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A spatial filter for mitigating radio interference and its application to CHIME/FRB Outriggers
Authors:
Shion Andrew,
Juan Mena-Parra,
Haochen Wang,
Antonios Argyriou,
Kiyoshi W. Masui,
Bridget C. Andersen,
Kevin Bandura,
Matt Dobbs,
Nina V. Gusinskaia,
Afrokk Khan,
Adam E. Lanman,
Mattias Lazda,
Calvin Leung,
Kenzie Nimmo,
Robert Pascua,
Aaron B. Pearlman,
Alexander W. Pollak,
Gurman Sachdeva,
Kendrick Smith
Abstract:
The sensitivity of radio telescopes is becoming increasingly limited by the presence of radio frequency interference (RFI), which will worsen as the radio spectrum becomes more crowded. One context where this poses a challenge is the field of fast radio burst (FRB) science, where there is increasing scientific interest in capturing as large of a population of bursts as possible and accurately meas…
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The sensitivity of radio telescopes is becoming increasingly limited by the presence of radio frequency interference (RFI), which will worsen as the radio spectrum becomes more crowded. One context where this poses a challenge is the field of fast radio burst (FRB) science, where there is increasing scientific interest in capturing as large of a population of bursts as possible and accurately measuring their celestial coordinates using interferometry. With several modern radio facilities actively collecting data for large FRB surveys that will be transformative to the field, properly mitigating unwanted interference is essential for the science goals of these surveys to be met. In this work, we present variations of a spatial filter based on the Karhunen-Loeve (KL) Transform to enhance the sensitivity of radio interferometers and demonstrate its applicability to FRB detection and localization. We derive a particular variation of the filter for the case of point-like radio pulses, which we show reduces to the maximum-signal-to-noise beamformer. We apply this filter to CHIME/FRB baseband data and demonstrate its capability to enhance the sensitivity and overall localization rate of CHIME/FRB Outriggers. We compare the cross-correlation signal-to-noise obtained using the spatial filter with that obtained using a spectral-kurtosis RFI flagger for a sample of 100 FRBs recorded by CHIME and its Outriggers, and show that this filter will double the total number of FRBs successfully localized with the CHIME/FRB Outrigger telescopes. While demonstrated here in the context of CHIME/FRB Outriggers, the spatial filter presented in this work--which we have made publicly available--is broadly applicable to other interferometric radio facilities engaged in FRB science and transient detection, including next-generation telescopes such as CHORD, DSA-2000, BURSTT, and CHARTS.
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Submitted 26 March, 2026;
originally announced March 2026.
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A steadily declining dispersion measure for the repeating fast radio burst FRB 20220529A: Evidence for an FRB engine embedded in an expanding supernova remnant
Authors:
Ayush Pandhi,
Kenzie Nimmo,
Shion Andrew,
Charanjot Brar,
Shami Chatterjee,
Amanda M. Cook,
Alice Curtin,
B. M. Gaensler,
Marcin Gawroński,
Jason Hessels,
Victoria M. Kaspi,
Afrokk Khan,
Franz Kirsten,
Mattias Lazda,
Calvin Leung,
Robert Main,
Kiyoshi W. Masui,
Ryan Mckinven,
Daniele Michilli,
Mason Ng,
Omar Ould-Boukattine,
Aaron B. Pearlman,
Ziggy Pleunis,
Alexander W. Pollak,
Sachin Pradeep E. T.
