Discovery Of Variability In The Very High Energy Gamma-Ray Emission Of 1es 1218+304 With Veritas,
2010
Department of Physical Sciences, Cork Institute of Technology, Bishopstown, Cork, Ireland
Discovery Of Variability In The Very High Energy Gamma-Ray Emission Of 1es 1218+304 With Veritas, P. T. Reynolds, Et Al
Physical Sciences Publications
We present results from an intensive VERITAS monitoring campaign of the high-frequency peaked BL Lac object 1ES 1218+304 in 2008/2009. Although 1ES 1218+304 was detected previously by MAGIC and VERITAS at a persistent level of ~6% of the Crab Nebula flux, the new VERITAS data reveal a prominent flare reaching ~20% of the Crab. While very high energy (VHE) flares are quite common in many nearby blazars, the case of 1ES 1218+304 (redshift z = 0.182) is particularly interesting since it belongs to a group of blazars that exhibit unusually hard VHE spectra considering their redshifts. When correcting the measured …
The Acs Survey Of Galactic Globular Clusters. Viii. Effects Of Environment On Globular Cluster Global Mass Functions,
2010
Whitman College
The Acs Survey Of Galactic Globular Clusters. Viii. Effects Of Environment On Globular Cluster Global Mass Functions, Nathaniel E. Q. Paust, I. Neill Reid, Giampaolo Piotto, Antonio Aparicio, Jay Anderson, Ata Sarajedini, Luigi R. Bedin, Brian Chaboyer
Dartmouth Scholarship
We have used observations obtained as part of the Hubble Space Telescope/ACS Survey of Galactic Globular Clusters to construct global present-day mass functions for 17 globular clusters utilizing multi-mass King models to extrapolate from our observations to the global cluster behavior. The global present-day mass functions for these clusters are well matched by power laws from the turnoff, ≈0.8 M ☉, to 0.2-0.3 M ☉ on the lower main sequence. The slopes of those power-law fits, α, have been correlated with an extensive set of intrinsic and extrinsic cluster properties to investigate which parameters may influence the form …
The Determination Of Reddening From Intrinsic Vr Colors Of Rr Lyrae Stars,
2010
Dartmouth College
The Determination Of Reddening From Intrinsic Vr Colors Of Rr Lyrae Stars, Andrea Kunder, Brian Chaboyer, Andrew Layden
Dartmouth Scholarship
New R-band observations of 21 local field RR Lyrae variable stars are used to explore the reliability of minimum light (V – R) colors as a tool for measuring interstellar reddening. For each star, R-band intensity mean magnitudes and light amplitudes are presented. Corresponding V-band light curves from the literature are supplemented with the new photometry, and (V – R) colors at minimum light are determined for a subset of these stars as well as for other stars in the literature. Two different definitions of minimum light color are examined, one which uses …
A Hybrid Particle-Continuum Method For Hydrodynamics Of Complex Fluids,
2010
San Jose State University
A Hybrid Particle-Continuum Method For Hydrodynamics Of Complex Fluids, Alejandro Garcia, A. Donev, J. B. Bell, B. Alder
Faculty Publications
A previously developed hybrid particle-continuum method [J. B. Bell, A. Garcia, and S. A. Williams, Multiscale Model. Simul., 6 (2008), pp. 1256–1280] is generalized to dense fluids and two- and three-dimensional flows. The scheme couples an explicit fluctuating compressible Navier–Stokes solver with the isotropic direct simulation Monte Carlo (DSMC) particle method [A. Donev, A. L. Garcia, and B. J. Alder, J. Stat. Mech. Theory Exp., 2009 (2009), article P11008]. To achieve bidirectional dynamic coupling between the particle (microscale) and continuum (macroscale) regions, the continuum solver provides state-based boundary conditions to the particle subdomain, while the particle solver provides flux-based boundary …
The Globular Cluster System Of Ngc 1399. V. Dynamics Of The Cluster System Out To 80 Kpc,
2010
Argelander-Institut für Astronomie
The Globular Cluster System Of Ngc 1399. V. Dynamics Of The Cluster System Out To 80 Kpc, Y. Schuberth, T. Richtler, M. Hilker, B. Dirsch, L. Bassino, Aaron J. Romanowsky, L. Infante
Faculty Publications
Globular clusters (GCs) are tracers of the gravitational potential of their host galaxies. Moreover, their kinematic properties may provide clues for understanding the formation of GC systems and their host galaxies. We use the largest set of GC velocities obtained so far of any elliptical galaxy to revise and extend the previous investigations (Richtler et al. 2004) of the dynamics of NGC 1399, the central dominant galaxy of the nearby Fornax cluster of galaxies. The GC velocities are used to study the kinematics, their relation with population properties, and the dark matter halo of NGC 1399. We have obtained 477 …
