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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.

We present an extensive contemporaneous X-ray and radio campaign performed on the repeating fast radio burst (FRB) source FRB 20220912A for eight weeks immediately following the source's detection by CHIME/FRB. This includes X-ray data from XMM-Newton, NICER, and Swift, and radio detections of FRB 20220912A from CHIME/Pulsar and Effelsberg. We detect no significant X-ray emission at the time of 30 radio bursts with upper limits on \\(0.5-10.0\\) keV X-ray fluence of \\((1.5-14.5)\\times 10^{-10}\\) erg cm\\(^{-2}\\) (99.7% credible interval, unabsorbed) on a timescale of 100 ms. Translated into a fluence ratio \\(\\eta_{\\text{ x/r}} = F_{\\text{X-ray}}/F_{\\text{radio}}\\), this corresponds to \\({\\eta}_{\\text{ x/r}} < 7\\times10^{6}\\). For persistent emission from the location of FRB 20220912A, we derive a 99.7% \\(0.5-10.0\\) keV isotropic flux limit of \\(8.8\\times 10^{-15}\\) erg cm\\(^{-2}\\) s\\(^{-1}\\) (unabsorbed) or an isotropic luminosity limit of 1.4\\(\\times10^{41}\\) erg s\\(^{-1}\\) at a distance of 362.4 Mpc. We derive a hierarchical extension to the standard Bayesian treatment of low-count and background-contaminated X-ray data, which allows the robust combination of multiple observations. This methodology allows us to place the best (lowest) 99.7% credible interval upper limit on an FRB \\({\\eta}_{\\text{ x/r}}\\) to date, \\({\\eta}_{\\text{ x/r}} < 2\\times10^6\\), assuming that all thirty detected radio bursts are associated with X-ray bursts with the same fluence ratio. If we instead adopt an X-ray spectrum similar to the X-ray burst observed contemporaneously with FRB-like emission from Galactic magnetar SGR 1935+2154 detected on 2020 April 28, we derive a 99.7% credible interval upper limit on \\({\\eta}_{\\text{ x/r}}\\) of \\(8\\times10^5\\), which is only 3 times the observed value of \\({\\eta}_{\\text{ x/r}}\\) for SGR 1935+2154.

Luminous interacting supernovae are a class of stellar explosions whose progenitors underwent vigorous mass loss in the years prior to core-collapse. While the mechanism by which this material is ejected is still debated, obtaining the full density profile of the circumstellar medium (CSM) could reveal more about this process. Here, we present an extensive multi-wavelength study of PS1-11aop, a luminous and slowly declining Type IIn SN discovered by the PanSTARRS Medium Deep Survey. PS1-11aop had a peak r-band magnitude of \\(-\\)20.5\\,mag, a total radiated energy \\(>\\) 8\\(\\times\\)10\\(^{50}\\)\\,erg, and it exploded near the center of a star-forming galaxy with super-solar metallicity. We obtained multiple detections at the location of PS1-11aop in the radio and X-ray bands between 4 and 10\\,years post-explosion, and if due to the SN, it is one of the most luminous radio supernovae identified to date. Taken together, the multiwavelength properties of PS1-11aop are consistent with a CSM density profile with multiple zones. The early optical emission is consistent with the supernova blastwave interacting with a dense and confined CSM shell which contains multiple solar masses of material that was likely ejected in the final \\(<\\)10-100 years prior to the explosion,(\\(\\sim\\)0.05\\(-\\)1.0 M\\(_{\\odot}\\)yr\\(^{-1}\\) at radii of \\(\\lesssim\\)10\\(^{16}\\)\\,cm). The radio observations, on the other hand, are consistent with a sparser environment (\\(\\lesssim\\)2\\(\\times 10^{-3}\\) M\\(_{\\odot}\\)yr\\(^{-1}\\) at radii of \\(\\sim\\)0.5-1\\(\\times\\)10\\(^{17}\\)\\,cm) -- thus probing the history of the progenitor star prior to its final mass loss episode.

