A deep dive into the activity-rotation relation in three key open clusters: the Hyades, Pleiades, and Praesepe

OBSERVATIONS OF SOLAR-TYPE STARS SHOW THAT ROTATION AND MAGNETIC ACTIVITY DECREASE AT THE SAME RATE OVER TIME WITH THE SPIN-DOWN LIKELY DUE TO ANGULAR MOMENTUM LOST THROUGH MAGNETIZED WINDS. THE COUPLING OF ROTATION AND THE STELLAR MAGNETIC FIELD MEANS THAT OBSERVABLE PROXIES FOR THE FIELD'S STRENGTH SUCH AS CORONAL X-RAY EMISSION ALSO WEAKEN OVER TIME. THIS AGE-ROTATION-ACTIVITY RELATION (ARAR) HAS GENERATED HOPE THAT MEASUREMENTS OF ROTATION OR ACTIVITY COULD BE USED TO DETERMINE THE AGES OF MAIN-SEQUENCE LOW-MASS FIELD STARS (<_ 1.2 M_) WHICH ARE OTHERWISE ESSENTIALLY UNKNOWABLE. SADLY AN ACCURATE QUANTITATIVE DESCRIPTION OF THE ARAR STILL ELUDES US. EFFORTS TO DEVELOP EMPIRICAL ARARS GENERALLY RELY ON OBSERVATIONS OF STARS IN OPEN CLUSTERS. THESE STARS' WELL-DEFINED AGES MAKE THEM VALUABLE TARGETS FOR MEASURING ROTATION PERIODS (PROT) AND INDICATORS OF MAGNETIC ACTIVITY. HOWEVER OPEN CLUSTERS ARE RELATIVELY RARE PARTICULARLY AT AGES >100 MYR SO THAT CALIBRATING THE ARAR BETWEEN 100 MYR AND THE AGE OF THE SUN IS DIFFICULT. AND UNTIL RECENTLY THERE WAS LITTLE OVERLAP BETWEEN THE CLUSTERS USED TO MEASURE PERIODS AND THOSE USED TO MEASURE ACTIVITY. THESE OBSERVATIONAL LIMITATIONS RESULTED IN EMPIRICAL ARARS THAT PRODUCE AGES WITH UNCERTAINTIES APPROX. 50%. THIS HAS GRAVE CONSEQUENCES: OUR INABILITY TO PROVIDE CONFIDENT AGES FOR LOW-MASS FIELD STARS LIMITS OUR UNDERSTANDING OF EVERYTHING FROM THE MILKY WAY'S STAR-FORMATION HISTORY TO THE DEVELOPMENT OF THEORIES FOR PLANET FORMATION AND EVOLUTION. THIS PROPOSAL PLANS TO: COMPLETE THE ROTATIONAL CENSUS FOR THE THREE CLUSTERS. MORE RECENT K2 AND TESS CAMPAIGNS HAVE PRODUCED NEW PUBLIC LIGHT CURVES FOR CLUSTER STARS WHICH COMBINED WITH NEW GAIA DATA ON THEIR MEMBERSHIP SHOULD BE USED TO UPDATE THESE MASS-PERIOD DISTRIBUTIONS MINE THE ARCHIVAL X-RAY DATA TO EXAMINE IN DETAIL THE RELATIONSHIP BETWEEN CORONAL EMISSION AND ROTATION AT 125 AND 700 MYR. THERE ARE PUBLIC XMM CHANDRA AND SWIFT OBSERVATIONS OF THESE THREE CLUSTERS THAT GO BACK NEARLY 20 YEARS AND HAVE YET TO BE FULLY EXPLOITED USE THE HUNDREDS OF GALEX DETECTIONS OF CLUSTER MEMBERS TO PROBE THE SHAPE OF THE ROTATION-ACTIVITY RELATION IN THE UV. BECAUSE EARTH-SIZED PLANETS CONTINUE TO BE DISCOVERED AROUND LOW-MASS STARS IT IS ESPECIALLY IMPORTANT THAT WE UNDERSTAND THE X-RAY AND UV EMISSION FROM THESE STARS AS BOTH SHAPE HABITABILITY USE PUBLIC AND ARCHIVAL OPTICAL SPECTROSCOPY TO COMPLETE THE ANALYSIS OF THE RELATIONSHIP BETWEEN CHROMOSPHERIC EMISSION AND ROTATION IN CLUSTER MEMBERS.