ASASSN-14ms:the Most Energetic Known Explosion of a Type Ibn Supernova and its Physical Origin

TL;DR

This paper reports on ASASSN-14ms, potentially the most luminous Type Ibn supernova, analyzing its spectral features, light curve, and the circumstellar material to understand its energetic explosion and physical origin.

Contribution

It presents detailed observations of the most luminous Type Ibn supernova, revealing insights into its CSM interaction and progenitor mass-loss history, which are novel for this supernova class.

Findings

ASASSN-14ms is the most luminous Type Ibn supernova observed.

The supernova's luminosity is driven by ejecta-CSM interaction involving 0.9 solar masses of helium-rich material.

More luminous SNe Ibn tend to have slower post-peak decline rates.

Abstract

ASASSN-14ms may represent the most luminous Type Ibn supernova (SN~Ibn) ever detected, with an absolute U-band magnitude brighter than -22.0 mag and a total bolometric luminosity >1.0x10^{44} erg/s near maximum light. The early-time spectra of this SN are characterized by a blue continuum on which are superimposed narrow P~Cygni profile lines of He I, suggesting the presence of slowly moving (~1000 km/s), He-rich circumstellar material (CSM). At 1--2 months after maximum brightness, the He I line profiles become only slightly broader, with blueshifted velocities of 2000--3000 km/s, consistent with the CSM shell being continuously accelerated by the SN light and ejecta. Like most SNe~Ibn, the light curves of ASASSN-14ms show rapid post-peak evolution, dropping by ~7 mag in the V band over three months. Such a rapid post-peak decline and high luminosity can be explained with interaction between SN ejecta and helium-rich CSM of 0.9~M_{\odot} at a distance of~10^{15} cm. The CSM around ASASSN-14ms is estimated to originate from a pre-explosion event with a mass-loss rate of 6.7~M_\odot /yr (assuming a velocity of ~1000 km/s), which is consistent with abundant He-rich material violently ejected during the late Wolf-Rayet (WN9-11 or Opfe) stage. After examining the light curves for a sample of SNe~Ibn, we find that the more luminous ones tend to have slower post-peak decline rates, reflecting that the observed differences may arise primarily from discrepancies in the CSM distribution around the massive progenitors.