Open Access. Powered by Scholars. Published by Universities.®
Stars, Interstellar Medium and the Galaxy Commons™
Open Access. Powered by Scholars. Published by Universities.®
- Keyword
-
- Astrochemistry (1)
- Atomic/Molecular Processes (1)
- B-emission stars (1)
- Be star (1)
- Binary system (1)
-
- Circumstellar Disks (1)
- Coherent Interactions (1)
- Data analysis (1)
- Decretion disks (1)
- Disk structure (1)
- Dust (1)
- Emission Line stars (1)
- H-alpha spectroscopy (1)
- Herbig Ae/Be stars (1)
- Hydrodynamics (1)
- Hysics (1)
- Interstellar Medium (1)
- Interstellar medium (1)
- Lines and bands (1)
- Maser (1)
- Mass function (1)
- Model fitting (1)
- Model selection (1)
- Molecules (1)
- Numerical simulations (1)
- Optical interferometry (1)
- Pre-main sequence stars (1)
- Spectroscopy (1)
- Star formation (1)
- Stellar clusters (1)
Articles 1 - 6 of 6
Full-Text Articles in Stars, Interstellar Medium and the Galaxy
The Geometry And Density Of B-Emission Star Disks From Statistical Analysis And Numerical Simulations, Isabelle H. Cyr
The Geometry And Density Of B-Emission Star Disks From Statistical Analysis And Numerical Simulations, Isabelle H. Cyr
Electronic Thesis and Dissertation Repository
This thesis is divided into 3 investigations. First we present a novel method to estimate the opening angles of Be star disks from interferometric axis ratio measurements, using Bayesian statistics and Monte Carlo techniques. A large set of theoretical axis ratios generated from disk models were compared to observational samples to determine which distribution best reproduces the observations. We find that the observed axis ratio distributions in the K-, H-, and N-band can best be explained by the presence of thin disks while measurements over the H$\alpha$ line point toward slightly thicker disks. Second, using a smoothed particle hydrodynamics (SPH) …
The Circumstellar Environments Of B-Emission Stars By Optical Interferometry, Bethany Grzenia
The Circumstellar Environments Of B-Emission Stars By Optical Interferometry, Bethany Grzenia
Electronic Thesis and Dissertation Repository
A series of B-emission (Be) stars was observed interferometrically and numerically modelled to be consistent with the observations. Uniform geometrical disks were used to make first-order inferences about the configuration of the disk systems’ extended structures and their extent on the sky. Later, the Bedisk-Beray-2dDFTpipeline was used to make sophisticated non-local thermodynamic equilibrium (LTE) calculations of the conditions within the disks. In the first instance, sixteen stars were observed in the near-infrared (K-band, 2.2 micron) with the Palomar Testbed Interferometer (PTI). The Bedisk portion of the pipeline was used to model disk temperature and density structures for B0, B2, B5 …
Dicke’S Superradiance In Astrophysics, Fereshteh Rajabi
Dicke’S Superradiance In Astrophysics, Fereshteh Rajabi
Electronic Thesis and Dissertation Repository
It is generally assumed that in the interstellar medium much of the emission emanating from atomic and molecular transitions within a radiating gas happen independently for each atom or molecule, but as was pointed out by R. H. Dicke in a seminal paper several decades ago this assumption does not apply in all conditions. As will be discussed in this thesis, and following Dicke’s original analysis, closely packed atoms/molecules can interact with their common electromagnetic field and radiate coherently through an effect he named superradiance. Superradiance is a cooperative quantum mechanical phenomenon characterized by high intensity, spatially compact, burst-like features …
The Spectral Variability Of Astronomical Pahs, Matthew Shannon
The Spectral Variability Of Astronomical Pahs, Matthew Shannon
Electronic Thesis and Dissertation Repository
Polycyclic aromatic hydrocarbons (PAHs) are highly abundant molecules found throughout the universe. Illuminated by ultraviolet photons, they can emit up to 10% of the total power output of star-forming galaxies and are involved in many important physical and chemical processes (e.g., gas heating). They produce prominent emission bands between 3-20 μm which vary strongly in intensity and spectral profile. The origins of these variations are not fully understood, which limits the use of PAHs as (ubiquitous) diagnostic tracers of physical conditions. To characterize their variability, we studied the relative intensities and profiles of the 10-20 μm PAH bands in a …
Modeling The Mass Function Of Stellar Clusters Using The Modified Lognormal Power-Law Probability Distribution Function, Deepakshi Madaan
Modeling The Mass Function Of Stellar Clusters Using The Modified Lognormal Power-Law Probability Distribution Function, Deepakshi Madaan
Electronic Thesis and Dissertation Repository
We use the Modified Lognormal Power-law (MLP) probability distribution function to model the behaviour of the mass function (MF) of young and populous stellar populations in different environments. We begin by modeling the MF of NGC1711, a simple stellar population (SSP) in the Large Magellanic Cloud as a pilot case. We then use model selection criterion to differentiate between candidate models. Using the MLP we find that the stellar catalogue of NGC1711 follows a pure power-law behaviour below the completeness limit with the slope α = 2.75 for dN/dlnm ∝ m^(−α+1) in the mass range 0.89 M⊙ to 7.75 M⊙. …
The Inner Gaseous Disks Of Herbig Be Stars, Parshati Patel
The Inner Gaseous Disks Of Herbig Be Stars, Parshati Patel
Electronic Thesis and Dissertation Repository
Herbig Ae/Be stars are intermediate mass (~2 to 20Msun) pre-main sequence stars that inherit a circumstellar disk of dust and gas from their formation phase. The region of this disk closest to the star is entirely gaseous because dust evaporates at the high temperatures there, and this gaseous region is currently poorly understood. Using non-LTE circumstellar disk codes to model the optical and near-infrared spectra of five, early-type (B0Ve to B2Ve) Herbig Be stars obtained with the Canada-France-Hawaii telescope ESPaDOnS instrument, the density structure of each inner gaseous disks was determined and estimates of the disk masses and …