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Multi-planetary Systems from Simulated TESS Transit Timing Variations

Hellström, Lucas LU (2018) In Lund Observatory Examensarbeten ASTK02 20181
Lund Observatory
Abstract
A transit is a phenomenon where a planet passes between its host star and an observer blocking out part of the light from the star. This decrease can be measured and used to gain information about the planet. The Kepler and TESS telescopes are examples of space telescopes using the transit method to detect exoplanets. For systems with more than one planet around the same star variations between the time a planet takes to transit might occur. These variations, called Transit Timing Variations, or TTVs, can be used to gain information about additional planets in the system.

TESS recently launched and this paper uses data from Sullivan et al (2015) and Kepler data from Q1-Q17 DR25 from the NASA Exoplanet Archive (Thompson et al. 2018) to... (More)
A transit is a phenomenon where a planet passes between its host star and an observer blocking out part of the light from the star. This decrease can be measured and used to gain information about the planet. The Kepler and TESS telescopes are examples of space telescopes using the transit method to detect exoplanets. For systems with more than one planet around the same star variations between the time a planet takes to transit might occur. These variations, called Transit Timing Variations, or TTVs, can be used to gain information about additional planets in the system.

TESS recently launched and this paper uses data from Sullivan et al (2015) and Kepler data from Q1-Q17 DR25 from the NASA Exoplanet Archive (Thompson et al. 2018) to create artificial systems like those that TESS might observe to predict what kind of results it might find. These systems are simulated using TTVFast (Deck et al. 2014) to obtain TTV signals which are then used to create a sky map to show the fraction of systems showing TTV signals in a given sample.

TESS have coverage of the ecliptic poles for a whole year which results in that many systems showing considerable TTV signals being located at the poles although there are systems located outside the poles still showing TTV signals. In the range of declination from about -40 degrees to 40 degrees CHEOPS will be able to further study the objects. As CHEOPS will study already known objects predictions for the results from TESS can be used to estimate the number of targets CHEOPS might study, how much observation time is required for each object and how to prioritise the most interesting systems. Using information about the planetary radius, period and stellar mass obtained from short-term observations the long term TTV amplitude can be estimated. From the results of this paper it is expected that CHEOPS can find a TTV signal from about every fourth transiting planet and the probability for a CHEOPS detectable TTV signal is high where the period ratio is below 2 but low for a higher fraction. (Less)
Popular Abstract (Swedish)
När vi letar efter exoplaneter finns det ett antal olika metoder för att hitta dem. Den mest framgångsrika är transitmetoden där ljusstyrkan hos en stjärna studeras under en längre tid. När en planet passerar mellan sin stjärna och en observatör kan en minsking i stjärnans ljusstyrka ses. Uppreras detta i regelbunda intervall kan slutsatsen att det finns en planet runt stjärnan dras. Genom att studera minskningen i ljusstyrka kan storleken på planeten beräknas vilket kombinerat med massan som fås av andra metoder ge en insikt i hur och vad planeten är uppbygd av. En transit är detta fenomen då en planet passerar mellan stjärnan och en observatör.

Genom att jämföra tiden mellan varje transit för en planet kan ibland variationer ses,... (More)
När vi letar efter exoplaneter finns det ett antal olika metoder för att hitta dem. Den mest framgångsrika är transitmetoden där ljusstyrkan hos en stjärna studeras under en längre tid. När en planet passerar mellan sin stjärna och en observatör kan en minsking i stjärnans ljusstyrka ses. Uppreras detta i regelbunda intervall kan slutsatsen att det finns en planet runt stjärnan dras. Genom att studera minskningen i ljusstyrka kan storleken på planeten beräknas vilket kombinerat med massan som fås av andra metoder ge en insikt i hur och vad planeten är uppbygd av. En transit är detta fenomen då en planet passerar mellan stjärnan och en observatör.

Genom att jämföra tiden mellan varje transit för en planet kan ibland variationer ses, vilket kallas Transit Timing Variations eller förkortat TTV. Detta beror på att det finns fler planeter runt stjärnan som med hjälp av gravitationskraften accelererar eller decelerera planeten som bevakas. Detta resulterar i att det är möjligt att hitta planeter som genom andra metoder är osynliga.

Keplerteleskopet är ett rymdbaserat teleskop som använder transitmetoden för att hitta exoplaneter. Det har sedan 2009 hittat över 1000 bekräftade exoplaneter vilket gör den till det hittils mest framgångsfulla uppdraget i jakten på exoplaneter. TESS, vilket står för Transiting-Exoplanet Survey Satellite, är ett teleskop som sköts upp den 18de april 2018 och använder transitmetoden för att hitta exoplaneter. TESS kommer bli det första rymdbaserade teleskopet att studera hela himlen och kommer observera över 200 000 stjärnor under uppdragets urspungliga längd på två år.

Detta projekt kommer använda data från Keplerteleskopet för att simulera data från TESS för att sedan använda den datan för att leta efter TTV signaler. Detta ska ge en uppfattning om hur många system som har fler än en planet inom ett givet område på himlen. (Less)
Please use this url to cite or link to this publication:
author
Hellström, Lucas LU
supervisor
organization
course
ASTK02 20181
year
type
M2 - Bachelor Degree
subject
keywords
Transit timing variations, TTV, TESS
publication/series
Lund Observatory Examensarbeten
report number
2018-EXA139
language
English
id
8957827
date added to LUP
2018-09-13 09:35:09
date last changed
2018-09-13 09:35:09
@misc{8957827,
  abstract     = {A transit is a phenomenon where a planet passes between its host star and an observer blocking out part of the light from the star. This decrease can be measured and used to gain information about the planet. The Kepler and TESS telescopes are examples of space telescopes using the transit method to detect exoplanets. For systems with more than one planet around the same star variations between the time a planet takes to transit might occur. These variations, called Transit Timing Variations, or TTVs, can be used to gain information about additional planets in the system.
	
	TESS recently launched and this paper uses data from Sullivan et al (2015) and Kepler data from Q1-Q17 DR25 from the NASA Exoplanet Archive (Thompson et al. 2018) to create artificial systems like those that TESS might observe to predict what kind of results it might find. These systems are simulated using TTVFast (Deck et al. 2014) to obtain TTV signals which are then used to create a sky map to show the fraction of systems showing TTV signals in a given sample.
	
	TESS have coverage of the ecliptic poles for a whole year which results in that many systems showing considerable TTV signals being located at the poles although there are systems located outside the poles still showing TTV signals. In the range of declination from about -40 degrees to 40 degrees CHEOPS will be able to further study the objects. As CHEOPS will study already known objects predictions for the results from TESS can be used to estimate the number of targets CHEOPS might study, how much observation time is required for each object and how to prioritise the most interesting systems. Using information about the planetary radius, period and stellar mass obtained from short-term observations the long term TTV amplitude can be estimated. From the results of this paper it is expected that CHEOPS can find a TTV signal from about every fourth transiting planet and the probability for a CHEOPS detectable TTV signal is high where the period ratio is below 2 but low for a higher fraction.},
  author       = {Hellström, Lucas},
  keyword      = {Transit timing variations,TTV,TESS},
  language     = {eng},
  note         = {Student Paper},
  series       = {Lund Observatory Examensarbeten},
  title        = {Multi-planetary Systems from Simulated TESS Transit Timing Variations},
  year         = {2018},
}