A multiwavelength view of the nearby Calcium-Strong Transient SN 2025coe in the X-Ray, Near-Infrared, and Radio Wavebands

Abstract

Calcium-strong transients (CaSTs) are a subclass of faint and rapidly evolving supernovae (SNe) that exhibit strong calcium features and notably weak oxygen features. The small but growing population of CaSTs exhibits some aspects similar to thermonuclear supernovae but others similar to massive star core-collapse events, leading to intriguing questions on their physical origins. SN~2025coe is one of the nearest CaSTs discovered to date, and our coordinated multi-wavelength observations obtained days to weeks post-explosion reveal new insights on these enigmatic transients. With the most robust NIR spectroscopic time-series of a CaST collected to date, SN 2025coe shows spectral signatures characteristic of Type Ib SNe (i.e. He-rich stripped-envelope SNe). SN~2025coe is the third X-ray detected CaST and our analysis of \textit{Swift} X-ray data suggest interaction with 0.12 $\pm 0.11M_{\odot }$ of circumstellar material (CSM) extending to at least $2\times 10^{15}$cm ($\sim 30,000R_{\odot }$, while our analysis of the 1--240 GHz radio non-detections gives an outer radius of that CSM of at most $\sim 5\times 10^{15}$ cm. This inferred nearby high-density CSM extending out to $(3.5\pm 1.5)\times 10^{15}$ cm is similar to that seen in the other two X-ray detected CaSTs, and its presence suggests that either intensive mass-loss from a massive star or some exotic pre-supernova mass ejection may be a common feature of this subclass. Our work also expands upon recent studies on the optical properties of SN 2025coe and explores our current understanding of different progenitor systems that could possibly produce CaSTs.

submitted to ApJ on Jan 26, 2026 accepted for publication May 14, 2026

References in corpus (22)

• From Shock Breakout to Peak and Beyond: Extensive Panchromatic Observations of the Type Ib Supernova 2008D associated with Swift X-ray Transient 080109
• Unifying Type II Supernova Light Curves with Dense Circumstellar Material
• The Zwicky Transient Facility Census of the Local Universe I: Systematic search for Calcium rich gap transients reveal three related spectroscopic sub-classes
• Two New Calcium-Rich Gap Transients in Group and Cluster Environments
• CAPTURE: A continuum imaging pipeline for the uGMRT
• The Radio Luminosity-Risetime Function of Core-Collapse Supernovae
• SN 2019ehk: A Double-Peaked Ca-rich Transient with Luminous X-ray Emission and Shock-Ionized Spectral Features
• MMT & Magellan Infrared Spectrograph
• Properties of Type Ibn Supernovae: Implications for the Progenitor Evolution and the Origin of a Population of Rapid Transients
• Carnegie Supernova Project-II: Near-infrared Spectroscopy of Stripped-Envelope Core-Collapse Supernovae
• iPTF15eqv: Multi-wavelength Exposé of a Peculiar Calcium-rich Transient
• Data Reduction Pipeline for the MMT and Magellan Infrared Spectrograph
• Carnegie Supernova Project-II: Near-infrared Spectroscopic Diversity of Type II Supernovae
• The origins of Calcium-rich supernovae from disruptions of CO white-dwarfs by hybrid He-CO white-dwarfs
• The Circumstellar Environments of Double-Peaked, Calcium-strong Supernovae 2021gno and 2021inl
• Modelling Type Ic Supernovae with TARDIS: Hidden Helium in SN1994I?
• The peculiar Ca-rich SN 2019ehk: Evidence for a Type IIb core-collapse supernova from a low mass stripped progenitor
• Near infrared spectroscopy of the type IIn SN 2010jl: evidence for high velocity ejecta
• A Physical Basis for the H-band Blue-edge Velocity and Light-Curve Shape Correlation in Context of Type Ia Supernova Explosion Physics
• SN 2020bio: A Double-peaked, H-poor Type IIb Supernova with Evidence of Circumstellar Interaction
• Carnegie Supernova Project-II: Near-infrared spectral diversity and template of Type Ia Supernovae
• The Search for Stable Nickel: Investigating the Origins of Type Ia Supernovae with Late-time NIR Spectroscopy from the Carnegie Supernova Project-II