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Articles 121 - 150 of 179
Full-Text Articles in Astrophysics and Astronomy
Grb 080913 At Redshift 6.7, J. Greiner, T. Krühler, J. P. U. Fynbo, A. Rossi, R. Schwarz, S. Klose, S. Savaglio, N. R. Tanvir, S. Mcbreen, T Totani, B B. Zhang, X F. Wu, D Watson, S D. Barthelmy, A P. Beardmore, P Ferrero, N Gehrels, D A. Kann, N Kawai, A Küpcü Yoldaş, P Mészáros, B Milvang-Jensen, S R. Oates, D Pierini, P Schady, K Toma, P M. Vreeswijk, A Yoldas, B Zhang, P Afonso, K Aoki, D N. Burrows, C Clemens, R Filgas, Z Haiman, Dieter H. Hartmann
Grb 080913 At Redshift 6.7, J. Greiner, T. Krühler, J. P. U. Fynbo, A. Rossi, R. Schwarz, S. Klose, S. Savaglio, N. R. Tanvir, S. Mcbreen, T Totani, B B. Zhang, X F. Wu, D Watson, S D. Barthelmy, A P. Beardmore, P Ferrero, N Gehrels, D A. Kann, N Kawai, A Küpcü Yoldaş, P Mészáros, B Milvang-Jensen, S R. Oates, D Pierini, P Schady, K Toma, P M. Vreeswijk, A Yoldas, B Zhang, P Afonso, K Aoki, D N. Burrows, C Clemens, R Filgas, Z Haiman, Dieter H. Hartmann
Publications
We report on the detection by Swift of GRB 080913, and subsequent optical/near-infrared follow-up observations by GROND, which led to the discovery of its optical/NIR afterglow and the recognition of its high-z nature via the detection of a spectral break between the i and z bands. Spectroscopy obtained at the ESO-VLT revealed a continuum extending down to λ = 9400 Å, and zero flux for 7500 Å<λ< 9400 Å, which we interpret as the onset of a Gunn–Peterson trough at z = 6.695± 0.025 (95.5% confidence level), making GRB 080913 the highest-redshift gamma-ray burst (GRB) to date, and more distant than the highest-redshift QSO. We note that many redshift indicators that are based on promptly available burst or afterglow properties have failed for GRB 080913. We report on our follow-up campaign and compare the properties of GRB 080913 with bursts at lower redshift. In particular, since the afterglow of this burst is fainter than typical for GRBs, we show that 2 m class telescopes can identify most high-redshift GRBs.
In Situ Probes Of The First Galaxies And Reionization: Gamma-Ray Bursts, Matthew Mcquinn, Joshua S. Bloom, Jonathan Grindlay, David Band, S. D. Barthemy, E. Berger, A. Corsi, S. Covino, G. J. Fishman, Steven R. Furlanetto, Neil Gehrels, Dieter H. Hartmann, Chryssa Kouveliotou, A S. Kutyrev, Abraham Loeb, S Harvard Moseley, Tsvi Piran, L Piro, J X. Prochaska, R Salvaterra, P Schady, A M. Soderberg, G Tagliaferri
In Situ Probes Of The First Galaxies And Reionization: Gamma-Ray Bursts, Matthew Mcquinn, Joshua S. Bloom, Jonathan Grindlay, David Band, S. D. Barthemy, E. Berger, A. Corsi, S. Covino, G. J. Fishman, Steven R. Furlanetto, Neil Gehrels, Dieter H. Hartmann, Chryssa Kouveliotou, A S. Kutyrev, Abraham Loeb, S Harvard Moseley, Tsvi Piran, L Piro, J X. Prochaska, R Salvaterra, P Schady, A M. Soderberg, G Tagliaferri
Publications
The first structures in the Universe formed at z > 7, at higher redshift than all currently known galaxies. Since GRBs are brighter than other cosmological sources at high redshift and exhibit simple power-law afterglow spectra that is ideal for absorption studies, they serve as powerful tools for studying the early universe. New facilities planned for the coming decade will be able to obtain a large sample of high-redshift GRBs. Such a sample would constrain the nature of the first stars, galaxies, and the reionization history of the Universe.
