Morpho-kinematic modeling of the expanding ejecta of the extremely slow
  nova V1280 Scorpii
  Morphology of nova ejecta is essential for fully understanding the physical
processes involved in nova eruptions. We studied the 3D morphology of the
expanding ejecta of the extremely slow nova V1280 Sco with a unique light
curve. Synthetic line profile spectra were compared to the observed [O III]
4959, 5007 and [N II] 5755 emission line profiles in order to find the best-fit
morphology, inclination angle, and maximum expansion velocity of the ejected
shell. We derive the best fitting expansion velocity, inclination, and squeeze
as $V_{\rm exp} = 2100^{+100}_{-100}$ \,km\,s$^{-1}$, $i = 80^{+1}_{-3}$ deg,
and $squ = 1.0^{+0.0}_{-0.1}$ using [O III] line profiles, and $V_{\rm exp} =
1600^{+100}_{-100}$ \,km\,s$^{-1}$, $i = 81^{+2}_{-4}$ deg, and $squ =
1.0^{+0.0}_{-0.1}$ using [N II] 5755 line profile. A high inclination angle is
consistent with the observational results showing multiple absorption lines
originating from clumpy gases which are produced in dense and slow equatorially
focused outflows. Based on additional observational features such as optical
flares near the maximum light and dust formation on V1280 Sco, a model of
internal shock interaction between slow ejecta and fast wind proposed for the
$\gamma$-ray emission detected in other novae seems to be applicable to this
extremely slow and peculiar nova. Increasing the sample size of novae whose
morphology is studied will be helpful in addressing long-standing mysteries in
novae such as the dominant energy source to power the optical light at the
maximum, optical flares near the maximum, clumpiness of the ejecta, and dust
formation.
