For the first time in radio: Type Ibn supernova detection reveals what was happening in the final years of a massive star
Astronomers led by a doctoral student from the University of Virginia (UVA) have published the first confirmed detection of radio waves from a rare type of stellar explosion known as a Type Ibn supernova. At the center of the research is the supernova SN 2023fyq, whose faint radio signals were tracked for about 18 months using the Very Large Array (VLA) radiotelescope in the state of New Mexico. The results were published in
The Astrophysical Journal Letters, and press releases from UVA (January 29, 2026) and the National Radio Astronomy Observatory (NRAO) emphasize that this is the first such radio detection for this class. For astronomy, this is an important shift because radio waves allow for "peering" into the final stages of a star's life that are often inaccessible or ambiguous in the optical range, especially when dealing with explosions in other galaxies.
It is common to infer a star's behavior before explosion only indirectly, based on optical light and spectral lines after the supernova outbreak. However, radio radiation generated in the collision of a shock wave with gas around the star allows, according to the authors, for the reconstruction of the "history" of mass loss in the years before death. In the UVA release, Baer-Way described this effect as a kind of time machine, because radio observations provide insight into the last decade of life, and particularly into the final five years when, according to their interpretation, the star was losing mass most intensely. The key is that the surrounding gas, which the star ejected before the explosion, becomes a measurable "backdrop": when the supernova shock slams into that material, radio waves are created that carry information about the density, distribution, and timing of the ejected matter.
- What is new: according to the authors, SN 2023fyq is the first Type Ibn supernova with a confirmed radio detection and systematic tracking long enough to see the signal's development.
- What radio reveals: from the strength, duration, and change of radio brightness over time, the density and distribution of the helium-rich surrounding material that the star ejected before the explosion are estimated.
- Key hypothesis: the team states that the extreme mass loss would most likely be triggered by a binary interaction, namely the influence of a companion in a two-star system.
- Message for practice: the releases highlight that radio telescopes should be involved earlier, as Type Ibn radio signals are transient and can disappear before standard tracking protocols are even activated.
What is a Type Ibn supernova and why is it rare
Type Ibn supernovae are among the rare explosions of massive stars that occur in environments poor in hydrogen but rich in helium. In the optical spectra of such events, astronomers usually see prominent helium lines, often relatively narrow compared to the wider lines coming from the rapidly expanding layers of the supernova, which is interpreted as a sign of strong interaction of the ejecta with previously ejected gas in the immediate vicinity. Because of this, this class is often described in literature as interaction-"powered": part of the brightness comes from the conversion of kinetic energy into radiation in the collision of the supernova with circumstellar material, and not just from standard processes of radioactive element decay and cooling of the expanded ejecta. Such physics makes Type Ibn particularly interesting because it allows for studying the direct link between the final episodes of mass loss and the outcome of a massive star's death itself. But at the same time, it makes statistical conclusions difficult, as the events are rare and often discovered only when the critical early phase has already passed.
The rarity of Type Ibn has a clear consequence. When such an event occurs, the window for collecting data in multiple wavelengths can be short, and without early tracking, it is difficult to distinguish a gradual stellar wind from a sudden, eruptive episode of mass ejection. A scientific paper in the
Monthly Notices of the Royal Astronomical Society often cited in the context of Type Ibn reminds that the class prototype, SN 2006jc, was associated with an eruptive episode recorded about two years before the supernova, which further fueled the idea that some progenitors are extremely unstable in the final years of life. Such observations suggest that Type Ibn is not "just another label," but potentially a window into rare but physically crucial phases of massive star evolution, where a large amount of helium-rich matter can be ejected in a short time.
