Abstract for Proposal 094484
Tracking the Wind of a Black Hole Low-Mass X-ray Binary in Spectral Transition
Winds in low mass X-ray binaries (LMXB) might carry away a significant
amount of matterand are thus able to regulate the evolution of these
systems. To make a decisivebreakthrough in our understanding of these
winds, we propose a Large Program of 10-day XMM-NuSTARconsecutive
monitoring (30 ks/day XMM, 20 ks/day NuSTAR), triggered by Optical
and X-ray alerts, of ahigh-inclination Black Hole LMXB during the
Hard-to-Soft transition. This will allow us to simultaneouslyand
accurately determine the X-ray broadband spectral shape and detect the
wind absorption lines.These are key ingredients to put firm constraints,
both on the evolution of the wind physical properties withthe accretion
state and its possible association with the jet (thanks to proprietary
simultaneous IR/radioobservations).
Details on Observing Strategy and Trigger Criteria
We ask for 10 days of XMM-NuSTAR monitoring: -XMM: 30ks/day, total:
300ks -NuSTAR: 20ks/day, total: 200ks We will use the ?X-ray Binary
New Early Warning System? in optical to anticipate a BH XrB outburst by
a few days to 1-2 weeks in order to start step 1 as early as possible.
Step 1: We will check if the BH XrB is a high-inclination system or if
it shows clear dips, if it will be visible with XMM-NuSTAR for long
enough to get monitor of the, and for NuSTAR star tracker blockage.
Once step 1 is validated, we will start a Swift/XRT daily monitoring
program when the source reaches a bright HS (F2?10keV > 3 ? 10?10 erg
cm?2 s?1). We request 1 ks/day of Swift/XRT observation (up to 40 ks). Few
hours after each acquisition, we will know the exact state of the source,
and will react in case of exceptional events. Step 2: The XMM-NuSTAR
monitoring will be triggered if a (type C) 1-2 Hz QPO in Swift indicates
an imminent transition, AND if the source is bright enough (F2?10keV >
1e?9 erg cm?2 s?1) for good absorption lines detection. The expected
reaction time is a few days, agreeing with the XMM-NuSTAR ToO 2-days
reaction time policy. The Swift monitoring will continue until the end
of the XMM-NuSTAR