We present optical photometric and spectroscopic observations of the Type Ibn ( SN 2006jc-like ) supernova iPTF13beo .
Detected by the intermediate Palomar Transient Factory \sim 3 hours after the estimated first light , iPTF13beo is the youngest and the most distant ( \sim 430 Mpc ) Type Ibn event ever observed .
The iPTF13beo light curve is consistent with light curves of other Type Ibn SNe and with light curves of fast Type Ic events , but with a slightly faster rise-time of two days .
In addition , the iPTF13beo R -band light curve exhibits a double-peak structure separated by \sim 9 days , not observed before in any Type Ibn SN .
A low-resolution spectrum taken during the iPTF13beo rising stage is featureless , while a late-time spectrum obtained during the declining stage exhibits narrow and intermediate-width He I and Si II features with FWHM \approx 2000–5000 km s ^ { -1 } and is remarkably similar to the prototypical SN Ibn 2006jc spectrum .
We suggest that our observations support a model of a massive star exploding in a dense He-rich circumstellar medium ( CSM ) .
A shock breakout in a CSM model requires an eruption releasing a total mass of \sim 0.1 M \odot over a time scale of couple of weeks prior to the SN explosion .