Hd 100453: A Link Between Gas-Rich Protoplanetary Disks And Gas-Poor Debris Disks, K A. Collins, C A. Grady, K Hamaguchi, J P. Wisniewski, Sean D. Brittain, M Sitko, W J. Carpenter, J P. Williams, G S. Mathews, G M. Williger, R Van Boekel, A Carmona, Th. Henning, M E. Van Den Ancker, G Meeus, X P. Chen, R Petre, B E. Woodgate
Hd 100453: A Link Between Gas-Rich Protoplanetary Disks And Gas-Poor Debris Disks, K A. Collins, C A. Grady, K Hamaguchi, J P. Wisniewski, Sean D. Brittain, M Sitko, W J. Carpenter, J P. Williams, G S. Mathews, G M. Williger, R Van Boekel, A Carmona, Th. Henning, M E. Van Den Ancker, G Meeus, X P. Chen, R Petre, B E. Woodgate
Publications
HD 100453 has an IR spectral energy distribution (SED) which can be fit with a power law plus a blackbody. Previous analysis of the SED suggests that the system is a young Herbig Ae star with a gas-rich, flared disk. We reexamine the evolutionary state of the HD 100453 system by refining its age (based on a candidate low-mass companion) and by examining limits on the disk extent, mass accretion rate, and gas content of the disk environment. We confirm that HD 100453B is a common proper motion companion to HD 100453A, with a spectral type of M4.0V-M4.5V, and derive …
Nuclear Resonances: The Quest For Large Column Densities And A New Tool, J. Greiner, S. Boggs, G. Dicocco, K. T. Freese, N. Gehrels, Dieter H. Hartmann, A. Iyudin, G. Kanbach, A. A. Zdziarski
Nuclear Resonances: The Quest For Large Column Densities And A New Tool, J. Greiner, S. Boggs, G. Dicocco, K. T. Freese, N. Gehrels, Dieter H. Hartmann, A. Iyudin, G. Kanbach, A. A. Zdziarski
Publications
Nuclear physics offers us a powerful tool: using nuclear resonance absorption lines to infer the physical conditions in astrophysical settings which are otherwise diffcult to deduce. Present-day technology provides an increase in sensitivity over previous gamma-ray missions large enough to utilize this tool for the first time. The most exciting promise is to measure gamma-ray bursts from the first star(s) at redshifts 20–60, but also active galactic nuclei are promising targets.
Magnetohydrodynamic Effects In Propagating Relativistic Jets: Reverse Shock And Magnetic Acceleration, Yosuke Mizuno, Bing Zhang, Bruno Giacomazzo, Ken-Ichi Nishikawa, Phillip E. Hardee, Shigehiro Nagataki, Dieter H. Hartmann
Magnetohydrodynamic Effects In Propagating Relativistic Jets: Reverse Shock And Magnetic Acceleration, Yosuke Mizuno, Bing Zhang, Bruno Giacomazzo, Ken-Ichi Nishikawa, Phillip E. Hardee, Shigehiro Nagataki, Dieter H. Hartmann
Publications
We solve the Riemann problem for the deceleration of an arbitrarily magne-tized relativistic flow injected into a static unmagnetized medium in one dimen-sion. We find that for the same initial Lorentz factor, the reverse shock becomes progressively weaker with increasing magnetization σ (the Poynting-to-kinetic energy flux ratio), and the shock becomes a rarefaction wave when σ exceeds a critical value, σc, defined by the balance between the magnetic pressure in the flow and the thermal pressure in the forward shock. In the rarefaction wave regime, we find that the rarefied region is accelerated to a Lorentz factor that is significantly …
Physics Of Type Ia Supernovae, Ginger Bryngelson
Physics Of Type Ia Supernovae, Ginger Bryngelson
All Theses
Type Ia supernovae (SNe Ia), the thermonuclear explosion of a white dwarf, were once considered standard candles. However, increased observations reveal inhomogeneities in chemical composition and luminosity behavior, roughly dividing SNe Ia into three luminosity classes; super-luminous, sub-luminous, and normally-luminous. After introducing the problem in the context of previous observations and modeling, this thesis explores the physical processes occurring in a SN Ia after explosion, and discusses observations of SN light curves.
