An Analysis of Spectral Variability in SIMPJ013656.57+093347.3 Over Three Epochs of Hubble Space Telescope Observations

Hall, Jumi, Astronomy, University of Virginia
Zhou, Yifan, AS-Astronomy (ASTR), University of Virginia

This thesis analyzes time-resolved spectra acquired over three time periods of data gathered from brown dwarf SIMPJ013656.57+093347.3 (SIMPJ0136 for short). It begins with an overview of exoplanet discovery methods and the value of brown dwarf atmospheric analysis on exoplanetary science. Specifically, we find that the atmosphere of SIMPJ0136 most resembles those of directly imaged planets. This leads to a summary of past findings concerning the brown dwarf SIMPJ0136, which includes conclusions from the paper whose data we re-analyze and replicate along with 2 other epochs' data. Then, spectral information is integrated over a range of wavelengths, producing light curves. Rotational modulations found in the light curves support a 2.4-hour period of rotation and the possibility of cloud structures. Phase-folded light curves from the three epochs are created, along with plots of the maximum and minimum spectra from each epoch. With data from the three epochs, we create a simple 2D plot of light flux produced from a blackbody to explore how a cold spot's temperature and coverage percentage may change the flux produced. Models of brown dwarf atmospheres with different temperatures and thicknesses are compared against our observational data, and the chi-square formula is used to determine the model of best fit. The model is then improved upon to find exact variations of cloud thickness and temperature in the atmosphere. Through light curve analysis, spectral ratio analyses, and best-fit modeling, this thesis concludes that the long-term variability present between the epochs does not exceed the rotational modulation of the epochs themselves. It concludes that over three epochs, the majority of the atmosphere on SIMPJ0136 consists of thin clouds at a temperature of 1200 Kelvin, with a patch of thick clouds covering 12 percent of one hemisphere in Epochs 1 and 2, and 6 percent of one hemisphere in Epoch 3.

BA (Bachelor of Arts)
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