add goals/current knowledge, fix some plots

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@ARTICLE{connection_starspots_flares_ms_kepler,
author = {{Roettenbacher}, Rachael M. and {Vida}, Kriszti{\'a}n},
title = "{The Connection between Starspots and Flares on Main-sequence Kepler Stars}",
journal = {\apj},
keywords = {stars: activity, stars: flare, stars: variables: general, starspots, Astrophysics - Solar and Stellar Astrophysics},
year = 2018,
month = nov,
volume = {868},
number = {1},
eid = {3},
pages = {3},
doi = {10.3847/1538-4357/aae77e},
archivePrefix = {arXiv},
eprint = {1810.04762},
primaryClass = {astro-ph.SR},
adsurl = {https://ui.adsabs.harvard.edu/abs/2018ApJ...868....3R},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@ARTICLE{flare_occurance_periodicity,
author = {{Howard}, Ward S. and {Law}, Nicholas M.},
title = "{EvryFlare. IV. Detection of Periodicity in Flare Occurrence from Cool Stars with TESS}",
journal = {\apj},
keywords = {Stellar rotation, Stellar flares, Stellar magnetic fields, Star-planet interactions, Starspots, Wide-field telescopes, 1629, 1603, 1610, 2177, 1572, 1800, Astrophysics - Solar and Stellar Astrophysics, Astrophysics - Earth and Planetary Astrophysics},
year = 2021,
month = oct,
volume = {920},
number = {1},
eid = {42},
pages = {42},
doi = {10.3847/1538-4357/ac142a},
archivePrefix = {arXiv},
eprint = {2107.06293},
primaryClass = {astro-ph.SR},
adsurl = {https://ui.adsabs.harvard.edu/abs/2021ApJ...920...42H},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@ARTICLE{au_mic_flaring_spi,
author = {{Ilin}, E. and {Poppenhaeger}, K.},
title = "{Searching for flaring star-planet interactions in AU Mic TESS observations}",
journal = {\mnras},
keywords = {planets and satellites: individual: AU Mic b, planet-star interactions, stars: flare, stars: individual: AU Mic, Astrophysics - Solar and Stellar Astrophysics, Astrophysics - Earth and Planetary Astrophysics},
year = 2022,
month = jul,
volume = {513},
number = {3},
pages = {4579-4586},
doi = {10.1093/mnras/stac1232},
archivePrefix = {arXiv},
eprint = {2204.14090},
primaryClass = {astro-ph.SR},
adsurl = {https://ui.adsabs.harvard.edu/abs/2022MNRAS.513.4579I},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@ARTICLE{faster_rot_stars_more_flares2,
author = {{McLean}, M. and {Berger}, E. and {Reiners}, A.},
title = "{The Radio Activity-Rotation Relation of Ultracool Dwarfs}",
journal = {\apj},
keywords = {brown dwarfs, radio continuum: stars, stars: activity, stars: low-mass, stars: magnetic field, Astrophysics - Solar and Stellar Astrophysics},
year = 2012,
month = feb,
volume = {746},
number = {1},
eid = {23},
pages = {23},
doi = {10.1088/0004-637X/746/1/23},
archivePrefix = {arXiv},
eprint = {1108.0415},
primaryClass = {astro-ph.SR},
adsurl = {https://ui.adsabs.harvard.edu/abs/2012ApJ...746...23M},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@ARTICLE{faster_rot_stars_more_flares1,
author = {{Mohanty}, Subhanjoy and {Basri}, Gibor},
title = "{Rotation and Activity in Mid-M to L Field Dwarfs}",
journal = {\apj},
keywords = {Stars: Activity, Stars: Low-Mass, Brown Dwarfs, Stars: Rotation, Astrophysics},
year = 2003,
month = jan,
volume = {583},
number = {1},
pages = {451-472},
doi = {10.1086/345097},
archivePrefix = {arXiv},
eprint = {astro-ph/0201455},
primaryClass = {astro-ph},
adsurl = {https://ui.adsabs.harvard.edu/abs/2003ApJ...583..451M},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@ARTICLE{doyle_2019,