, et al. (7 additional authors not shown)
Abstract:
We present the discovery and subsequent 3.2 year monitoring campaign of the repeating fast radio burst FRB 20220529A with CHIME/FRB. We observe a gradual dispersion measure (DM) decline of $-0.881\pm0.001~\mathrm{pc}~\mathrm{cm}^{-3}~\mathrm{year}^{-1}$ ($-1.235\pm0.001~\mathrm{pc}~\mathrm{cm}^{-3}~\mathrm{year}^{-1}$ in the rest frame), implying a $\geq3.5\pm0.2$% decrease of the total electron c…
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We present the discovery and subsequent 3.2 year monitoring campaign of the repeating fast radio burst FRB 20220529A with CHIME/FRB. We observe a gradual dispersion measure (DM) decline of $-0.881\pm0.001~\mathrm{pc}~\mathrm{cm}^{-3}~\mathrm{year}^{-1}$ ($-1.235\pm0.001~\mathrm{pc}~\mathrm{cm}^{-3}~\mathrm{year}^{-1}$ in the rest frame), implying a $\geq3.5\pm0.2$% decrease of the total electron column in the source environment, and we see scattering timescale variations over weeks to years. We observe a short-lived excursion in which the DM rises by $\sim 1~\mathrm{pc}~\mathrm{cm}^{-3}$, immediately preceding a transient $\sim 2000~\mathrm{rad}~\mathrm{m}^{-2}$ Faraday rotation measure (RM) increase previously reported for this source, before returning to its gradual DM decline. We identify a local line-of-sight magnetic field around FRB 20220529A during this DM/RM excursion of $3.4 \pm 0.2~\mathrm{mG}$, corresponding to one of the most strongly magnetized FRB environments. We measure a decrease in the linear polarization fraction of FRB 20220529A bursts with decreasing frequency that we attribute to depolarization from multi-path propagation in the source environment. We also place a $5σ$ upper limit on the spectral luminosity of an associated persistent radio source of $\leq 5\times10^{28}~\mathrm{erg}~\mathrm{s}^{-1}~\mathrm{Hz}^{-1}$ at 1.5 GHz. These observations are consistent with FRB 20220529A originating from a young ($\sim$ years to centuries old) expanding supernova remnant, with short-lived DM and RM variability arising from interactions with the supernova remnant or with a binary companion.
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Submitted 17 March, 2026; v1 submitted 25 February, 2026;
originally announced February 2026.
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The Second CHIME/FRB Catalog of Fast Radio Bursts
Authors:
The CHIME/FRB Collaboration,
:,
Thomas Abbott,
Bridget C. Andersen,
Shion Andrew,
Kevin Bandura,
Mohit Bhardwaj,
Yash Bhusare,
Charanjot Brar,
Tomas Cassanelli,
Shami Chatterjee,
Jean-Francois Cliche,
Amanda M. Cook,
Alice Curtin,
Matt Dobbs,
Fengqiu Adam Dong,
Gwendolyn Eadie,
Tarraneh Eftekhari,
Emmanuel Fonseca,
B. M. Gaensler,
Deborah Good,
Mark Halpern,
Jason W. T. Hessels,
Adaeze Ibik,
Naman Jain
, et al. (50 additional authors not shown)
Abstract:
We present a catalog of 4539 fast radio bursts (FRBs) observed with the Canadian Hydrogen Intensity Mapping Experiment (CHIME) telescope between 25 July 2018 and 15 September 2023. These bursts originate from 3641 unique sources, including 981 bursts from 83 known repeating sources. For each FRB, the catalog provides a $O(10')$ estimate of sky location along with corresponding measurements of cumu…
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We present a catalog of 4539 fast radio bursts (FRBs) observed with the Canadian Hydrogen Intensity Mapping Experiment (CHIME) telescope between 25 July 2018 and 15 September 2023. These bursts originate from 3641 unique sources, including 981 bursts from 83 known repeating sources. For each FRB, the catalog provides a $O(10')$ estimate of sky location along with corresponding measurements of cumulative exposure time and survey sensitivity over the observing period. It includes a total-intensity dynamic spectrum between 400 and 800 MHz at 0.983 ms resolution. From this spectrum, we constrain a model of the burst morphology and measure key parameters such as arrival time, intrinsic temporal width, dispersion measure, scattering time, and flux density. This second catalog includes all FRBs from the first catalog, with every event reprocessed using a uniform and improved analysis framework. We show that previously published inferences remain valid under the updated measurements. We assess consistency of the detection rate across observational parameters, present initial distributions of burst properties, and outline ongoing and future studies that will use this catalog to investigate the nature of FRBs and their utility as astrophysical and cosmological probes.
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Submitted 14 January, 2026;
originally announced January 2026.
