Aavso paper Session I sunday Sunday, May 22, 2011, 9: 30 am – 12: 00 pm

High Energy, Cosmology and Other Topics

Poster Session

Essex Ballroom

410.01

8:00 AM - 12:00 PM

Calculations of the orbits of galaxies in and around the Local Group constrained by their redshifts, TRGB high quality distances, and the measurements of proper motions of M33 and IC10 are shown. Description is given of a powerful new technique that uses N-body calculations running backwards in time (constrained by present positions and velocities) in conjunction with Peebles' Numerical Action Method that ensures early time motions are consistent with linear growth models.

410.02

Chasing a WHIM: The Changing Picture of an Important Baryon Reservoir

Lara A. Phillips¹, A. Snedden^1
1University of Notre Dame.

8:00 AM - 12:00 PM

Baryons hidden in the cosmic web, and in particular in the warm/hot intergalactic medium (WHIM,) may help solve the missing baryon problem.  Increasingly detections of intergalactic OVI absorption features in quasar spectra are coupled with follow-up galaxy redshift surveys of the absorber neighborhood. The availability and analysis of these systems, the prospect of new high-resolution low-energy X-ray spectroscopic observations of the cosmic web, as well as higher resolution large scale simulations which include the effects of galactic superwind feedback and non-equilibrium ionization, compel us to revisit the theoretical picture of the baryons in the cosmic web. We use a modified computer vision algorithm to identify and extract structures in large-scale simulations (clusters, filaments, voids.) We present the redshift history and structure dependence of the temperature-density distribution of the intergalactic medium (IGM). Our understanding of the physical properties and extent of IGM structures is enhanced by progressing beyond a threshold-based definition of the components of the IGM and leads to a clearer interpretation of their role in the evolution of galaxies and of their signature in current and future observations.

410.03

Spherical accretion with modified dynamics

Nirupam Roy^1
1National Radio Astronomy Observatory.

8:00 AM - 12:00 PM

The MOdified Newtonian Dynamics (MOND) is one alternative to the dark matter assumption that can explain the observed flat rotation curve of galaxies. Here, spherically symmetrical hydrodynamic accretion in MOND regime is considered to critically check the consistency, and to constrain the physical interpretation of this theory. The modified Euler's equation has physical solution for modification of the law of dynamics, but has no solution for an acceleration-scale-dependent modification of the gravitational law. The astrophysical and cosmological implications of these results, pointing out a potential incompleteness of MOND, are presented in this work.

410.04

How The Expansion Rate Evolves: The Role Of Dark Energy, Textures, And Curvature

Jeremy R. Mould¹, B. Schmidt^2
1Swinburne University, Australia, ²Australian National University, Australia.

8:00 AM - 12:00 PM

From a luminosity distance observer’s viewpoint, the evolution of the square of the expansion rate H(z)/H₀ can be fit by a polynomial expansion ΣΩ_na^-n. Two of the first five coefficients, Ω₃ and Ω₄ are associated with matter and radiation. But the other three are physically more obscure: Ω₀ is dark energy; Ω₂ is called curvature; textures can be associated with Ω₁. A strong constraint on the overall sum, ΣΩ_n, is that it is unity, observationally from the cosmic microwave background, and theoretically because the horizon problem demands inflation. Cosmic density observations suggest Ω₃ ~ 0.27. However, supernova observations are agnostic as to the distribution of 1-Ω₃ over Ω₀, Ω₁ and Ω₂ provided Ω₀ > 0.5 approximately. Baryonic Acoustic Oscillation observations at z ~ 2 and the Dark Energy Survey will be more selective. In summary, one may introduce two additional parameters into the concordance cosmology, which are analytically, rather than physically, motivated. They can be measured via experiments outlined here. Observationally, textures and curvature may be ruled out, but only by future experiments.

410.05

8:00 AM - 12:00 PM

We are using the Green Bank Telescope to make 21-cm intensity maps of cosmic structure in a 0.15 Gpc^3 box at redshift of z~1. The intensity mapping technique combines the flux from many galaxies in each pixel, allowing much greater mapping speed than the traditional redshift survey. Measurement is being made at z~1 to take advantage of a window in frequency around 700 MHz where terrestrial radio frequency interference (RFI) is currently at a minimum. This minimum is due to a reallocation of this frequency band from analog television to wide area wireless internet and public service usage. We will report progress of our attempt to detect autocorrelation of the 21-cm signal. The ultimate goal of this mapping is to use Baryon Acoustic Oscillations to provide more precise constraints to dark energy models.

