A DECADE ON, WHICH BEES ARE STILL BUZZING? MONITORING STARSPOT EVOLUTION IN PRAESEPE FROM PTF TO K2

SKUMANICH (1972) PROPOSED THAT ROTATION AND CHROMOSPHERIC ACTIVITY A PROXY FOR THE STRENGTH OF THE UNDERLYING MAGNETIC FIELD DECREASE AT ROUGHLY THE SAME RATE FOR SOLAR-TYPE STARS BETWEEN THE AGES OF 100 MYR AND 5 GYR. WHILE WORK IN THE ENSUING DECADES HAS ED THIS GENERAL PICTURE MANY DETAILS STILL ELUDE US PARTICULARLY FOR STARS LESS MASSIVE THAN THE SUN. WE CONTINUE TO TRY TO CONSTRAIN THE DEPENDENCE OF ROTATION AND ACTIVITY ON AGE HOWEVER BECAUSE A WELL-CALIBRATED AGE-ROTATION-ACTIVITY RELATION (ARAR) FOR THESE STARS WOULD BE VERY VALUABLE. EARTH-LIKE PLANETS ARE MOST LIKELY TO BE DISCOVERED IN THE HABITABLE ZONES OF NEARBY OLD LOWMASS STARS (CF. THE SEVEN PLANETS ORBITING TRAPPIST-1). TO UNDERSTAND THESE PLANETS' POTENTIAL HABITABILITY WE NEED A ROBUST ARAR TO APPLY TO THEIR PARENT STARS. CURRENTLY HOWEVER WE INVERT THE PROCESS ADOPTING CANONICAL AGES FOR FIELD STARS TO CONSTRAIN THE BEHAVIOR OF THE ARAR AT THE OLDEST AGES. OPEN CLUSTERS WITH THEIR SINGLE-AGED POPULATIONS ARE THE IDEAL ENVIRONMENT FOR EMPIRICALLY CONSTRAINING THE ARAR. HOWEVER FEW OPEN CLUSTERS HAVE BEEN SYSTEMATICALLY SURVEYED FOR ROTATION AND ACTIVITY IN STARS<1 SOLAR MASS AND THERE ARE FEW ACCESSIBLE CLUSTERS OLDER THAN ~150 MYR. THE HYADES AND PRAESEPE THE BEEHIVE CLUSTER BOTH ~650 MYR AND NEARBY (~50 AND 180 PC RESPECTIVELY) SERVE AS THE ONLY ANCHORS FOR OUR UNDERSTANDING OF ACTIVITY ACROSS A WIDE RANGE OF (LOW) MASSES BETWEEN A FEW 100 MYR AND THE AGE OF FIELD STARS (>2 GYR). WE HAVE ALREADY EXTENSIVELY SURVEYED BOTH CLUSTERS FOR ROTATION PERIODS FIRST WITH THE PALOMAR TRANSIENT FACTORY (PTF) AND THEN WITH K2 AND FOR X-RAY AND H-ALPHA EMISSION. HAVING MONITORED PRAESEPE STARS FOR CLOSE TO A DECADE WE CAN NOW EXPLORE HOW CHANGES IN THEIR MAGNETIC ACTIVITY IMPACT THEIR LIGHT CURVES AND THEREFORE THE LONG-TERM STABILITY AND APPLICABILITY OF ANY ARAR. WE PROPOSE TO COMBINE DATA FROM K2'S C5 C16 AND C18 WITH GROUND-BASED LIGHT CURVES OBTAINED BY PTF AND HATNET TO EXAMINE PHOTOMETRIC VARIABILITY IN PRAESEPE STARS. TO OUR KNOWLEDGE THERE HAS BEEN NO LARGE-SCALE ATTEMPT TO REVISIT ROTATION PERIOD MEASUREMENTS FOR OPEN-CLUSTER STARS AND OUR OBSERVATIONS WILL PROVIDE VALUABLE INSIGHT INTO THE STABILITY OF STARSPOT DISTRIBUTIONS AND MAGNETIC-FIELD STRUCTURES OVER BASELINES OF WEEKS TO A DECADE.