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VLBI Observations of SN 2012au Reveal a Compact Radio Source a Decade Post Explosion
Authors:
Mattias Lazda,
Kenzie Nimmo,
Maria R. Drout,
Benito Marcote,
Jason W. T. Hessels,
Eli Wiston,
Raffaella Margutti,
Omar Ould-Boukattine,
Tanmoy Laskar,
Jacco Vink,
Ryan Chornock,
James K. Leung,
Deanne L. Coppejans,
Dan Milisavljevic,
Juan Mena-Parra,
Dan Patnaude
Abstract:
Three leading models have been put forth to justify the observed radio re-brightening associated with stripped-envelope supernovae (SESNe) years post-explosion: radiation from an emerging pulsar wind nebula (PWN), shock interaction with a dense circumstellar medium (CSM), or emission from off-axis, relativistic jets. SN 2012au is a particularly intriguing SESN in this regard as observations obtain…
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Three leading models have been put forth to justify the observed radio re-brightening associated with stripped-envelope supernovae (SESNe) years post-explosion: radiation from an emerging pulsar wind nebula (PWN), shock interaction with a dense circumstellar medium (CSM), or emission from off-axis, relativistic jets. SN 2012au is a particularly intriguing SESN in this regard as observations obtained $\gtrsim$ 6 years post-explosion have shown both (i) optical emission features consistent with a young PWN and (ii) a radio re-brightening. We present the results of our Very-Long-Baseline-Interferometric (VLBI) observations of SN 2012au performed between 8 to 13 years post core-collapse. Our VLBI observations reveal a luminous, steadily fading radio source that remains compact ($\leq1.4\times10^{17}~\mathrm{cm}$) and stationary ($\leq0.36c$) over the course of our campaign. Overall, we find that our VLBI measurements can be readily explained by a $\sim$decade-old PWN, potentially explained by shock interaction with specific CSM geometries, and are unlikely to be explained by emission from an off-axis, relativistic jet. Assuming a PWN origin, our observations require that the initial spin-down luminosity of the central pulsar be between $10^{36}~\mathrm{erg~s^{-1}}\leq\dot{E}_0\leq {4\times10^{42}}~\mathrm{erg~s^{-1}}$ and radio efficiency factor be $η_\mathrm{R}\geq {3\times10^{-7}}$ (both quoted at the $ {99.7\%}$ confidence interval). These results are consistent with independent inferences obtained using optical spectroscopy of SN 2012au, alongside inferences of known Galactic systems. If a PWN origin is confirmed, SN 2012au would represent the first extragalactic PWN emerging from a modern day SN, providing a novel opportunity to study the formation properties of a decade-old pulsar.
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Submitted 6 April, 2026; v1 submitted 9 January, 2026;
originally announced January 2026.
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A milliarcsecond localization associates FRB 20190417A with a compact persistent radio source and an extreme magneto-ionic environment
Authors:
Alexandra M. Moroianu,
Shivani Bhandari,
Maria R. Drout,
Jason W. T. Hessels,
Danté M. Hewitt,
Franz Kirsten,
Benito Marcote,
Ziggy Pleunis,
Mark P. Snelders,
Navin Sridhar,
Uwe Bach,
Emmanuel K. Bempong-Manful,
Vladislavs Bezrukovs,
Richard Blaauw,
Justin D. Bray,
Salvatore Buttaccio,
Shami Chatterjee,
Alessandro Corongiu,
Roman Feiler,
B. M. Gaensler,
Marcin P. Gawroński,
Marcello Giroletti,
Adaeze L. Ibik,
Ramesh Karuppusamy,
Mattias Lazda
, et al. (16 additional authors not shown)
Abstract:
We report the milliarcsecond localization of a high (1379 pc/cc) dispersion measure (DM) repeating fast radio burst, FRB 20190417A. Combining European VLBI Network detections of five repeat bursts, we confirm the FRB's host to be a low-metallicity, star-forming dwarf galaxy at z = 0.12817, similar to the hosts of FRBs 20121102A, 20190520B and 20240114A. We also confirm that it is associated with a…
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We report the milliarcsecond localization of a high (1379 pc/cc) dispersion measure (DM) repeating fast radio burst, FRB 20190417A. Combining European VLBI Network detections of five repeat bursts, we confirm the FRB's host to be a low-metallicity, star-forming dwarf galaxy at z = 0.12817, similar to the hosts of FRBs 20121102A, 20190520B and 20240114A. We also confirm that it is associated with a previously reported persistent radio source (PRS), which is compact on milliarcsecond scales. Visibility-domain model fitting constrains the transverse physical size of the PRS to < 23 pc and yields an integrated flux density of 191(39) microJy at 1.4 GHz. Though we do not find significant evidence for DM evolution, FRB 20190417A exhibits a time-variable rotation measure (RM) ranging between +3958(11) and +5061(24) rad/m2 over three years. We find no evidence for intervening galaxy clusters in the FRB's line-of-sight and place a conservative lower limit on the rest-frame host DM contribution of 1228 pc/cc (90% confidence) -- the largest known for any FRB so far. This system strengthens the emerging picture of a rare subclass of repeating FRBs with large and variable RMs, above-average host DMs, and luminous PRS counterparts in metal-poor dwarf galaxies. Our results suggest that these systems are the result of environmental selection, or a distinct engine for FRB emission.
