MASS LOSS IN EVOLVED MASSIVE STARS IS ONE OF THE LEAST UNDERSTOOD YET FUNDAMENTAL ASPECTS OF STELLAR EVOLUTION. HOW AND WHEN DO MASSIVE STARS LOSE THEIR H-ENVELOPES? THIS CENTRAL QUESTION MOTIVATES THIS PROPOSAL. WE REQUEST A CONTINUATION OF OUR SUCCESSFUL NUSTAR PROGRAM THAT LED TO THE FIRST DETECTION OF A H-POOR EXTRAGALACTIC SN IN THE HARD X-RAYS. WE REQUEST NUSTAR OBSERVATIONS TO MAP THE UNIQUE SITUATION OF THE INTERACTION OF THE H-STRIPPED SN2014C WITH A H-RICH SHELL EJECTED BY ITS PROGENITOR STAR AS PART OF OUR APPROVED GAMMA-RAY TO RADIO FOLLOW-UP. OUR GOAL IS TO COMPLETE THE MAPPING OF THE DENSITY PROFILE OF THE H-RICH MATERIAL AT R>7D17 CM TO DETERMINE ITS LOCATION AND TOTAL MASS AND HENCE THE MASS-LOSS HISTORY OF THE PROGENITOR IN THE YEARS BEFORE STELLAR DEATH. 1

Northwestern University, Evanston IL

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