Generation Of Coherent Structures After Cosmic Inflation,
2011
Dartmouth College
Generation Of Coherent Structures After Cosmic Inflation, Marcelo Gleiser, Noah Graham, Nikitas Stamatopoulos
Dartmouth Scholarship
We investigate the nonlinear dynamics of hybrid inflation models, which are characterized by two real scalar fields interacting quadratically. We start by solving numerically the coupled Klein-Gordon equations in static Minkowski spacetime, searching for possible coherent structures. We find long-lived, localized configurations, which we identify as a new kind of oscillon. We demonstrate that these two-field oscillons allow for “excited” states with much longer lifetimes than those found in previous studies of single-field oscillons. We then solve the coupled field equations in an expanding Friedmann-Robertson-Walker spacetime, finding that as the field responsible for inflating the Universe rolls down to oscillate …
The Effect Of Tidal Disruptions On Giant Stars In The Galactic Center,
2011
Butler University
The Effect Of Tidal Disruptions On Giant Stars In The Galactic Center, Brian B. Geiss
Undergraduate Honors Thesis Collection
Recent observational data suggest the depletion of late-type giant stars in the inner most region of the Galactive Nucleus. Using dynamically evolving Fokker-Planck models of the Galactic Nucleus, we have followed in detail the stellar distribution as it evolves through the postmain-sequence phases. Of particular interest was the effect of stellar collisions and tidal disruptions by the central massive black hole on post main sequence stars as they expand in size. B y modeling tidal disruptions and stellar collisions, we have found that there should be a significant depletion of the giant stars in the innermost regions of the nucleus. …
Broad Lyα Emission From Three Nearby Bl Lacertae Objects,
2011
University of Colorado, Boulder
Broad Lyα Emission From Three Nearby Bl Lacertae Objects, John T. Stocke, Charles W. Danforth, Eric S. Perlman
Aerospace, Physics, and Space Science Faculty Publications
We present far-UV HST/COS spectra of four nearby BLLac objects. BLLac spectra are dominated by a smooth, power-law continuum which arises in a relativistic jet. However, the spectra are not necessarily featureless; weak, broad- and/or narrow-line emission is sometimes seen in high-quality optical spectra. We present detections of Lyα emission in HST/COS spectra of Mrk421 (z = 0.030) and PKS2005-489 (z = 0.071) as well as an archival HST/GHRS observation of Mrk501 (z = 0.0337). Archival HST/STIS observations of PKS2155-304 (z = 0.116) show no Lyα emission to a very low upper limit. Using the assumption that the broad-line region …
Sdss J162520.29+120308.7 – A New Su Ursae Majoris Star In The Period Gap,
2011
Nicolaus Copernicus Astronomical Center
Sdss J162520.29+120308.7 – A New Su Ursae Majoris Star In The Period Gap, A. Olech, E. De Miguel, M. Otulakowska, J. R. Thorstensen
Dartmouth Scholarship
We report results of an extensive world-wide observing campaign devoted to the recently discovered dwarf nova SDSS J162520.29+120308.7 (SDSS J1625). The data were obtained during the July 2010 eruption of the star and in August and September 2010 when the object was in quiescence.
Polarization Of The Charge-Exchange X-Rays Induced In The Heliosphere,
2011
University of Connecticut
Polarization Of The Charge-Exchange X-Rays Induced In The Heliosphere, M. Gacesa, H.-R. Müller, R. Côté, V. Kharchenko
Dartmouth Scholarship
We report results of a theoretical investigation of polarization of the X-ray emissions induced in charge-exchange collisions of fully stripped solar wind ions C6+and O8+ with the heliospheric hydrogen atoms. The polarization of X-ray emissions has been computed for line-of-sight observations within the ecliptic plane as a function of solar wind ion velocities, including a range of velocities corresponding to the slow and fast solar wind, and Coronal Mass Ejections. To determine the variability of polarization of heliospheric X-ray emissions, the polarization has been computed for solar minimum conditions with self-consistent parameters of the solar wind plasma and heliospheric gas …
Uv, Optical, And Infrared Imaging Of The Interacting Galaxy Arp 107 And Its Star Forming Regions.,
2011
East Tennessee State University
Uv, Optical, And Infrared Imaging Of The Interacting Galaxy Arp 107 And Its Star Forming Regions., Ryen C. Lapham
Undergraduate Honors Theses
