APIRP: The Automated Photometric Data Reduction Package

For decades the Image Reduction and Analysis Facility (IRAF) has been the standard for processing CCD-based image datasets. During that time, technology has advanced and the astronomical record greatly expanded. However, the discovery process is often bogged down by the time consuming procedures of image reduction. To keep up with demand and shorten reduction steps programmers have developed a series of command languages (CL) for IRAF and most recently, within only the past five years, the Python-based language, Pyraf. Python is a robust and powerful language that combines syntactical simplicity with versatile and dynamic file management, database access and software development capabilities, to name just a few features. Pyraf, by extension, incorporates all of the qualities of IRAF CL, with all of the power and flexibility provided by Python. Pyraf scripts may be written to automate file processing at the same time that reduction tasks are called from IRAF. Thus, the potential to write fully automated reduction procedures is here; tightening the gaps of scientific advancement. We have created such a tool for CCD Photometry. Our Automated Photometric Image Reduction Package (APIRP) uses a range of graphical user interfaces (GUI\u27s) to form an interactive yet non-overbearing user environment. A combination of built-in file management and procedural variability makes APIRP a perfect choice for both amateur and professional astronomers. Due to the programs design, it can be run from anywhere on your computer and users can specify exactly what steps of reduction they wish to execute. Thus, setup is easy with no need for cumbersome documentation and tasks may be preformed piecewise or in blocks, depending on the users needs

Rotational Variability of Asteroid 490 Veritas in the Near-Infrared

We present rotationally resolved spectra of asteroid 490 Veritas in the near-infrared (NIR) that show interesting differences. Dynamical arguments indicate that 490 Veritas is the main fragment of a recent (8.3 My) asteroidal break-up. We obtained NIR spectra (0.8-2.4 microns) on UT May 11, 2008, using the SpeX instrument on NASA\u27s Infrared Telescope Facility (IRTF) on Mauna Kea, Hawaii. Since published visible spectra of 490 Veritas show some variability, we decided to observe its NIR spectrum at four distinct rotational phases. Veritas\u27s rotational light curve has a period of 7.93 hours with amplitudes ranging from 0.3 to 0.5 magnitudes in the visible. We define the time of our first observation as zero rotational phase and our subsequent observations are at 0.29, 0.52, and 0.70. Our reflectance spectra show a range of slopes. To characterize these slope differences, we normalized each spectrum to 1.0 reflectance at 1.25 microns and measured the reflectance at 2.2 microns. The values obtained are reflectances of 0.99, 1.02, 0.98, and 0.93 at rotational phase 0.00, 0.29, 0.52, and 0.70, respectively. The uncertainty in each reflectance value is ± 3%. In this work, we consider possible causes of this variability, including heterogeneity of the parent body and/or space weathering i.e., from different surfaces having experienced various exposure ages

Principal Component Analysis of Dynamically Distinct D-Type Asteroids

Principal Component Analysis (PCA), a common statistically based classification technique, has been used to classify asteroids into broad spectral categories. In some cases, a spectral superclass considered in isolation may undergo sub-classification (e.g. S-type subclasses). Since D-type asteroids populate at least three distinct dynamical regions in the asteroid belt -- namely Hilda, L4 Trojans and L5 Trojans, and since the recently-developed Nice” model (Morbidelli et al. 2005. Nature 435, 462; Levison et al. 2008, ACM 2008 abstract #8156) hypothesizes that these regions may share a common origin, examining the appropriateness of a D-type sub-classification scheme is warranted. Toward this end, we performed PCA on the D-type L4, L5, and Hilda asteroids. Our PCA was based on the Sloan Digital Sky Survey broadband colors (u - g, g - r, r - i, and i - z) of 31 L4, 24 L5, and 32 Hilda asteroids with radii ranging from approximately 5 to 45 km. PCA showed 90.2% of the variance in the spectra could be condensed into the first two principal components, PC1 and PC2, with the first and second component accounting for 50.7% and 39.4% respectively. No significant clustering is observed on a PC1 vs. PC2 plot suggesting the D-type L4, L5, and Hilda asteroids do not form three independent groups, but rather are spectrally indistinguishable. We performed several statistical analyses of the means and variances of the principal components to test the validity of this conclusion. No statistically significant difference in the means among the three groups was found, nor was there any such difference in the variances, although the statistic comparing the L4 Trojans and Hildas was close to the critical value. Further measurements of colors of both large and small Trojans and Hildas will let us continue to investigate the spectral diversity of these objects