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Submitted 11 December, 2025; v1 submitted 5 September, 2025;
originally announced September 2025.
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Stellar Mass-Dispersion Measure Correlations Constrain Baryonic Feedback in Fast Radio Burst Host Galaxies
Authors:
Calvin Leung,
Sunil Simha,
Isabel Medlock,
Daisuke Nagai,
Kiyoshi W. Masui,
Lordrick A. Kahinga,
Adam E. Lanman,
Shion Andrew,
Kevin Bandura,
Alice P. Curtin,
B. M. Gaensler,
Nina Gusinskaia,
Ronniy C. Joseph,
Mattias Lazda,
Lluis Mas-Ribas,
Bradley W. Meyers,
Kenzie Nimmo,
Aaron B. Pearlman,
J. Xavier Prochaska,
Mawson W. Sammons,
Kaitlyn Shin,
Kendrick Smith,
Haochen Wang
Abstract:
Low redshift fast radio bursts (FRBs) provide robust measurements of the host-galaxy contribution to the dispersion measure (DM), which can constrain the circumgalactic medium (CGM) of the hosts. We curate a sample of 20 nearby FRBs with low scattering timescales and face-on host galaxies with stellar masses ranging from $10^9 < M^* / M_\odot < 10^{11}$. We fit the distribution of the host galaxy…
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Low redshift fast radio bursts (FRBs) provide robust measurements of the host-galaxy contribution to the dispersion measure (DM), which can constrain the circumgalactic medium (CGM) of the hosts. We curate a sample of 20 nearby FRBs with low scattering timescales and face-on host galaxies with stellar masses ranging from $10^9 < M^* / M_\odot < 10^{11}$. We fit the distribution of the host galaxy DM to a quadratic model as a function of stellar mass with a mass-independent scatter and find that the more massive the host, the lower its host DM. We report that this relation has a negative slope of $m = -97 \pm 44$ pc/cm$^{-3}$ per dex in stellar mass. We compare this measurement to similar fits to three sub-grid models implemented in the CAMELS suite of simulations from Astrid, IllustrisTNG, and SIMBA and find that fine-tuning of the host ISM contribution as a function of stellar mass is required in order to reconcile the observational data with the predictions of the fiducial CAMELS-Astrid model. More generally, models which attribute a positive correlation between stellar mass and host dispersion measure ($m > 0$) to the CGM are in tension with our measurement. We show that this conclusion is robust to a wide range of assumptions, such as the offset distribution of FRBs from their hosts and the statistics of the cosmic contribution to the DM budget along each sightline. Our results indirectly imply a lower limit on the strength of baryonic feedback in the Local Universe $(z < 0.2)$ in isolated $\sim L^*$ halos, complementing results from weak lensing surveys and kSZ observations which target higher halo mass and redshift ranges.
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Submitted 22 July, 2025;
originally announced July 2025.
