Abstract for Proposal 094376
ToO : Comparing the early rise and decay phases of X-ray binaries outbursts
Recent studies suggest different behaviours between the rising and
decaying hard states of black hole X-ray binaries outbursts. However
the nature of this change eludes us, mainly due to a lack of data. We
propose a ToO monitoring of a future outburst of a known BH XrB composed
of 10 XMM/NuSTAR simultaneous observations, 10 ks/obs for XMM + 20 ks/obs
NuSTAR (total of 100ks XMM and 200ks NuSTAR) to catch the early rising (5
observations) and decaying phases (5 observations) in the same hard X-ray
flux range. The trigger conditions will be based on the "X-ray Binary New
Early Warning System” in optical, anticipating X-ray outbursts by a few
days/weeks. Quasi-simultaneous ATCA and MeerKAT observations are planned.
Details on Observing Strategy and Trigger Criteria
The target will be a single known black hole X-ray binary entering
outburst. A list of 32 possible targets is presented below. The first
observation is put as unknown and represent the requested monitoring. To
catch the outburst as early as possible, the trigger conditions will
be based on the "X-ray Binary New Early Warning System? in optical
(D. Russell and K. Alabarta are Co-I of this proposal), anticipating
X-ray outbursts by a 1-2 weeks. As soon as they alert and confirm to
us of the start of an optical outburst, we would like to trigger the
XMM/NuSTAR monitoring whithin 2 days. A case study demonstrating this
trigger condition is presented in the scientific justification. The
monitoring will consist of two phases: - early rise of the outburst. With
5 XMM/NuSTAR observations (10ks XMM, 20ks NuSTAR) each spaced by 1 to 2
days - decay of the outburst, a few months later (triggered by following
the X-ray evolution through Swift all-sky survey or any other X-ray
mission observing the source). Once again with 5 XMM/NuSTAR observations
(10ks XMM, 20ks NuSTAR) each spaced by 1 to 2 days Ideally, we will catch
the same range of X-ray flux for both the rising and the decaying phase.