The Potential of AutoClass as an Asteroidal Data Mining Tool

AutoClass-C, an artificial intelligence program designed to classify large data sets, was developed by NASA to classify stars based upon their infrared colors. Wanting to investigate its ability to classify asteroidal data, we conducted a preliminary test to determine if it could accurately reproduce the Tholen taxonomy using the data from the Eight Color Asteroid Survey (ECAS). For our initial test, we limited ourselves to those asteroids belonging to S, C, or X classes, and to asteroids with a color difference error of less than +/- 0.05 magnitudes. Of those 406 asteroids, AutoClass was able to confidently classify 85%: identifying the remaining asteroids as belonging to more than one class. Of the 346 asteroids that AutoClass classified, all but 3 (\u3c1%) were classified as they had been in the Tholen classification scheme. Inspired by our initial success, we reran AutoClass, this time including IRAS albedos and limiting the asteroids to those that had also been observed and classified in the Bus taxonomy. Of those 258 objects, AutoClass was able to classify 248 with greater than 75% certainty, and ranked albedo, not color, as the most influential factor. Interestingly, AutoClass consistently put P type objects in with the C class (there were 19 P types and 7 X types mixed in with the other 154 C types), and omitted P types from the group associated with the other X types (which had only one rogue B type in with its other 49 X-types). Autoclass classified the remaining classes with a high accuracy: placing one A and one CU type in with an otherwise perfect S group; placing three P type and one T type in an otherwise perfect D group; and placing the four remaining asteroids (V, A, R, and Q) into a class together

Exploring the Enigma of 4709 Ennomos

Large Trojan asteroids are characteristically dark, having albedos that are typically in the range 0.03 to 0.08 (Fernandez et al., 2003). One notable exception is 4709 Ennomos with an unusually high measured albedo of about 0.13 (Fernandez et al., 2003). This corresponds to an albedo of more than 10 standard deviations above the mean of the group of 32 large Trojans sampled by Fernandez et al (2003). There are two main explanations for the anomalous albedo: Ennomos\u27s surface composition may truly be different from similarly-sized Trojans and be richer in more highly-reflective species, or the assumptions that go into the modeling used to derive diameter and albedo are inapplicable to Ennomos because of unusual physical or thermal properties. For the first hypothesis, so far only upper limits to compositional signatures have been found (e.g. Yang and Jewitt 2007). In this work we address the second hypothesis. One plausible explanation is that Ennomos’ rotation period is sufficiently fast or its thermal inertia is sufficiently high so as to preclude the use of a zero-thermal memory thermal model (Lebofsky and Spencer 1989, Harris 1998) i.e. the model actually used to calculate its albedo. An alternative explanation is that shape or topographic anomalies conspired to reduce the thermal emission, causing the model - which assumes a spherical body - to underestimate the diameter. To address these issues, we obtained BVRI time-series CCD photometry of Ennomos with the University of Hawaii\u27s 88 inch telescope on February 8, 9, and 10, 2003. The goals were to determine Ennomos’ rotation period, basic shape, and visible colors, and we will present these results. We will also discuss what the results imply about the nature of Ennomos\u27s surface

