JAPC - Searching for Dying Pulse Trains in RXTE Observations of Cyg X-1

Speaker: Dr. Joseph Dolan, SDSU Dept. of Astronomy

Topic: "Searching for Dying Pulse Trains in RXTE Observations of Cyg X-1"

Time: 2:00 PM, Friday, May 2nd, 2008

Place: P-148 (refreshments will be served at 1:45 PM in P145A)

Abstract: Dying pulse trains (DPT's) – decreasing intensity pulses of radiation with decreasing intervals between them - are predicted by theory to occur from material spiraling into an event horizon after detaching from the last stable orbit in an accretion disk around a black hole. Two events resembling DPT's were detected in 3 hours observation of Cyg X-1 in the far UV using the high Speed Photometer on the Hubble Space Telescope (Dolan 2001). We observed Cyg X-1, a leading candidate for a black hole, in the 2-15 keV X-ray region using the proportional counter array on RXTE. No dying pulse trains with a characteristic timescale between pulses between 1 - 40 ms were detected in 10 hours of observation during Cyg X-1's high luminosity state, low luminosity state, and transitions between states, although individual pulses are clearly detectable in data with temporal resolution > 1 ms. Our results are consistent with Cyg X-1 being an extreme Kerr black hole (a = cJ/GM2 ~ 1) having a characteristic timescale between DPT pulses less than 1 ms.

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