Photometric Techniques for Exoplanet Detection

249 Pages·2014·8.06 MB·English

by  Kuhn_ Rudolf Bruwer

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Photometric techniques for Exoplanet detection: The construction
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and deployment of the KELT-South telescope
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Rudolf Bruwer Kuhan
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Octobeor 2014

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A project submitted in partial fulfilment of the requirements for the degree PhD.
in the Department of Astronomy
UNIVERSITY OF CAPE TOWN
Supervisors: Prof. P. A. Whitelock and Dr. J. W. Menzies
In Collaboration with Dr. J. A. Pepper at Lehigh University
and Prof. K. G. Stassun at Vanderbilt University
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The copyright of this thesis vests in the author. No
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quotation from it or information derived from it is to be

published without full acknowledgeement of the source.
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The thesis is to be used for private study or non-
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commercial research purposes only.

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Published by the Universit y of Cape Town (UCT) in terms
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of the non-exclusive license granted to UCT by the author.
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Abstract
InthisthesisIpresenttheworkIperformedduringtheinitialconstructionanddeployment
of the second telescope in the KELT project and I report the results of the search for tran-
siting exoplanets and variable stars using one of the first commissioning datasets obtained
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with the telescope. The KELT-South telescope is located in Sutherland, Swouth Africa and
construction started in 2008. The telescope has been operating at full capacity since 2010,
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after two commissioning seasons from late 2008 to early 2010. I developed all the code that
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allows it to be fully automatic and robotic and over the last 5 years I have been responsible

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for the observing operations and general maintenance of the telescope. I also developed
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many other software tools that help with the identification of the exoplanet candidates.
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The Kilodegree Extremely Little Telescope (KELT) project at present consists of two
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robotic, wide field, small aperture telescopes that are designed primarily to find transiting

exoplanets around bright stars in the magnitude range 8 < V < 11. Transiting planets
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orbiting bright stars can be studied with intense follow-up programs with relative ease on

largertelescopes,makingthemfavourableytargetstodeterminetheatmosphericcomposition
of the planet as well as a host of othter properties that cannot be obtained from planets
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orbiting fainter stars. Of the known 1811 (August 2014) exoplanets only 60 are transiting
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stars with V < 11 and only 1e6 of those have been found from the southern hemisphere.
The discovery of more of thvese exoplanets will help constrain the theories of formation and
evolution of short periodi, gas giant exoplanets.
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DatareductionoUnoneofthecommissioningdatasetswascompletedin2012. Thedataset
spans 46 days and lightcurves for 78297 objects were obtained. I performed a search for
periodicities in the lightcurves and found that 1411 stars showed clear signs of variability
and these objects were compiled into a catalogue of possible variable stars. 1018 of the
catalogue members were not previously known to be variable. I searched for planetary
transits and eight possible exoplanet candidates were identified. Photometric follow-up
observations of two targets eliminated them as exoplanet candidates, each being a blended
eclipsingbinarysystem. Theremainingsixcandidatesareawaitingfollow-upobservationsat
present. Although the commissioning dataset served primarily to refine the data reduction
pipeline and the procedures I used to find variable stars, I have demonstrated that the
KELT-South telescope is capable of detecting the kinds of signals required for exoplanet
discovery.
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Acknowledgements
I would like to thank the many individuals who assisted me in all aspects of this thesis
and those that helped me through the rough times without being directly involved with the
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Firstly, andmostimportantly, Iwouldliketothankmyparentsfortheloveandsupport
throughout my entire life. A special thanks to my Dad who taught moe the names of the
planets in our Solar System before I could read, which is probabTly the initial seed that
sparked my lifelong fascination with astronomy. To my Mom, thanks for listening to my
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endless questions, always trying to understand what I was struggling with and encouraging
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me to find the answers myself when no one else was able to provide them. This thesis is
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dedicated to both of you. C
I would like to express my appreciation for all the love and support I received from
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Stephanie, my soon to be wife. You might notohave been part of this thesis from the start,
butyouwereinstrumentalinitscompletion . Yourwordsanddeedsofencouragementmade
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the last few months much easier and I cannot imagine how I would have been able to finish
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this task without you. I am truly bslessed to have someone as “ama–zing” as you in my life.
I was fortunate to have superrvisors that allowed me the freedom to explore my own
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interests and offered support and guidance whenever I needed it. Patricia and John, you
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have made the last couplie of years much easier by letting me do my own thing, but getting
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me back on the right path when I strayed too far.
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A huge thank you has to go to my unofficial supervisor on this project, Josh. Without
you the KELT-South project would never have happened and I would never have had the
opportunity to work on an amazing project like this. I appreciate all the time and guidance
you provided even though I wasn’t officially your student to mentor. I would really like
to thank Keivan for giving me the opportunity to visit the USA on three occasions and
providing all the financial support that enabled those trips. I learned so much about being
the best possible scientist from all the people at Vanderbilt and I thank you for all the
insightful discussions.
To my sister (and your four amazing kids) I would like to extend a special thank you.
You’vebeentherefromthestartandyoualwaysbelievedinyour“bigbrother”,you’vebeen
a true inspiration to me over these last few years. To all my school friends, although we’ve
not had much time to chat in the last few years, you’ve been supportive every time we did
have a change to meet and I really appreciate the encouragement.
A very special mention to all my office mates at SAAO over the last couple of years,
thanks for all the encouragement, guidance, sharing of ideas and many unforgettable trips
toSutherland. Coldnightsfixingtelescopesweremucheasierknowingthatanicehotcoffee
(and a laugh) was always available when I needed it. I would never have made it through
to the end without you. Thanks to my colleagues (that became life long friends) Marissa,
Enrico and Paul, you have been vital in the completion of this thesis and I cannot thank
you enough for all the support.
To all my friends and colleagues at Vanderbilt University, thanks for making me feel at
home the minute I arrived in Nashville for the very first time. Y’all made the second and
third trips so much easier knowing that I had friends I could call on. To Joey, thanks for
taking over the telescope operations and maintenance duties over the last few months while
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I concentrated all efforts on typing up this thesis. KELT-South is in good hands and I look
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forward to working with you in future on all aspects related to KELT-South.
Everybody at SAAO should also get a mention, especially Poiet, Willie, Gareth, Simon,
Nimrod, Chantal, Hamish and Amanda. All of you were wiTlling to help in all aspects of
the KELT-South project and provided enormous amounts of advice on telescope hardware,
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electricalsystems,computers,codeandsomuchmore. Iwouldalsoliketothanktheamazing
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ladiesattheSutherlandobservinghostelthatproviadedawesomemealsthreetimesaday(and
sometimes so extras) during my eight month sCtay in Sutherland during the construction of
KELT-South. ThankstoJohn, Jaci, Hennie, Michael, andallothermembersofthesupport

