«STUDENT RESEARCH PAPERS SUMMER 2011 VOLUME 22 REU DIRECTOR UMESH GARG, PH.D. REU Student Research Papers – Summer 2011 University of Notre Dame – ...»
2009. Though the rest of the images we will discuss are monthly images, it appears these were taken in three successive days. The Kepler Quarters 5 and 9 observations occurred from April to June 2010 and 2011, respectively. Quarter 5 included three images, one from the latter part of each month, while Quarter 9 contained only two images, as the one from June is not yet released.
Image Reduction and Analysis Facility (IRAF), a software system with the purpose of processing astronomical data, was used to prepare the images. After all thirteen images were downloaded from Kepler, we utilized IRAF to separate each of the images into their respective 84 channels, funneling them into 84 subdirectories. We applied a script to each of the subdirectories that combined all of the Quarter 1 images into a template image. The brightness values of the template and Quarters 5 and 9 images were then divided by 100,000 in order for the next few steps to run more smoothly.
To prepare for the alignment and subtraction of the images, pixel coordinates of at least three non-saturated, well-focused stars were written into a.stamps file. This provides markers for the program, so it can recognize what to use for matching the point-spread function of the
by Brian Schmidt, a researcher at Australian National University, in order to align each channel’s Quarters 5 and 9 images to the respective template; the template was then subtracted from each of the respectively aligned images.
I visually searched for events and stellar objects that were incommensurable in the subtractions with “ds9”, an imaging and data visualization application that displays.fits images. For every variant, I noted the celestial coordinates and a comment about the characteristic of the variant recognized. This was done to compare the results with current catalogs of extra-solar bodies, such as the Set of Identifications, Measurements, and Bibliography for Astronomical Data (SIMBAD) and the General Catalog of Variable Stars (GCVS). SIMBAD includes a catalog of known variables in the Kepler field.
Shown in Fig. 2 is a 1024x1100-pixel template image from channel 50. Noticeable traits are the star cluster NGC 6819 2 and scattered bright stars, separated by dimmer stars as a light background.
Information about this star cluster can be seen at http://helas.astro.uni.wroc.pl/data/kepler/pulsating_stars_Kepler_FOV/OC_Kepler.html.
Figure 3 is a display of a candidate transient found in channel 58 at right ascension 19:28:36.52 and declination +47:51:22.70. The transient is the faint object that lies directly above and to the right of the crosshairs.
Table 1: “Channel” refers to one of the 84 channels from which the significant variable/transient came. “RA” is right ascension while “Dec” is declination. “SIMBAD” refers to the name SIMBAD recognized if the object existed in the catalog.
A meticulous search for variables and transients in all 84 channels of the Kepler Quarters 5 and 9 monthly images resulted in 1042 candidates being found. Of these 1042, 14 candidate variables/transients have been marked as unique or significant. This marking signifies that the candidate was peculiar or dissimilar to the others in a noticeable manner. These can be seen in Table 1. For example, in Figure 3, the object identified as the possible transient is not noticeable in the template image, a compilation of images from April 2009. However, nearly two years later, it is recorded as existing in the two Quarter 9 images and subtractions.
Though many of the 1042 candidates may be known stellar objects and variables/transients, we suppose that a number of these are objects yet to be identified from the Kepler Mission data. Providing 1042 candidates for the catalog, SIMBAD recognized 240 as having celestial coordinates within 20 arc seconds of their identified stars, while only one of the 14 significant variables/transients was recognized by congruent standards. Further analysis will be done in the future to determine the significance of these findings, and some will be selected for further study by Kepler in Cycle 3.
The Kepler Mission, starting in the spring of 2009, monitors ~156,000 stars in a field of view within the constellations Cygnus and Lyra. Utilizing the data collected since the beginning of the mission, we have processed images from Quarters 1, 5 and 9 to search for variable stars and
1042 candidates. In this paper we display a table of 14 significant, or unique, candidates. These candidates are compared with known variable star catalogs, i.e. SIMBAD and GCVS, to determine which are newly identified variables/transients; furthermore, a portion of the 1042 candidates will be chosen for study by Kepler in Cycle 3.
Borucki, W. J., et al. 2010, Science, 327, 977 Borucki, W. J., for the Kepler Mission, 2010, arXiv:1006.2799 Borucki, W. J., et al. 2011, arXiv:1102.0541 Gilliland, R. L., et al. 2011, arXiv:1107.5207 Hayden, B. T., et al. 2010, arXiv:1008.4797