A Lightcurve and Color Analysis of Asteroid 4709 Ennomos

We will present results from our study of the Jovian Trojan asteroid 4709 Ennomos, an asteroid with an unusually high estimated albedo. Large Trojan asteroids (radius \u3e 25 km) have a mean V-band geometric albedo of 0.041 with very little variation (standard deviation = 0.007 ; Fernandez et. al. 2003). Smaller Trojan asteroids, with radius \u3c 25 km, have both higher albedo (mean = 0.12) and wider variation (standard deviation = 0.065; Fernandez et. al. 2010). Asteroid 4709 Ennomos has a radius of about 38 km and a geometric albedo of about 0.15: several standard deviations above the mean albedo of other large Trojans, but very similar to the albedos of small Trojans. One plausible explanation of Ennomos’ apparently high albedo is that its rotation period may be sufficiently fast so as to invalidate the use of a low-thermal memory thermal model to calculate its size and albedo--the model used for Ennomos. To test this hypothesis, we obtained time series CCD photometry of Ennomos’ light curve using the University of Hawaii 88-inch telescope on UT February 8 through 10, 2003. Analysis of Ennomos’ light curve and rotation period will determine if an isothermal latitude model is more appropriate. Since asteroids of Ennomos’ size, both Trojans and Main-Belt, tend to be relatively slow rotators, a high rotation speed would be unusual. We therefore also consider some of the other hypotheses to explain Ennomos’ high albedo. For example, comparing Ennomos’ colors to those of other asteroid groups can give clues to the reason for an elevated albedo. To this end, we also obtained BVRI colors of Ennomos during our 2003 observing run. We will present a comparison between Ennomos’ colors, other published large Trojan and small Trojan colors (e.g. Jewitt & Luu 1990), and small asteroid colors (e.g. Karlsson et al. 2009)

Application of the AutoClass Artificial Intelligence Program to Asteroidal Data

As our digital databases grow, datasets become less tractable and investigating alternative analysis techniques such as artificial intelligence algorithms becomes more important. One such program, AutoClass, which was developed by NASA\u27s Artificial Intelligence Branch, uses Bayesian classification theory to automatically choose the most probable classification distribution to describe a dataset. To investigate its usefulness to the Planetary community, we tested its ability to reproduce the taxonomic classes as defined by Tholen and Barucci (1989). We started our evaluation by entering all Tholen identified C, S, or X type Eight Color Asteroid Survey asteroids with a color difference error of less than +/- 0.05 magnitudes. Of these 406 asteroids, AutoClass was able to firmly classify 346 (85%), identifying the remaining 60 asteroids as belonging to more than one class. Of the 346 asteroids that AutoClass classified, all but 3 (\u3c1%) were classified as they had been in the Tholen classification scheme. The three that were misclassified had color errors estimated to be greater than +/- 0.04 magnitudes (though several other asteroids with such errors were classified correctly). To further test AutoClass, we expanded our reach to include all taxonomic types in the ECAS data, and further to include the nine wavelengths used to create the Bus and Binzel taxonomic superclasses (2002), with similar results. The initial successes of AutoClass and its ability to scan large domains for natural classes, showcase its exciting potential as a new discovery tool for Planetary scientists

Evidence for Space Weathering in the Near-Infrared Spectra of Primitive Asteroids

We present initial results of a comparative near-infrared (NIR) spectroscopic study of the Themis and Veritas asteroid families. These two families are compositionally primitive (mainly Tholen C-types) and likely formed in the same region of the protoplanetary disk. However, their disruption ages are at opposite extremes: 2.5 Gy and 8.3 My, respectively, providing insight into evolutionary processes since their disruption. Our study was motivated in part by the Nesvorny et al. (2005) detection of visible color trends between young and old asteroids families, with these two families at opposite ends of their trend. Our 0.8 to 2.4 micron spectra of four Themis and six Veritas asteroids were obtained using the SpeX instrument on NASA\u27s Infrared Telescope Facility (IRTF). We normalized these spectra using solar analog stars; our reflectance spectra do not exhibit any clear absorption features but they do show a range of slopes. The four Themis family members (older surfaces) have red” (positive) slopes; in contrast, the six Veritas family members (younger surfaces) have significantly flatter” slopes (this result includes objects with similar radii so it does not appear to be a function of asteroid size). The clustering of the spectra into two groups with statistically distinct average slopes is consistent with space weathering being a significant modifier of the near-infrared spectral shape of primitive asteroids. In other words, space weathering of primitive asteroids surfaces appears to make them redder” in the NIR (this work) and less red in the visible (Nesvorny et al. 2005)