Kavli Affiliate: Robert Simcoe
| First 5 Authors: Charlotte Myers, Kishalay De, Lin Yan, Jacob E. Jencson, Nicholas Earley
| Summary:
While core-collapse supernovae (SNe) often show early and consistent signs of
circumstellar (CSM) interaction, some exhibit delayed signatures due to
interaction with distant material around the progenitor star. Here we present
the discovery in NEOWISE data of WTP19aalnxx, a luminous mid-infrared (IR)
transient in the outskirts of the galaxy KUG 0022-007 at $approx 190$ Mpc.
First detected in 2018, WTP19aalnxx reaches a peak absolute (Vega) magnitude of
$approx-22$ at $4.6 , mu$m in $approx3$ yr, comparable to the most luminous
interacting SNe. Archival data reveal a $gtrsim 5times$ fainter optical
counterpart detected since 2015, while follow-up near-IR observations in 2022
reveal an extremely red ($Ks-W2 approx 3.7$ mag) active transient. Deep
optical spectroscopy confirm strong CSM interaction signatures via
intermediate-width Balmer emission lines and coronal metal lines. Modeling the
broadband spectral energy distribution, we estimate the presence of $gtrsim
10^{-2}$ M$_odot$ of warm dust, likely formed in the shock interaction region.
Together with the lack of nebular Fe emission, we suggest that WTP19aalnxx is a
missed, low (optical) luminosity SN in an emerging family of core-collapse SNe
distinguished by their CSM-interaction-powered mid-IR emission that outshines
the optical bands. Investigating the Zwicky Transient Facility sample of SNe in
NEOWISE data, we find $17$ core-collapse SNe ($gtrsim 3$% in a volume-limited
sample) without early signs of CSM interaction that exhibit delayed IR
brightening, suggestive of dense CSM shells at $lesssim 10^{17}$cm. We suggest
that synoptic IR surveys offer a new route to revealing late-time CSM
interaction and the prevalence of intense terminal mass loss in massive stars.
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