In a previous paper we reported on a discontinuity in the extreme horizontal branch ( EHB ) of the Galactic globular cluster NGC6752 , which we called the second U -jump .
This feature was attributed to a combination of post zero-age horizontal branch evolution and diffusion effects .
In this follow-up study we analyze other EHB clusters and show that the second U -jump is a common feature among EHB clusters reaching T _ { eff } \geq 23 , 000 K , and that its onset in different clusters converges around T _ { eff } \sim 21 , 000 \pm 3 , 000 K. We also present near-ultraviolet diagrams of \omega Cen and NGC2808 , the only two objects with spectroscopically confirmed “ blue hook ” stars ( T _ { eff } \geq 35 , 000 K ) .
We confirm predictions of a photometric discontinuity separating late from early-helium flashers .
Moreover , we present empirical evidence that the second U -jump population might be mainly composed by early-helium flashers .
Lastly , we revisit the discussion on the ubiquitous nature of the gaps and jumps so far identified in the blue HB tails , suggesting a possible discrete nature of the distribution in temperature of the HB stars .