A simple model of the expanding ejecta calculates the energy deposition from the decay of radioactive Ni56 as well as photon diffusion. It produces light curves that match …
Probing Grb Environments Through X-Ray Absorption, Hala Eid
Probing Grb Environments Through X-Ray Absorption, Hala Eid
All Theses
Although long-duration GRBs (LGRBs) are highly transient in nature, their early afterglow can in principle be detected to very high redshifts (Lamb & Reichart, 2000). This makes them potent probes of the chemical evolution and content of the high-redshift universe. In this work, we use photoelectric absorption observed in the XRT spectra of LGRBs to investigate the evolution of metallicities and hydrogen column densities of LGRB host galaxies. Using a high-quality sample of LGRBs indicates the presence of a weak anti-correlation between the abundances and redshift. We also find an evolution trend in intrinsic column density. To confirm these correlations, …
Multiwavelength Analysis Of The Intriguing Grb 061126: The Reverse Shock Scenario And Magnetization, A. Gomboc, S. Kobayashi, C. Guidorzi, A. Melandri, V. Mangano, B. Sbarufatti, C. G. Mundell, P. Schady, R. J. Smith, A C. Updike, D A. Kann, K Misra, E Rol, A Pozanenko, A J. Castro-Tirado, G C. Anupama, D Bersier, M F. Bode, D Carter, P Curran, A Fruchter, J Graham, Dieter H. Hartmann, M Ibrahimov, A Levan, A Monfardini, C J. Mottram, P T. O'Brien, P Prema, D K. Sahu, I A. Steele, N R. Tanvir, K Wiersema
Multiwavelength Analysis Of The Intriguing Grb 061126: The Reverse Shock Scenario And Magnetization, A. Gomboc, S. Kobayashi, C. Guidorzi, A. Melandri, V. Mangano, B. Sbarufatti, C. G. Mundell, P. Schady, R. J. Smith, A C. Updike, D A. Kann, K Misra, E Rol, A Pozanenko, A J. Castro-Tirado, G C. Anupama, D Bersier, M F. Bode, D Carter, P Curran, A Fruchter, J Graham, Dieter H. Hartmann, M Ibrahimov, A Levan, A Monfardini, C J. Mottram, P T. O'Brien, P Prema, D K. Sahu, I A. Steele, N R. Tanvir, K Wiersema
Publications
We present a detailed study of the prompt and afterglow emission from Swift GRB 061126 using BAT, XRT, UVOT data and multicolor optical imaging from 10 ground-based telescopes. GRB 061126 was a long burst (T90 ¼191 s) with four overlapping peaks in its -ray light curve. The X-ray afterglow, observed from 26 minutes to 20 days after the burst, shows a simple power-law decay with X ¼1:290 Æ0:008. Optical observations presented here cover the time range from 258 s (Faulkes Telescope North) to 15 days (Gemini North) after the burst; the decay rate of the optical afterglow shows a steep-to-shallow …
Poet: Polarimeters For Energetic Transients, J. E. Hill, M. L. Mcconnell, P. Bloser, J. Legere, J. Macri, J. Ryan, S. Barthelmy, L. Angelini, T. Sakamoto, J K. Black, Dieter H. Hartmann, P Kaaret, B Zhang, K Ioka, T Nakamura, K Toma, R Yamazaki, X Wu
Poet: Polarimeters For Energetic Transients, J. E. Hill, M. L. Mcconnell, P. Bloser, J. Legere, J. Macri, J. Ryan, S. Barthelmy, L. Angelini, T. Sakamoto, J K. Black, Dieter H. Hartmann, P Kaaret, B Zhang, K Ioka, T Nakamura, K Toma, R Yamazaki, X Wu
Publications
POET (Polarimeters for Energetic Transients) is a Small Explorer mission concept proposed to NASA in January 2008. The principal scientific goal of POET is to measure GRB polarization between 2 and 500 keV. The payload consists of two wide FoV instruments: a Low Energy Polarimeter (LEP) capable of polarization measurements in the energy range from 2-15 keV and a high energy polarimeter (Gamma-Ray Polarimeter Experiment – GRAPE) that will measure polarization in the 60-500 keV energy range. Spectra will be measured from 2 keV up to 1 MeV. The POET spacecraft provides a zenith-pointed platform for maximizing the exposure to …