author = {{Doyle}, L. and {Ramsay}, G. and {Doyle}, J.~G. and {Wu}, K.},
title = "{Probing the origin of stellar flares on M dwarfs using TESS data sectors 1-3}",
journal = {\mnras},
keywords = {stars: activity, stars: flare, stars: low-mass, stars: magnetic fields, Astrophysics - Solar and Stellar Astrophysics},
year = 2019,
month = oct,
volume = {489},
number = {1},
pages = {437-445},
doi = {10.1093/mnras/stz2205},
archivePrefix = {arXiv},
eprint = {1908.02698},
primaryClass = {astro-ph.SR},
adsurl = {https://ui.adsabs.harvard.edu/abs/2019MNRAS.489..437D},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@ARTICLE{doyle_2018,
author = {{Doyle}, L. and {Ramsay}, G. and {Doyle}, J.~G. and {Wu}, K. and {Scullion}, E.},
title = "{Investigating the rotational phase of stellar flares on M dwarfs using K2 short cadence data}",
journal = {\mnras},
keywords = {stars: activity, stars: flare, stars: low-mass, stars: magnetic field, Astrophysics - Solar and Stellar Astrophysics},
year = 2018,
month = oct,
volume = {480},
number = {2},
pages = {2153-2164},
doi = {10.1093/mnras/sty1963},
archivePrefix = {arXiv},
eprint = {1807.08592},
primaryClass = {astro-ph.SR},
adsurl = {https://ui.adsabs.harvard.edu/abs/2018MNRAS.480.2153D},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@ARTICLE{kepler_411_210_comparison,
author = {{Ara{\'u}jo}, Alexandre and {Valio}, Adriana},
title = "{The connection between starspots and superflares: a case study of two stars}",
journal = {\mnras},
keywords = {Activity, Flare, Solar-type, Starspots, Astrophysics - Solar and Stellar Astrophysics, Astrophysics - Earth and Planetary Astrophysics},
year = 2023,
month = jun,
volume = {522},
number = {1},
pages = {L16-L20},
doi = {10.1093/mnrasl/slad034},
archivePrefix = {arXiv},
eprint = {2303.16051},
primaryClass = {astro-ph.SR},
adsurl = {https://ui.adsabs.harvard.edu/abs/2023MNRAS.522L..16A},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@ARTICLE{kepler_411_study,
author = {{Ara{\'u}jo}, Alexandre and {Valio}, Adriana},
title = "{Kepler-411 Star Activity: Connection between Starspots and Superflares}",
journal = {\apjl},
keywords = {498, 1572, 1603, 1580, Astrophysics - Solar and Stellar Astrophysics},
year = 2021,
month = dec,
volume = {922},
number = {2},
eid = {L23},
pages = {L23},
doi = {10.3847/2041-8213/ac3767},
archivePrefix = {arXiv},
eprint = {2111.05452},
primaryClass = {astro-ph.SR},
adsurl = {https://ui.adsabs.harvard.edu/abs/2021ApJ...922L..23A},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@ARTICLE{althukair_starlist,
author = {{Althukair}, A.~K. and {Tsiklauri}, D.},
title = "{Main Sequence Star Super-flare Frequency based on Entire Kepler Data}",
journal = {Research in Astronomy and Astrophysics},
keywords = {Sun: flares, stars: flare, stars: solar-type, (stars:) starspots, stars: statistics, stars: rotation, stars: activity, Astrophysics - Solar and Stellar Astrophysics},
year = 2023,
month = aug,
volume = {23},
number = {8},
eid = {085017},
pages = {085017},
doi = {10.1088/1674-4527/acdc09},
archivePrefix = {arXiv},
eprint = {2212.10224},
primaryClass = {astro-ph.SR},
adsurl = {https://ui.adsabs.harvard.edu/abs/2023RAA....23h5017A},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@PHDTHESIS{koi_256_effects_of_magnetic, @PHDTHESIS{koi_256_effects_of_magnetic,
author = {{Morgan}, D.~P.}, author = {{Morgan}, D.~P.},
