WTP 19aalnxx: Discovery of a Bright Mid-infrared Transient in the Emerging Class of Low-luminosity Supernovae Revealed by Delayed Circumstellar Interaction

Creators: Myers, Charlotte¹; De, Kishalay¹; Yan, Lin²; Jencson, Jacob E.³; Earley, Nicholas²; Fremling, Christoffer²; Hiramatsu, Daichi^{4, 5}; Kasliwal, Mansi M.²; Lau, Ryan M.⁶; MacLeod, Morgan⁴; Masterson, Megan¹; Panagiotou, Christos¹; Simcoe, Robert¹; Tinyanont, Samaporn⁷

1. Massachusetts Institute of Technology
2. California Institute of Technology
3. Johns Hopkins University
4. Harvard-Smithsonian Center for Astrophysics
5. AI Institute for Artificial Intelligence and Fundamental Interactions
6. NOIRLab
7. National Astronomical Research Institute of Thailand

Abstract

While core-collapse supernovae (SNe) often show early and consistent signs of circumstellar medium (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 WTP 19aalnxx, a luminous mid-infrared (MIR) transient in the outskirts of the galaxy KUG 0022-007 at ≈190 Mpc. First detected in 2018, WTP 19aalnxx reaches a peak absolute (Vega) magnitude of ≈−22 at 4.6 μm in ≈3 yr, comparable to the most luminous interacting SNe. Archival data reveal a ≳5× fainter optical counterpart detected since 2015, while follow-up near-infrared observations in 2022 reveal an extremely red (Ks − W2 ≈ 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 ≳10⁻²M_⊙ of warm dust, likely formed in the cold dense shell. Together with the lack of nebular Fe emission, we suggest that WTP 19aalnxx is a missed, low (optical) luminosity SN in an emerging family of core-collapse SNe distinguished by their CSM-interaction-powered MIR emission that outshines the optical bands. Investigating the Zwicky Transient Facility sample of SNe with NEOWISE data, we find 16 core-collapse SNe (≳3% in a volume-limited sample) without early signs of CSM interaction that exhibit delayed IR brightening, suggestive of dense CSM shells at ≲10¹⁷ 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.

Copyright and License

Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.

Acknowledgement

We thank the anonymous referee for a careful reading of the manuscript and providing valuable feedback that improved the manuscript. We thank Y. Sharma for providing the optical spectra of SN Ia-CSM events, and J. Sollerman for providing helpful feedback on the manuscript. K.D. was supported by NASA through the NASA Hubble Fellowship grant #HST-HF2-51477.001 awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555. This work was supported by a NASA Keck PI Data Award, administered by the NASA Exoplanet Science Institute. Data presented herein were obtained at the W. M. Keck Observatory from telescope time allocated to the National Aeronautics and Space Administration through the agency's scientific partnership with the California Institute of Technology and the University of California. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. This research has made use of the Keck Observatory Archive (KOA), which is operated by the W. M. Keck Observatory and the NASA Exoplanet Science Institute (NExScI), under contract with the National Aeronautics and Space Administration. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile. Based in part on observations obtained at the Southern Astrophysical Research (SOAR) telescope, which is a joint project of the Ministério da Ciência, Tecnologia e Inovações do Brasil (MCTI/LNA), the US National Science Foundation's NOIRLab, the University of North Carolina at Chapel Hill (UNC), and Michigan State University (MSU).

Funding

K.D. was supported by NASA through the NASA Hubble Fellowship grant #HST-HF2-51477.001 awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555.

Facilities

NEOWISE - , Keck:I - KECK I Telescope (LRIS), Keck:II - KECK II Telescope (NIRES), Magellan:Baade - Magellan I Walter Baade Telescope (FIRE), Magellan:Clay - Magellan II Landon Clay Telescope (LDSS-3), SOAR - The Southern Astrophysical Research Telescope (Goodman, Spartan), Hale - Palomar Observatory's 5.1m Hale Telescope (WIRC), PO:1.2m - Palomar Observatory's 1.2 meter Samuel Oschin Telescope (ZTF), ATLAS - , PS1 - Panoramic Survey Telescope and Rapid Response System Telescope #1 (Pan-STARRS), and Spitzer - Spitzer Space Telescope satellite.

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