Explore the vast range of titles available.

Fast radio bursts (FRBs) are microsecond-to-millisecond-duration radio transients 1 that originate mostly from extragalactic distances. The FRB emission mechanism remains debated, with two main competing classes of models: physical processes that occur within close proximity to a central engine 2 , 3 – 4 ; and relativistic shocks that propagate out to large radial distances 5 , 6 , 7 – 8 . The expected emission-region sizes are notably different between these two types of models 9 . Here we present the measurement of two mutually coherent scintillation scales in the frequency spectrum of FRB 20221022A 10 : one originating from a scattering screen located within the Milky Way, and the second originating from its host galaxy or local environment. We use the scattering media as an astrophysical lens to constrain the size of the observed FRB lateral emission region 9 to ≲3 × 10 4  kilometres. This emission size is inconsistent with the expectation for the large-radial-distance models 5 , 6 , 7 – 8 , and is more naturally explained by an emission process that operates within or just beyond the magnetosphere of a central compact object. Recently, FRB 20221022A was found to exhibit an S-shaped polarization angle swing 10 , most likely originating from a magnetospheric emission process. The scintillation results presented in this work independently support this conclusion, while highlighting scintillation as a useful tool in our understanding of FRB emission physics and progenitors. The detection of scintillation caused by inhomogeneous plasma near a fast radio burst indicates an emission process that occurs within or just beyond the magnetosphere of a compact object.

Fast radio bursts (FRBs) are millisecond-duration flashes of radio waves that are visible at distances of billions of light years. The nature of their progenitors and their emission mechanism remain open astrophysical questions. Here we report the detection of the multicomponent FRB 20191221A and the identification of a periodic separation of 216.8(1) ms between its components, with a significance of 6.5σ. The long (roughly 3 s) duration and nine or more components forming the pulse profile make this source an outlier in the FRB population. Such short periodicity provides strong evidence for a neutron-star origin of the event. Moreover, our detection favours emission arising from the neutron-star magnetosphere, as opposed to emission regions located further away from the star, as predicted by some models.

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.

The precise origins of fast radio bursts (FRBs) remain unknown. Multiwavelength observations of nearby FRB sources can provide important insights into the enigmatic FRB phenomenon. Here we present results from a sensitive, broadband X-ray and radio observational campaign of FRB 20200120E, the closest known extragalactic repeating FRB source (located 3.63 Mpc away in an ~10-Gyr-old globular cluster). We place deep limits on the persistent and prompt X-ray emission from FRB 20200120E, which we use to constrain possible origins for the source. We compare our results with various classes of X-ray sources, transients and FRB models. We find that FRB 20200120E is unlikely to be associated with ultraluminous X-ray bursts, magnetar-like giant flares or an SGR 1935+2154-like intermediate flare. Although other types of bright magnetar-like intermediate flares and short X-ray bursts would have been detectable from FRB 20200120E during our observations, we cannot entirely rule them out as a class. We show that FRB 20200120E is unlikely to be powered by an ultraluminous X-ray source or a young extragalactic pulsar embedded in a Crab-like nebula. We also provide new constraints on the compatibility of FRB 20200120E with accretion-based FRB models involving X-ray binaries. These results highlight the power of multiwavelength observations of nearby FRBs for discriminating between FRB models. Deep X-ray limits are placed on the source of the closest fast radio burst, FRB 20200120E, ruling out an ultraluminous X-ray source or a young extragalactic pulsar embedded in a Crab-like nebula as its origin.

NRC publication: Yes

We use the Canadian Hydrogen Intensity Mapping Experiment (CHIME) Fast Radio Burst (FRB) Project to search for FRBs that are temporally and spatially coincident with gamma-ray bursts (GRBs) occurring between 2018 July 7 and 2023 August 3. We do not find any temporal (within 1 week) and spatial (within overlapping 3 sigma localization regions) coincidences between any CHIME/FRB candidates and all GRBs with 1 sigma localization uncertainties <1 deg. As such, we use CHIME/FRB to constrain the possible FRB-like radio emission for 27 short gamma-ray bursts (SGRBs) that were within 17 deg. of CHIME/FRB's meridian at a point either 6 hrs prior up to 12 hrs after the high-energy emission. Two SGRBs, GRB 210909A and GRB 230208A, were above the horizon at CHIME at the time of their high-energy emission and we place some of the first constraints on simultaneous FRB-like radio emission from SGRBs. While neither of these two SGRBs have known redshifts, we construct a redshift range for each GRB based on their high-energy fluence and a derived SGRB energy distribution. For GRB 210909A, this redshift range corresponds to z = [0.009, 1.64] with a mean of z=0.13. Thus, for GRB 210909A, we constrain the radio luminosity at the time of the high-energy emission to L <2 x 10e46 erg s-1, L < 5 x 10e44 erg s-1, and L < 3 x 10e42 erg s-1 assuming redshifts of z=0.85, z=0.16, and z=0.013, respectively. We compare these constraints with the predicted simultaneous radio luminosities from different compact object merger models.

