We present All-Sky Automated Survey data starting 25 days before the discovery of the recent type IIn SN 2010jl , and we compare its light curve to other luminous IIn SNe , showing that it is a luminous ( M _ { I } \approx - 20.5 ) event .
Its host galaxy , UGC 5189 , has a low gas-phase oxygen abundance ( 12 + log ( O / H ) = 8.2 \pm 0.1 ) , which reinforces the emerging trend that over-luminous core-collapse supernovae are found in the low-metallicity tail of the galaxy distribution , similar to the known trend for the hosts of long GRBs .
We compile oxygen abundances from the literature and from our own observations of UGC 5189 , and we present an unpublished spectrum of the luminous type Ic SN 2010gx that we use to estimate its host metallicity .
We discuss these in the context of host metallicity trends for different classes of core-collapse objects .
The earliest generations of stars are known to be enhanced in [ O/Fe ] relative to the Solar mixture ; it is therefore likely that the stellar progenitors of these overluminous supernovae are even more iron-poor than they are oxygen-poor .
A number of mechanisms and massive star progenitor systems have been proposed to explain the most luminous core-collapse supernovae .
Any successful theory that tries to explain these very luminous events will need to include the emerging trend that points towards low-metallicity for the massive progenitor stars .
This trend for very luminous supernovae to strongly prefer low-metallicity galaxies should be taken into account when considering various aspects of the evolution of the metal-poor early universe , such as enrichment and reionization .