Central Dark Matter Content Of Early-Type Galaxies: Scaling Relations And Connections With Star Formation Histories, N. R. Napolitano, Aaron J. Romanowsky, A. J. Tortora
Faculty Publications
We examine correlations between masses, sizes and star formation histories for a large sample of low-redshift early-type galaxies, using a simple suite of dynamical and stellar population models. We confirm an anticorrelation between the size and stellar age and go on to survey for trends with the central content of dark matter (DM). An average relation between the central DM density and galaxy size of 〈ρDM〉∝R−2eff provides the first clear indication of cuspy DM haloes in these galaxies – akin to standard Λ cold dark matter haloes that have undergone adiabatic contraction. The DM density scales with galaxy mass as …
A Long-Period Planet Orbiting A Nearby Sun-Like Star,
2010
University of Hertfordshire
A Long-Period Planet Orbiting A Nearby Sun-Like Star, Hugh R. A. Jones, R. Paul Butler, Chris Tinney, Simon O'Toole, Rob Wittenmyer, Gregory W. Henry, Stefano Meschiari, Steve Vogt, Eugenio Rivera, Greg Laughlin, Brad D. Carter, Jeremy Bailey, James S. Jenkins
Information Systems and Engineering Management Research Publications
The Doppler wobble induced by the extra-solar planet HD 134987b was first detected by data from the Keck Telescope nearly a decade ago, and was subsequently confirmed by data from the Anglo-Australian Telescope (AAT). However, as more data have been acquired for this star over the years since, the quality of a single Keplerian fit to that data has been getting steadily worse. The best-fitting single Keplerian to the 138 Keck and AAT observations now in hand has an root-mean-square (rms) scatter of 6.6 m s−1. This is significantly in excess of both the instrumental precision achieved by both the …
Observations Of Ozone Production In A Dissipating Tropical Convective Cell During Tc4,
2010
Valparaiso University
Observations Of Ozone Production In A Dissipating Tropical Convective Cell During Tc4, Gary A. Morris, A. M. Thompson, K. E. Pickering, S. Chen, E. J. Bucsela, P. A. Kucera
Physics and Astronomy Faculty Publications
From 13 July–9 August 2007, 25 ozonesondes were launched from Las Tablas, Panama as part of the Tropical Composition, Cloud, and Climate Coupling (TC4) mission. On 5 August, a strong convective cell formed in the Gulf of Panama. World Wide Lightning Location Network (WWLLN) data indicated 563 flashes (09:00–17:00 UTC) in the Gulf. NO2 data from the Ozone Monitoring Instrument (OMI) show enhancements, suggesting lightning production of NOx. At 15:05 UTC, an ozonesonde ascended into the southern edge of the now dissipating convective cell as it moved west across the Azuero Peninsula. The balloon oscillated from 2.5–5.1 km five times …
A Model For Predicting Extragalactic Jet Lifetimes,
2010
Drexel University
A Model For Predicting Extragalactic Jet Lifetimes, Daniel S. Spicer, Robert Bingham, Stephen O'Sullivan
Articles
Abstract. In this letter, we propose a model to explain the disintegration of ex- tragalactic jets and to predict the associated timescale. The model assumes that a jet is current and charge neutral as well as collimated at its source; however, the forward electron current gradually decays producing a magnetic field transverse to the direction of jet propagation. This growing transverse magnetic field eventually causes the jet to disintegrate.
A Two-Dimensional, Linear–Elastic Model To Explain Radial Extensional Fractures, Pantheon Fossae, Caloris Basin, Mercury,
2010
Bridgewater State University
A Two-Dimensional, Linear–Elastic Model To Explain Radial Extensional Fractures, Pantheon Fossae, Caloris Basin, Mercury, Brianne Mcdonough
Undergraduate Review
In this study, two-dimensional linear elasticity theory is used to model the lithospheric stress field that produces radial extensional fractures observed at Pantheon Fossae in the Caloris Basin of Mercury. These fractures were imaged by the MESSENGER mission flyby of Mercury on January 14, 2008 and show radial fractures extending outward from a 40-kilometer impact crater named Apollodorus. Recent studies have proposed several different mechanisms to explain these fractures, including magmatic processes, central basin uplift, and stresses produced by the formation of the impact crater itself.
