Chandra X-ray Constraints on the Candidate Ca-rich Gap Transient SN 2016hnk

TL;DR

This study uses Chandra X-ray observations to test if SN 2016hnk was caused by a white dwarf being tidally detonated by an intermediate-mass black hole, finding no X-ray evidence to support this model.

Contribution

The paper provides the first X-ray constraints on the tidal detonation scenario for Ca-rich gap transients, challenging the intermediate-mass black hole hypothesis.

Findings

No X-ray emission detected 28 days post-discovery.

Rules out intermediate-mass black hole tidal detonation for SN 2016hnk.

Supports alternative explanations for Ca-rich gap transients.

Abstract

We present a Chandra observation of SN 2016hnk, a candidate Ca-rich gap transient. This observation was specifically designed to test whether or not this transient was the result of the tidal detonation of a white dwarf by an intermediate-mass black hole. Since we detect no X-ray emission 28 days after the discovery of the transient, as predicted from fall-back accretion, we rule out this model. Our upper limit of $\sim 10$ M$_\odot$ does not allow us to rule out a neutron star or stellar-mass black hole detonator due limits on the sensitivity of Chandra to soft X-rays and unconstrained variables tied to the structure of super-Eddington accretion disks. Together with other Chandra and multiwavelength observations, our analysis strongly argues against the intermediate-mass black hole tidal detonation scenario for Ca-rich gap transients more generally.