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James Webb Space Telescope Observations of the Nearby and Precisely-Localized FRB 20250316A: A Potential Near-IR Counterpart and Implications for the Progenitors of Fast Radio Bursts
Authors:
Peter K. Blanchard,
Edo Berger,
Shion E. Andrew,
Aswin Suresh,
Kohki Uno,
Charles D. Kilpatrick,
Brian D. Metzger,
Harsh Kumar,
Navin Sridhar,
Amanda M. Cook,
Yuxin Dong,
Tarraneh Eftekhari,
Wen-fai Fong,
Walter W. Golay,
Daichi Hiramatsu,
Ronniy C. Joseph,
Victoria M. Kaspi,
Mattias Lazda,
Calvin Leung,
Kiyoshi W. Masui,
Juan Mena-Parra,
Kenzie Nimmo,
Aaron B. Pearlman,
Vishwangi Shah,
Kaitlyn Shin
, et al. (1 additional authors not shown)
Abstract:
We present deep James Webb Space Telescope near-infrared imaging to search for a quiescent or transient counterpart to FRB 20250316A, which was precisely localized with the CHIME/FRB Outriggers array to an area of $11\times13$ pc in the outer regions of NGC 4141 at $d\approx40$ Mpc. Our F150W2 image reveals a faint source near the center of the FRB localization region ("NIR-1";…
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We present deep James Webb Space Telescope near-infrared imaging to search for a quiescent or transient counterpart to FRB 20250316A, which was precisely localized with the CHIME/FRB Outriggers array to an area of $11\times13$ pc in the outer regions of NGC 4141 at $d\approx40$ Mpc. Our F150W2 image reveals a faint source near the center of the FRB localization region ("NIR-1"; $M_{\rm F150W2}\approx-2.5$ mag; probability of chance coincidence $\approx0.36$), the only source within $\approx2.7σ$. We find that it is too faint to be a globular cluster, young star cluster, red supergiant star, or a giant star near the tip of the red giant branch (RGB). It is instead consistent with a red giant near the RGB "clump" or a massive ($\gtrsim20$ M$_{\odot}$) main sequence star, although the latter explanation is less likely. The source is too bright to be a supernova remnant, Crab-like pulsar wind nebula, or isolated magnetar. Alternatively, NIR-1 may represent transient emission, namely a dust echo from an energetic outburst associated with the FRB, in which case we would expect it to fade in future observations. We explore the stellar population near the FRB and find that it is composed of a mix of young massive stars ($\sim10-100$ Myr) in a nearby HII region that extends to the location of FRB 20250316A, and old evolved stars ($\gtrsim$ Gyr). The overlap with a young stellar population, containing stars of up to $\approx20$ M$_\odot$, may implicate a neutron star / magnetar produced in the core collapse of a massive star as the source of FRB 20250316A.
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Submitted 23 June, 2025;
originally announced June 2025.
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FRB 20250316A: A Brilliant and Nearby One-Off Fast Radio Burst Localized to 13 parsec Precision
Authors:
The CHIME/FRB Collaboration,
:,
Thomas C. Abbott,
Daniel Amouyal,
Shion E. Andrew,
Kevin Bandura,
Mohit Bhardwaj,
Kalyani Bhopi,
Yash Bhusare,
Charanjot Brar,
Alice Cai,
Tomas Cassanelli,
Shami Chatterjee,
Jean-François Cliche,
Amanda M. Cook,
Alice P. Curtin,
Evan Davies-Velie,
Matt Dobbs,
Fengqiu Adam Dong,
Yuxin Dong,
Gwendolyn Eadie,
Tarraneh Eftekhari,
Wen-fai Fong,
Emmanuel Fonseca,
B. M. Gaensler
, et al. (62 additional authors not shown)
Abstract:
Precise localizations of a small number of repeating fast radio bursts (FRBs) using very long baseline interferometry (VLBI) have enabled multiwavelength follow-up observations revealing diverse local environments. However, the 2--3\% of FRB sources that are observed to repeat may not be representative of the full population. Here we use the VLBI capabilities of the full CHIME Outriggers array for…
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Precise localizations of a small number of repeating fast radio bursts (FRBs) using very long baseline interferometry (VLBI) have enabled multiwavelength follow-up observations revealing diverse local environments. However, the 2--3\% of FRB sources that are observed to repeat may not be representative of the full population. Here we use the VLBI capabilities of the full CHIME Outriggers array for the first time to localize a nearby (40 Mpc), bright (kJy), and apparently one-off FRB source, FRB 20250316A, to its environment on 13-pc scales. We use optical and radio observations to place deep constraints on associated transient emission and the properties of its local environment. We place a $5σ$ upper limit of $L_{\mathrm{9.9~\mathrm{GHz}}} < 2.1\times10^{25}~\mathrm{erg~s^{-1}~Hz^{-1}}$ on spatially coincident radio emission, a factor of 100 lower than any known compact persistent radio source associated with an FRB. Our KCWI observations allow us to characterize the gas density, metallicity, nature of gas ionization, dust extinction and star-formation rate through emission line fluxes. We leverage the exceptional brightness and proximity of this source to place deep constraints on the repetition of FRB 20250316A, and find it is inconsistent with all well-studied repeaters given the non-detection of bursts at lower spectral energies. We explore the implications of a measured offset of 190$\pm20$ pc from the center of the nearest star-formation region, in the context of progenitor channels. FRB 20250316A marks the beginning of an era of routine localizations for one-off FRBs on tens of mas-scales, enabling large-scale studies of their local environments.
