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1. Neutron-proton pairing in the N=Z radioactive fp-shell nuclei 56Ni and 52Fe probed by pair transfer

   https://doi.org/10.1016/j.physletb.2022.137057  

   Le Crom, B. ; Assié, M. ; Blumenfeld, Y. ; Guillot, J. ; Sagawa, H. ; Suzuki, T. ; Honma, M. ; Achouri, N.L. ; Bastin, B. ; Borcea, R. ; et al ( June 2022 , Physics Letters B)
2. Enormous explosion energy of Type IIP SN 2017gmr with bipolar 56Ni ejecta

   https://doi.org/10.1093/mnras/stab1369  

   Utrobin, Victor P ; Chugai, Nikolai N ; Andrews, Jennifer E ; Smith, Nathan ; Jencson, Jacob ; Howell, D Andrew ; Burke, Jamison ; Hiramatsu, Daichi ; McCully, Curtis ; Bostroem, K Azalee ( May 2021 , Monthly Notices of the Royal Astronomical Society)

   null (Ed.)

   ABSTRACT The unusual Type IIP SN 2017gmr is revisited in order to pinpoint the origin of its anomalous features, including the peculiar light curve after about 100 d. The hydrodynamic modelling suggests the enormous explosion energy of ≈1052 erg. We find that the light curve with the prolonged plateau/tail transition can be reproduced either in the model with a high hydrogen abundance in the inner ejecta and a large amount of radioactive 56Ni, or in the model with an additional central energy source associated with the fallback/magnetar interaction in the propeller regime. The asymmetry of the late H α emission and the reported linear polarization are reproduced by the model of the bipolar 56Ni ejecta. The similar bipolar structure of the oxygen distribution is responsible for the two-horn structure of the [O i] 6360, 6364 Å emission. The bipolar 56Ni structure along with the high explosion energy are indicative of the magneto-rotational explosion. We identify narrow high-velocity absorption features in H α and He i10 830 Å lines with their origin in the fragmented cold dense shell formed due to the outer ejecta deceleration in a confined circumstellar shell. 

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3. Carnegie Supernova Project-II: Using Near-infrared Spectroscopy to Determine the Location of the Outer 56Ni in Type Ia Supernovae

   Ashall, C. ; Hsiao, E. Y. ; Hoeflich, P. ; Stritzinger, M. ; Phillips, M. M. ; Morrell, N. ; Davis, S. ; Baron, E. ; Piro, A. L. ; Burns, C ( April 2019 , Astrophysical journal)

   We present the H-band wavelength region of 37 postmaximum light near-infrared spectra of three normal, nine transitional, and four subluminous type Ia supernovae (SNe Ia), extending from +5 days to +20 days relative to the epoch of B-band maximum. We introduce a new observable, the blue-edge velocity, v edge, of the prominent Fe/Co/Ni-peak H-band emission feature, which is quantitatively measured. The v edge parameter is found to decrease over subtype ranging from around −14,000 km s−1 for normal SNe Ia, to −10,000 km s−1 for transitional SNe Ia, down to −5000 km s−1 for the subluminous SNe Ia. Furthermore, inspection of the +10 ± 3 days spectra indicates that v edge is correlated with the color-stretch parameter, s BV , and hence with peak luminosity. These results follow the previous findings that brighter SNe Ia tend to have 56Ni located at higher velocities as compared to subluminous objects. As v edge is a model-independent parameter, we propose it can be used in combination with traditional observational diagnostics to provide a new avenue to robustly distinguish between leading SNe Ia explosion models. 

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4. 57Zn β-delayed proton emission establishes the 56Ni rp-process waiting point bypass

   https://doi.org/10.1016/j.physletb.2022.137059  

   Saxena, M. ; -J Ong, W. ; Meisel, Z. ; Hoff, D.E.M. ; Smirnova, N. ; Bender, P.C. ; Burcher, S.P. ; Carpenter, M.P. ; Carroll, J.J. ; Chester, A. ; et al ( June 2022 , Physics Letters B)
5. The core normal Type Ia supernova 2019np – an overall spherical explosion with an aspherical surface layer and an aspherical 56Ni core

   https://doi.org/10.1093/mnras/stad172  

   Hoeflich, Peter ; Yang, Yi ; Baade, Dietrich ; Cikota, Aleksandar ; Maund, Justyn R. ; Mishra, Divya ; Patat, Ferdinando ; Patra, Kishore C. ; Wang, Lifan ; Wheeler, J. Craig ; et al ( January 2023 , Monthly Notices of the Royal Astronomical Society)

   Optical spectropolarimetry of the normal thermonuclear supernova (SN) 2019np from −14.5 to +14.5 d relative to B-band maximum detected an intrinsic continuum polarization (pcont) of 0.21 ± 0.09 per cent at the first epoch. Between days −11.5 and  +0.5, pcont remained ∼0 and by day +14.5 was again significant at 0.19 ± 0.10 per cent. Not considering the first epoch, the dominant axis of ${\rm Si\, {\small II}}$ λ6355 was roughly constant staying close the continuum until both rotated in opposite directions on day  +14.5. Detailed radiation-hydrodynamical simulations produce a very steep density slope in the outermost ejecta so that the low first-epoch pcont ≈ 0.2 per cent nevertheless suggests a separate structure with an axis ratio ∼2 in the outer carbon-rich (3.5–4) × 10−3 M⊙. Large-amplitude fluctuations in the polarization profiles and a flocculent appearance of the polar diagram for the ${\rm Ca\, {\small II}}$ near-infrared triplet (NIR3) may be related by a common origin. The temporal evolution of the polarization spectra agrees with an off-centre delayed detonation. The late-time increase in polarization and the possible change in position angle are also consistent with an aspherical 56Ni core. The pcont and the absorptions due to ${\rm Si\, {\small II}}$ λ6355 and ${\rm Ca\, {\small II}}$ NIR3 form in the same region of the extended photosphere, with an interplay between line occultation and thermalization producing p. Small-scale polarization features may be due to small-scale structures, but many could be related to atomic patterns of the quasi-continuum; they hardly have an equivalent in the total-flux spectra. We compare SN 2019np to other SNe and develop future objectives and strategies for SN Ia spectropolarimetry.

    

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