title = "{The effects of close binaries on the magnetic activity of M dwarfs as probed using close white dwarf companions}", title = "{The effects of close binaries on the magnetic activity of M dwarfs as probed using close white dwarf companions}",
@@ -28,8 +213,6 @@ archivePrefix = {arXiv},
adsnote = {Provided by the SAO/NASA Astrophysics Data System} adsnote = {Provided by the SAO/NASA Astrophysics Data System}
} }
@ARTICLE{conch_shell_m_dwarfs, @ARTICLE{conch_shell_m_dwarfs,
author = {{Gaidos}, E. and {Mann}, A.~W. and {L{\'e}pine}, S. and {Buccino}, A. and {James}, D. and {Ansdell}, M. and {Petrucci}, R. and {Mauas}, P. and {Hilton}, E.~J.}, author = {{Gaidos}, E. and {Mann}, A.~W. and {L{\'e}pine}, S. and {Buccino}, A. and {James}, D. and {Ansdell}, M. and {Petrucci}, R. and {Mauas}, P. and {Hilton}, E.~J.},
title = "{Trumpeting M dwarfs with CONCH-SHELL: a catalogue of nearby cool host-stars for habitable exoplanets and life}", title = "{Trumpeting M dwarfs with CONCH-SHELL: a catalogue of nearby cool host-stars for habitable exoplanets and life}",
@@ -86,8 +269,6 @@ archivePrefix = {arXiv},
adsnote = {Provided by the SAO/NASA Astrophysics Data System} adsnote = {Provided by the SAO/NASA Astrophysics Data System}
} }
@ARTICLE{tess_1st_year_superflares, @ARTICLE{tess_1st_year_superflares,
author = {{Tu}, Zuo-Lin and {Yang}, Ming and {Zhang}, Z.~J. and {Wang}, F.~Y.}, author = {{Tu}, Zuo-Lin and {Yang}, Ming and {Zhang}, Z.~J. and {Wang}, F.~Y.},
title = "{Superflares on Solar-type Stars from the First Year Observation of TESS}", title = "{Superflares on Solar-type Stars from the First Year Observation of TESS}",
@@ -107,8 +288,6 @@ archivePrefix = {arXiv},
adsnote = {Provided by the SAO/NASA Astrophysics Data System} adsnote = {Provided by the SAO/NASA Astrophysics Data System}
} }
@ARTICLE{V471tau_magnetic_activity, @ARTICLE{V471tau_magnetic_activity,
author = {{K{\H{o}}v{\'a}ri}, Zs. and {Kriskovics}, L. and {Ol{\'a}h}, K. and {Odert}, P. and {Leitzinger}, M. and {Seli}, B. and {Vida}, K. and {Borkovits}, T. and {Carroll}, T.}, author = {{K{\H{o}}v{\'a}ri}, Zs. and {Kriskovics}, L. and {Ol{\'a}h}, K. and {Odert}, P. and {Leitzinger}, M. and {Seli}, B. and {Vida}, K. and {Borkovits}, T. and {Carroll}, T.},
title = "{A confined dynamo: Magnetic activity of the K-dwarf component in the pre-cataclysmic binary system V471 Tauri}", title = "{A confined dynamo: Magnetic activity of the K-dwarf component in the pre-cataclysmic binary system V471 Tauri}",
@@ -146,8 +325,6 @@ archivePrefix = {arXiv},
adsnote = {Provided by the SAO/NASA Astrophysics Data System} adsnote = {Provided by the SAO/NASA Astrophysics Data System}
} }
@misc{spectral_type_color_table, @misc{spectral_type_color_table,
title={Intrinsic colours as a function of spectral type}, title={Intrinsic colours as a function of spectral type},
url={https://www.stsci.edu/~inr/intrins.html}, url={https://www.stsci.edu/~inr/intrins.html},
@@ -1,3 +1,3 @@
\chapter{Discussion} \chapter{Discussion \label{sec:discussion}}
\label{sec:discussion}
@@ -2,10 +2,17 @@
%Example chapter on Asteroseismology %Example chapter on Asteroseismology
\chapter{Introduction \label{sec:intro}} \chapter{Introduction \label{sec:intro}}
%\cleanchapterquote{Shoot for the moon. Even if you miss, you'll land among the stars.}{Les Brown} %optional, if you want to place something here. %\cleanchapterquote{Shoot for the moon. Even if you miss, you'll land among the stars.}{Les Brown} %optional, if you want to place something here.