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Submitted 23 June, 2025;
originally announced June 2025.
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Searching for Historical Extragalactic Optical Transients Associated with Fast Radio Bursts
Authors:
Y. Dong,
C. D. Kilpatrick,
W. Fong,
A. P. Curtin,
S. Opoku,
B. C. Andersen,
A. M. Cook,
T. Eftekhari,
E. Fonseca,
B. M. Gaensler,
R. C. Joseph,
J. F. Kaczmarek,
L. A. Kahinga,
V. Kaspi,
A. E. Lanman,
M. Lazda,
C. Leung,
K. W. Masui,
D. Michilli,
K. Nimmo,
A. Pandhi,
A. B. Pearlman,
M. Sammons,
P. Scholz,
V. Shah
, et al. (2 additional authors not shown)
Abstract:
We present a systematic search for past supernovae (SNe) and other historical optical transients at the positions of fast radio burst (FRB) sources to test FRB progenitor systems. Our sample comprises 83 FRBs detected by the Canadian Hydrogen Intensity Mapping Experiment (CHIME) and its KKO Outrigger, along with 93 literature FRBs representing all known well-localized FRBs. We search for optical t…
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We present a systematic search for past supernovae (SNe) and other historical optical transients at the positions of fast radio burst (FRB) sources to test FRB progenitor systems. Our sample comprises 83 FRBs detected by the Canadian Hydrogen Intensity Mapping Experiment (CHIME) and its KKO Outrigger, along with 93 literature FRBs representing all known well-localized FRBs. We search for optical transients coincident in position and redshift with FRBs and find no significant associations within the 5-sigma FRB localization uncertainties except for a previously identified potential optical counterpart to FRB 20180916B. By constraining the timescale for SN ejecta to become transparent to FRB emission, we predict that it takes at least 6-10 years before the FRB emission can escape. From this, we infer that approximately 7% of matched optical transients, up to 30% of currently known SNe, and up to 40% of core-collapse SNe could have an observable FRB based on timescales alone. We derive the number of new, well-localized FRBs required to produce one FRB-SN match by chance, and find it will take ~ 22,700 FRBs to yield one chance association at the projected CHIME/FRB Outrigger detection rate. Looking forward, we demonstrate redshift overlap between SNe detected by the upcoming Vera C. Rubin Observatory and CHIME/FRB Outrigger FRBs, indicating the prospect of an increase in potential associations at redshift z < 1. Our framework is publicly available, flexible to a wide range of transient timescales and FRB localization sizes, and can be applied to any optical transient populations in future searches.
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Submitted 23 October, 2025; v1 submitted 6 June, 2025;
originally announced June 2025.
