Had I special: The Astronomical Contributions of the Herschel Family




НазваниеHad I special: The Astronomical Contributions of the Herschel Family
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"These Frenchmen fly at one like wild cats": The French Press Attacks on British Claims for a Role in the Discovery of Neptune

Craig B. Waff1
1Air Force Research Laboratory.

5:00 PM - 5:20 PM

Room 613/614

In a letter to the editor of the Athenaeum (a weekly British intellectual periodical) that appeared in its 3 October 1846 issue, John Herschel revealed that a young Cambridge fellow, John Couch Adams, had performed calculations, as yet not published or otherwise publicly announced, that were similar to those made by Urbain Jean Joseph Le Verrier in predicting a position for a hypothetical planet disturbing the motion of Uranus. As is well known, a plea from Le Verrier led Johann Gottfried Galle to search for and optically discover, on 23 September 1846, a transuranian object near Le Verrier’s predicted position. Shortly after the appearance of Herschel’s letter, he and Adams, as well as Cambridge Observatory director James Challis and Astronomer Royal George Airy, became the targets of an intense month-long public attack by various Parisian newspapers and magazines, which perceived a British attempt to “steal” the discovery of the new planet, soon to be named Neptune. It was this attack that led to the despairing comment in Herschel’s diary that appears in the title of my talk. Although this attack has been frequently mentioned by commentators on the controversies surrounding the discovery of Neptune, the actual French publications have virtually never been examined in detail. An analysis of some of these articles, as well as British responses to them, is presented here.

The Neptune Affair: American Mathematicians Find the World Stage

Deborah Kent1
1Hillsdale College.

5:20 PM - 5:40 PM

Room 613/614

The sensational news of Neptune’s observation reached the United States about a month after the initial sighting at the Berlin observatory on 23 September 1846. The ensuing dispute over the priority of discovery captured both popular interest and scientific attention in America. A handful of ambitious scientists viewed the Neptune affair as an opportunity to establish the legitimacy of American science, especially in response to the perceived superiority of European science. This talk will focus on the role of Harvard mathematician Benjamin Peirce in questioning the mathematical particulars of the discovery and shaping related rhetoric to advance the professionalization of American science.

A Clear Yet Distant Echo: Modern-day Analogues of the Scientific Interest and Controversies Surrounding the Discovery of Neptune

Greg Laughlin1, M. Brown2
1UC Santa Cruz, 2Caltech.

5:40 PM - 6:00 PM

Room 613/614

Our understanding of the solar system and the physical Universe has progressed almost immeasurably during the 164.79 years that constitute an orbit of Neptune. Nevertheless, the drama surrounding the discovery of Neptune still resonates with an immediacy that is both completely relevant and entirely up to date. In this talk, we will argue that the central themes surrounding Neptune's discovery (including issues of priority, improvements in observational and theoretical technique, and the nature of what constitutes an acceptably specific scientific prediction) all have readily evident analogues in the planet-hunting and solar system discovery efforts that are being carried out today. To support our arguments, we will make specific connections to (1) the ongoing effort to map and characterize the solar system's trans-Neptunian inventory, and (2) the search for extrasolar planets orbiting nearby stars.

Monday, January 10, 2011, 8:30 AM - 9:20 AM

101

Kavli Lecture: Cassini Eyes the Rings of Saturn

Invited Session

Ballroom 6AB

101.01

Cassini Eyes the Rings of Saturn

Carolyn C. Porco1
1CICLOPS, Space Science Institute.

Ballroom 6AB

For the past 6.5 years, NASA's Cassini spacecraft has been in orbit around the planet Saturn. In that time, Saturn has journeyed from the height of southern summer through early northern spring, allowing ample opportunity to observe changes in the planet's rings under a variety of lighting and viewing conditions. This presentation will highlight some of Cassini's most significant discoveries in this disk of icy rubble, emphasizing the connection between Saturn's rings and other astrophysical disk systems, such as protoplanetary disks and the giant spiral galaxies.

Monday, January 10, 2011, 9:00 AM - 6:30 PM

139

NANOGrav Posters

Poster Session

Exhibit Hall

139.01

Using Cyclic Spectroscopy of Pulsars to Correct for Interstellar Propagation Delay

Dan Stinebring1, A. Spatzier1, J. Nelson1, S. Giri1, C. Haddad1, K. Kundert1, M. Larkin1, J. N. Nelson1
1Oberlin College.

Exhibit Hall

Recently, Demorest et al. (2010) have demonstrated that, for pulsar observations, the phase of the e-m wave can be determined through a technique called cyclic spectroscopy. This is a major advance in high precision pulsar timing. We report on studies of how cyclic spectroscopy can be used to correct for interstellar propagation delays down to the 100 ns level. Substantial observing time on large telescopes will be necessary to put this important technique into practice.

