A Search for Transiting Extrasolar Planets from the Southern Hemisphere Duane Willis Hamacher II Faculty of Science University of New South Wales A thesis submitted in satisfaction of the requirements for the degree of Master of Science 28 July 2008 For Melvin... RIP. STATEMENT OF ORIGINALITY I hereby declare that this submission is my own work and to the best of my knowl- edge it contains no materials previously published or written by another person, nor material to which a substantial extent has been accepted for the award of any other degree or diploma at UNSW or any other educational institution, except where due acknowledgment is made in this thesis. I also declare that the intellectual content of this thesis is the product of my own work, except to the extent that assistance from others in the project’s design and conception or in style, presentation and linguistic expression is acknowledged. (Signed)............................................................. ii PREFACE The majority of the work in this thesis focused on APT observations and follow– up observations of planet candidates and is being submitted for publication in Hamacher et al. (2008). Below is a summary of the work in which the candidate participated, noting work that was used in this thesis but was not done by the candidate: The remote observing operating procedures of the APT as well as mainte- • nance, repairs, and modifications were implemented and carried out by M. Ashley and A. Phillips. The transit detection algorithm was written by Aigrain & Irwin (2004). • The data reduction pipeline was written by M. Irwin and implemented • by M. Hidas and M. Ashley. Modifications to the pipeline in order to accommodate 40-inch telescope data were performed by J. Christiansen and M. Ashley. APT observations up to February 2006 were conducted by M. Hidas, J. • Christainsen, M. Ashley, J. Webb., A. Phillips, A. Derekas, S. Crothers, and R. Smalley. Observations from February 2006 to March 2007 were conducted by the candidate, M. Hidas, M. Ashley, J. Christiansen, J. Webb, S. Curran, T. Britton, and T. Young. Visual inspection of the APT light curves was done by the candidate, J. • Christiansen, T. Young, T. Britton, and M. Hidas. 40-inch telescope observations were conducted by the candidate, M. Hidas, • J. Christiansen, T. Britton, and T. Young – the details of which are given in Table A. 2.3-m telescope observations were conducted by J. Christiansen, T. Young, • T. Britton, and the candidate. 2.3-m spectroscopic data were reduced by J. Christiansen. • iii 3.9-m AAT spectroscopic data were obtained by C. Tinney and reduced by • J. Christiansen. S. Curran assisted in reduction of 40-inch data, though the candidate later • re-reduced all of the data after making modifications to the pipeline and using a new set of quality dome flats. Candidate selection criteria were discussed in detail with M. Hidas and J.K. • Webb. Details of the data reduction pipeline can be found in Hidas et al. (2005) • and Irwin & Lewis (2001). The candidate’s role in this project primarily involved: Assisting with APT observations; • Assisting in reduction of APT data; • Period estimation and initial candidate selection; • Applying selection criteria to all candidates; • Data mining of all candidates; • Adaptation and implementation of the new selection strategy; • Selecting priority candidates for follow-up observations; • Assisting in the initial development of a systematics identification program • (with M. Kardan); Operation of the 40-inch telescope, data reduction, and analysis of APT • and SuperWASP candidates that were followed-up ( 50 nights); ∼ Analysis of APT candidate spectra. • iv Acknowledgements I would like to thank my advisor John Webb and co-advisor Michael Ashley for providing me with the opportunity and funding to work on this project to completion. I wish to thank Marton Hidas and the other members of the APT group for their assistance, Sue Fraser and Di Edler in the First Year Physics labs for providing me with free Panadol while supervising First Year labs, the technicians and staff at SSO (including Bob Shobbrook, Donna Burton, Andre Phillips, and Peter Wood), Michael Gillon and David Weldrake at the ESO, family and friends, PHD Comics, the UNSW Judo Club, ANU for allotting me time on the SSO telescopes, and the ASA for hosting the annual Harley Wood Winter School (aka Alcohol Tolerance School). And finally, Tui Britton – my better half – whom has been there through the rough and rocky road of my thesis. Abstract To date, more than 300 planets