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The CHIME/FRB Discovery of the Extremely Active Fast Radio Burst Source FRB 20240114A
Authors:
Kaitlyn Shin,
Alice Curtin,
Maxwell Fine,
Ayush Pandhi,
Shion Andrew,
Mohit Bhardwaj,
Shami Chatterjee,
Amanda M. Cook,
Emmanuel Fonseca,
B. M. Gaensler,
Jason Hessels,
Naman Jain,
Victoria M. Kaspi,
Bikash Kharel,
Adam E. Lanman,
Mattias Lazda,
Calvin Leung,
Robert Main,
Kiyoshi W. Masui,
Daniele Michilli,
Mason Ng,
Kenzie Nimmo,
Aaron B. Pearlman,
Ue-Li Pen,
Ziggy Pleunis
, et al. (6 additional authors not shown)
Abstract:
Among the thousands of observed fast radio bursts (FRBs), a few sources exhibit exceptionally high burst activity observable by many telescopes across a broad range of radio frequencies. Almost all of these highly active repeaters have been discovered by CHIME/FRB, due to its daily observations of the entire Northern sky as a transit radio telescope. FRB 20240114A is a source discovered and report…
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Among the thousands of observed fast radio bursts (FRBs), a few sources exhibit exceptionally high burst activity observable by many telescopes across a broad range of radio frequencies. Almost all of these highly active repeaters have been discovered by CHIME/FRB, due to its daily observations of the entire Northern sky as a transit radio telescope. FRB 20240114A is a source discovered and reported by CHIME/FRB to the community in January 2024; given its low declination, even the detection of a few bursts hints at a high burst rate. Following the community announcement of this source as a potentially active repeater, it was extensively followed up by other observatories and has emerged as one of the most prolific FRB repeaters ever observed. This paper presents the five bursts CHIME/FRB observed from FRB 20240114A, with channelized raw voltage data saved for two bursts. We do not observe changes in the DM of the source greater than ~1.3 pc cm$^{-3}$ in our observations over nearly a year baseline. We find an RM of ~ +320 rad m$^{-2}$. We do not find evidence for scattering at the level of < 0.3 ms in the bursts, and we find no evidence for astrophysical scintillation. In our observations of FRB 20240114A, we see a burst rate ~49x higher than the median burst rate of apparent non-repeaters also discovered by CHIME/FRB. Each discovery of highly active FRBs provides a valuable opportunity to investigate whether there is a fundamental difference between repeating and apparently non-repeating sources.
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Submitted 19 May, 2025;
originally announced May 2025.
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CHIME/FRB Outriggers: Design Overview
Authors:
The CHIME/FRB Collaboration,
Mandana Amiri,
Bridget C. Andersen,
Shion Andrew,
Kevin Bandura,
Mohit Bhardwaj,
Kalyani Bhopi,
Vadym Bidula,
P. J. Boyle,
Charanjot Brar,
Mark Carlson,
Tomas Cassanelli,
Alyssa Cassity,
Shami Chatterjee,
Jean-François Cliche,
Alice P. Curtin,
Rachel Darlinger,
David R. DeBoer,
Matt Dobbs,
Fengqiu Adam Dong,
Gwendolyn Eadie,
Emmanuel Fonseca,
B. M. Gaensler,
Nina Gusinskaia,
Mark Halpern
, et al. (44 additional authors not shown)
Abstract:
The Canadian Hydrogen Intensity Mapping Experiment (CHIME) has emerged as the world's premier facility for studying fast radio bursts (FRBs) through its fast transient search backend CHIME/FRB\@. The CHIME/FRB Outriggers project will augment this high detection rate of 2--3 FRBs per day with the ability to precisely localize them using very long baseline interferometry (VLBI). Using three strategi…
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The Canadian Hydrogen Intensity Mapping Experiment (CHIME) has emerged as the world's premier facility for studying fast radio bursts (FRBs) through its fast transient search backend CHIME/FRB\@. The CHIME/FRB Outriggers project will augment this high detection rate of 2--3 FRBs per day with the ability to precisely localize them using very long baseline interferometry (VLBI). Using three strategically located stations in North America and deploying recently developed synoptic VLBI observing techniques, the Outriggers will provide $\sim 50$~milliarcsecond localization precision for the majority of detected FRBs. This paper presents an overview of the design and implementation of the Outriggers, covering their geographic distribution, structural design, and observational capabilities. We detail the scientific objectives driving the project, including the characterization of FRB populations, host galaxy demographics, and the use of FRBs as cosmological probes. We also discuss the calibration strategies available to mitigate ionospheric and instrumental effects, ensuring high-precision localization. With two stations currently in science operations, and the third in commissioning, the CHIME/FRB Outriggers project is poised to become a cornerstone of the FRB field, offering unprecedented insights into this enigmatic cosmic phenomenon.
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Submitted 7 April, 2025;
originally announced April 2025.