139.02

Pulsar Phase Jitter and Cyclic Spectroscopy Derived Arrival Times

Nipuni Palliyaguru1, M. McLaughlin1, D. Stinebring2
1West Virginia University, 2Oberlin College.

Exhibit Hall

In searching for gravitational waves with high-precision pulsar timing, we have analyzed the possibility of applying the method of cyclic spectroscopy (CS) to correct for the arrival time fluctuations of the signals. The main causes of these delays are interstellar medium effects such as electron density variations and multi-path scattering, timing noise, pulse shape changes, and pulse-to-pulse jitter. These phenomena affect the electromagnetic wave of the pulsar in both amplitude and phase. The CS method, developed recently by Demorest and collaborators (2010), takes into account the observed voltage signal of the pulsar in the frequency domain and computes a stable, integrable quantity. This quantity can, in principle, be used to determine the impulse response of the system, q(t). Determining q(t) at several observing frequencies should allow frequency dependent effects to be separated from achromatic effects. We have used simulated data assuming the observed signal to be a convolution of the intrinsic pulsar signal and q(t), with additive noise and phase jitter included. We can reconstruct the impulse response function from the simulated data and find an estimate of q(t). When done at several frequencies this allows an estimate for the true delay of the signal. We present the results of these simulations, focusing attention on the effects of pulse phase jitter.

139.03

Progress Towards a Pipeline for Continuous Gravitational Wave Searches in Pulsar Timing Data

Justin Ellis1, F. Jenet2, M. McLaughlin1
1West Virginia University, 2University of Texas Brownsville.

Exhibit Hall

Gravitational Waves (GWs) are tiny ripples in the fabric of space-time predicted by Einstein’s General Relativity. Pulsar timing arrays (PTAs) are well poised to detect low frequency (10-9 - 10-7 Hz) GWs in the near future. There has been a significant amount of research into the detection of a stochastic background of GWs from supermassive black hole binaries (SMBHBs). Recent work (Sesana et al 2010) has shown that single continuous sources standing out above the background may be detectable by PTAs operating at a sensitivity sufficient to detect the stochastic background. The main source of continuous GWs in the pulsar timing frequency band are extremely massive and/or nearby SMBHs. Here we present progress towards a fully functional pipeline for continuous GW searches in pulsar timing data. This pipeline is based on a frequentist approach that relies on a matched filtering search of constructed template banks. We present methods for determining the optimal grid size in template space that maximizes the likelihood of detection and characterization of a given GW source. We also report progress on implementation of this pipeline into the TEMPO2 pulsar timing software package, in which the gravitational wave signal will be fit for in the pulsar timing residuals using a least squares fitting routine. This pipeline is versatile in that it can also be used for binary system parameter estimation and upper limit calculations on possible sources.

139.04

Optimizing a Pulsar Timing Array

Ryan Shannon1, J. Cordes1
1Cornell Univ..

Exhibit Hall

Nanohertz gravitational radiation can be detected through the long term analysis of pulse arrival times from a set of millisecond pulsars (a pulsar timing array). The sources of this emission include inspiraling massive black hole binaries and cosmic strings.
Here, we assess the sensitivity of pulsar timing arrays to gravitational waves in the presence of a diverse range of noise sources both intrinsic and extrinsic to the pulsar.
Noise sources intrinsic to the pulsar include terms associated with pulsar rotational irregularities (timing noise) and jitter of the radio emission region. Extrinsic noise includes terms associated with reflex motion of the pulsar about unmodeled circumpulsar asteroid belts and propagation of the pulsar radio emission through turbulent plasma in the interstellar medium. We describe the amenability of these noise sources to various mitigation techniques, such as observing with higher sensitivity telescopes and multi-frequency time of arrival fitting.
We find that observations of more pulsars, observed with higher throughput (longer integrations times or faster observing cadences) are required to make a significant detection of gravitational radiation at cosmological levels and perform subsequent characterization of gravitational wave emitting sources. From this we conclude that pulsar timing is optimally conducted by using telescopes with a range of collecting areas, which can be achieved through coordinated global efforts utilizing current telescopes or a large array-based telescope.

139.05

Precision Millisecond Pulsar Timing: Space Velocities and Equivalence Principles

Ingrid H. Stairs1, M. E. Gonzalez1, R. D. Ferdman2, P. C. C. Freire3, D. J. Nice4, P. B. Demorest5, S. M. Ransom5, R. N. Manchester6, G. B. Hobbs6, A. G. Lyne2, M. Kramer3, F. Camilo7
1Univ. of BC, Canada, 2University of Manchester, United Kingdom, 3MPIfR, Germany, 4Lafayette College, 5NRAO, 6CASS, Australia, 7Columbia University.

