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Observationally, kilonovae are astrophysical transients powered by the radioactive decay of nuclei heavier than iron, thought to be synthesized in the merger of two compact objects 1 – 4 . Over the first few days, the kilonova evolution is dominated by a large number of radioactive isotopes contributing to the heating rate 2 , 5 . On timescales of weeks to months, its behaviour is predicted to differ depending on the ejecta composition and the merger remnant 6 – 8 . Previous work has shown that the kilonova associated with gamma-ray burst 230307A is similar to kilonova AT2017gfo (ref. 9 ), and mid-infrared spectra revealed an emission line at 2.15 micrometres that was attributed to tellurium. Here we report a multi-wavelength analysis, including publicly available James Webb Space Telescope data 9 and our own Hubble Space Telescope data, for the same gamma-ray burst. We model its evolution up to two months after the burst and show that, at these late times, the recession of the photospheric radius and the rapidly decaying bolometric luminosity ( L bol  ∝  t −2.7±0.4 , where t is time) support the recombination of lanthanide-rich ejecta as they cool. A modelling analysis shows that an unusually long gamma-ray burst gave rise to a lanthanide-rich kilonova following the merger of a neutron star–neutron star or of a neutron star–black hole.

Fast radio bursts (FRBs) last for milliseconds and arrive at Earth from cosmological distances. Although their origins and emission mechanisms are unknown, their signals bear similarities with the much less luminous radio emission generated by pulsars within our Miky Way Galaxy 1 , with properties suggesting neutron star origins 2 , 3 . However, unlike pulsars, FRBs typically show minimal variability in their linear polarization position angle (PA) curves 4 . Even when marked PA evolution is present, their curves deviate significantly from the canonical shape predicted by the rotating vector model (RVM) of pulsars 5 . Here we report on FRB 20221022A, detected by the Canadian Hydrogen Intensity Mapping Experiment Fast Radio Burst project (CHIME/FRB) and localized to a nearby host galaxy (about 65 Mpc), MCG+14-02-011. This FRB shows a notable approximately 130° PA rotation over its about 2.5 ms burst duration, resembling the characteristic S-shaped evolution seen in many pulsars and some radio magnetars. The observed PA evolution supports magnetospheric origins 6 , 7 – 8 over models involving distant shocks 9 , 10 – 11 , echoing similar conclusions drawn from tempo-polarimetric studies of some repeating FRBs 12 , 13 . The PA evolution is well described by the RVM and, although we cannot determine the inclination and magnetic obliquity because of the unknown period or duty cycle of the source, we exclude very short-period pulsars (for example, recycled millisecond pulsars) as the progenitor. FRB 20221022A, detected by the Canadian Hydrogen Intensity Mapping Experiment Fast Radio Burst project, shows a pronounced change in polarization during the burst, providing important clues into the nature of the source.

Cosmic neutrinos provide a unique window into the otherwise hidden mechanism of particle acceleration in astrophysical objects. The IceCube Collaboration recently reported the likely association of one high-energy neutrino with a flare from the relativistic jet of an active galaxy pointed towards the Earth. However a combined analysis of many similar active galaxies revealed no excess from the broader population, leaving the vast majority of the cosmic neutrino flux unexplained. Here we present the likely association of a radio-emitting tidal disruption event, AT2019dsg, with a second high-energy neutrino. AT2019dsg was identified as part of our systematic search for optical counterparts to high-energy neutrinos with the Zwicky Transient Facility. The probability of finding any coincident radio-emitting tidal disruption event by chance is 0.5%, while the probability of finding one as bright in bolometric energy flux as AT2019dsg is 0.2%. Our electromagnetic observations can be explained through a multizone model, with radio analysis revealing a central engine, embedded in a UV photosphere, that powers an extended synchrotron-emitting outflow. This provides an ideal site for petaelectronvolt neutrino production. Assuming that the association is genuine, our observations suggest that tidal disruption events with mildly relativistic outflows contribute to the cosmic neutrino flux. The tidal disruption event AT2019dsg is probably associated with a high-energy neutrino, suggesting that such events can contribute to the cosmic neutrino flux. The electromagnetic emission is explained in terms of a central engine, a photosphere and an extended synchrotron-emitting outflow.

Gamma-ray bursts (GRBs) are divided into two populations 1 , 2 ; long GRBs that derive from the core collapse of massive stars (for example, ref.  3 ) and short GRBs that form in the merger of two compact objects 4 , 5 . Although it is common to divide the two populations at a gamma-ray duration of 2 s, classification based on duration does not always map to the progenitor. Notably, GRBs with short (≲2 s) spikes of prompt gamma-ray emission followed by prolonged, spectrally softer extended emission (EE-SGRBs) have been suggested to arise from compact object mergers 6 – 8 . Compact object mergers are of great astrophysical importance as the only confirmed site of rapid neutron capture ( r -process) nucleosynthesis, observed in the form of so-called kilonovae 9 – 14 . Here we report the discovery of a possible kilonova associated with the nearby (350 Mpc), minute-duration GRB 211211A. The kilonova implies that the progenitor is a compact object merger, suggesting that GRBs with long, complex light curves can be spawned from merger events. The kilonova of GRB 211211A has a similar luminosity, duration and colour to that which accompanied the gravitational wave (GW)-detected binary neutron star (BNS) merger GW170817 (ref.  4 ). Further searches for GW signals coincident with long GRBs are a promising route for future multi-messenger astronomy. A possible kilonova associated with a nearby, long-duration gamma-ray burst suggests that gamma-ray bursts with long and complex light curves can be spawned from the merger of two compact objects, contrary to the established gamma-ray burst paradigm.

