Observations of the very young Type Ia Supernova 2019np with early-excess emission

ABSTRACT Early-time radiative signals from Type Ia supernovae (SNeIa) can provide important constraints on the explosion mechanism and the progenitor system. We present observations and analysis of SN2019np, a nearby SNIa discovered within 12days after the explosion. Follow-up observations were conducted in optical, ultraviolet, and near-infrared bands, covering the phases from 16.7d to +367.8d relative to its B-band peak luminosity. The photometric and spectral evolutions of SN2019np resemble the average behaviour of normal SNeIa. The absolute B-band peak magnitude and the post-peak decline rate are Mmax(B)= 19.520.47mag and m15(B) =1.040.04mag, respectively. No Hydrogen line has been detected in the nebular-phase spectra of SN2019np. Assuming that the 56Ni powering the light curve is centrally located, we find that the bolometric light curve of SN2019np shows a flux excess up to 5.0percent in the early phase compared to the radiative diffusion model. Such an extra radiation perhaps suggests the presence of an additional energy source beyond the radioactive decay of central nickel. Comparing the observed colour evolution with that predicted by different models, such as interactions of SN ejecta with circumstellar matter (CSM)/companion star, a double-detonation explosion from a sub-Chandrasekhar mass white dwarf (WD) and surface 56Ni mixing, we propose that the nickel mixing is more favoured for SN 2019np.

Sai, H., Wang, X., Elias-Rosa, N., Yang, Y. i., Zhang, J., Lin, W., ... Zhang, X.

Sai, Hanna||Wang, Xiaofeng||Elias-Rosa, Nancy||Yang(杨轶), Yi||Zhang, Jujia||Lin, Weili||Mo, Jun||Piro, Anthony L||Zeng, Xiangyun||Andrea, Reguitti||Brown, Peter||Burns, Christopher R||Cai, Yongzhi||Fiore, Achille||Hsiao, Eric Y||Isern, Jordi||Itagaki, K||Li, Wenxiong||Li, Zhitong||Pessi, Priscila J||Phillips, MM||Schuldt, Stefan||Shahbandeh, Melissa||Stritzinger, Maximilian D||Tomasella, Lina||Vogl, Christian||Wang, Bo||Wang, Lingzhi||Wu, Chengyuan||Yang, Sheng||Zhang, Jicheng||Zhang, Tianmeng||Zhang, Xinghan

Observations of the very young Type Ia Supernova 2019np with early-excess emission Academic Article