The first black hole candidate ultra-compact X-ray binary in a globular cluster and its twisted accretion
Abstract
47 Tuc X9 is a low mass X-ray binary in the globular cluster 47 Tucanae, and was previously thought to be a cataclysmic variable (a white dwarf accreting from a main sequence star). Recently, we measured strong radio emission from this object, suggesting that the accretor is a black hole. I present result of our deep simultaneous study of this source in X-rays (with Chandra and NuSTAR) and in Radio (ATCA). We find a clear 28.18 minute periodic modulation in the Chandra data, which we identify as the orbital period, confirming this system as an ultracompact X-ray binary (orbital period < 80 mins) indicating the donor is a white dwarf. Additionally, we show evidence for clear signs of photo-ionized emission from oxygen VII and VIII in the system, providing additional evidence that the system is an ultra-compact X-ray binary and showing the donor is a Carbon/Oxygen white dwarf. Finally we detect a 6.8 day periodic modulation in the X-ray light curve, which indicates the presence of a warped accretion disk.
By: Arash Bahramian University of Albetra, Canada
Time: Monday, 8 August / 18 Mordad, 11 AM
Place: Particles and Astronomy seminar room, Larak building
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