How the signal was caught: 18 months of tracking with the Very Large Array interferometer
Measurements of SN 2023fyq were conducted on the Very Large Array instrument, an interferometric system of 27 radio antennas set up in a characteristic "Y" configuration on a plateau in New Mexico. According to NRAO data, combining the signals from the antennas results in the effect of an instrument with a much larger diameter, which allows for high sensitivity and resolution in centimeter wavelengths. Precisely such sensitivity is key for supernovae in other galaxies, where radio signals can be barely above the noise level and require carefully planned, repeated observations. The VLA is part of the infrastructure managed by the National Radio Astronomy Observatory for the U.S. National Science Foundation, which in practice means it is an instrument intended for long-term tracking programs and large campaigns that link different observatories.
The team, according to the scientific paper and the NRAO release, tracked the radio emission for about 18 months after the explosion. The analysis emphasizes that the early radio signal is best explained by synchrotron radiation, i.e., radiation from relativistic electrons in magnetic fields, with part of the signal weakening due to absorption in the surrounding gas. Such modeling is not a mere formality: from it, estimates of gas density, the distance at which it is located, and thus the timeframe in which it was ejected are obtained. In other words, radio observations do not just say "there is gas," but give a numerical story about how dense the gas is and when it likely left the star. This is particularly important for Type Ibn because it is precisely the helium-rich material, ejected before the explosion, that defines this class and shapes its brightness in multiple wavebands.
A "time machine" for the final years: what the radio and X-ray data showed
Study leader Raphael Baer-Way, a doctoral student of astronomy at UVA and the main author of the paper, emphasized in statements accompanying the publication that with radio observations they could "see" approximately the last decade of the star's life, with an emphasis on the final few years when the mass loss was most intense. The idea is that the ejected gas acts as a kind of mirror: although the progenitor in another galaxy is usually too faint for direct tracking before the explosion, the material it ejected remains in the vicinity and becomes a "stage" on which the interaction takes place after the explosion. When the supernova shock wave slams into that material, shocks are created that accelerate particles and create radio emission. From this, conclusions can be drawn about the density and distribution of the gas, and indirectly about how much the star was "falling apart" and losing mass in the years before death. Baer-Way describes this process as a way to "turn back the clock" and study the final stages of a massive star's life that are often more hidden in the optical range.
According to the NRAO release, the combination of radio and X-ray data allowed for an estimate of the density and reach of the helium-rich surrounding matter. The release states that astronomers concluded that the star, in a short, intense phase, could have been losing mass at a rate corresponding up to approximately 0.4% of the Sun's mass per year, which in popular interpretation speaks of an extremely "wasteful" end of life. The scientific paper itself, in a more detailed framework of assumptions, describes an episode of elevated mass loss on a timescale of approximately 0.7 to 3 years before the explosion and states rates in the order of magnitude of several thousandths of the Sun's mass per year, noting that the figures depend on parameters such as wind speed and the geometry of the material. It is also important that the authors, along with early detections, use later non-detections to set limits on density further from the star. Such a combination suggests that the environment is not a simple, constant wind, but a structure with a distinct, more compact zone of elevated density that corresponds to material ejected immediately before the explosion.
For the reader, the key point is that radio waves serve not only to confirm "that something exists," but also to determine when it was created. In the distances at which the ejected material is located, temporal information is actually "inscribed": gas at a larger radius represents an older ejection, and gas closer to the star corresponds to the most recent episodes. When the supernova shock breaks through those layers, the radio signal changes, and from that development, one can reconstruct how the mass loss changed over time. Combined with other wavelengths, the team gains a more consistent narrative about when the star "ramped up" its ejection of helium-rich matter and how short that period was relative to the star's entire life. That is precisely why the authors emphasize that radio observations provide information that optics alone cannot provide.
