Robotic telescopes & Doppler imaging [Elektronische Ressource] : measuring differential rotation on long-period active stars / Michael Weber

AstrophysikalischesInstitutPotsdamStellarActivityGroupAnderSternwarte16D 14482PotsdamROBOTIC TELESCOPES&DOPPLER IMAGINGMeasuringdifferentialrotationonlong periodactivestarsDissertationzurErlangungdesakademischenGrades„Doctorrerumnaturalium“(Dr. rer. nat.)eingereichtanderMathematisch NaturwissenschaftlichenFakultätderUniversitätPotsdamvonMichaelWeberPotsdam,den13. August2004EsistnichtallesSchwindel,aberdasmeiste.FontaneEverythingyouknowiswrong.ChumbawambaAbstractThe sun shows a wide variety of magnetic activity related phenomena. The mag neticfieldresponsibleforthisisgeneratedbyadynamoprocesswhichisbelievedtooperateinthetachocline,whichislocatedatthebottomoftheconvectionzone.This dynamo is driven in part by differential rotation and in part by magneticturbulences in the convection zone. The surface differential rotation, one key in gredientofdynamotheory,canbemeasuredbytracingsunspotpositions.To extend the parameter space for dynamo theories, one can extend these mea surements to other stars than the sun. The primary obstacle in this endeavor isthe lack of resolved surface images on other stars. This can be overcome by theDoppler imaging technique, which uses the rotation induced Doppler broadeningof spectral lines to compute the surface distribution of a physical parameter liketemperature. To obtain the surface image of a star, high resolution spectroscopicobservations, evenly distributed over one stellar rotation period are needed.