Date of Award

January 2020

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Space Studies

First Advisor

Ronald Fevig

Abstract

Classifying asteroids by color and spectral features is important for understanding their compositions, linkages to meteorite types, and formation and evolution of the Solar System in general. Large data collection efforts such as the Sloan Digital Sky Survey (SDSS) have allowed for more comprehensive studies of the asteroid population. However, the repeatability and therefore reliability of such observations comes into question, especially as Szabo et al. (2004) and Carvano et al. (2010) reported sizable fractions of asteroids observed by SDSS exhibiting taxonomic variability.

This research studied two near-Earth asteroids (NEAs) with just one observation each by SDSS: 2059 Baboquivari and 96744 (1999 OW3). Observations using the 1 m Yale/SMARTS telescope at Cerro-Tololo Inter-American Observatory (CTIO) were conducted in order to investigate whether g, r, i, and z spectrophotometry was consistent with spectrophotometry by SDSS.

2059 Baboquivari’s root mean square z filter and z – i reflectance values did not show a statistically significant difference compared to those values from its SDSS observation. However, individual measurements of z filter and z – i reflectance values compared to those values from its SDSS observation varied up to the 3.8σ level, demonstrating a large dispersion in these z filter and z – i reflectance values. Using photometric spectra from these observations, 2059 Baboquivari could be classified as an S-/Q-type, C-complex, or P-/D-type asteroid. A rotational period could not be determined from the observations. However, 2059 Baboquivari’s light curve appeared flat across observation runs, suggesting z filter variability is not due to rotational effects. Comparing the brightness of bright stars not used in the calibration process during observations eliminated changing sky conditions as a cause of 2059 Baboquivari’s photometric variability. A test of the Kron algorithm used for photometry eliminated the algorithm’s significant contribution to observed z filter variability, which gives evidence that this variability is not due to the data analysis process. 2059 Baboquivari did not exhibit significant phase reddening of its i – g slope between phase angles of ~22 and ~45 – 50 degrees, but z – i 1 μm band depth generally decreased between phase angles of ~22 to ~45 – 50 degrees.

It was found that 96744 (1999 OW3) likely has a rotational period of ~2 hours or a multiple of ~2 hours. Observations in g, r, i, and z filters showed a repeating correlation between i – g spectral slope, z – i band depth, and C (clear) filter magnitude variation. This suggests that the composition of 96744 may vary across its surface. There were no clear relationships between spectral slope, band depth, and phase angle. However, i – g values showed a steeper visible spectral slope and z – i values showed a shallower 1 μm band depth for 8 Jan 2020 observations compared to those for 10 and 11 Jan 2020 observations.

In conclusion, although significant advances in the characterization of 2059 Baboquivari and 96744 (1999 OW3) were achieved, further study is needed to more precisely determine the properties of these two near-Earth asteroids.

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