We present photospheric-phase observations of LSQ12gdj , a slowly-declining , UV-bright Type Ia supernova .
Classified well before maximum light , LSQ12gdj has extinction-corrected absolute magnitude M _ { B } = -19.8 , and pre-maximum spectroscopic evolution similar to SN 1991T and the super-Chandrasekhar-mass SN 2007if .
We use ultraviolet photometry from Swift , ground-based optical photometry , and corrections from a near-infrared photometric template to construct the bolometric ( 1600–23800 Å ) light curve out to 45 days past B -band maximum light .
We estimate that LSQ12gdj produced 0.96 \pm 0.07 M _ { \odot } of ^ { 56 } \mathrm { Ni } , with an ejected mass near or slightly above the Chandrasekhar mass .
As much as 27 % of the flux at the earliest observed phases , and 17 % at maximum light , is emitted bluewards of 3300 Å .
The absence of excess luminosity at late times , the cutoff of the spectral energy distribution bluewards of 3000 Å , and the absence of narrow line emission and strong Na i D absorption all argue against a significant contribution from ongoing shock interaction .
However , \sim 10 % of LSQ12gdj ’ s luminosity near maximum light could be produced by the release of trapped radiation , including kinetic energy thermalized during a brief interaction with a compact , hydrogen-poor envelope ( radius < 10 ^ { 13 } cm ) shortly after explosion ; such an envelope arises generically in double-degenerate merger scenarios .