Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 13 of 13 for “"stellar activity"”.
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Unearth: Revealing the Effects of Stellar Activity on Exoplanet Host Stars
… this thesis, I investigate the effect activity has on stellar spectra, using HARPS data of the well observed K1 V star α Centauri B. I compare spectra from high- and low-activity periods (as traced by log R′HK) of α Cen B. I produce ‘relative spectra’ by dividing the high-activity …
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Exoplanetary system WASP-3 : measurement of the projected spin-orbit angle and evidence for stellar activity
… angle between the planetary orbital axis and the stellar rotation axis, ... degrees. I use the new photometric data to refine the system parameters. Additionally, I present evidence for stellar activity, as the spectra obtained on UT June 19, 2008 reveal an increase in radial velocity to a peak …
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Understand thy star, understand thy planet
… Earth-analogue planets. However, it is now stellar activity that poses a critical challenge on the pathway to detect habitable Earth-like worlds. This thesis is therefore dedicated to understanding the effect stellar activity has on spectroscopically observed radial-velocity (RV) variations …
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Precise radial velocities and simultaneous magnetic flux estimates from intensity spectra
… smaller than 1 m/s are drowned out by the stars' activity. The detection of Earth analogues causing an RV effect of about 10 cm/s is, therefore, out of reach at the time of writing. A few avenues are being explored to resume the trend to detect ever lighter planets. These include improving (a) …
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Effects of starspots activity on optical and near infrared observations of planetary transits
… thesis, I report on the effects that magnetic stellar activity of solar-type stars induces on stellar light curves involved in the photometric technique for the detection and characterization of transiting extra-solar planets that is one of the most effective detection methods, the first being …
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Exoplanet Atmospheric Characterization using High-Precision Photometry
… identify exoplanet's atmospheric scattering and stellar activity imprints on the transmission spectrum. Finally, I present a set of Kepler and K2 Ultra Short Period(USP)planets which shows secondary eclipse and phase curve variations. In extension to that I also explored to investigate the …
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Enshrouded Exoplanetary Systems
… period planets can show anomalously low apparent stellar activity values caused by planetary mass-loss enshrouding the system. The resulting circumstellar absorption depresses the cores of the Ca II H&K lines, where the activity index log(R'<sub>HK</sub>) is measured. I searched for this effect in …
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Spot evolution on the red giant star XX Triangulum
Spots on stellar surfaces are thought to be stellar analogues of sunspots. Thus, starspots are direct manifestations of strong magnetic fields. Their decay rate is directly related to the magnetic diffusivity, which itself is a key quantity for the deduction of an activity cycle length. So far, no …
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Characterization of exoplanetary systems combining transit timing techniques and radial velocities: From secular perturbations to resonant chains
… that challenge our understanding of stellar evolution and tidal dissipation. I then focus on sub-Neptune characterization in multi-planet systems, notably focusing on the multi-planet system HIP 41378, where I performed a joint dynamical modelling of the TTV and RV signals of the two …
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Ground-based transmission spectroscopy of three inflated Hot Jupiter exoplanets
… photometrically to correct for influences of stellar activity if necessary. The obtained measurements of the three objects all favor featureless spectra. A variety of atmospheric compositions can explain the lack of a wavelength dependent absorption. But the broad trend of featureless spectra …
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Optimising the Detection of Temperate, Terrestrial Planets around Ultra-Cool Dwarfs with SPECULOOS
… image reduction, cross-matches with preexisting stellar catalogues, and performs precise aperture and differential photometry every night. With the SSO Pipeline, I address both the instrumental and atmospheric contamination that can prevent detecting small planets. I tackle the first and …
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Robotic telescopes & Doppler imaging : measuring differential rotation on long-period active stars
Auf der Sonne sind viele Phänomene zu sehen die mit der solaren magnetischen Aktivität zusammenhängen. Das dafür zuständige Magnetfeld wird durch einen Dynamo erzeugt, der sich vermutlich am Boden der Konvektionszone in der sogenannten Tachocline befindet. Angetrieben wird der Dynamo teils von der …
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Zeeman-Doppler Imaging of active late-type stars
Stellare Magnetfelder spielen eine wichtige Rolle bei der Entstehung und Entwicklung von Sternen. Leider entziehen sie sich aber, aufgrund ihrer großen Entfernung zur Erde, einer direkten Beobachtung. Dies gilt zumindest für derzeitige und in naher Zukunft zur Verfügung stehende Instrumente. Um …