In the version of this article initially published, there was in an error in the third-to-last sentence of the abstract, now reading, in part, “we calculate a rate of 0.02–0.01 +0.04 Gpc–3 yr–1”, where Gpc was spelled out as gigapascals, not gigaparsecs. Also, the scale label (2″) was missing in the lower-left corner of Fig. 1b. The errors have been corrected in the HTML and PDF versions of the article.

Accurately localising fast radio bursts (FRBs) is essential for understanding their birth environments and for their use as cosmological probes. Recent advances in radio interferometry, particularly with MeerKAT, have enabled the localisation of individual bursts with arcsecond precision. In this work, we present the localisation of 15 apparently non-repeating FRBs detected with MeerKAT. Two of the FRBs, discovered in 2022, were localised in 8 second images from the projects which MeerTRAP was commensal to, while eight were localised using the transient buffer (TB) pipeline, and another one through SeeKAT, all with arcsecond precision. Four additional FRBs lacked TB triggers and sufficient signal, limiting their localisation only to arcminute precision. For eight of the FRBs in our sample, we identify host galaxies with greater than 90% confidence, and one with 80% confidence, while two FRBs have ambiguous associations. We measured spectroscopic redshifts for six host galaxies, ranging from 0.33 to 0.85, demonstrating MeerKAT's sensitivity to high redshift FRBs. We modelled the spectral energy distributions of host galaxies with sufficient photometric coverage to derive their stellar population and star formation properties. This work represents one of the largest uniform samples of well-localised distant FRBs to date, laying the groundwork for using MeerKAT FRBs as cosmological probes and understand how FRB hosts evolve at high redshift.

We present GeMS/GSAOI observations of five fast radio burst (FRB) host galaxies with sub-arcsecond localizations. We examine and quantify their spatial distributions and locations with respect to their host galaxy light distributions, finding a median host-normalized offset of 2.09 r_e and in fainter regions of the host. When combined with the FRB sample from Mannings et al. (2021), we find that FRBs are statistically distinct from Ca-rich transients in terms of light and from SGRBs and LGRBs in terms of host-normalized offset. We further find that most FRBs are in regions of elevated local stellar mass surface densities in comparison to the mean global values of their hosts. This, in combination with the combined FRB sample trace the distribution of stellar mass, points towards a possible similarity of the environments of CC-SNe and FRBs. We also find that 4/5 FRB hosts exhibit distinct spiral arm features, and the bursts originating from such hosts tend to appear on or close to the spiral structure of their hosts, with a median distance of 0.53 kpc. With many well-localized FRB detections looming on the horizon, we will be able to better characterize the properties of FRB environments relative to their host galaxies and other transient classes.

We present pre-explosion photometry of the likely progenitor star of the Type II supernova (SN II) 2017eaw in NGC 6946. We use a Hubble Space Telescope (HST) image of SN 2017eaw to perform relative astrometry with HST and Spitzer Space Telescope (Spitzer) imaging, finding a single point source consistent with its position. We detect the progenitor star in \\(>\\)40 epochs of HST and Spitzer imaging covering 12.9 years to 43 days before discovery. While the progenitor luminosity was roughly constant for most of this period, there was a \\(\\sim\\)20% increase in its \\(4.5~\\mu\\)m luminosity over the final 3 years before explosion. We interpret the bright mid-infrared emission as a signature of circumstellar dust around the progenitor system. Using the pre-explosion photometry and assuming some circumstellar dust, we find the progenitor is most likely a red supergiant with \\(\\log(L/L_{\\odot}) = 4.9\\) and \\(T = 3350\\) K, obscured by a \\(>2\\times10^{-5}~M_{\\odot}\\) dust shell with \\(R = 4000~R_{\\odot}\\) and \\(T = 960\\) K. Comparing to single-star evolutionary tracks, we find that the progenitor star had an initial mass of \\(13~M_{\\odot}\\) and a mass-loss rate of \\(2\\times10^{-7}~M_{\\odot}~\\text{yr}^{-1}\\), consistent with the population of SN II progenitor stars.

EP241217a is an X-ray transient detected by the Einstein Probe (EP) lasting for about 100 seconds and without accompanying \\(\\)-ray detection. The optical spectroscopy reveals the redshift of EP241217a is 4.59. By combining the \\(\\)-ray upper limit provided by GECAM-C, there is a considerable possibility that EP241217a is a typical Type II gamma-ray burst (GRB), but it is fainter than the detection threshold of any available \\(\\)-ray monitors (i.e., \\(E_ iso10^53\\) erg). The X-ray light curve exhibits a plateau lasting for \\(510^4\\) seconds. However, the joint analysis with optical data suggests the presence of an achromatic bump peaking at \\(310^4\\) s after the trigger, indicating the actual duration of the X-ray plateau may be significantly shorter than it appears. To interpret the achromatic bump, we adopt the scenario of a mildly relativistic jet coasting in a wind-like medium and encountering a rapid density enhancement of the circumburst medium, which is likely induced by the the interaction of the progenitor's stellar wind and the interstellar medium. However, this model cannot fully explain observed data, and some issues do exist, e.g., the observed spectrum is harder than the model prediction. Consequently, we conclude that the scenario of a mildly relativistic jet coasting in the wind-like medium cannot explain all observed features of EP241217a. In addition, some alternative models commonly invoked to explain X-ray plateaus are discussed, but there are more or less issues when they are applied to EP241217a. Therefore, further theoretical modeling is encouraged to explore the origin of EP241217a.