In this study we present GALEX UV, Sloan Digital Sky Survey, and Spitzer infrared imaging, along with an optical Hα map of the interacting galaxy pair Arp 107. IRAF photometry was used to analyze 29 star forming regions identified in previous work done with Spitzer colors. In this paper further analysis of the clumps of newly formed stars was done by creating Spectral Energy Distribution plots to sort the clumps as quiescent or starbursts. Color - color plots were used to estimate the ages and extinctions of the clumps by comparing magnitudes to stellar population synthesis models. Results seem to …
Grips - Gamma-Ray Imaging, Polarimetry And Spectroscopy,
2011
MPI für extraterrestrische Physik
Grips - Gamma-Ray Imaging, Polarimetry And Spectroscopy, Jochen Greiner, Karl Mannheim, Felix Aharonian, Marco Ajello, Lajos G. Balaz, Guido Barbiellini, Ronaldo Bellazzini, Shawn Bishop, Gennady S. Bisnoyatij-Kogan, Steven Boggs, Andrej Bykov, Guido Dicocco, Roland Diehl, Dominik Elsasser, Suzanne Foley, Claes Fransson, Neil Gehrels, Lorraine Hanlon, Dieter H. Hartmann
Publications
We propose to perform a continuously scanning all-sky survey from 200 keV to 80 MeV achieving a sensitivity which is better by a factor of 40 or more compared to the previous missions in this energy range (COMPTEL, INTEGRAL; see Fig. 1). The Gamma-Ray Imaging, Polarimetry and Spectroscopy (“GRIPS”) mission addresses fundamental questions in ESA’s Cosmic Vision plan. Among the major themes of the strategic plan, GRIPS has its focus on the evolving, vio-lent Universe, exploring a unique energy window. We propose to investigate γ-ray bursts and blazars, the mechanisms behind supernova explosions, nucleosynthesis and spallation, the enigmatic origin of …
An Introduction To The Chandra Carina Complex Project,
2011
Swarthmore College
An Introduction To The Chandra Carina Complex Project, L. K. Townsley, P. S. Broos, M. F. Corcoran, E. D. Feigelson, M. Gagné, T. Montmerle, M. S. Oey, N. Smith, G. P. Garmire, K. V. Getman, M. S. Povich, N. R. Evans, Y. Nazé, E. R. Parkin, T. Preibisch, J. Wang, S. J. Wou, Y.-H. Chu, David H. Cohen, R. A. Gruendl, K. Hamaguchi, R. R. King, M.-M. M. Low, M. J. Mccaughrean, A. F.J. Moffat, L. M. Oskinova, J. M. Pittard, K. G. Stassun, A. Ud-Doula, N. R. Walborn, W. L. Waldron, E. Churchwell, J. S. Nictiols, S. P. Owocki, N. S. Schulz
Physics & Astronomy Faculty Works
The Great Nebula in Carina provides an exceptional view into the violent massive star formation and feedback that typifies giant H II regions and starburst galaxies. We have mapped the Carina star-forming complex in X-rays, using archival Chandra data and a mosaic of 20 new 60 ks pointings using the Chandra X-ray Observatory's Advanced CCD Imaging Spectrometer, as a testbed for understanding recent and ongoing star formation and to probe Carina's regions of bright diffuse X-ray emission. This study has yielded a catalog of properties of > 14,000 X-ray point sources;> 9800 of them have multiwavelength counterparts. Using Chandra's unsurpassed X-ray …
Global X-Ray Properties Of The O And B Stars In Carina,
2011
Swarthmore College
Global X-Ray Properties Of The O And B Stars In Carina, Y. Nazé, P. S. Broos, L. M. Oskinova, L. K. Townsley, David H. Cohen, M. F. Corcoran, N. R. Evans, M. Gagné, A. F.J. Moffat, J. M. Pittard, G. Rauw, A. Ud-Doula, N. R. Walborn
Physics & Astronomy Faculty Works
The key empirical property of the X-ray emission from O stars is a strong correlation between the bolometric and X-ray luminosities. In the framework of the Chandra Carina Complex Project, 129 O and B stars have been detected as X-ray sources; 78 of those, all with spectral type earlier than B3, have enough counts for at least a rough X-ray spectral characterization. This leads to an estimate of the L-X-L-BOL ratio for an exceptional number of 60 O stars belonging to the same region and triples the number of Carina massive stars studied spectroscopically in X-rays. The derived log(L-X/L-BOL) is …
Simulation Of Relativistic Jets And Associated Self-Consistent Radiation,
2011
National Space Science and Technology Center, Huntsville, AL
Simulation Of Relativistic Jets And Associated Self-Consistent Radiation, K.-I. Nishikawa, E. J. Choi, K. Min, P. Hardee, Y. Mizuno, C. Zhang, J. Niemiec, M. Medvedev, A. Norlund, J Frederiksen, M Pohl, H Sol, Dieter H. Hartmann, G J. Fishman
Publications
Plasma instabilities excited in collisionless shocks are responsible for particle acceleration. We have investigated the particle acceleration and shock structure associated with an unmagnetized relativistic electron-positron jet propagating into an unmagnetized electron-positron plasma. Cold jet electrons are thermalized and slowed while the ambient electrons are swept up to create a par-tially developed hydrodynamic-like shock structure. In the leading shock, electron density increases by a factor of about 3.5 in the simulation frame. Strong electromagnetic fields are generated in the trailing shock and provide an emission site. These magnetic fields contribute to the electrons transverse deflection behind the shock. Our initial …
