What are the fast X-ray transients found by Einstein Probe?
In plain words
Since 2024 the Einstein Probe satellite has found many short X-ray flashes from distant galaxies, some with no gamma rays; they may be gamma-ray bursts seen from the side, weaker jets, or something new.
Precise statement
Einstein Probe (launched 2024) detects extragalactic fast X-ray transients lasting $\sim 1\mathrm{e}2\ \text{to}\ 1\mathrm{e}4\,\mathrm{s}$, several with redshifts, some followed by broad-lined type Ic supernovae, and many without gamma-ray detection. Determine the fractions due to off-axis classical jets, intrinsically slow (low-Lorentz-factor or choked) jets, and shock breakout, and the rate relative to long GRBs. Answer: class fractions and rates from a sample with redshifts and counterparts.
What would settle it
A complete Einstein Probe sample with redshifts, afterglow modeling and supernova searches, compared with predicted off-axis and low-Lorentz-factor populations.
Status in the literature
Unverified note
2024-2025: some Einstein Probe transients, for example EP240414a, were followed by broad-lined type Ic supernovae, linking them to collapsing stripped stars.