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Articles 1 - 12 of 12
Full-Text Articles in Physical Sciences and Mathematics
Molecular Processes In Astrophysics: Calculations Of H + H2 Excitation, De-Excitation, And Cooling, Matthew Kelley
Molecular Processes In Astrophysics: Calculations Of H + H2 Excitation, De-Excitation, And Cooling, Matthew Kelley
UNLV Theses, Dissertations, Professional Papers, and Capstones
The implications of H+H2 cooling in astrophysics is important to several applications. One of the most significant and pure applications is its role in cooling in the early universe. Other applications would include molecular dynamics in nebulae and their collapse into stars and astrophysical shocks. Shortly after the big bang, the universe was a hot primordial gas of photons, electrons, and nuclei among other ingredients. By far the most dominant nuclei in the early universe was hydrogen. In fact, in the early universe the matter density was 90 percent hydrogen and only 10 percent helium with small amounts of lithium …
The Metallicity Of The Cm Draconis System, Ryan C. Terrien, Scott W. Fleming, Suvrath Mahadevan, Rohit Deshpande, Gregory A. Feiden
The Metallicity Of The Cm Draconis System, Ryan C. Terrien, Scott W. Fleming, Suvrath Mahadevan, Rohit Deshpande, Gregory A. Feiden
Dartmouth Scholarship
The CM Draconis system comprises two eclipsing mid-M dwarfs of nearly equal mass in a 1.27-day orbit. This well-studied eclipsing binary has often been used for benchmark tests of stellar models, since its components are amongst the lowest mass stars with well-measured masses and radii (~ 1% relative precision). However, as with many other low-mass stars, non-magnetic models have been unable to match the observed radii and effective temperatures for CM Dra at the 5-10% level. To date, the uncertain metallicity of the system has complicated comparison of theoretical isochrones with observations. In this Letter, we use data from the …
Supernova Resonance-Scattering Line Profiles In The Absence Of A Photosphere, Brian Friesen, E. Baron, David Branch, Bin Chen, Jerod T. Parrent, R. C. Thomas
Supernova Resonance-Scattering Line Profiles In The Absence Of A Photosphere, Brian Friesen, E. Baron, David Branch, Bin Chen, Jerod T. Parrent, R. C. Thomas
Dartmouth Scholarship
In supernova (SN) spectroscopy relatively little attention has been given to the properties of optically thick spectral lines in epochs following the photosphere's recession. Most treatments and analyses of post-photospheric optical spectra of SNe assume that forbidden-line emission comprises most if not all spectral features. However, evidence exists that suggests that some spectra exhibit line profiles formed via optically thick resonance-scattering even months or years after the SN explosion. To explore this possibility, we present a geometrical approach to SN spectrum formation based on the "Elementary Supernova" model, wherein we investigate the characteristics of resonance-scattering in optically thick lines while …
The 1.17 Day Orbit Of The Double-Degenerate (Da+Dq) Nltt 16249, S. Vennes, A. Kawka, S. J. O'Toole, J. R. Thorstensen
The 1.17 Day Orbit Of The Double-Degenerate (Da+Dq) Nltt 16249, S. Vennes, A. Kawka, S. J. O'Toole, J. R. Thorstensen
Dartmouth Scholarship
New spectroscopic observations show that the double degenerate system NLTT 16249 is in a close orbit (a = 5.6+/-0.3 R_sun) with a period of 1.17 d. The total mass of the system is estimated between 1.47 and 2.04 M_sun but it is not expected to merge within a Hubble time-scale (t_merge ~ 10^11 yr). Vennes & Kawka (2012, ApJ, 745, L12) originally identified the system because of the peculiar composite hydrogen (DA class) and molecular (C_2--DQ class--and CN) spectra and the new observations establish this system as the first DA plus DQ close double degenerate. Also, the DQ component was …
High-Velocity Outflows Without Agn Feedback: Eddington-Limited Star Formation In Compact Massive Galaxies, Aleksandar M. Diamond-Stanic, John Moustakas, Christy A. Tremonti, Alison L. Coil, Ryan C. Hickox
High-Velocity Outflows Without Agn Feedback: Eddington-Limited Star Formation In Compact Massive Galaxies, Aleksandar M. Diamond-Stanic, John Moustakas, Christy A. Tremonti, Alison L. Coil, Ryan C. Hickox
Dartmouth Scholarship
We present the discovery of compact, obscured star formation in galaxies at z ~ 0.6 that exhibit 1000 km s–1 outflows. Using optical morphologies from the Hubble Space Telescope and infrared photometry from the Wide-field Infrared Survey Explorer, we estimate star formation rate (SFR) surface densities that approach ΣSFR ≈ 3000 M ☉ yr–1 kpc–2, comparable to the Eddington limit from radiation pressure on dust grains. We argue that feedback associated with a compact starburst in the form of radiation pressure from massive stars and ram pressure from supernovae and stellar winds is sufficient …
Spectroscopy And Photometry Of Cataclysmic Variable Candidates From The Catalina Real Time Survey, John R. Thorstensen, Julie N. Skinner
Spectroscopy And Photometry Of Cataclysmic Variable Candidates From The Catalina Real Time Survey, John R. Thorstensen, Julie N. Skinner
Dartmouth Scholarship
The Catalina Real Time Survey (CRTS) has found over 500 cataclysmic variable (CV) candidates, most of which were previously unknown. We report here on follow-up spectroscopy of 36 of the brighter objects. Nearly all of the spectra are typical of CVs at minimum light. One object appears to be a flare star, while another has a spectrum consistent with a CV but lies, intriguingly, at the center of a small nebulosity. We measured orbital periods for eight of the CVs, and estimated distances for two based on the spectra of their secondary stars. In addition to the spectra, we obtained …