Neutrino-Nucleus Reaction Cross Sections For Light Element Systhesis In Supernova Explosions, Takashi Yoshida, Toshio Suzuki, Satoshi Chiba, Toshitaka Kajino, Hidekazu Yokomakura, Keiichi Kimura, Akira Takamura, Dieter H. Hartmann
Neutrino-Nucleus Reaction Cross Sections For Light Element Systhesis In Supernova Explosions, Takashi Yoshida, Toshio Suzuki, Satoshi Chiba, Toshitaka Kajino, Hidekazu Yokomakura, Keiichi Kimura, Akira Takamura, Dieter H. Hartmann
Publications
The neutrino-nucleus reaction cross sections of 4He and 12C are evaluated using new shell model Hamiltoni-ans. Branching ratios of various decay channels are calculated to evaluate the yields of Li, Be, and B producedthrough the ν -process in supernova explosions. The new cross sections enhance the yields of7Li and11B pro-duced during the supernova explosion of a 16.2 M⊙star model compared to the case using the conventionalcross sections by about 10%. On the other hand, the yield of10B decreases by a factor of two. The yieldsof6Li,9Be, and the radioactive nucleus10 Be are found at a level of ∼ 10−11M⊙. The temperature …
A Photometric Redshift Of Z = 1.8{+0.4}{-0.3} For The Agile Grb 080514b, A. Rossi, A. De Ugarte Postigo, P. Ferrero, D. A. Kann, S. Klose, S. Schulze, J. Greiner, P. Schady, R. Filgas, E E. Gonsalves, A Küpcü Yoldaş, T Krühler, G Szokoly, A Yoldas, P.M.J. Afonso, C Clemens, J S. Bloom, D A. Perley, J.P.U. Fynbo, A J. Castro-Tirado, J Gorosabel, P Kubanek, A C. Updike, Dieter H. Hartmann, A Giuliani, S T. Holland, L Hanlon, M Bremer, J French, G Melady, D A. Garcia-Hernandez
A Photometric Redshift Of Z = 1.8{+0.4}{-0.3} For The Agile Grb 080514b, A. Rossi, A. De Ugarte Postigo, P. Ferrero, D. A. Kann, S. Klose, S. Schulze, J. Greiner, P. Schady, R. Filgas, E E. Gonsalves, A Küpcü Yoldaş, T Krühler, G Szokoly, A Yoldas, P.M.J. Afonso, C Clemens, J S. Bloom, D A. Perley, J.P.U. Fynbo, A J. Castro-Tirado, J Gorosabel, P Kubanek, A C. Updike, Dieter H. Hartmann, A Giuliani, S T. Holland, L Hanlon, M Bremer, J French, G Melady, D A. Garcia-Hernandez
Publications
The AGILE gamma-ray burst GRB 080514B is the first detected to have emission above 30 MeV and an optical afterglow. However, no spectroscopic redshift for this burst is known. We report on our ground-based optical/NIR and millimeter follow-up observations of this event at several observatories, including the multi-channel imager GROND on La Silla, supplemented by Swift UVOT and Swift XRT data. The spectral energy distribution (SED) of the optical/NIR afterglow is found to decline sharply bluewards to the UV bands, which can be utilized in estimating the redshift. Fitting the SED from the Swift UVOT uvw2bandto the H band, we …
Erratum: "Warm Hcn, C2h2, And Co In The Disk Of Gv Tau'', E L. Gibb, K A. Vanbrunt, Sean D. Brittain, T W. Rettig
Erratum: "Warm Hcn, C2h2, And Co In The Disk Of Gv Tau'', E L. Gibb, K A. Vanbrunt, Sean D. Brittain, T W. Rettig
Publications
This is an Erratum for the article 2007 ApJ 660 1572
The Rapidly Flaring Afterglow Of The Very Bright And Energetic Grb 070125, Adria C. Updike, Josh B. Haislip, Melissa C. Nysewander, Andrew S. Fruchter, D. Alexander Kann, Sylvio Klose, Peter A. Miline, G. Grant Williams, Weikang Zheng, Carl W. Hergenrother
The Rapidly Flaring Afterglow Of The Very Bright And Energetic Grb 070125, Adria C. Updike, Josh B. Haislip, Melissa C. Nysewander, Andrew S. Fruchter, D. Alexander Kann, Sylvio Klose, Peter A. Miline, G. Grant Williams, Weikang Zheng, Carl W. Hergenrother
Publications
