We present an optical photometric and spectroscopic analysis of the fast-declining hydrogen-rich Type II supernova (SN) 2019nyk. The light curve properties of SN 2019nyk align well with those of other fast-declining Type II SNe, such as SNe 2013by and 2014G. SN 2019nyk exhibits a peak absolute magnitude of −18.09 ± 0.17 mag in theVband, followed by a rapid decline at 2.84 ± 0.03 mag (100 d)−1during the recombination phase. The early spectra of SN 2019nyk exhibit high-ionisation emission features as well as narrow H Balmer lines, persisting until 4.1 d since explosion, indicating the presence of circumstellar material (CSM) in close proximity. A comparison of these features with other Type II SNe displaying an early interaction reveals similarities between these features and those observed in SNe 2014G and 2023ixf. We also compared the early spectra to literature models, estimating a mass-loss rate of the order of 10−3M⊙yr−1. Radiation hydrodynamical modelling of the light curve also suggests the mass loss from the progenitor within a short period prior to explosion, totalling 0.16M⊙of material within 2900R⊙of the progenitor. Furthermore, light curve modelling infers a zero-age main sequence mass of 15M⊙for the progenitor, a progenitor radius of 1031R⊙, and an explosion energy of 1.1 × 1051erg.
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SN 2015an: a normal luminosity type II supernova with low expansion velocity at early phases
ABSTRACT We present the photometry and spectroscopy of SN 2015an, a type II Supernova (SN) in IC 2367. The recombination phase of the SN lasts up to 120 d, with a decline rate of 1.24 mag/100d, higher than the typical SNe IIP. The SN exhibits bluer colours than most SNe II, indicating higher ejecta temperatures. The absolute V-band magnitude of SN 2015an at 50 d is −16.83 ± 0.04 mag, pretty typical for SNe II. However, the 56Ni mass yield, estimated from the tail V-band light curve to be 0.021 ± 0.010 M⊙, is comparatively low. The spectral properties of SN 2015an are atypical, with low H α expansion velocity and presence of high-velocity component of H α at early phases. Moreover, the continuum exhibits excess blue flux up to 50 d, which is interpreted as a progenitor metallicity effect. The high-velocity feature indicates ejecta-circumstellar material interaction at early phases. The semi-analytical modelling of the bolometric light curve yields a total ejected mass of 12 M⊙, a pre-SN radius of 388 R⊙ and explosion energy of 1.8 foe.
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- Award ID(s):
- 1813176
- PAR ID:
- 10183685
- Date Published:
- Journal Name:
- Monthly Notices of the Royal Astronomical Society
- Volume:
- 490
- Issue:
- 2
- ISSN:
- 0035-8711
- Page Range / eLocation ID:
- 1605 to 1619
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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