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.

Extragalactic studies have demonstrated there is a moderately tight (\\(\\approx\\)0.3 dex) relationship between galaxy stellar mass (\\(M_{\\star}\\)) and star formation rate (SFR) that holds for star-forming galaxies at \\(M_{\\star} \\sim 3 \\times 10^8\\)-10\\(^{11}~M_{\\odot}\\), i.e., the \"star formation main sequence.\" However, it has yet to be determined whether such a relationship extends to even lower mass galaxies, particularly at intermediate or higher redshifts. We present new results using observations for 714 narrowband H\\(\\alpha\\)-selected galaxies with stellar masses between \\(10^6\\) and \\(10^{10}~M_{\\odot}\\) (average of \\(10^{8.2}~M_{\\odot}\\)) at \\(z \\approx\\) 0.07-0.5. These galaxies have sensitive UV to near-infrared photometric measurements and optical spectroscopy. The latter allows us to correct our H\\(\\alpha\\) SFRs for dust attenuation using Balmer decrements. Our study reveals: (1) for low-SFR galaxies, our H\\(\\alpha\\) SFRs systematically underpredict compared to FUV measurements, consistent with other studies; (2) at a given stellar mass (\\(\\approx \\)10\\( ^{8}~M_{\\odot}\\)), log(specific SFR) evolves as \\( A \\log(1+z) \\) with \\( A = 5.26 \\pm 0.75 \\), and on average, specific SFR increases with decreasing stellar mass; (3) the SFR-\\(M_{\\star}\\) relation holds for galaxies down to \\(\\sim\\)10\\(^6~M_{\\odot}\\) (\\(\\sim\\)1.5 dex below previous studies), and over lookback times of up to 5 Gyr, follows a redshift-dependent relation of \\(\\log{({\\rm SFR})} \\propto \\alpha \\log(M_{\\star}/M_{\\odot}) + \\beta z\\) with \\(\\alpha = 0.60 \\pm 0.01\\) and \\(\\beta = 1.86 \\pm 0.07\\); and (4) the observed dispersion in the SFR-\\(M_{\\star}\\) relation at low stellar masses is \\(\\approx\\)0.3 dex. Accounting for survey selection effects using simulated galaxies, we estimate the true dispersion is \\(\\approx\\)0.5 dex.

The precise origins of fast radio bursts (FRBs) remain unknown. Multiwavelength observations of nearby FRB sources can provide important insights into the enigmatic FRB phenomenon. Here, we present results from a sensitive, broadband X-ray and radio observational campaign of FRB 20200120E, the closest known extragalactic repeating FRB source (located 3.63 Mpc away in an ~10-Gyr-old globular cluster). We place deep limits on the persistent and prompt X-ray emission from FRB 20200120E, which we use to constrain possible origins for the source. We compare our results with various classes of X-ray sources, transients, and FRB models. We find that FRB 20200120E is unlikely to be associated with ultraluminous X-ray bursts, magnetar-like giant flares, or an SGR 1935+2154-like intermediate flare. Although other types of bright magnetar-like intermediate flares and short X-ray bursts would have been detectable from FRB 20200120E during our observations, we cannot entirely rule them out as a class. We show that FRB 20200120E is unlikely to be powered by an ultraluminous X-ray source or a young extragalactic pulsar embedded in a Crab-like nebula. We also provide new constraints on the compatibility of FRB 20200120E with accretion-based FRB models involving X-ray binaries. These results highlight the power of multiwavelength observations of nearby FRBs for discriminating between FRB models.

Fast Radio Bursts (FRBs) are a class of highly energetic, mostly extragalactic radio transients lasting for a few milliseconds. While over 600 FRBs have been published so far, their origins are presently unclear, with some theories for extragalactic FRBs predicting accompanying high-energy emission. In this work, we use the Canadian Hydrogen Intensity Mapping Experiment (CHIME) Fast Radio Burst (CHIME/FRB) Project to explore whether any FRB-like radio emission coincides in space and time with 81 gamma-ray bursts (GRBs) detected between 2018 July 17 and 2019 July 8 by Swift/BAT and Fermi/GBM. We do not find any statistically significant, coincident pairs within 3sigma of each other's spatial localization regions and within a time difference of up to one week. In addition to searching for spatial matches between known FRBs and known GRBs, we use CHIME/FRB to constrain FRB-like radio emission before, at the time of, or after the reported high-energy emission at the position of 39 GRBs. Our most constraining radio flux limits in the 400- to 800-MHz band for short gamma-ray bursts (SGRBs) are <50 Jy at 18.6 ks pre-high-energy emission, and <5 Jy at 28.4 ks post-high-energy emission, assuming a 10-ms radio burst width with each limit valid for 60 seconds. We use these limits to constrain models that predict FRB-like prompt radio emission before and after SGRBs. We also place limits as low as 2 Jy for long gamma-ray bursts (LGRBs), but there are no strong theoretical predictions for coincident FRB-like radio emission for LGRBs.