Carina Ob Stars: X-Ray Signatures Of Wind Shocks And Magnetic Fields,
2011
Swarthmore College
Carina Ob Stars: X-Ray Signatures Of Wind Shocks And Magnetic Fields, M. Gagné, G. Fehon, M. R. Savoy, David H. Cohen, L. K. Townsley, P. S. Broos, M. S. Povich, M. F. Corcoran, N. R. Walborn, N. R. Evans, A. F.J. Moffat, Y. Nazé, L. M. Oskinova
Physics & Astronomy Faculty Works
The Chandra Carina Complex contains 200 known O- and B-type stars. The Chandra survey detected 68 of the 70 O stars and 61 of 127 known B0-B3 stars. We have assembled a publicly available optical/X-ray database to identify OB stars that depart from the canonical L-X/L-bol relation or whose average X-ray temperatures exceed 1 keV. Among the single O stars with high kT we identify two candidate magnetically confined wind shock sources: Tr16-22, O8.5 V, and LS 1865, O8.5 V((f)). The O4 III(fc) star HD 93250 exhibits strong, hard, variable X-rays, suggesting that it may be a massive binary with …
Abundances Of Stars With Planets: Trends With Condensation Temperature,
2011
National Optical Astronomy Observatory
Abundances Of Stars With Planets: Trends With Condensation Temperature, Simon C. Schuler, Davin Flateau, Katia Cunha, Jeremy R. King, Luan Ghezzi, Verne V. Smith
Publications
Precise abundances of 18 elements have been derived for 10 stars known to host giant planets from high signal-to-noise ratio, high-resolution echelle spectroscopy. Internal uncertainties in the derived abundances are typically 0.05 dex. The stars in our sample have all been previously shown to have abundances that correlate with the condensation temperature (Tc) of the elements in the sense of increasing abundances with increasing Tc; these trends have been interpreted as evidence that the stars may have accreted H-depleted planetary material. Our newly derived abundances also correlate positively with Tc, although slopes of linear least-square fits to the [m/H]–Tc relations …
Measurements Of Mass Accretion Rates In Herbig Ae/Be Stars,
2011
Clemson University
Measurements Of Mass Accretion Rates In Herbig Ae/Be Stars, Brian Donehew
All Dissertations
Herbig Ae/Be stars(HAeBes) are young stellar objects of spectral class F2 through B0, with the central star often surrounded by a circumstellar disk of gas and dust. They are the higher mass analogs to T Tauri stars. The interaction between the star and the disk is not well understood, nor is the disk structure. The central star will often accrete mass from the disk, and the mass accretion rate is an important parameter for modeling the disk structure and evolution. The methods for measuring mass accretion rates of T Tauri stars are generally not applicable to HAeBe stars. As such, …
3-D Mesoscale Mhd Simulations Of A Cusp-Like Magnetic Configuration: Method And First Results,
2011
University of Alaska, Fairbanks
3-D Mesoscale Mhd Simulations Of A Cusp-Like Magnetic Configuration: Method And First Results, E. Adamson, A. Otto, K. Nykyri
Publications
We present a local mesoscale model of the magnetospheric cusp region with high resolution (up to 300 km). We discuss the construction and implementation of the initial configuration and give a detailed description of the numerical simulation. An overview of simulation results for the case of strongly northward interplanetary magnetic field (IMF) is then presented and compared with data from Cluster 2 spacecraft from 14 February 2003. Results show a cusp diamagnetic cavity (CDC) with depth normal to the magnetospheric boundary on the order of 1–2Re and a much larger extent of ~5–9Re tangential to the boundary, bounded by a …
A Study Of Carbon Features In Type Ia Supernova Spectra,
2011
Dartmouth College
A Study Of Carbon Features In Type Ia Supernova Spectra, Jerod T. Parrent, R. C. Thomas, Robert A. Fesen, G. H. Marion
Dartmouth Scholarship
One of the major differences between various explosion scenarios of Type Ia supernovae (SNe Ia) is the remaining amount of unburned (C+O) material and its velocity distribution within the expanding ejecta. While oxygen absorption features are not uncommon in the spectra of SNe Ia before maximum light, the presence of strong carbon absorption has been reported only in a minority of objects, typically during the pre-maximum phase. The reported low frequency of carbon detections may be due to low signal-to-noise data, low abundance of unburned material, line blending between C II 6580 and Si II 6355, ejecta temperature differences, asymmetrical …