We present panchromatic observations and modeling of supernova (SN) 2020tlf, the first normal type II-P/L SN with confirmed precursor emission, as detected by the Young Supernova Experiment transient survey with the Pan-STARRS1 telescope. Pre-explosion emission was detected in \\(riz-\\)bands at 130 days prior to SN 2020tlf and persisted at relatively constant flux until first light. Soon after discovery, \"flash\" spectroscopy of SN 2020tlf revealed prominent narrow symmetric emission lines (\\(v_w < 300\\) km s\\(^{-1}\\)) that resulted from the photo-ionization of unshocked circumstellar material (CSM) shedded in progenitor mass loss episodes in the final weeks to months before explosion. Surprisingly, this novel display of pre-SN emission and associated mass loss occurred in a RSG progenitor with ZAMS mass of only 10-12 M\\(_{\\odot}\\), as inferred from nebular spectra. Modeling of the light curve and multi-epoch spectra with the non-LTE radiative transfer code CMFGEN and radiation-hydrodynamical (RHD) code HERACLES suggests a dense CSM limited to \\(r \\approx 10^{15}\\) cm, and mass loss rate of \\(10^{-2}\\) M\\(_{\\odot}\\) yr\\(^{-1}\\). The subsequent luminous light-curve plateau and persistent blue excess indicates an extended progenitor, compatible with a RSG model with \\(R_{\\star} = 1100\\) R\\(_{\\odot}\\). Inferences from the limits on the shock-powered X-ray and radio luminosity are consistent with these conclusions and suggest a CSM density of \\(\\rho < 2 \\times 10^{-16}\\) g cm\\(^{-3}\\) for distances of \\(r \\approx 5 \\times 10^{15}\\) cm, as well as a mass loss rate of \\(\\dot M<1.3 \\times 10^{-5}\\,\\rm{M_{\\odot}\\,yr^{-1}}\\) at larger distances. A promising power source for the observed precursor emission is the ejection of stellar material following energy disposition into the stellar envelope as a result of gravity waves emitted during either neon/oxygen burning or a nuclear flash from silicon combustion.

The identification of persistent radio sources (PRSs) coincident with two repeating fast radio bursts (FRBs) supports FRB theories requiring a compact central engine. However, deep non-detections in other cases highlight the diversity of repeating FRBs and their local environments. Here, we perform a systematic search for radio sources towards 37 CHIME/FRB repeaters using their arcminute localizations and a combination of archival surveys and targeted observations. Through multi-wavelength analysis of individual radio sources, we identify two (20181030A-S1 and 20190417A-S1) for which we disfavor an origin of either star formation or an active galactic nucleus in their host galaxies and thus consider them candidate PRSs. We do not find any associated PRSs for the majority of the repeating FRBs in our sample. For 8 FRB fields with Very Large Array imaging, we provide deep limits on the presence of PRSs that are 2--4 orders of magnitude fainter than the PRS associated with FRB\\,20121102A. Using Very Large Array Sky Survey imaging of all 37 fields, we constrain the rate of luminous (\\(\\gtrsim\\)10\\(^{40}\\) erg s\\(^{-1}\\)) PRSs associated with repeating FRBs to be low. Within the context of FRB-PRS models, we find that 20181030A-S1 and 20190417A-S1 can be reasonably explained within the context of magnetar, hypernebulae, gamma-ray burst afterglow, or supernova ejecta models -- although we note that both sources follow the radio luminosity versus rotation measure relationship predicted in the nebula model framework. Future observations will be required to both further characterize and confirm the association of these PRS candidates with the FRBs.

The Canadian Hydrogen Intensity Mapping Experiment Fast Radio Burst (CHIME/FRB) project has discovered the most repeating fast radio burst (FRB) sources of any telescope. However, most of the physical conclusions derived from this sample are based on data with a time resolution of \\(\\sim\\)1 ms. In this work, we present for the first time a morphological analysis of the raw voltage data for 118 bursts from 32 of CHIME/FRB's repeating sources. We do not find any significant correlations amongst fluence, dispersion measure (DM), burst rate, and burst duration. Performing the first large-scale morphological comparison at timescales down to microseconds between our repeating sources and 125 non-repeating FRBs, we find that repeaters are narrower in frequency and broader in duration than non-repeaters, supporting previous findings. However, we find that the duration-normalized sub-burst widths of the two populations are consistent, possibly suggesting a shared physical emission mechanism. Additionally, we find that the spectral fluences of the two are consistent. When combined with the larger bandwidths and previously found larger DMs of non-repeaters, this suggests that non-repeaters may have higher intrinsic specific energies than repeating FRBs. We do not find any consistent increase or decrease in the DM (\\(\\lessapprox 1\\) pc cm\\(^{-3}\\) yr\\(^{-1}\\)) and scattering timescales (\\(\\lessapprox 2\\) ms yr\\(^{-1}\\)) of our sources over \\(\\sim2-4\\) year periods.

We present a search for host galaxy associations for the third set of repeating fast radio burst (FRB) sources discovered by the CHIME/FRB Collaboration. Using the \\(\\sim\\) 1 arcmin CHIME/FRB baseband localizations and probabilistic methods, we identify potential host galaxies of two FRBs, 20200223B and 20190110C at redshifts of 0.06024(2) and 0.12244(6), respectively. We also discuss the properties of a third marginal candidate host galaxy association for FRB 20191106C with a host redshift of 0.10775(1). The three putative host galaxies are all relatively massive, fall on the standard mass-metallicity relationship for nearby galaxies, and show evidence of ongoing star formation. They also all show signatures of being in a transitional regime, falling in the ``green valley'' which is between the bulk of star-forming and quiescent galaxies. The plausible host galaxies identified by our analysis are consistent with the overall population of repeating and non-repeating FRB hosts while increasing the fraction of massive and bright galaxies. Coupled with these previous host associations, we identify a possible excess of FRB repeaters whose host galaxies have \\(M_{\\mathrm{u}}-M_{\\mathrm{r}}\\) colors redder than the bulk of star-forming galaxies. Additional precise localizations are required to confirm this trend.

