Abstract Details
| Name: Kishalay De Affiliation: Indian Institute of Science Conference ID: ASI2016_475 Title : The puzzling orbital period evolution of the LMXB AX J1745.6-2901 Authors and Co-Authors : Gabriele Ponti (MPE, Garching), Teo Munoz-Darias (Instituto de Astrofisica de Canarias; Departamento de astrofisica, Univ. de La Laguna, Tenerife), Luigi Stella (INAF, Rome) and Kirpal Nandra (MPE, Garching). Abstract Type : Poster Abstract Category : Stars, The Milky Way Galaxy and its neighbours Abstract : The orbital period evolution of X-ray binaries provides fundamental clues to understanding mechanisms of angular momentum loss from these systems. We present an X-ray eclipse timing analysis of the transient low mass X-ray binary AX J1745.6-2901. This system shows full eclipses and thus is one of the few objects for which accurate orbital evolution studies using this method can be carried out. We report on XMM Newton and ASCA observations covering 30 complete X-ray eclipses spanning an interval of more than 20 years. We improve the determination of the orbital period to a relative precision of 2 x 10^{-8}, two orders of magnitudes better than previous estimates. We determine, for the first time, a highly significant rate of decrease of the orbital period \dot{P}_{orb}=-4.03\pm0.32\times10^{-11}$~s/s. This is at least one order of magnitude larger than expected from conservative mass transfer and angular momentum losses due to gravitational waves and magnetic breaking, and might result from non-conservative mass transfer. Imprinted on the long term evolution of the orbit, we observe highly significant eclipse leads-delays of 10-20 s, characterised by a clear state dependence in which, on average, eclipses occur earlier during the hard state. |