parameter Measurement Constraints On The Redshift Of The Deceleration-Acceleration Transition, Dynamical Dark Energy, And Space Curvature, Muhammad O. Farooq, Foram R. 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 …

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Perihelion Precession In The General Theory Of Relativity, Charles G. Torre Jan 2017

Perihelion Precession In The General Theory Of Relativity, Charles G. Torre

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This is a relatively quick and informal sketch of a demonstration that general relativistic corrections to the bound Kepler orbits introduce a perihelion precession. Any decent textbook on the general theory of relativity will derive this result. My analysis aligns with that found in the good old text "Introduction to General Relativity", by Adler, Bazin and Schiffer.

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