Arecibo Palfa Survey And Einstein@Home: Binary Pulsar Discovery By Volunteer Computing,
2011
Expanding Frontiers
Arecibo Palfa Survey And Einstein@Home: Binary Pulsar Discovery By Volunteer Computing, B. Knispel, P. Lazarus, B. Allen, D. Anderson, C. Aulbert, N. D.R. Bhat, O. Bock, S. Bogdanov, A. Brazier, Fredrick A. Jenet
Physics & Astronomy Faculty Publications
We report the discovery of the 20.7ms binary pulsar J1952+2630, made using the distributed computing project Einstein@Home in Pulsar ALFA survey observations with the Arecibo telescope. Follow-up observations with the Arecibo telescope confirm the binary nature of the system. We obtain a circular orbital solution with an orbital period of 9.4hr, a projected orbital radius of 2.8lt-s, and a mass function of f = 0.15 M ⊙ by analysis of spin period measurements. No evidence of orbital eccentricity is apparent; we set a 2σ upper limit e ≲ 1.7 × 10 -3 . The orbital parameters suggest a massive white …
Modeling Gamma-Ray Bursts,
2011
University of Nevada, Las Vegas
Modeling Gamma-Ray Bursts, Amanda Maxham
UNLV Theses, Dissertations, Professional Papers, and Capstones
Discovered serendipitously in the late 1960s, gamma-ray bursts (GRBs) are huge explosions of energy that happen at cosmological distances. They provide a grand physical playground to those who study them, from relativistic effects such as beaming, jets, shocks and blastwaves to radiation mechanisms such as synchrotron radiation to galatic and stellar populations and history. Through the Swift and Fermi space telescopes dedicated to observing GRBs over a wide range of energies(from keV to GeV), combined with accurate pinpointing that allows ground based follow-up observations in the optical, infrared and radio, a rich tapestry of GRB observations has emerged. The general …
A Multi-Wavelength Study On Gamma-Ray Bursts And Their Afterglows,
2011
University of Nevada, Las Vegas
A Multi-Wavelength Study On Gamma-Ray Bursts And Their Afterglows, Binbin Zhang
UNLV Theses, Dissertations, Professional Papers, and Capstones
During the prompt emission and afterglow phases, GRBs(Gamma-Ray Bursts) release their huge amount of energy not limited in gamma-ray, but in a wide range of muti-wavelengths, from radio band to GeV gamma-rays. Thanks to the recent missions of Swift and Fermi, I was able to use their multi-wavelength observation data of GRBs and study their physical natures. I have processed all the Swift BAT/XRT and Fermi GBM/LAT GRB observation data. Based on the Swift data, I have studied the following comprehensive topics: (1) high-latitude "curvature effect" of early X-ray tails of GRBs Swift XRT afterglow (2) diverse physical origins of …
Gamma-Ray Burst Populations,
2011
University of Nevada, Las Vegas
Gamma-Ray Burst Populations, Francisco J. Virgili
UNLV Theses, Dissertations, Professional Papers, and Capstones
Over the last fifty years the field of gamma-ray bursts has shown incredible growth, but the amassing of data has also left observers and theorists alike wondering about some of the basic questions surrounding these phenomena. Additionally, these events show remarkable individuality and extrema, ranging in redshift throughout the observable universe and over ten orders of magnitude in energy. This work focuses on analyzing groups of bursts that are different from the general trend and trying to understand whether these bursts are from different intrinsic populations and if so, what can be said about their progenitors. This is achieved through …
Numerical Simulations Of Accretion Disks And Extrasolar Planets,
2011
University of Nevada, Las Vegas
Numerical Simulations Of Accretion Disks And Extrasolar Planets, Stefan Luketic
UNLV Theses, Dissertations, Professional Papers, and Capstones
We study mass outflows from astrophysical objects. Using numerical hydrodynamical simulations, we investigate outflows from accretion disks and exoplanets. In the first part of this dissertation, we present the results of Zeus 2D hydrodynamical simulations of the disk photosphere irradiated by strong X–rays that are produced in the innermost part of the disk of an accreting black hole. As expected, the irradiation heats the photosphere and drives a thermal wind. To apply our results to the well– studied X–ray transient source GRO J1655–40, we utilized the observed mass of its black hole and the observed properties of its X–ray radiation …
