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The power-law slope of the rest-UV continuum($f_{\lambda}\propto\lambda^{\beta}$) is a key metric of early star forminggalaxies, providing one of our only windows into the stellar populations andphysical conditions of $z>10$ galaxies. Expanding upon previous studies withlimited sample sizes, we leverage deep imaging from JADES to investigate the UVslopes of 179 $z>9$ galaxies with apparent magnitudes of $m_{\rm F200W}=26-31$,which display a median UV slope of $\beta=-2.4$. We compare to a statisticalsample of $z=5-9$ galaxies, finding a shift toward bluer rest-UV colors at all$\rm~M_{UV}$. The most UV-luminous $z>9$ galaxies are significantly bluer thantheir lower-redshift counterparts, representing a dearth of moderately-redgalaxies in the first $500~$Myr. At yet earlier times, the $z>11$ galaxypopulation exhibits very blue UV slopes, implying very low attenuation fromdust. We identify a robust sample of 44 galaxies with $\beta<-2.8$, which haveSEDs requiring models of density-bounded HII regions and median ionizing photonescape fractions of $0.51$ to reproduce. Their rest-optical colors imply thatthis sample has weaker emission lines (median $m_{\rm F356W}-m_{\rmF444W}=0.19$ mag) than typical galaxies (median $m_{\rm F356W}-m_{\rmF444W}=0.39$ mag), consistent with the inferred escape fractions. This samplehas relatively low stellar masses (median $\log(M/M_{\odot})=7.5$), andspecific star-formation rates (median$=79\rm/Gyr$) nearly twice that of ourfull sample (median$=44\rm/Gyr$), suggesting they are more common among systemsexperiencing a recent upturn in star formation. We demonstrate that the shutoffof star formation provides an alternative solution for modelling of extremelyblue UV colors, making distinct predictions for the rest-optical emission ofthese galaxies. Future spectroscopy will be required to distinguish betweenthese physical pictures.

The UV Continuum Slopes of Early Star-Forming Galaxies in JADES