410.06

Pathfinder for a HI Dark Energy Survey

Kevin Bandura¹, Cylindrical Radio Telescope Team
¹Carnegie Mellon.

8:00 AM - 12:00 PM

The 21cm Hydrogen spin flip transition has great potential to constrain the standard model of cosmology. A standard galaxy survey requires high resolution and sensitivity to identify individual galaxies. Instead using 21-cm emission, a low-resolution intensity mapping technique that resolves only large-scale linear cosmic structure will be much more efficient.

410.07

8:00 AM - 12:00 PM

Between 2005 and 2010, the LIGO gravitational wave detectors collected two and a half years of data at the strain sensitivity predicted by their original design. In October of 2010, the three detectors were decommissioned and are now offline undergoing a major upgrade; the first interferometer is scheduled to see ``first light'' in 2013, and all three by the end of 2014. The advanced detectors, collectively dubbed Advanced LIGO, will implement improvements on many opto-mechanical fronts in order to achieve the designed strain sensitivity: a factor of 10 improvement in the most sensitive frequency band and above, and by many orders of magnitude in lower third of the detectors' bandwidth. When the designed sensitivity is achieved, the astrophysical range out to which each detector would see an optimally-oriented, binary neutron-star system will increase from 35 Mpc to 0.45 Gpc, increasing the expected observation rate from 0.02 to 40 per year. We present a debriefing of the initial design, introduce the details of the upgraded design, and show construction progress thus far.

410.08

Searches for Gravitational Waves from Compact Binary Coalescence with the LIGO and Virgo detectors.

Ruslan Vaulin¹, LIGO and Virgo Scientific Collaboration
¹MIT.

8:00 AM - 12:00 PM

Coalescence of spiraling binary neutron stars or black holes are among the most likely and, at the same time, the most interesting sources of gravitational waves detectable by the ground based interferometers. If detected, these signals would not only represent another triumph of general relativity that predicted them, but also are expected to provide invaluable information about the strong field regime of gravity and the astrophysical properties of such systems/objects. We present an overview of the searches for these signals in the data recorded by LIGO-Virgo network of ground based interferometers. We discuss the specifics and the challenges arising in the data analysis and highlight some of the most recent results. We conclude with the outlook in the future -- in the era of advanced ground based interferometers, in which the low latency searches for gravitational waves from compact binary coalescence paired up with the rapid followup observations by optical, X-ray and radio telescopes become a reality and open the field of gravitational-wave, multi-messenger astronomy.

410.09

Searches for Gravitational-wave Bursts

Erotokritos Katsavounidis¹, LIGO Scientific Collaboration and Virgo Collaboration
¹MIT.

8:00 AM - 12:00 PM

The km-scale laser interferometers LIGO and Virgo completed in 2010 their joint running in their first generation configurations. Several searches were performed including ones for gravitational-wave un-modeled transients of unknown origin (all-sky) as well as associated with Gamma Ray Bursts (GRBs), Soft Gamma Repeaters (SGRs) and neutron star glitches. In this presentation we survey the searches performed and discuss their interpretation in terms of upper limits.

410.10

8:00 AM - 12:00 PM

In the 2009-2010 science run of the LIGO and Virgo instruments, low-latency searches for gravitational-wave transients were implemented. Such searches allowed prompt identification and sky localization of gravitational-wave candidates that may originate from highly energetic astrophysical events like core-collapse supernovae and compact-binary mergers. Starting from these low-latency searches we have implemented for the first time in LIGO-Virgo an electromagnetic follow-up program of gravitational-wave candidate events. This program aims to search for electromagnetic counterparts to gravitational-wave sources by pointing promptly to candidate source locations with ground-based wide-field optical telescopes and the Swift X-ray satellite. The program's role in providing confidence in the first detection and understanding the source astrophysics is expected to be significant. We describe the challenges we have addressed, the overall implementation of the low-latency search for transients, and the current status of this program. We also discuss its prospects when LIGO and Virgo return to coincidence running in the advanced detector regime in ~2015.

