I am a third year PhD student in the Astronomy and Astrophysics group at the University of Warwick, supervised by Prof. Don Pollacco. My primary research is focussed on using data from the TESS mission along with terrestrial follow-up to discover and characterise transiting exoplanets around young stars. Originally from Auckland, New Zealand, I completed a 5-year BE(Hons)/BSc conjoint degree in Physics and Mechanical Engineering at the University of Auckland in 2017.

Research Overview

Research

Exoplanets around Young Stars

Despite the wealth of known exoplanets (over 4000 as of August 2020) there are still many unanswered questions about their formation history and early evolution, so young exoplanets offer a key window into this dynamic and changeable period of a planetary system's life. However, stars of these ages offer significant challenges for detection via either of the traditionally most powerful transit and radial velocity detection methods, since these young stars typically are rotating much faster and are considerably more active than the background stellar population. This leads to photometric light-curves dominated by stellar variability that can be on a similar timescale but considerably larger in amplitude than the signal of any exoplanet around that star (e.g. see the top of Figure 1 below), seriously hampering detection through the transit method.

I have developed tools to remove the stellar variability from these young stars (illustrated below in Figure 1) in order to discover new transiting exoplanets, and thus learn further about early planetary system evolution. My primary data source is the Transiting Exoplanet Survey Satellite (TESS), which has already completed a 2-year nearly all-sky mission to search for transiting exoplanets, and is now moving into its extended mission. In my first paper I use this pipeline to search through young stars in the first five sectors of TESS data for new exoplanets, and show how the developed pipeline can significantly improve detection of smaller exoplanets through an injection/recovery study.

I am currently expanding the search for young exoplanets with this pipeline into the first two years of TESS data, continuing to update the pipeline to handle alternative datasets, new young stellar targets and more difficult forms of activity. In my third paper (in prep) I use Self-Organising Maps to explore this variability further, and introduce the YOUNGSTER program which uses machine learning methods to classify and selectively detrend a wide range of young star variability.

Figure 1: Example of developed light-curve detrending technique, showing the recovery of the newly discovered young exoplanet around DS Tuc A/HIP 116748 A (originally identified as TOI 200.01). Above: Overplotted detrending model over original TESS FFI light-curve. Below: Detrending light-curve phase folded by the known planetary period.

Kepler Ephemeris Maintenance with TESS

The Kepler mission was game-changing in the exoplanet field, revealing a vast array of interesting new exoplanets and changing our view of what a 'normal' exoplanet system looks like. Further characterisation of promising Kepler planets with future instruments such as the PLATO satellite and the James Webb Space Telescope will be crucial to understanding the atmospheres and interiors of planets in general. However, with the main Kepler mission ending in 2013 due to a reaction wheel failure, many of these objects have not been re-observed in at least seven years, increasing the uncertainty in their expected future transit times.

In an attempt to save these planets from being lost in time, in my second paper I used new 2min-cadence observations of the Kepler field from the second year of TESS's primary mission to improve the ephemerides of these planets, and prepare them for future characterisation.

Publications

First Author:

• Battley, Armstrong & Pollacco (2022). YOUNG Star detrending for Transiting Exoplanet Recovery (YOUNGSTER) II: Using Self-Organising Maps to explore young star variability in Sectors 1-13 of TESS data, MNRAS (accepted)
• Battley, Kunimoto, Armstrong & Pollacco (2021). Revisiting the Kepler field with TESS: Improved ephemerides using TESS 2 min data, MNRAS, 503, 3.
• Battley, Pollacco & Armstrong (2020). A search for young exoplanets in Sectors 1-5 of the TESS full-frame images, MNRAS, 496, 2.

Contributing Author:

• Triaud, Standing, Heidari, Martin, Boisse, et al. - including Battley - (2022). BEBOP III. Observations and an independent mass measurement of Kepler-16 (AB) b – the first circumbinary planet detected with radial velocities, MNRAS (accepted)
• Martin, El-Badry, Hodzic, Triaud, Angus, et al. - including Battley - (2021). TOI-1259Ab - a gas giant planet with 2.7 per cent deep transits and a bound white dwarf companion, MNRAS, 507, 3
• Swayne, Maxted, Triaud, Sousa, Broeg, et al. - including Battley - (2021). The EBLM project - VIII. First results for M-dwarf mass, radius, and effective temperature measurments using CHEOPS light curves, MNRAS, 506, 1
• Acton, Goad, Burleigh, Casewell, Breytenbach, et al. - including Battley - (2021). NGTS-19b: A high mass transiting brown dwarf in a 17-day eccentric orbit, MNRAS, 505, 2
• Amirpour, Kim, Battley, Kelly, Bickerton & Covic (2021). Coupled Electromagnetic-thermal analysis of roadway Inductive Power Transfer pads within a model pavement, Applied Thermal Engineering, 189, 116710
• Espinoza, Brahm, Henning, Jordan, Dorn, et al. - including Battley - (2019). HD 213885b: a transiting 1-d-period super-Earth with an Earth-like composition around a bright (V= 7.9) star unveiled by TESS, MNRAS, 491, 2.

Teaching, Tutoring and Departmental Responsibilities

Alongside my research I currently work as a Lab Demonstrator in the second-year undergraduate Astronomy Labs at the University of Warwick, where I instruct students in topics relating to spectroscopy and practical astronomy.

I also hold or have held the following positions on the PGSSLC: Postgraduate Wellbeing Rep (2020-2021), Postgraduate Seminar Organiser (2019-2020), Astro Rep (2019-2020), International Rep (2018-2019).

During my undergraduate degree I also tutored Physics and Mathematics to school and early university-aged students both privately and for Ardent Education in Auckland, NZ.

Conferences/Meetings

• TESS Science Conference 2, MIT (Virtual), 2-6th August, 2021
  • Contributed Talk ("Revisiting the Kepler Field with TESS")
• Circumstellar Disks and Young Planets - 2021 Sagan Summer Workshop, California Institute of Technology (Virtual), 19-23 July, 2021
  • Poster + Pop ("The YOUNGSTER Program: Extending the search for young transiting exoplanets")
• UK Exoplanet Community Meeting, University of Birmingham (Virtual), 22 April, 2021
  • Contributed Talk ("Tracking Exoplanets through Time with TESS")
• STScI Summer Symposium: Towards the Comprehensive Characterization of Exoplanets: Science at the Interface of Multiple Measurement Techniques, Space Telescope Science Institute (Virtual), 19-23rd April, 2021
  • Contributed Talk ("The Curious Case of Young Exoplanets: Unlocking the secrets of young exoplanets with multi-instrument observations")
• Exoplanets III, University of Heidelberg (Virtual), 27-31st July, 2020
  • Poster ("A Search for Young Exoplanets in the S1-5 TESS FFIs")
• "Extreme Precision Radial Velocity" - 2020 Sagan Exoplanet Summer Workshop, California Institute of Technology (Virtual), 20-24th July, 2020
  • Poster ("Searching for Young Exoplanets with TESS")
• Annual Conference in Research in Natural Sciences - ACORNS, University of Warwick, 9 December 2019
  • Invited Talk: "Fantastic Planets and how to find them"
• PLATO ESP 2019 - "Single, Shallow & Strange Transits", University of Warwick, 2nd-4th September 2019
  • Poster ("Searching for Young Planets with TESS") and presenting summary of 'Strange transits' discussion.
• Stars and their Variability observed from space, University of Vienna, 19th-23rd August 2019
• UK Exoplanet Community Meeting, Imperial College London, 15-17 April 2019

Observing and Outreach

As part of my PhD I have also had the opportunity to complete two 7-night observing runs on the SOPHIE instrument at Haute-Provence Observatory (OHP) in Southern France.

I also frequently volunteer with the Warwick Planetarium, visiting schools of typically years 2-3 or 4-6 to inspire them with talks about the search for extraterrestrial life and our place in the Universe.

Other Experience

I have completed five separate 3-month periods of work experience in university and industry environments in areas ranging from spacecraft design, testing and analysis (at NZ/US aerospace company Rocket Lab) to inductive charging technology for electric vehicles. My final year engineering project involved designing and testing a system to interface CubeSat satellites with the main Rocket Lab launch vehicle, which won the prize for the best final year project in mechanical engineering at the University of Auckland (2016). I still have a great interest in aerospace engineering, and in particular mechanical design of rockets and spacecraft payloads.

I also have been heavily involved in hiking clubs at both the University of Auckland (Safety Officer 2014; Club Captain 2015-2016; Vice-President 2017) and the University of Warwick (Treasurer 2019-2020, Captain 2020-2021, Vice-President 2021-2022). Consequently when not looking for planets, you can usually find me up a mountain somewhere hiking or trail running.