We report on multiwavelength observations, ranging from X-ray to radio wave bands, of the IPN-localized gamma-ray burst GRB 070125. Spectroscopic observations reveal the presence of absorption lines due to O i,Si ii,and C iv, implying a likely redshift of z ¼1:547. The well-sampled light curves, in particular from 0.5 to 4 days after the burst, suggest a jet break at 3.7 days, corresponding to a jet opening angle of $7.0, and implying an intrinsic GRB energy in the 1Y10,000 keV band of around E ¼(6:3Y6:9) ; 1051 ergs (based on the fluences measured by the gamma-ray de-tectorsof the IPN).GRB070125 is …
A Spectroscopic Analysis Of Hd 134439 And Hd 134440, Yu Chen
A Spectroscopic Analysis Of Hd 134439 And Hd 134440, Yu Chen
All Theses
We analyze elemental abundances of the common proper motion pair HD 134439 and HD 134440 to understand their formation history. This pair of metal-poor ([Fe/H]$\sim -1.50$) halo dwarfs are known, from previous studies, to exhibit abnormally low [$\alpha$/Fe] ratios compared to typical Galactic halo stars. Some have attributed this to planetesimal accretion; others believe these stars formed in the dusty part of a dwarf spheroidal galaxy and were later captured by our Galaxy. To investigate this anomaly, we measure carbon, nitrogen, and oxygen abundances for HD 134439 and HD 134440 from near-UV molecular features using high-resolution spectra obtained with Keck …
The Robotic Super-Lotis Telescope: Results & Future Plans, G. G. Williams, P. A. Milne, H. S. Park, S. D. Barthelmy, Dieter H. Hartmann, A. Updike, K. Hurley
The Robotic Super-Lotis Telescope: Results & Future Plans, G. G. Williams, P. A. Milne, H. S. Park, S. D. Barthelmy, Dieter H. Hartmann, A. Updike, K. Hurley
Publications
We provide an overview of the robotic Super-LOTIS (Livermore Optical Transient Imaging System) telescope and present results from gamma-ray burst (GRB) afterglow observations using Super-LOTIS and other Steward Observatory telescopes. The 0.6-m Super-LOTIS telescope is a fully robotic system dedicated to the measurement of prompt and early time optical emission from GRBs. The system began routine operations from its Steward Observatory site atop Kitt Peak in April 2000 and currently operates every clear night. The telescope is instrumented with an optical CCD camera and a four position filter wheel. It is capable of observing Swift Burst Alert Telescope (BAT) error …
Relativistic Particle-In-Cell Simulation Of Prompt And Early Afterglows From Grbs, K.-I. Nishikawa, P. Hardee, Y. Mizuno, M. Medvedev, B. Zhang, Dieter H. Hartmann, G. J. Fishman
Relativistic Particle-In-Cell Simulation Of Prompt And Early Afterglows From Grbs, K.-I. Nishikawa, P. Hardee, Y. Mizuno, M. Medvedev, B. Zhang, Dieter H. Hartmann, G. J. Fishman
Publications
Nonthermal radiation observed from astrophysical systems containing relativistic jets and shocks, e.g., gamma-ray bursts (GRBs), active galactic nuclei (AGNs), and microquasars commonly exibit power-law emission spectra. Recent PIC simulations of relativistic electro-ion (or electron-positron) jets injected into a stationary medium show that particle acceleration occurs within the downstream jet. In collisionless, relativistic shocks, particle (electron, positron, and ion) acceleration is due to plasma waves and their associated instabilities (e.g., the Weibel (filamentation) instability) created in shock region. The simulations show that the Weibel instability in responsible for generating and amplifying highly non-uniform, small-scale magnetic fields. These fields contribute to the …
