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Characterization of online archives of astronomical imaging vis-(&)#224;-vis serendipitous asteroids, and their astrometric properties
Title
Characterization of online archives of astronomical imaging vis-(&)#224;-vis serendipitous asteroids, and their astrometric properties.
Creator
Denis, Jean-Marc, Fernandez, Yanga, Britt, Daniel, Schelling, Patrick, University of Central Florida
Abstract / Description
The identification of known asteroids on existing CCD pictures would allow us to obtain accurate astrometric and photometric asteroid properties. Some asteroids might have ambiguous orbital elements, thus their identification along with their exact positions on multiple picture frames could significantly improve their orbital elements. Furthermore, the possibility of identifying known asteroids on older pictures, sometimes preceding their discovery date, might allow the study of non...
Show moreThe identification of known asteroids on existing CCD pictures would allow us to obtain accurate astrometric and photometric asteroid properties. Some asteroids might have ambiguous orbital elements, thus their identification along with their exact positions on multiple picture frames could significantly improve their orbital elements. Furthermore, the possibility of identifying known asteroids on older pictures, sometimes preceding their discovery date, might allow the study of non-gravitational effects like the Yarkovsky effect.Identifying a potential Yarkovsky effect on asteroids is challenging because it is extremely weak. However, this effect cumulates with time, therefore, it is necessary to find astronomical pictures that are as old as possible. In addition, we need to collect high quality CCD pictures and use a methodology that would allow obtaining a statistically significant sample of asteroids. To accomplish this, we decided to use the online archive of the Subaru telescope at Mauna Kea Hawaii because it has a prime-focus camera with a very high resolution of 80 millions pixels very well suited to capture serendipitous asteroids. In addition, the Subaru online archive has pictures from the last 10 years.The methodology used in this thesis is to build a database that contains the orbital elements of all the known asteroids, allowing us to write a program that calculates the approximate position of all the asteroids at the date and time of each CCD picture we collect. To obtain a more precise position, the program also interfaces the JPL NASA Horizons on-line computation service. Every time an asteroid is found on a picture, Horizons sends its theoretical location back to the program. A later visual identification of this asteroid at this theoretical location on the picture triggers its input into our sample for further study. This method allowed us to visually confirm 508 distinct asteroids on 692 frames with an average diameter of 3.6 km. Finally, we use the theory (given in appendix A) to calculate the theoretical drift of these asteroids that we compare with the one we measured on the CCD pictures.
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Date Issued
2012
Identifier
CFE0004299, ucf:49460
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0004299
Detecting and Characterizing Exoplanets: The GJ 436 and HD 149026 Systems
Title
Detecting and Characterizing Exoplanets: The GJ 436 and HD 149026 Systems.
Creator
Stevenson, Kevin, Harrington, Joseph, Peale, Robert, Fernandez, Yanga, Deming, Drake, University of Central Florida
Abstract / Description
This dissertation investigates two stellar systems known to contain extrasolar planets. It is comprised of five chapters that are readily divided into three independent but related analyses. Chapter 1 reports on the analysis of low signal-to-noise secondary-eclipse observations of the Neptune-sized exoplanet GJ 436b using the Spitzer Space Telescope in multiple infrared channels. The measured wavelength-dependent eclipse depths provide constraints on the planet's dayside atmospheric...
Show moreThis dissertation investigates two stellar systems known to contain extrasolar planets. It is comprised of five chapters that are readily divided into three independent but related analyses. Chapter 1 reports on the analysis of low signal-to-noise secondary-eclipse observations of the Neptune-sized exoplanet GJ 436b using the Spitzer Space Telescope in multiple infrared channels. The measured wavelength-dependent eclipse depths provide constraints on the planet's dayside atmospheric composition and thermal profile. The analysis indicates that GJ 436b's atmosphere is abundant in carbon monoxide and deficient in methane relative to thermochemical equilibrium models for the predicted hydrogen-dominated atmosphere.Chapter 2 discusses the techniques used to analyze GJ 436b, introduces the Least Asymmetry centering method and compares its effectiveness to two existing techniques, and describes the functions used to model Spitzer's position- and time-dependent systematics. Additionally, it includes best-fit parameters with uncertainties, histograms of the free parameters, and correlation plots between free parameters.Chapter 3 reports on the analysis of eleven HD 149026b secondary-eclipse observations at five Spitzer wavelengths plus three primary-transit observations at 8.0 microns. Chemical-equilibrium models find no indication of a temperature inversion in the dayside atmosphere of HD 149026b. The best-fit model favors large amounts of CO and CO2, moderate heat redistribution (f = 0.5), and a strongly enhanced metallicity. These analyses use BiLinearly-Interpolated Subpixel Sensitivity (BLISS) mapping and parameter orthogonalization. The former is a new technique to model two position-dependent systematics, intrapixel variability and pixelation. The latter is a technique that accelerates the convergence of Markov chains that employ the Metropolis random walk sampler.Chapter 4 reports on the detection of GJ 436c, a 0.65 +/- 0.04 Earth-radii exoplanet transiting a nearby M-dwarf star with a period of 1.365862 +/- 8x10^{-6} days. It also presents evidence for a similarly sized exoplanet candidate (currently labeled UCF-1.02) orbiting the same star with an undetermined period. Assuming an Earth-like density of 5.515 g/cm^{3}, GJ 436c has a predicted mass of 0.28 Earth-masses (2.6 Mars-masses) and a surface gravity of 0.65 g (where g is the gravity on Earth). Its weak gravitational field and close proximity to its host star imply that GJ 436c is unlikely to have retained its original atmosphere; however, a transient atmosphere is possible if recent impacts or tidal heating were to supply volatiles to the surface. Chapter 5 presents numerical simulations of the GJ 436 system using the Mercury N-body integrator and detailed calculations used to constrain the atmospheric composition of the sub-Earth-sized planet GJ 436c. The simulations find a ~35-year periodic trend in the osculating elements wherein GJ 436c's eccentricity varies between 0 and 0.21, its peak-to-trough inclination amplitude is 3.2 degrees, and transit-timing variations range from +/-200 to +/-3 minutes.
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Date Issued
2012
Identifier
CFE0004640, ucf:49889
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0004640