STUDYING THE ONSET OF PROPELLER ACCRETION IN SAX J1808.43658 WITH NUSTAR AND SWIFTWE PROPOSE A JOINT PROGRAM WITH NUSTAR AND SWIFT TO MONITOR THE ACCRETING MILLISECOND PULSAR SAX J1808.43658 DURING ITSRETURN TO QUIESCENCE AT THE END OF A TRANSIENT OUTBURST. THE GOAL OF THIS CAMPAIGN IS TO MEASURE THE HARD X RAY SPECTRUM AND TO DETECT PULSATIONS FROM THE SOURCE IN THE TAIL OF THE OUTBURST. THIS WILL PROBE THE ROLE OF THE MAGNETOSPHERE IN THE "PROPELLER" ACCRETION REGIME AND EXPLORE WHETHER MAGNETICALLY CHANNELED ACCRETION STILL OCCURS THERE. THE FLEXIBLE MONITORING CAPABILITY OF SWIFT WILL BE USED TO TRIGGER HIGH SENSITIVITY NUSTAR HARD X RAY OBSERVATIONS AT THE APPROPRIATE FLUX LEVEL DURING THE DECAY OF AN OUTBURST. BASED ON THE PREVIOUS OUTBURST HISTORY OF SAX J1808.43658 WE ESTIMATE A HIGH LIKELIHOOD THAT THE SOURCE WILL OUTBURST AGAIN DURING SWIFT CYCLE 11.

Massachusetts Institute Of Technology, Cambridge MA

Investigators