Implications Of Cosmological Gamma-Ray Absorption. Ii. Modifications Of Gamma-Ray Spectra, Dieter H. Hartmann, T. M. Kneiske, T. Bretz, K. Mannheim
Implications Of Cosmological Gamma-Ray Absorption. Ii. Modifications Of Gamma-Ray Spectra, Dieter H. Hartmann, T. M. Kneiske, T. Bretz, K. Mannheim
Publications
Bearing on the model for the time-dependent metagalactic radiation field developed in the first paper of this series, we compute the gamma-ray attenuation due to pair production in photon-photon scattering. Emphasis is on the effects of varying the star formation rate and the fraction of UV radiation assumed to escape from the star forming regions, the latter being important mainly for high-redshift sources. Conversely, we investigate how the metagalactic radiation field can be measured from the gamma-ray pair creation cutoff as a function of redshift, the Fazio-Stecker relation. For three observed TeV-blazars (Mkn501, Mkn421, H1426+428) we study the effects of …
Exist's Gamma-Ray Burst Sensitivity, D. L. Band, J. E. Grindlay, A. Garson Iii, H. Krawczynski, Dieter H. Hartmann, S. Barthemy, N. Gehrels, G. Skinner
Exist's Gamma-Ray Burst Sensitivity, D. L. Band, J. E. Grindlay, A. Garson Iii, H. Krawczynski, Dieter H. Hartmann, S. Barthemy, N. Gehrels, G. Skinner
Publications
We use semianalytic techniques to evaluate the burst sensitivity of designs for the EXIST hard X-ray survey mis-sion. Applying these techniques to the mission design proposed for the Beyond Einstein program,we find that with its very large field of view and faint gamma-ray burst detection threshold, EXIST will detect and localize approximately two bursts per day, a large fraction of which may be at high redshift. We estimate that EXIST’s maximum sensitivity will be ~4 times greater than that of Swift’s Burst Alert Telescope. Bursts will be localized to better than 40" at thresh-old, with a burst position as good …
A Magnetohydrodynamic Boost For Relativistic Jets, Yosuke Mizuno, Phillip Hardee, Dieter H. Hartmann, Ken-Ichi Nishikawa, Bing Zhang
A Magnetohydrodynamic Boost For Relativistic Jets, Yosuke Mizuno, Phillip Hardee, Dieter H. Hartmann, Ken-Ichi Nishikawa, Bing Zhang
Publications
We performed relativistic magnetohydrodynamic simulations of the hydrodynamic boosting mechanism for relativistic jets explored by Aloy & Rezzolla (2006) using the RAISHIN code. Simulation results show that the presence of a magnetic field changes the properties of the shock interface between the tenuous, overpressured jet (Vzj) flowing tangentially to a dense external medium. Magnetic fields can lead to more efficient acceleration of the jet, in comparison to the pure-hydrodynamic case. A "polodial" magnetic field (Bz), tangent to the interface and parallel to the jet flow, produces both a stronger outward moving shock and a stronger inward moving rarefaction wave. This …
Constraints On An Optical Afterglow And On Supernova Light Following The Short Burst Grb 050813, P. Ferreo, S. F. Sanchez, D. A. Kann, S. Klose, J. Greiner, J. Gorosabel, Dieter H. Hartmann, A. A. Henden, P. Møller, E. Palazzi
Constraints On An Optical Afterglow And On Supernova Light Following The Short Burst Grb 050813, P. Ferreo, S. F. Sanchez, D. A. Kann, S. Klose, J. Greiner, J. Gorosabel, Dieter H. Hartmann, A. A. Henden, P. Møller, E. Palazzi
Publications
We report early follow-up observations of the error box of the short burst GRB 050813 using the telescopes at Calar Alto and Observatorio Sierra Nevada, followed by deep VLT FORS2 I-band observations obtained under very good seeing conditions 5.7 and 11.7 days after the event. Neither a fading afterglow nor a rising SN component was found, so the potential GRB host galaxy has not been identified based on a comparison of the two VLT images taken at different epochs. We discuss whether any of the galaxies present in the original 1000 XRTerror circle could be the host.In anycase, the optical …