Exhibit Hall

We present high-precision timing results for 5 millisecond pulsars (MSPs), using data acquired with the Parkes and Arecibo telescopes. We measure the proper motion for each pulsar, infer 2-D space velocities, and update velocity distribution investigations of the MSP population, finding that binary and isolated MSPs have indistinguishable velocity distributions. We constrain binary inclination angles and hence masses for 2 of the pulsars in our sample. We use all the known wide-orbit pulsar--white-dwarf binaries to update previous limits on violation of the Strong Equivalence Principle and on a parameter describing violation of Lorentz invariance and momentum
conservation.

139.06

High Precision Timing of Millisecond Pulsars at Arecibo and Green Bank

David J. Nice1, P. B. Demorest2, M. E. Gonzalez3, R. D. Ferdman4, S. M. Ransom2, I. H. Stairs3, NANOGrav
1Lafayette College, 2NRAO, 3UBC, Canada, 4University of Manchester, United Kingdom.

Exhibit Hall

The NANOGrav consortium uses Arecibo and the GBT to make high-precision timing observations of twenty millisecond pulsars. All sources are observed at two frequencies using software coherent dedispersion systems. This program is motivated both by the search for a gravitational wave background and more traditional pulsar timing applications such as measuring binary orbits to test theories of gravitation and to measure neutron star masses. We will discuss the observing program and data analysis, and we will give highlights from the last five years of observations.

139.07

Characterizing the Radio Frequency Timing Stability of Fast and Millisecond Pulsars

Isabel Mette Kloumann1, J. M. Rankin1
1University of Vermont.

Exhibit Hall

We propose measuring the average profile stabilization rate in millisecond pulsars. We consider the correlations between a pulsar's global average profile and subaverage profiles constructed using increasing numbers of pulses, thereby quantifying the number of pulses required to build a stable average profile. We adopt the methodology developed by Helfand, Manchester, and Taylor (Ap. J., 1975) and later employed by Rathnasree & Rankin (Ap. J., 1995) to calculate the stabilization rates of a sample of both fast and millisecond pulsars. A correlation coefficient is obtained by averaging the correlation coefficients of the global average profile with each subaverage profile of n pulses. By plotting how the correlation coefficient increases with n one can observe how the star's profile stabilizes as the number of pulses used to construct it increases. We look for values of n for which the correlation coefficient is statistically significant and interpret this value as the number of pulses required to compute a stable average profile of a given star. We expect n to be smaller for millisecond pulsars, as they typically exhibit very few intrinsic variations. This work considers the stars studied by Rathnasree & Rankin, as well as millisecond pulsars that are of interest to the pulsar timing community and in particular the NANOGrav (North American Nanohertz Observatory for Gravitational Waves) initiative. The authors would like to acknowledge support from the US National Science Foundation.

139.08

ARCC@UWM: The Arecibo Remote Command Center at the University of Wisconsin--Milwaukee

Xavier Siemens1, C. Biwer1, J. Clayton1, J. Creighton1, D. Day1, D. Erb1, K. Gustavson2, F. Jenet3, D. Kaplan1, R. Karr1, M. Rohr1, K. Stovall3
1University of Wisconsin -- Milwaukee, 2Nicolet High School, 3University of Texas Brownsville.

Exhibit Hall

A low frequency stochastic background of gravitational waves could be detected by pulsar timing experiments in the next five to ten years. Increasing the number of time of arrival data sets available for gravitational wave searches will improve the sensitivity of a pulsar based gravitational wave detector. To achieve this goal, a group of faculty, staff, postdoctoral researchers, and a graduate student at the University of Wisconsin--Milwaukee are participating in a broad effort to increase the number of known stable pulsars collecting and analyzing the pulsar Arecibo L-band Feed Array (P-ALFA) survey data, and the Green Bank Northern Celestial Cap survey data. We have followed the pioneering model started at the University of Texas-Brownsville (UTB) to involve undergraduate and high school students in this research. In close collaboration with the group at UTB we have engaged two local high school teachers, several high school students, and about 15 UWM undergraduates in remotely commanding and observing using the Arecibo radio telescope and the Green Bank telescope, in searches in the collected data for new candidate pulsars, and follow-up observations of of potential pulsar candidates. In addition, the group is using its expertise in LIGO data analysis to improve gravitational wave searches in pulsar timing data.

140

Kepler Posters

Poster Session

Exhibit Hall

140.01
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