Observations of the very young Type Ia Supernova 2019np with early-excess emission. Issue 3 (2nd June 2022)

• Record Type: Journal Article
• Authors: 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, M M; 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;
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 514:Issue 3(2022)
• Page Start: 3541
• Page End: 3558
• Publication Date: 2022-06-02
• Subjects: supernovae: general -- supernovae: individual: (SN 2019np); Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stac1525
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: Early-time radiative signals from Type Ia supernovae (SNe Ia) can provide important constraints on the explosion mechanism and the progenitor system. We present observations and analysis of SN 2019np, a nearby SN Ia discovered within 1–2 days after the explosion. Follow-up observations were conducted in optical, ultraviolet, and near-infrared bands, covering the phases from ∼−16.7 d to ∼+ 367.8 d relative to its B -band peak luminosity. The photometric and spectral evolutions of SN 2019np resemble the average behaviour of normal SNe Ia. The absolute B -band peak magnitude and the post-peak decline rate are M max ( B ) = −19.52 ± 0.47 mag and Δ m 15 ( B ) = 1.04 ± 0.04 mag, respectively. No Hydrogen line has been detected in the nebular-phase spectra of SN 2019np. Assuming that the 56 Ni powering the light curve is centrally located, we find that the bolometric light curve of SN 2019np shows a flux excess up to 5.0 per cent 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 56 Ni mixing, we propose that the nickel mixing is more favoured for SN 2019np.