An Examination Of Colliding Galaxy Clusters: Recreating 1e 0657-56 With Gadget-2, Joseph Johnson
An Examination Of Colliding Galaxy Clusters: Recreating 1e 0657-56 With Gadget-2, Joseph Johnson
All Theses
In this thesis I use the publicly available smooth particle hydrodynamics (SPH) code GADGET-2 to investigate and recreate the phenomenon of two merging galaxy clusters, as currently seen in the hot X-ray cluster 1E 0657-56 (the 'bullet cluster'). In this scenario, the stellar and dark matter components of the galaxies pass through the collision without experiencing strong stopping forces, but the intra-cluster gas is significantly slowed by ram pressure. This leads to a spatial separation between the galaxies and the intra-cluster gas, which provides a testing ground for gravitational theories. Weak gravitational lensing in the cluster has been used to …
Supernova Injection Of Short-Lived Radionuclides Into The Presolar Cloud: A Feasibility Study, Keith Davis
Supernova Injection Of Short-Lived Radionuclides Into The Presolar Cloud: A Feasibility Study, Keith Davis
All Dissertations
Meteorite inclusions show that the early solar system was radioactive with species of short lifetimes compared to the formation time of the solar system. Transporting the radioactive material from the creation site to the formation site of the sun was expected to take enough time that these species should have decayed to nonexistence. Some special series of events seems necessary to speed the process along. Cameron & Truran (1977) suggested that the source of these short-lived radionuclides could have been a supernova. Numerical hydrodynamic studies have shown that slow shockwaves can inject material into a small, dense cloud core. Most …
The Evolution Of Protoplanetary Disks: A Decade Of Hst Coronagraphy, Sean Brittain, C Grady, G Schneider, B E. Woodgate, J P. Wisniewski, M L. Sitko, K Collins
The Evolution Of Protoplanetary Disks: A Decade Of Hst Coronagraphy, Sean Brittain, C Grady, G Schneider, B E. Woodgate, J P. Wisniewski, M L. Sitko, K Collins
Presentation
No abstract provided.
Searching For H3+ In The Atmosphere Of The Exoplanet Hd 209458b, Matthew Troutman
Searching For H3+ In The Atmosphere Of The Exoplanet Hd 209458b, Matthew Troutman
All Theses
This thesis searches or the H3+ molecule in the atmosphere of HD 209458b. This exoplanet has been well studied since its initial discovery. H3+ is a diagnostic of the thermal regulation in the ionosphere of the exoplanet, and therefore is an advantageous molecule to test both atmospheric models and observational limits. Both models and observational limits need to be constrained as steps towards the ultimate goal of detecting biomarkers in the atmospheres of exoplanets. The exoplanet HD 209458b was observed during transit using PHOENIX on Gemini South in 2005.
Gamma Ray Burst Afterglow Observations, Adria Updike
Gamma Ray Burst Afterglow Observations, Adria Updike
All Theses
Gamma ray bursts (GRBs) are among the most luminous explosions in the universe. We present an overview of the observational history of GRBs and the mechanisms involved, then focus on one burst in particular, GRB 070125 and our observational campaign. Finally, we present the results of a model of the global optical response to GRBs, and make recommendations as to how we could improve the global response in preparation for upcoming satellite missions.
