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In this paper, we report observations of a peculiar Type Ia supernovaiPTF13asv (a.k.a., SN2013cv) from the onset of the explosion to months afterits peak. The early-phase spectra of iPTF13asv show absence of iron absorption,indicating that synthesized iron elements are confined to low-velocity regionsof the ejecta, which, in turn, implies a stratified ejecta structure along theline of sight. Our analysis of iPTF13asv's light curves and spectra shows thatit is an intermediate case between normal and super-Chandrasekhar events. Onthe one hand, its light curve shape (B-band $\Delta m_{15}=1.03\pm0.01$) andoverall spectral features resemble those of normal Type Ia supernovae. On theother hand, similar to super-Chandrasekhar events, it shows large peak opticaland UV luminosity ($M_B=-19.84\,\rm{mag}$, $M_{uvm2}=-15.5\,\rm{mag}$) arelatively low but almost constant \ion{Si}{2} velocities of about$10,000\,\rm{km}\,\rm{s}^{-1}$, and persistent carbon absorption in thespectra. We estimate a $^{56}$Ni mass of $0.81^{+0.10}_{-0.18}M_\odot$ and atotal ejecta mass of $1.59^{+0.45}_{-0.12}M_\odot$. The large ejecta mass ofiPTF13asv and its stratified ejecta structure together seemingly favor adouble-degenerate origin.

An Intermediate Type Ia Supernova Between Normal And Super-Chandrasekhar