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تسجيل مستخدم جديد450 Days of Type II SN 2013ej in Optical and Near-Infrared
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We present optical and near-infrared photometric and spectroscopic observations of SN 2013ej, in galaxy M74, from 1 to 450 days after the explosion. SN 2013ej is a hydrogen-rich supernova, classified as a Type IIL due to its relatively fast decline following the initial peak. It has a relatively high peak luminosity (absolute magnitude M$_rm{V}$ = -17.6) but a small $^{56}$Ni production of ~0.023 M$_odot$. Its photospheric evolution is similar to other Type II SNe, with shallow absorption in the H{alpha} profile typical for a Type IIL. During transition to the radioactive decay tail at ~100 days, we find the SN to grow bluer in B - V colour, in contrast to some other Type II supernovae. At late times, the bolometric light curve declined faster than expected from $^{56}$Co decay and we observed unusually broad and asymmetric nebular emission lines. Based on comparison of nebular emission lines most sensitive to the progenitor core mass, we find our observations are best matched to synthesized spectral models with a M$_rm{ZAMS}$ = 12 - 15 M$_odot$ progenitor. The derived mass range is similar to but not higher than the mass estimated for Type IIP progenitors. This is against the idea that Type IIL are from more massive stars. Observations are consistent with the SN having a progenitor with a relatively low-mass envelope.
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om just after explosion to +500 days. The contribution of the NIR flux to the bolometric light curve is estimated to increase from 15% at explosion to around 50% at the end of the plateau and then declines to 40% at 300 days. SN 2004et is one of the most luminous IIP SNe which has been well studied, and with a luminosity of log L = 42.3 erg/s, it is 2 times brighter than SN 1999em. We provide parametrised bolometric corrections as a function of time for SN 2004et and three other IIP SNe that have extensive optical and NIR data, which can be used as templates for future events. We compare the physical parameters of SN 2004et with those of other IIP SNe and find kinetic energies spanning the range of 10^50-10^51 ergs. We compare the ejected masses calculated from hydrodynamic models with the progenitor masses and limits derived from prediscovery images. Some of the ejected mass estimates are significantly higher than the progenitor mass estimates, with SN 2004et showing perhaps the most serious mass discrepancy. With current models, it appears difficult to reconcile 100 day plateau lengths and high expansion velocities with the low ejected masses of 5-6 Msun implied from 7-8 Msun progenitors. The nebular phase is studied using very late time HST photometry, along with optical and NIR spectroscopy. The light curve shows a clear flattening at 600 days in the optical and the NIR, which is likely due to the ejecta impacting on the CSM. We further show that the [Oi] 6300,6364 Angstrom line strengths of four type IIP SNe imply ejected oxygen masses of 0.5-1.5 Msun.
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