Keck Hires Spectroscopy Of Candidate Post T Tauri Stars, Eric Bubar
Keck Hires Spectroscopy Of Candidate Post T Tauri Stars, Eric Bubar
All Theses
This work utilizes an age-oriented method to identify isolated post T Tauri stars in a 13-star sample of high resolution spectroscopy from the 10-m Keck telescope. This analysis utilizes qualitative age information derived from lithium abundances, chromospheric emission indices and UVW kinematic motions in analyzing positions in the the H-R diagram. Once qualitatively assigned a ``young'' age, pre-main sequence isochrones are utilized to determine stellar mass and age estimates. Through this method, 5 of the 13 stars have been confirmed as being in the post T Tauri class. We also examine irregular photometric variability of PTTs and compare the homology …
Warm Gas In The Inner Disks Around Young Intermediate-Mass Stars, Sean D. Brittain, Theodore Simon, Joan R. Najita, Terrence W. Rettig
Warm Gas In The Inner Disks Around Young Intermediate-Mass Stars, Sean D. Brittain, Theodore Simon, Joan R. Najita, Terrence W. Rettig
Publications
The characterization of gas in the inner disks around young stars is of particular interest because of its connection to planet formation. In order to study the gas in inner disks, we have obtained high-resolution K- and M-band spectroscopy of 14 intermediate-mass young stars. In sources that have optically thick inner disks, i.e., E(K-L)>1, our detection rate of the rovibrational CO transitions is 100%, and the gas is thermally excited. Of the five sources that do not have optically thick inner disks, we only detect the rovibrational CO transitions from HD 141569. In this case, we show that the …
Infrared High-Resolution Spectroscopy Of Post-Agb Circumstellar Disks. I. Hr 4049: The Winnowing Flow Observed?, Kenneth H. Hinkle, Sean D. Brittain, David L. Lambert
Infrared High-Resolution Spectroscopy Of Post-Agb Circumstellar Disks. I. Hr 4049: The Winnowing Flow Observed?, Kenneth H. Hinkle, Sean D. Brittain, David L. Lambert
Publications
High-resolution infrared spectroscopy in the 2.3-4.6 micron region is reported for the peculiar A supergiant, single-lined spectroscopic binary HR 4049. Lines from the CO fundamental and first overtone, OH fundamental, and several H2O vibration-rotation transitions have been observed in the near-infrared spectrum. The spectrum of HR 4049 appears principally in emission through the 3 and 4.6 micron region and in absorption in the 2 micron region. The 4.6 micron spectrum shows a rich 'forest' of emission lines. All the spectral lines observed in the 2.3-4.6 micron spectrum are shown to be circumbinary in origin. The presence of OH and H2O …
Possible Identification Of A Metal-Rich Old Moving Group: High-Resolution Spectroscopy Of Candidate Members, Abigail R. Daane, Jeremy R. King, Simon C. Schuler
Possible Identification Of A Metal-Rich Old Moving Group: High-Resolution Spectroscopy Of Candidate Members, Abigail R. Daane, Jeremy R. King, Simon C. Schuler
Publications
Using new high-resolution spectroscopic observations from both the McDonald Observatory 2.7 m and Kitt Peak National Observatory 4 m telescopes, we observed four candidate members of the Ursa Major moving group previously suggested to instead belong to a significantly older kinematic assemblage. The Fe abundances we measure strongly suggest that these stars are not UMa members but form a more metal-rich group of stars (+0.10 ≤ [Fe/H] ≤ +0.18) with an age near 3 Gyr. Our [Ca/H] determinations corroborate this result. The apparent similarities in metallicity and previously discovered UVW space motions lend credence to prior suggestions that these stars …
Warm Hcn, C2h2, And Co In The Disk Of Gv Tau, E L. Gibb, K A. Vanbrunt, Sean D. Brittain, T W. Rettig
Warm Hcn, C2h2, And Co In The Disk Of Gv Tau, E L. Gibb, K A. Vanbrunt, Sean D. Brittain, T W. Rettig
Publications
We present the first high-resolution, ground-based observations of HCN and C2H2 toward the T Tauri binary star system GV Tau. We detected strong absorption due to HCN nu3 and weak C2H2 [nu3 and nu2+(nu4+nu5)0+] absorption toward the primary (GV Tau S) but not the infrared companion. We also report CO column densities and rotational temperatures, and present abundances relative to CO of HCN/CO~0.6% and C2H/CO~1.2% and an upper limit for CH4/CO