410.11

8:00 AM - 12:00 PM

We present age constraints on 13 X-ray binaries located within the drop-through ring galaxy NGC 922. Star-formation is ongoing within NGC 922 as a result of a shock-wave propagating through the galaxy, caused by a collision between NGC 922 and a neighbouring dwarf galaxy ~ 330 Myrs ago. The majority of the sources are associated with the ongoing star-formation, which is occurring in both a ring close to the edge of the galaxy, and in a region close to the galactic nucleus. By estimating the ages of clusters associated with these sources, we find that those associated with star-formation are no more than 10 Myrs old. Those that are not associated with star-formation have age constraints much higher than this. The X-ray spectral characteristics of the binaries vary from one to the next. We see that both the older sources and the sources located within the star-forming ring have highly absorbed spectra, unlike the more central sources, whose spectra display low levels of absorption.

410.12

A New High-precision Relativistic Many-body Method For Predicting Dielectronic Recombination Resonances In Low-energy Cosmic Plasmas

Andrei Derevianko¹, V. A. Dzuba², M. G. Kozlov^3
1University of Nevada, ²University of New South Wales, Australia, ³Petersburg Nuclear Physics Institute, Russian Federation.

8:00 AM - 12:00 PM

Reliable ionization balance calculations are central for analyzing cosmic spectra, in particular in deriving elemental abundances. One of the important atomic processes governing ionic charge abundances in plasmas is dielectronic recombination (DR).

410.13

8:00 AM - 12:00 PM

Over the past few decades, the symbiotic binary CH Cyg, in which a white dwarf accretes from the wind of a red giant companion star, has produced several spacially resolvable jets in radio, X-ray, and optical. Often, this jet production has been associated with changes in the optical brightness. This change may be caused by changes in the state of the accretion disk, as with accretion for young stellar objects or X-ray binaries, and could be evidence for a larger connection between the state of the accretion disk and the presence of a jet. After a major optical decline in late 2006, we carried out a series of VLA multi-band observations for over a year. We obtained multiple images of a developing jet with a large component to the southwest of the unresolved central binary, and tracked the changes in flux density and spectral index. The flux density rose between March and July of 2007, after which there was a steady decline lasting at least until August 2008. While the spectral index remained fairly constant during this period, the jet spectrum rose with frequency and flattened at higher frequencies, and there is some indication that the plasma may be close to optically thin. The timing of the increases in the flux density suggests a connection between the jet event and the optical decline. We discuss the implications of our results regarding the nature of the jet ejection, the velocity of its expansion, and possible constraints for the amount of mass ejected.

410.14

The Anatomy of Major Radio/X-ray Flares in the Enigmatic Microquasar Cygnus X-3

Karri Kolojonen¹, M. McCollough², D. Hannikainen¹, G. Pooley³, S. Trushkin⁴, M. Tavani⁵, R. Droulans^6
1Aalto University Metsahovi Radio Observatory, Finland, ²Smithsonian Astrophysical Observatory, ³Astrophysics Group, Cavendish Laboratory, United Kingdom, ⁴Special Astrophysical Observatory RAS, Russian Federation, ⁵INAF-IASF, Italy, ⁶CESR/CNRS, France.

8:00 AM - 12:00 PM

Cygnus X-3 exhibits major radio flares/jet ejection events like no other microquasar with radio flux densities up to 20 Jy. During these major flares Cygnus X-3 displays a variety of phenomena across the electromagnetic spectrum including specific temporal properties such as gamma-ray flares observed before the onset of major radio flare to quasi-periodic oscillations observed during the major radio flare decay. Here we try to form a more unified picture of the nature of these jet ejection events by dissecting the multiwavelength observations with a view to examining the emission processes from the components of the system: the disk, the corona and the jet.

410.15

The Connection Between X-ray Binaries and Star Clusters in the Antennae

Blagoy Rangelov¹, R. Chandar¹, A. Prestwich^2
1The University of Toledo, ²Harvard-Smithsonian Center for Astrophysics.