Sensitivity Of Planetary Boundary Layer To Varying Volumetric Soil Moisture: A Mesoscale Models Comparision,
2010
Western Kentucky U\
Sensitivity Of Planetary Boundary Layer To Varying Volumetric Soil Moisture: A Mesoscale Models Comparision, Asrid Suarez Gonzalez
Mahurin Honors College Capstone Experience/Thesis Projects
A comparison between two Mesoscale models, Colorado State University Regional Atmospheric Model System (RAMS) version 4.4 coupled with the Land‐Ecosystem– Atmosphere Feedback Model (LEAF2) and Penn State/NCAR’s Mesoscale Model (MM5) coupled with NOAH Land Surface Model, was conducted in order to assess the sensitivity of forecasted boundary layer variables to anomalous volumetric soil moistures. The study elaborates on the findings of Quintanar et al. (2008) using the study’s experimental design as a template for our numerical model comparison. The experiments were conducted using the same synoptic events examined by Quintanar et al. (2008): June 11, June 17 and June 22, …
Solar Observations During A Solar Minimum Using A Small Radio Telescope,
2010
Bridgewater State University
Solar Observations During A Solar Minimum Using A Small Radio Telescope, Gary Forrester
Undergraduate Review
The Sun is currently in a quiescent phase called solar minimum. We used Bridgewater State College’s (B.S.C.’s) Small Radio Telescope (SRT) to observe solar radio emission during this quiet phase and correlated our data to solar X-ray data readily available through the National Oceanic and Atmospheric Administration (NOAA). Previous observations made during a period of high solar activity (solar maximum) using one of M.I.T.’s SRTs showed that some solar radio and X-ray events were correlated, while others were not. We made observations during solar minimum and found one event where there was a correlation between radio and X-ray emission.
The Horizontal Electric Field Induced By A Lightning Return Stroke,
2010
Trinity University
The Horizontal Electric Field Induced By A Lightning Return Stroke, S L. Meredith, S K. Earles, Niescja E. Turner
Physics and Astronomy Faculty Research
Problem statement: Develop a new formula which describes the horizontal electric field induced by a lightning return stroke in contact with an imperfect conductive surface. Approach: A new method for describing the horizontal electric field induced by a lightning return stroke will be presented. The method presented here had utilized an approach which purposely downplayed the physics of how image theory was employed in the presence of an imperfect conductive surface. It did so by adopting a technique which had focused on the geometry that existed between the lightning channel and surface ground. In doing so, new expressions …
A New Method To Describe Image Theory For An Imperfect Conductor,
2010
Trinity University
A New Method To Describe Image Theory For An Imperfect Conductor, S L. Meredith, S K. Earles, Niescja E. Turner
Physics and Astronomy Faculty Research
Problem statement: Modify the equations associated with image theory in order to account for perfect and imperfect conductors. Approach: A novel approach for describing the application of image theory for an imperfect conductive surface was presented. The method presented here purposely downplays the physics of how image theory was employed to account for a charge which is in the presence of an imperfect conductive surface. In turn, it adopted an approach which focused on the geometry that existed between the charged particle and surface ground. In doing so, the proposed method formulated a solution that had minimized the …
Dual Gamma-Ray Mission,
2010
Space Sciences Laboratory, University of California
Dual Gamma-Ray Mission, S. Boggs, C. Wunderer, P. Von Ballmoos, T. Takahashi, N. Gehrels, J. Tueller, M. Baring, J. Beacom, R. Diehl, J Greiner, E Grove, Dieter H. Hartmann
Publications
Gamma-rays at MeV energies provide a unique window on the high energy Universe, especially so for nuclear astrophysics. The potential for significant contributions, e.g., to the understanding of SNe Ia as well as the large potential for new discoveries has long been recognized, but technical progress in this challenging energy band has been slow. The groundbreaking discoveries of CGRO’s COMPTEL, however, have inspired and driven the development of powerful new instrumentation over the past decade. Novel detector technologies developed in the US and Japan enable compact Compton telescopes, greatly improving the efficiency and field-of-view achievable with this technique successfully employed …
The Dynamic X-Ray Sky Of The Local Universe,
2010
Space Sciences Laboratory, University of California, Berkeley