Binary interaction as a candidate: why the "second star" becomes a central theme
One of the most intriguing conclusions, also highlighted in the authors' statements, is that the progenitor of SN 2023fyq could be part of a binary system – two stars orbiting each other. Baer-Way said in the UVA release that it is difficult to explain such an amount of ejected material in such a short period without the gravitational influence of a companion, i.e., without two bodies "bound" in a system that facilitates mass transfer or destabilizes the outer layers. In practice, binary interaction can mean that one star "strips" the envelope of the other, that episodes of sudden gas overflow through Lagrange points occur, or that orbital dynamics change as the system approaches. All this can lead to the creation of densely distributed material around the system, and it is precisely such material that Type Ibn "seeks" in order to create a characteristic spectrum and light curve. In that sense, the conclusion about binarity is not just an additional detail, but a key assumption that links the observations with a physical mechanism.
The NRAO release goes a step further and offers an illustrative scenario: a helium-rich star, already stripped of hydrogen, could be orbiting a compact companion, such as a neutron star, whereby helium begins to overflow toward the companion and forms a dense disk or ring of material. When the explosion eventually occurs, the ejecta slams into that disk and creates shocks that produce the radio radiation that the team detected. NRAO explicitly states that the cause of the explosion itself in such "exotic" configurations can remain unclear, i.e., that without additional data, it might not be possible to say unequivocally whether it is a classic core collapse or a scenario in which binary dynamics leads to a merger or another "trigger." This is an important caveat because it shows that radio detection does not solve all questions, but strongly narrows the set of possible explanations for extreme mass loss.
The same release quotes co-authors who emphasize what can be extracted from such a case. A. J. Nayana, co-leader of the research, points out that the study probes material ejected years before the explosion and that an intense phase of mass loss in the final 0.7 to 3 years of the star's life is particularly clearly seen. Wynn Jacobson-Galan, one of the lead authors and involved in the VLA program, emphasizes the need for systematic radio tracking with instruments like the VLA and GMRT, because only a larger sample of similar events can show how common binary interaction is and what different "architectures" of the environment it can create. Such emphases suggest that SN 2023fyq is not only interesting as an individual case, but as a "testing ground" for observation strategies and for models that link binary evolution and the final explosions of massive stars. In other words, the radio signal is treated here as a diagnostic tool for the physics of the system, not just as a confirmation of the existence of interaction.
SN 2023fyq and the optical context: precursors before the explosion and additional traces
SN 2023fyq is also interesting because of earlier analyses in the optical range, which provide additional background for the interpretation of the new radio signal. In a separate paper published on arXiv in 2024, an international team of astronomers presented photometric and spectroscopic observations of this supernova and reported long-standing "precursor" activity at the position of the future explosion. According to that paper, changes in brightness and outbursts could be tracked up to almost three years before the supernova, with an intensification of activity in the final 100 days or so before the explosion. The authors of that paper link the precursors to binary interaction and mass transfer, whereby a disk of material can form around the system, and then the interaction of the supernova with that disk powers part of the brightness after the explosion. Importantly, this optical context suggests that "something was happening" even before the explosion itself, which is consistent with the general picture of Type Ibn as events in which the environment is shaped immediately before the death of the star. That is why the new radio detection comes as complementary evidence that allows for quantifying the density and timing of that environment.
The location context is also interesting: the authors of the 2024 paper state that SN 2023fyq occurred in the galaxy NGC 4388 at a distance of about 18 megaparsecs, which is approximately 59 million light-years. This relative "proximity" by extragalactic standards is one of the reasons why the event was suitable for more detailed tracking and why it was possible at all to hunt for weak radio signals. The same paper considers an interpretation according to which the precursor activity best fits mass transfer in a binary system of a helium star and a compact companion, with the possibility that additional, densely distributed material ejected weeks before the explosion is also located in the environment. If such a picture is confirmed in other objects as well, it would mean that part of Type Ibn originates from specific binary configurations that produce both longer-lasting precursors and a dense environment that then strongly affects the observed brightness. Thus, SN 2023fyq becomes an important link between observations in optics and radio, as it offers a rare case where both channels can be placed into the same, temporally synchronized story.