8:00 AM - 12:00 PM

High Mass X-ray Binaries (HMXBs) are believed to form in massive, compact star clusters. However the correlation between these young binary star systems and properties of their parent clusters are still poorly known. We compare the locations of 82 X-ray binaries detected in the merging Antennae galaxies by Zezas et al. (2006) based on observations taken with the Chandra Space Telescope, with a catalog of optically selected star clusters presented recently by Whitmore et al. (2010) based on observations taken with the Hubble Space Telescope. We find 22 X-ray binaries coincident or nearly coincident with star clusters. The ages of the clusters were estimated by comparing their UBVIH_α colors with predictions from stellar evolutionary models. We find that 14 of the 22 coincident sources (64%) are hosted by star clusters with ages of ~ 6 Myr or less. At these very young ages, only stars initially more massive than M ≥ 30 M_sun have evolved into compact remnants, almost certainly black holes. Therefore, these 14 sources are likely to be black hole binaries. Five of the XRBs are hosted by young clusters with ages τ ~ 30-50 Myr, while three are hosted by intermediate age clusters with τ ~ 100-300 Myr. We suggest that these older X-ray binaries likely have neutron stars as the compact object. We conclude that precision age-dating of star clusters, which are spatially coincident with XRBs in nearby star forming galaxies, is a powerful method of constraining the nature of the XRBs.

410.16

8:00 AM - 12:00 PM

We present Far UV data of close, massive binary stars observed by FUSE. The target sample includes detached and semi-detached systems that are at pre and post Roche lobe overflow evolutionary stages. The binaries are generally double-line spectroscopic binaries, many are eclipsing systems, with well-determined orbits and periods in the range 1.6 - 12 days. The far-UV spectra are being used to determine stellar wind mass loss rates and terminal velocities from species tracing a range of wind ionization states. The spectral features are being modelled to study photospheric abundances and evidence for CNO enhancements as the result of mass transfer. We searched for spectroscopic evidence of mass transfer and wind-wind collision effects. Some of the systems are observed more than once to sample different orbital phases and spectral variability. The ISM properties of the sight lines are also being analyzed.

410.17

The Extreme Spin of the Black Hole Cygnus X-1

Lijun Gou¹, J. McClintock¹, M. Reid¹, J. Orosz², J. Steiner¹, R. Narayan¹, J. Xiang¹, R. Remillard³, K. Arnaud⁴, S. Davis^5
1Harvard-Smithosian Center for Astrophysics, ²San Diego State University, ³Kavli Institute for Astrophysics and Space Research, MIT, ⁴NASA Goddard Space Flight Center, ⁵CITA, University of Toronto, Canada.

8:00 AM - 12:00 PM

Cygnus X-1 was the first black hole to be established via dynamical observations. There exist thousands of archival X-ray spectra of this source. Remarkably, however, only one of them is suitable for the measurement of spin via the continuum-fitting method that we employ. In July 2010, the source entered its rare soft state, thereby allowing us to obtain two more such spectra by making simultaneous observations with Chandra and RXTE. In other work, we have determined the source distance, black hole mass and orbital inclination angle. Inputting our accurate values of these three essential parameters, we fitted our X-ray spectra to the relativistic accretion-disk model of Novikov and Thorne and determined that Cygnus X-1 is a near-extreme Kerr black hole.

411

Education

Poster Session

Essex Ballroom

411.01
Short-course Astronomical Research Seminars for High School and College Students

Jolyon Johnson^1
1California State University, Chico.

8:00 AM - 12:00 PM

Essex Ballroom

Since 2008, I have helped lead several short-course astronomical research seminars with Russell M. Genet. These seminars have ranged from semester-long courses at Cuesta College in San Luis Obispo, California to long weekends at the University of Oregon's Pine Mountain Observatory. Each seminar is led by an experienced observer or group of observers who guide high school and college students through the scientific process from observations to publication. The students (anywhere from half a dozen to twenty in number) participate in and contribute to every step. Being a coauthor on one or more research papers offers students an advantage on college and scholarship applications. Similarly, graduate schools often prefer students with research experience. Many topics of research are appropriate for these short-courses including variable star, exoplanet, and asteroid photometry. However, the most successful topic has been visual double stars because the observations required are straitforward and the equipment is relatively inexpensive. The Journal of Double Star Observations is also welcoming of student research and provides swift publication. A detailed description of the short-course seminars can be found in the recent Collins Foundation Press volume titled Small Telescopes and Astronomical Research.