This chapter gives an introduction to the goals of this study. It also gives a summary of the current knowledge related to this study. Afterwards there will be summaries on topics related to this study, giving explanations on the various spectral types of stars, flares and spots, as well as giving an introduction to the space missions whichs data was used.
\section{Current knowledge \label{sec:intro:cur_knowledge}} \section{Goals and current knowledge \label{sec:intro:cur_knowledge}}
The goal of this study is to relate the appearance of flares/superflares to that of star spots on a large sample of stars of various spectral types. This is done by folding the lightcurves and the normalizing the phases. Due to the appearance of spots on the stars surface, the star is slightly dimmed, causing a local minimum in the lightcurve. This dimming can be observed with the Kepler and TESS (Transiting Exoplanet Survey Satellite) space missions.
\cite{kepler_411_study} focused on Kepler-411 by investigating the relation between superflares and star spots on that star. They found a positive correlation between the energy of flares and the area of star spots (\cite{kepler_411_study}) on Kepler-411. They then compared their results for Kepler-411, which produced multiple superflares, with Kepler-210, which did not produce superflares while having the same number of spots (\cite{kepler_411_210_comparison}). They found the spots on Kepler-210 to be larger, warmer and therefor being magnetically weaker/less complex compared to Kepler-411 and concluded that the area of starspots is not the only relevant parameter for superflare occurance (\cite{kepler_411_210_comparison}).\\
\cite{doyle_2018} studied 34 M dwarfs from the K2 mission, using short cadence observational data. They confirmed that stars with a rotational period of less than 10 days showed more flares, which was already shown previously (\cite{faster_rot_stars_more_flares1}, \cite{faster_rot_stars_more_flares2}). Furthermore they found no star with a preference for when flares occured during the rotational phase (\cite{doyle_2018}). A similar study using TESS 2 minute cadence data has been conducted by \cite{doyle_2019}. In this study they used data of 167 M dwarfs and found a total of 1834 flares. Similar to the study on K2 data, they found no preference for roational phase (\cite{doyle_2019}).\\
Another possible cause for a periodic increase in flares is star-planet interaction (SPI), which is studied by \cite{au_mic_flaring_spi} for the star AU Mic. While they found a signal in their used TESS lightcurves correlating with the orbital period of AU Mic b, they require more observation time to get a $>3\sigma$ detection (\cite{au_mic_flaring_spi}).\\
Further analysis on periodic flare occurance was done by \cite{flare_occurance_periodicity}, who studied lightcurves of 284 M dwarfs. They found three targets (TIC 80427281, TIC 95328477, TIC 220432563) with a confirmed flare periodicity, which correlates to their rotational period or half of it.\\
\cite{connection_starspots_flares_ms_kepler} investigated a sample of 119 stars from spectral types M to F. They found that flares which increase the stellar flux by 1\% to 5\% appear more often while larger starspots are visible, while flares which increase the flux by more that 5\% do not seem to have this dependency (\cite{connection_starspots_flares_ms_kepler}).
% motivation for the thesis
\section{Spectral Types \label{sec:intro:spectral_types}} \section{Spectral Types \label{sec:intro:spectral_types}}
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