orbiting stars other than our sun have been discovered using a range of observing techniques, with new discoveries occuring monthly. The work in this thesis focused on the detection of exoplanets using the transit method. Planets orbiting close to their host stars have a roughly 10 per cent chance of eclipsing (transiting) the star, with Jupiter–sized planets causing a one per cent dip in the flux of the star over a few hours. A wealth of orbital and physical information on the system can be extracted from these systems, including the planet density which is essential in constraining models of planetary formation. To detect these types of planets requires monitoring tens of thousands of stars over a period of months. To accomplish this, we conduct a wide-field survey using the 0.5-meter Automated Patrol Telescope (APT) at Siding Spring Observatory (SSO) in NSW, Australia. Once candidates were selected from the data–set, selection criteria were ap- plied to separate the likely planet candidates from the false–positives. For this thesis, the methods and instrumentation used in attaining data and selecting planet candidates are discussed, as well as the re- sults and analysis of the planet candidates selected from star fields observed from 2004–2007. Of the 65 planet candidates initially selected from the 25 target fields observed, only two were consistent with a planet transit. These candi- dates were later determined to be eclipsing binary stars based on fol- low up observations using the 40-inch telescope, 2.3-m telescope, and the 3.9-m Anglo-Australian Telescope, all located at SSO. Addition- ally, two planet candidates from the SuperWASP-North consortium were observed on the 40-inch telescope. Both proved to be eclipsing binary stars. While no planets were found, our search methods and results are consistent with successful transit surveys targeting simi- lar fields with stars in a similar magnitude range and using similar methods. Contents 1 Introduction 1 1.1 Foreword . 1 1.2 A Brief History of Planet Hunting . 2 1.3 Basic Physics . 3 1.3.1 Kepler’s Laws of Planetary Motion . 4 1.3.2 Radial Velocity Derivation . 6 1.4 Types of Planet Searches . 7 1.4.1 Radial Velocity . 8 1.4.2 Microlensing . 9 1.4.3 Direct Imaging . 12 1.4.4 Astrometry . 13 1.4.5 Pulsar Timing . 14 1.4.6 Polarimetry . 14 1.4.7 Transit . 15 1.4.7.1 Transit Timing . 20 1.4.7.2 The Rossiter–McLaughlin Effect . 20 2 Methods 22 2.1 Observing Site and Telescope . 23 2.1.1 Siding Spring Observatory . 23 2.1.2 Automated Patrol Telescope . 23 2.1.3 APT Operation . 24 2.2 Photometric Precision . 25 2.2.1 Identifying Noise Sources . 25 2.2.2 Poisson Noise . 26 viii CONTENTS 2.2.3 Atmospheric Effects . 27 2.2.3.1 Scintillation . 27 2.2.3.2 Atmospheric Seeing . 27 2.2.3.3 Colour–Dependence of Extinction . 28 2.2.4 CCD Effects . 28 2.2.4.1 Flat–Fielding . 29 2.2.4.2 Blending . 29 2.2.4.3 Under–sampling of Images . 30 2.2.4.4 Intra–pixel Sensitivity Variations . 30 2.2.5 Raster Scan Technique . 30 2.3 Observing Strategy . 31 2.4 Data Reduction . 34 2.4.1 Why Aperture Photometry? . 34 2.4.2 Image Processing . 34 2.4.3 Sky Subtraction . 35 2.4.4 Object Detection & Catalogue Generation . 35 2.4.5 Aperture Photometry . 37 2.4.6 Photometric Calibration . 37 2.5 Systematics Removal . 39 2.5.1 Sources of Systematics . 39 2.5.2 Trend Filtering Algorithm . 40 2.6 Transit Detection . 45 2.6.1 Transit Detection Algorithm . 45 2.6.2 Visual Inspection . 45 2.7 Transit Characteristics . 46 2.7.1 Period . 46 2.7.2 Transit Depth . 47 2.7.3 Transit Shape . 50 2.7.4 Out–of–Transit Features . 50 2.7.4.1 Secondary Transit . 51 2.7.4.2 Ellipsoidal Variations . 51 2.8 Candidate Selection Strategy . 55 2.9 Phase 1 – Initial Selection . 56 ix CONTENTS 2.9.1 Selecting Priority Candidates . 59 2.9.1.1 The Colour Index Method . 60 2.9.1.2 The Seager & Mallen–Ornelas Method . 60 2.9.1.3 The Mandel & Algol Method . 63 2.9.1.4 The Photometric Diagnostic . 64 2.9.1.5 Separating Giants and Dwarfs . 65 2.10 Phase 2: Higher–Resolution Photometry . 67 2.10.1 The 40-inch Telescope . 68 2.10.2 40-inch Telescope Data Reduction . 69 2.11 Phase 3: Medium–Resolution Spectroscopy . 70 2.12 Phase 4: High–Resolution Spectroscopy . 71 2.13 Summary of Methodology . 72 3 Results & Analysis 75 3.1 Candidate Selection Flowchart . 75 3.1.1 High Priority . 76 3.1.2 Low Priority . 76 3.2 Initial Results . 77 3.3 Phase 1 Candidates . 79 3.4 Phase 2 and 3 Candidates . 79 3.4.1 UNSW-TR-29 . 87 3.4.2 UNSW-TR-41 . 89 3.5 Follow-up of Non–Priority Candidates . 92 3.5.1 UNSW-TR-54 . 97 3.5.2 UNSW-TR-55 .