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staff in Sutherland that were always avoailable with extra hands when one pair just wasn’t
enough to get things done.
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WithaprojectsuchasKELT-South,therearefarmorepeoplethatIneedtothankthan
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there is space in this thesis∗. Iiappreciate all the help I received and will never forget your
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contributions that allowedrKELT-South to evolve from a pile of bricks to a fully automated
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machine capable of finding other worlds.
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∗Thisresearchmadeuseofdataproductsfrom:
• TheTwoMicronAllSkySurvey,whichisajointprojectoftheUniversityofMassachusettsandthe
Infrared Processing and Analysis Centre/California Institute of Technology, funded by the National
AeronauticsandSpaceAdministrationandtheNationalScienceFoundation.
• TheVizieRcatalogueaccesstoolandtheSIMBADdatabase,operatedatCDS,Strasbourg,France.
• The International Variable Star Index (VSX) database, operated at AAVSO, Cambridge, Mas-
sachusetts,USA.
• The NASA Exoplanet Archive, which is operated by the California Institute of Technology, under
contractwiththeNationalAeronauticsandSpaceAdministrationundertheExoplanetExploration
Program.
• TheExoplanetOrbitDatabaseandtheExoplanetDataExplorerathttp://www.exoplanets.org.
• TheExoplanetEncyclopaediaathttp://www.exoplanets.eu.
• TheTransitingExoplanetCatalogueathttp://www.astro.keele.ac.uk/jkt/tepcat/tepcat.html.
Plagiarism Declaration
I, Rudolf B. Kuhn, know that plagiarism is wrong. Plagiarism is the use of
anotherperson’sideasorpublishedworkandtopretendthatitisone’sown. This
therefore amounts to theft. Each significant contribution to, and quotation in
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this work that I have obtained from other people’s published works or uwnpublished
sourceshasbeenattributed,andhasbeencitedandfullyreferenced. Thisresearch
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report is my own original work and I expect reviewers to regard it as such and
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that I alone am responsible for any incomplete references that may remain in my

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work.
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Contents
1 Introduction 1
1.1 Definition of a Planet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
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1.2 Exoplanet Nomenclature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
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1.3 Methods of Finding Exoplanets . . . . . . . . . . . . . . . . . . . . . . . . . . 6
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1.3.1 Radial Velocity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
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1.3.2 Transit Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

1.3.3 Common Types of False Positives and Follow-uep Strategies . . . . . . 10
1.4 Transiting Exoplanet Lightcurves . . . . . . . . . p. . . . . . . . . . . . . . . . 13
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1.4.1 Geometric Equations of the System . . . . . . . . . . . . . . . . . . . 15
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1.4.2 Physical Scale Equations of the System . . . . . . . . . . . . . . . . . 15
1.4.3 Dimensionless Quantities . . . . . . . . . . . . . . . . . . . . . . . . . 16
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1.4.4 Analytical Solution of the Planetary System . . . . . . . . . . . . . . . 16

1.4.5 Simplified DimensionlessyQuantities . . . . . . . . . . . . . . . . . . . 17
1.4.6 Limb Darkening . . .t. . . . . . . . . . . . . . . . . . . . . . . . . . . 18
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1.4.7 Numerical Solution of Exoplanet System Parameters . . . . . . . . . . 20
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1.5 Known Exoplanets . e. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
1.5.1 Exoplanet Fvormation Theories . . . . . . . . . . . . . . . . . . . . . . 21
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1.5.2 CurrentnStatus of Exoplanets . . . . . . . . . . . . . . . . . . . . . . . 21
1.5.3 TranUsiting Exoplanets . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
1.5.4 Host Star Properties and Exoplanet Frequency Trends . . . . . . . . . 25
1.6 Transiting Exoplanet Surveys . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
1.6.1 Ground Based Surveys . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
1.6.2 Space Based Surveys . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
1.6.3 Future Transit Surveys. . . . . . . . . . . . . . . . . . . . . . . . . . . 31
1.7 KELT-South Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
1.8 Thesis Outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
2 KELT-South Construction, Facilities, Hardware and Software 37
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
2.2 Observing Site . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
2.3 The KELT-South Observatory . . . . . . . . . . . . . . . . . . . . . . . . . . 40
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