411.02

The Solar System Ballet: A Kinesthetic Spatial Astronomy Activity

Inge Heyer¹, T. F. Slater¹, S. J. Slater², Center for Astronomy & Physics Education ResearchCAPER
¹University of Wyoming, ²Center for Astronomy & Physics Education Research CAPER.

8:00 AM - 12:00 PM

Essex Ballroom

The Solar System Ballet was developed in order for students of all ages to learn about the planets, their motions, their distances, and their individual characteristics. To teach people about the structure of our Solar System can be revealing and rewarding, for students and teachers. Little ones (and some bigger ones, too) often cannot yet grasp theoretical and spatial ideas purely with their minds. Showing a video is better, but being able to learn with their bodies, essentially being what they learn about, will help them understand and remember difficult concepts much more easily. There are three segments to this activity, which can be done together or separately, depending on time limits and age of the students. Part one involves a short introductory discussion about what students know about the planets. Then students will act out the orbital motions of the planets (and also moons for the older ones) while holding a physical model. During the second phase we look at the structure of the Solar System as well as the relative distances of the planets from the Sun, first by sketching it on paper, then by recreating a scaled version in the class room. Again the students act out the parts of the Solar System bodies with their models. The third segment concentrates on recreating historical measurements of Earth-Moon-Sun system. The Solar System Ballet activity is suitable for grades K-12+ as well as general public informal learning activities.

411.03

Advanced Multibeam Spectrometer for the Green Bank Telescope

D. Anish Roshi¹, M. Bloss¹, P. Brandt¹, S. Bussa¹, H. Chen², P. Demorest¹, T. Filiba², R. J. Fisher¹, J. Ford¹, D. Frayer¹, R. Garwood¹, S. Gowda², G. Jones³, B. Mallard², J. Masters¹, R. McCullough¹, G. Molera², K. O'Neil¹, J. Ray¹, S. Scott², A. Shelton¹, A. Siemion², M. Wagner², G. Watts¹, D. Werthimer², M. Whitehead^1
1National Radio Astronomy Observatory, ²University of California, ³Caltech.

8:00 AM - 12:00 PM

Essex Ballroom

The National Science Foundation Advanced Technologies and Instrumentation (NSF-ATI) program is funding a new spectrometer backend for the Green Bank Telescope (GBT). This spectrometer is being built by the CICADA collaboration -- a collaboration between the National Radio Astronomy Observatory (NRAO) and the Center for Astronomy Signal Processing and Electronics Research (CASPER) at the University of California Berkeley. The new backend will replace capabilities of the existing spectrometers and will support data processing from focal plane array systems. The spectrometer will be capable of processing up to 1.25 GHz bandwidth from 8 dual polarized beams or a bandwidth up to 10 GHz from a dual polarized beam. The spectrometer will be using 8 bit analog to digital converters (ADC), which give better dynamic range than existing GBT spectrometers. There will be 8 tunable digital sub-bands within the 1.25 GHz bandwidth, which will enhance the capability of simultaneous observation of multiple spectral transitions. The maximum spectral dump rate to disk will be about 0.5 msec. The vastly enhanced backend capabilities will support several new science projects with the GBT. The projects include mapping temperature and density structure of molecular clouds; searches for organic molecules in the interstellar medium; determination of the fundamental constants of our evolving Universe; redshifted spectral features from galaxies across cosmic time and survey for pulsars in the extreme gravitational environment of the Galactic Center.

411.04

First Student Project at the University of Tennessee at Martin Observatory

Lionel J. Crews¹, K. Turner¹, P. Wesner^1
1University of Tennessee at Martin.

8:00 AM - 12:00 PM

Essex Ballroom

The University of Tennessee at Martin has recently completed the construction and setup of an observatory. The dome houses a 16" Meade telescope with SBIG STL-11000M CCD. For its first project, observations of the Delta Scuti type variable SZ Lynx were taken in March and analyzed using MiraPRO. A simple ephemeris calculation was done, and compared to previous results. This project was done under the University Scholars program, a four year scholarship program which includes a faculty-mentored research project.

Download 2.63 Mb.

Share with your friends: