Planet compositions from disintegrating exoplanets

Lead Research Organisation: Open University
Department Name: Physical Sciences

Abstract

Our recent work has focussed on extremely close-in exoplanets which are losing mass as a result of their proximity to their host star. These systems are particularly interesting because they offer the potential to assess their chemical composition by the technique of transmission spectroscopy (e.g. Fossati et al 2010; Haswell et al 2012). This information provides key constraints to models of planet formation and evolution, and helps place our own Solar System in context. Our Hubble Space Telescope observations revealed that mass loss from the extreme hot Jupiter, WASP-12b, feeds a diffuse gas shroud around the planetary system, completely absorbing the starlight at the centres of the MgII h&k lines.
Meanwhile at least two very close-in transiting small disintegrating planets have been discovered in the Kepler database. The best-studied is KIC 1255b, which is a ~0.1 MEarth planet in a 16 hour orbit. The planet is hot enough for direct sublimation of the rocky surface at the sub-stellar point, and a time-variable cloud of dust and metal-rich vapour from KIC 1255b produces periodic transits of varying depth (Rappaport et al 2012). Systems like this can also reveal the planet composition by transmission spectroscopy, but the objects found by the narrow & deep Kepler survey transit apparently faint distant stars, which limits the signal to noise that can be obtained. Fortunately, however, we have shown that a further opportunity to examine the composition of such planets is provided by observing and modelling the dust extinction properties (Bochinski et al 2014). This is particularly exciting as these objects may be the remnant cores of evaporated hot Jupiter planets: consequently we can directly sample the composition of giant planet cores, something not possible even for the Solar System giants.
This project will focus on identifying and characterising disintegrating exoplanets (WASP-12b and KIC 1255b analogues) orbiting around bright, nearby stars. There are data and bespoke software in hand to begin the project, but the student will be expected to develop new software as required and to perform new observations using a variety of telescopes. The Open University Exoplanets Group benefits from the expertise of numerous internationally distinguished planetary scientists who work in the same department.

Publications

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Studentship Projects

Project Reference Relationship Related To Start End Student Name
ST/N50421X/1 01/10/2015 31/03/2021
1653424 Studentship ST/N50421X/1 01/10/2015 30/09/2018 Joseph Andrew Cooper
 
Title CDE Identification 
Description A process of using the output of the Unfolded Fitting Algorithm (UFA), which measures the variability of signals in a stellar lightcurve, to pick out potential Catastrophically Disintegrating Exoplanets (CDE). This process involved looking at the individual lightcurve and comparing these to known CDEs, as well as using stellar information on each target to estimate the viability of each candidate exoplanet. 
Type Of Material Data handling & control 
Year Produced 2017 
Provided To Others? Yes  
Impact CDEs identified using this process have been followed up with further observations and the results from these observations will be published. 
 
Title Unfolded Fitting Algorithm 
Description An algorithm designed to analyse the lightcurves of potential exoplanet hosts and record the variability of each object's transit signal. This is done in a fast and efficient manner to expedite the processing of exoplanet candidates. 
Type Of Material Computer model/algorithm 
Year Produced 2017 
Provided To Others? No  
Impact This tool is used to pick out potential Catastrophically Disintegrating Exoplanets (CDE) from the SuperWASP archive. These candidate CDE are then oberved further by our team and the results of this will be published. The SuperWASP archive is an archive of stellar lightcurves, some of which may host an exoplanet. 
 
Description OU Open Days 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Undergraduate students
Results and Impact Giving tours of the facilities available at the OU and discussing the demands of doing a PhD etc.
Year(s) Of Engagement Activity 2018
 
Description Yearly OU Presentation 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Postgraduate students
Results and Impact This is a yearly presentation, giving an overview of the work I have done in the first, second and third year of my PhD.
Year(s) Of Engagement Activity 2016,2017,2018