Analysis Of The Early-Time Optical Spectra Of Sn 2011fe In M101, J. T. Parrent, D. A. Howell, B. Friesen, R. C. Thomas
Analysis Of The Early-Time Optical Spectra Of Sn 2011fe In M101, J. T. Parrent, D. A. Howell, B. Friesen, R. C. Thomas
Dartmouth Scholarship
The nearby Type Ia supernova SN 2011fe in M101 (cz=241 km s^-1) provides a unique opportunity to study the early evolution of a "normal" Type Ia supernova, its compositional structure, and its elusive progenitor system. We present 18 high signal-to-noise spectra of SN 2011fe during its first month beginning 1.2 days post-explosion and with an average cadence of 1.8 days. This gives a clear picture of how various line-forming species are distributed within the outer layers of the ejecta, including that of unburned material (C+O). We follow the evolution of C II absorption features until they diminish near maximum light, …
Late-Time Optical Emission From Core-Collapse Supernovae, Dan Milisavljevic, Robert A. Fesen, Roger A. Chevalier, Robert P. Kirshner
Late-Time Optical Emission From Core-Collapse Supernovae, Dan Milisavljevic, Robert A. Fesen, Roger A. Chevalier, Robert P. Kirshner
Dartmouth Scholarship
Ground-based optical spectra and Hubble Space Telescope images of 10 core-collapse supernovae (CCSNe) obtained several years to decades after outburst are analyzed with the aim of understanding the general properties of their late-time emissions. New observations of SN 1957D, 1970G, 1980K, and 1993J are included as part of the study. Blueshifted line emissions in oxygen and/or hydrogen with conspicuous line substructure are a common and long-lasting phenomenon in the late-time spectra. Followed through multiple epochs, changes in the relative strengths and velocity widths of the emission lines are consistent with expectations for emissions produced by interaction between SN ejecta and …
The Ages And Metallicities Of Type Ia Supernova Host Galaxies From The Nearby Galaxies Supernova Search Program, Suzanna Sadler
The Ages And Metallicities Of Type Ia Supernova Host Galaxies From The Nearby Galaxies Supernova Search Program, Suzanna Sadler
Mahurin Honors College Capstone Experience/Thesis Projects
We seek to better understand the physical constraints under which White Dwarf stars ultimately become Type Ia supernovae (SNe Ia), an important test of the robustness of these tools in precisely measuring Dark Energy, as the definite progenitor system still remains elusive. The host galaxy environments of Type Ia supernovae provide our best opportunity for constraining the mechanism(s) of SN Ia production, i.e., the stars involved and the incubation times (tied to stellar ages), and the sensitivity of SNe Ia to changes in the local metallicity. We have measured the ages and metallicities of approximately 60 galaxies from a sample …
Spitzer Imaging And Spectral Mapping Of The Oxygen-Rich Supernova Remnant G292.0+1.8, Parviz Ghavamian, Knox S. Long, William P. Blair, Sangwook Park, Robert Fesen
Spitzer Imaging And Spectral Mapping Of The Oxygen-Rich Supernova Remnant G292.0+1.8, Parviz Ghavamian, Knox S. Long, William P. Blair, Sangwook Park, Robert Fesen
Dartmouth Scholarship
We present mid-infrared continuum and emission line images of the Galactic oxygen-rich supernova remnant (SNR) G292.0+1.8, acquired using the MIPS and IRS instruments on the Spitzer Space Telescope. The MIPS 24 μm and 70 μm images of G292.0+1.8 are dominated by continuum emission from a network of filaments encircling the SNR. The morphology of the SNR, as seen in the mid-infrared, resembles that seen in X-rays with the Chandra X-Ray Observatory. Most of the mid-infrared emission in the MIPS images is produced by circumstellar dust heated in the non-radiative shocks around G292.0+1.8, confirming the results of earlier mid-IR …
Essentials Of The Theory Of Abstraction - Lecture, Subhajit Kumar Ganguly
Essentials Of The Theory Of Abstraction - Lecture, Subhajit Kumar Ganguly
Subhajit Kumar Ganguly
In not favouring solutions or sets of solutions, the principle of zero-postulation drives away any unwanted incompleteness from the description of the world. It is the interactions between the possible exhaustive set of solutions that creates the impression pointedness or directiveness in the universe, leading to the formation of clusters, as discussed earlier. These interactions may be chaotic in nature, giving rise to attractor points where the directiveness inside any given system asymptotically seem to approach. It is this directiveness, in turn, inside a given system or in the universe as a whole, that is the cause of all known …
Quantization And Discretization At Large Scales, Florentin Smarandache, Victor Christianto, Pavel Pintr
Quantization And Discretization At Large Scales, Florentin Smarandache, Victor Christianto, Pavel Pintr
Branch Mathematics and Statistics Faculty and Staff Publications
The ongoing search of extrasolar planets is one of the most attractive fields of research in astrophysics and astronomy. Up to now, 360 extrasolar planets have been discovered near stars with similar mass as the Sun. There is also discovery related to the so-called Earth-like planets. With regards to these discoveries, one intriguing question is whether there is relationship between orbit distance of the planets and their stars. Various formulas have been suggested since 1990s, and they suggest that there may be reason to accept quantization of distances of those planets both in our solar system and also in extrasolar …