Abstract for Proposal 096168
The diversity of the progenitors of Fast X-ray Transients
Fast X-ray transients (FXTs) are extra-galactic flashes of
X-rays. Einstein Probe (EP) carries the promise to revolutionise
the field, quickly (<<1 d) informing us on each of the many FXTs
it discovers (>50 in ~0.5 year). However, obtaining the diagnostics
required to determine their progenitors has been hard. The 2 best-studied
FXTs include a peculiar z~5 long gamma-ray burst and a relativistic
supernova with properties linking it to luminous fast blue optical
transients. The question is if these are two examples of the extreme
ends of the luminosity function of the same population or is the new EP
detection method allowing us to extend the range of progenitors that we
probe? To understand this we urgently need new the diagnostic power that
XMM-Newton, VLT/MUSE and JWST can provide.
Details on Observing Strategy and Trigger Criteria
Einstein-Probe discovered FXT with flux (0.5-4 keV)>5E-10 cgs and an EP
position accurate to 10-20" that allows to assess through optical archival
imaging that the FXT cannot be due to a dwarf flare star. 2 observations
of 25 + 50 ksec requested per trigger. 3 triggers requested. First
observation ~36 hr after the trigger, second ~7 days after the trigger.