The nearby type II supernova, SN2023ixf in M101 exhibits signatures of early-time interaction with circumstellar material in the first week post-explosion. This material may be the consequence of prior mass loss suffered by the progenitor which possibly manifested in the form of a detectable pre-supernova outburst. We present an analysis of the long-baseline pre-explosion photometric data in \\(g\\), \\(w\\), \\(r\\), \\(i\\), \\(z\\) and \\(y\\) filters from Pan-STARRS as part of the Young Supernova Experiment, spanning \\(\\sim\\)5,000 days. We find no significant detections in the Pan-STARRS pre-explosion light curve. We train a multilayer perceptron neural network to classify pre-supernova outbursts. We find no evidence of eruptive pre-supernova activity to a limiting absolute magnitude of \\(-7\\). The limiting magnitudes from the full set of \\(gwrizy\\) (average absolute magnitude \\(\\approx\\)-8) data are consistent with previous pre-explosion studies. We use deep photometry from the literature to constrain the progenitor of SN2023ixf, finding that these data are consistent with a dusty red supergiant (RSG) progenitor with luminosity $\\log\\left(L/L_\\odot\\right)$$\\approx\\(5.12 and temperature \\)\\approx\\(3950K, corresponding to a mass of 14-20 M\\)_\\odot$

We present the host galaxies of four apparently non-repeating fast radio bursts (FRBs), FRBs 20181223C, 20190418A, 20191220A, and 20190425A, reported in the first Canadian Hydrogen Intensity Mapping Experiment (CHIME/FRB) catalog. Our selection of these FRBs is based on a planned hypothesis testing framework where we search all CHIME/FRB Catalog-1 events that have low extragalactic dispersion measure (< 100 pc cm\\(^{-3}\\)), with high Galactic latitude (|b| > 10\\(\\deg\\)) and saved baseband data. We associate the selected FRBs to galaxies with moderate to high star-formation rates located at redshifts between 0.027 and 0.071. We also search for possible multi-messenger counterparts, including persistent compact radio and gravitational wave (GW) sources, and find none. Utilizing the four FRB hosts from this study along with the hosts of 14 published local Universe FRBs (z < 0.1) with robust host association, we conduct an FRB host demographics analysis. We find all 18 local Universe FRB hosts in our sample to be spirals (or late-type galaxies), including the host of FRB 20220509G, which was previously reported to be elliptical. Using this observation, we scrutinize proposed FRB source formation channels and argue that core-collapse supernovae are likely the dominant channel to form FRB progenitors. Moreover, we infer no significant difference in the host properties of repeating and apparently non-repeating FRBs in our local Universe FRB host sample. Finally, we find the burst rates of these four apparently non-repeating FRBs to be consistent with those of the sample of localized repeating FRBs observed by CHIME/FRB. Therefore, we encourage further monitoring of these FRBs with more sensitive radio telescopes.

Fast radio bursts (FRBs) last for milliseconds and arrive at Earth from cosmological distances. While their origin(s) and emission mechanism(s) are presently unknown, their signals bear similarities with the much less luminous radio emission generated by pulsars within our Galaxy and several lines of evidence point toward neutron star origins. For pulsars, the linear polarisation position angle (PA) often exhibits evolution over the pulse phase that is interpreted within a geometric framework known as the rotating vector model (RVM). Here, we report on a fast radio burst, FRB 20221022A, detected by the Canadian Hydrogen Intensity Mapping Experiment (CHIME) and localized to a nearby host galaxy (\\(\\sim 65\\; \\rm{Mpc}\\)), MCG+14-02-011. This one-off FRB displays a \\(\\sim 130\\) degree rotation of its PA over its \\(\\sim 2.5\\; \\rm{ms}\\) burst duration, closely resembling the \"S\"-shaped PA evolution commonly seen from pulsars and some radio magnetars. The PA evolution disfavours emission models involving shocks far from the source and instead suggests magnetospheric origins for this source which places the emission region close to the FRB central engine, echoing similar conclusions drawn from tempo-polarimetric studies of some repeating sources. This FRB's PA evolution is remarkably well-described by the RVM and, although we cannot determine the inclination and magnetic obliquity due to the unknown period/duty cycle of the source, we can dismiss extremely short-period pulsars (e.g., recycled millisecond pulsars) as potential progenitors. RVM-fitting appears to favour a source occupying a unique position in the period/duty cycle phase space that implies tight opening angles for the beamed emission, significantly reducing burst energy requirements of the source.