The Dynamic X-Ray Sky Of The Local Universe, S. Boggs, C. Wunderer, P. Von Ballmoos, T. Takahashi, N. Gehrels, J. Tueller, M. Baring, J. Beacom, R. Diehl, Dieter H. Hartmann
Publications
Over the next decade, we can expect time domain astronomy to flourish at optical and radio wavelengths. In parallel with these efforts, a dedicated transient "machine" operating at higher energies (X-ray band through soft gamma-rays) is required to reveal the unique subset of events with variable emission predominantly visible above 100 eV. Here we focus on the transient phase space never yet sampled due to the lack of a sensitive, wide-field and triggering facility dedicated exclusively to catching high energy transients and enabling rapid coordinated multi-wavelength follow-up. We first describe the advancements in our understanding of known X-ray transients that …
On The Origin Of The Highest Redshift Gamma-Ray Bursts,
2010
Los Alamos National Laboratory & Astronomical Observatory, University of Warsaw &
On The Origin Of The Highest Redshift Gamma-Ray Bursts, Krzysztof Belczynski, Daniel E. Holz, Chris L. Fryer, Edo Berger, Dieter H. Hartmann, Brain O'Shea
Publications
GRB 080913 and GRB 090423 are the most distant gamma-ray bursts (GRBs) known to date, with spectroscop-ically determined redshifts of z = 6.7 and z = 8.1, respectively. The detection of bursts at this early epoch of the universe significantly constrains the nature of GRBs and their progenitors. We perform population synthesis studies of the formation and evolution of early stars, and calculate the resulting formation rates of short- and long-duration GRBs at high redshift. The peak of the GRB rate from Population II stars occurs at z ∼ 7for a model with efficient/fast mixing of metals, while it is …
Star Formation And Uv Colors Of The Brightest Cluster Galaxies In The Representative Xmm-Newton Cluster Structure Survey,
2010
Michigan State University
Star Formation And Uv Colors Of The Brightest Cluster Galaxies In The Representative Xmm-Newton Cluster Structure Survey, Megan Donahue, Seth Bruch, Emily Wang, G. Mark Voit
University Faculty Publications and Creative Works
We present UV broadband photometry and optical emission-line measurements for a sample of 32 brightest cluster galaxies (BCGs) in clusters of the Representative XMM-Newton Cluster Structure Survey (REXCESS) with z = 0.06-0.18. The REXCESS clusters, chosen to study scaling relations in clusters of galaxies, have X-ray measurements of high quality. The trends of star formation and BCG colors with BCG and host properties can be investigated with this sample. The UV photometry comes from the XMM-Newton Optical Monitor, supplemented by existing archival Galaxy Evolution Explorer photometry. We detected Hα and forbidden line emission in seven (22%) of these BCGs, in …
Brightest Cluster Galaxies And Core Gas Density In Rexcess Clusters,
2010
Calvin University
Brightest Cluster Galaxies And Core Gas Density In Rexcess Clusters, Deborah B. Haarsma, Luke Leisman, Megan Donahue, Seth Bruch
University Faculty Publications and Creative Works
We investigate the relationship between brightest cluster galaxies (BCGs) and their host clusters using a sample of nearby galaxy clusters from the Representative XMM-Newton Cluster Structure Survey. The sample was imaged with the Southern Observatory for Astrophysical Research in R band to investigate the mass of the old stellar population. Using a metric radius of 12 h -1kpc, we found that the BCG luminosity depends weakly on overall cluster mass as L BCG M 0.180.07cl, consistent with previous work. We found that 90% of the BCGs are located within 0.035 r 500 of the peak of the X-ray emission, including …
Star Formation And Uv Colors Of The Brightest Cluster Galaxies In The Representative Xmm-Newton Cluster Structure Survey,
2010
Michigan State University
Star Formation And Uv Colors Of The Brightest Cluster Galaxies In The Representative Xmm-Newton Cluster Structure Survey, Megan Donahue, Seth Bruch, Emily Wang, G. Mark Voit
University Faculty Publications and Creative Works
We present UV broadband photometry and optical emission-line measurements for a sample of 32 brightest cluster galaxies (BCGs) in clusters of the Representative XMM-Newton Cluster Structure Survey (REXCESS) with z = 0.06-0.18. The REXCESS clusters, chosen to study scaling relations in clusters of galaxies, have X-ray measurements of high quality. The trends of star formation and BCG colors with BCG and host properties can be investigated with this sample. The UV photometry comes from the XMM-Newton Optical Monitor, supplemented by existing archival Galaxy Evolution Explorer photometry. We detected Hα and forbidden line emission in seven (22%) of these BCGs, in …