When that optical context is placed alongside the new radio detection, a more consistent picture is obtained. Optics show that the supernova strongly interacts with helium-rich material and that the interaction can last, while radio, through modeling of the strength and quenching of the signal, gives additional insight into the density and geometry of the material that was ejected before the explosion. This reduces the risk that conclusions about "dramatic" mass loss are based on only one type of measurement and increases the possibility that different models – from a stable wind to eruptive episodes and disks – are tested on concrete data. In practical terms, such a multi-channel image also helps in planning future campaigns: if precursors or specific light curve shapes are seen in optics, radio observations can be purposefully involved earlier. For scientists, this opens the way toward more reliable mapping of the final stages of massive star evolution in different environments.
Why radio changes the game and what follows after the first detection
Maryam Modjaz, a professor of astronomy at UVA and co-author of the study, emphasized in a statement accompanying the publication that the result "opens a new window" and suggests that radio telescopes should be pointed earlier than previously assumed to catch transient Type Ibn signals. This message has operational weight: modern sky surveys reveal more and more transients, but the scientific value depends on fast multi-wavelength tracking and on whether the critical phase of interaction will be caught. In this study, precisely continuous tracking over a longer period allowed early detections to be compared with later non-detections and for constraints on the structure of the surrounding gas to be derived from that. Such an approach represents a shift from a "one-time catch" toward "filming" the supernova development, which is key when trying to reconstruct events from the years before the explosion. Radio is particularly useful in that sense because it is sensitive to shocks and the density of the surrounding matter, so it often gives data that are hidden in optics or difficult to interpret without additional assumptions.
According to the UVA release, Baer-Way announced that the next step is to study a larger sample of supernovae to see how common episodes of extreme mass loss are and what they say about the evolution of massive stars. In practice, this means a change in strategy: radio observations should no longer be just a "subsequent check" after the optical brightness begins to fade, but part of the early response as soon as a candidate for Type Ibn is discovered. The NRAO release in the same tone emphasizes the need for systematic tracking with multiple instruments, including VLA and GMRT, to obtain a larger statistical sample and verify how general the conclusions from SN 2023fyq are. The scientific logic is clear: one event can open a window, but only a larger number of examples can show whether binary interaction is the dominant mechanism or if there are multiple different paths to Type Ibn. In that sense, this detection is both a warning and an opportunity: if the radio window is short, it must be caught in time, but if it is caught, it can offer a unique insight into the last years of the lives of massive stars.
In a broader sense, this detection shows how much contemporary astronomy relies on multiple wavelengths and the coordination of observatories, from optical surveys to radio campaigns and X-ray observations. For rare events like Type Ibn, where statistics are small and physics is complex, every additional piece of information carries more weight than in "more frequent" types of supernovae. SN 2023fyq now has a special place because for the first time in radio, what was assumed for years based on optics has been confirmed: that some massive stars in the final years of life go through extremely intense episodes of mass loss, leaving behind a helium-rich "trail" that, at the moment of explosion, lights up in radio.
Sources:- University of Virginia (UVA) – news and statements from the authors about the first radio detection of a Type Ibn supernova ( link )- National Radio Astronomy Observatory (NRAO) – official release on the detection of the radio signal from SN 2023fyq, interpretation of mass loss, and quotes from team members ( link )- arXiv – preprint of the paper “The first radio view of a type Ibn supernova in SN 2023fyq: Understanding the mass-loss history in the last decade before the explosion” (Astrophysical Journal Letters, 2025) ( link )- arXiv – paper “SN2023fyq: A Type Ibn Supernova With Long-standing Precursor Activity Due to Binary Interaction” (2024) ( link )- NRAO – basic information about the Very Large Array (VLA) radiotelescope and the operation of the interferometric system ( link )- Monthly Notices of the Royal Astronomical Society – scientific paper on supernovae exploding in a helium-rich environment, including the context of the Type Ibn class and SN 2006jc ( link )
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