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A Catalog of Local Universe Fast Radio Bursts from CHIME/FRB and the KKO Outrigger
Authors:
The CHIME/FRB Collaboration,
:,
Mandana Amiri,
Daniel Amouyal,
Bridget C. Andersen,
Shion Andrew,
Kevin Bandura,
Mohit Bhardwaj,
P. J. Boyle,
Charanjot Brar,
Alyssa Cassity,
Shami Chatterjee,
Alice P. Curtin,
Matt Dobbs,
Fengqiu Adam Dong,
Yuxin Dong,
Gwendolyn M. Eadie,
Tarraneh Eftekhari,
Wen-fai Fong,
Emmanuel Fonseca,
B. M. Gaensler,
Mark Halpern,
Jason W. T. Hessels,
Hans Hopkins,
Adaeze L. Ibik
, et al. (41 additional authors not shown)
Abstract:
We present the first catalog of fast radio burst (FRB) host galaxies from CHIME/FRB Outriggers, selected uniformly in the radio and the optical by localizing 81 new bursts to 2'' x ~60'' accuracy using CHIME and the KKO Outrigger, located 66 km from CHIME. Of the 81 localized bursts, we use the Probabilistic Association of Transients to their Hosts (PATH) algorithm to securely identify 21 new FRB…
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We present the first catalog of fast radio burst (FRB) host galaxies from CHIME/FRB Outriggers, selected uniformly in the radio and the optical by localizing 81 new bursts to 2'' x ~60'' accuracy using CHIME and the KKO Outrigger, located 66 km from CHIME. Of the 81 localized bursts, we use the Probabilistic Association of Transients to their Hosts (PATH) algorithm to securely identify 21 new FRB host galaxies, and compile spectroscopic redshifts for 19 systems, 15 of which are newly obtained via spectroscopic observations. The most nearby source is FRB 20231229A, at a distance of 90 Mpc. One burst in our sample is from a previously reported repeating source in a galaxy merger (FRB 20190303A). Three new FRB host galaxies (FRBs 20230203A, 20230703A, and 20231206A) are found towards X-ray and optically selected galaxy clusters, potentially doubling the sample of known galaxy cluster FRBs. A search for radio counterparts reveals that FRB 20231128A is associated with a luminous persistent radio source (PRS) candidate with high significance ($P_{cc} \sim 10^{-2}$). If its compactness is confirmed, it would be the nearest known compact PRS at $z = 0.1079$. Our catalog significantly increases the statistics of the Macquart relation at low redshifts ($z < 0.2$). In the near future, the completed CHIME/FRB Outriggers array will produce hundreds of FRBs localized with very long baseline interferometry (VLBI). This will significantly expand the known sample and pave the way for future telescopes relying on VLBI for FRB localization.
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Submitted 24 March, 2025; v1 submitted 16 February, 2025;
originally announced February 2025.
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A repeating fast radio burst source in the outskirts of a quiescent galaxy
Authors:
V. Shah,
K. Shin,
C. Leung,
W. Fong,
T. Eftekhari,
M. Amiri,
B. C. Andersen,
S. Andrew,
M. Bhardwaj,
C. Brar,
T. Cassanelli,
S. Chatterjee,
A. P. Curtin,
M. Dobbs,
Y. Dong,
F. A. Dong,
E. Fonseca,
B. M. Gaensler,
M. Halpern,
J. W. T. Hessels,
A. L. Ibik,
N. Jain,
R. C. Joseph,
J. Kaczmarek,
L. A. Kahinga
, et al. (24 additional authors not shown)
Abstract:
We report the discovery of the repeating fast radio burst source FRB 20240209A using the CHIME/FRB telescope. We have detected 22 bursts from this repeater between February and July 2024, six of which were also recorded at the Outrigger station KKO. The 66-km long CHIME-KKO baseline can provide single-pulse FRB localizations along one dimension with $2^{\prime\prime}$ accuracy. The high declinatio…
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We report the discovery of the repeating fast radio burst source FRB 20240209A using the CHIME/FRB telescope. We have detected 22 bursts from this repeater between February and July 2024, six of which were also recorded at the Outrigger station KKO. The 66-km long CHIME-KKO baseline can provide single-pulse FRB localizations along one dimension with $2^{\prime\prime}$ accuracy. The high declination of $\sim$86 degrees for this repeater allowed its detection with a rotating range of baseline vectors, enabling the combined localization region size to be constrained to $1^{\prime\prime}\times2^{\prime\prime}$. We present deep Gemini observations that, combined with the FRB localization, enabled a robust association of FRB 20240209A to the outskirts of a luminous galaxy (P(O|x) = 0.99; $L \approx 5.3 \times 10^{10}\,L_{\odot}$). FRB 20240209A has a projected physical offset of $40 \pm 5$ kpc from the center of its host galaxy, making it the FRB with the largest host galaxy offset to date. When normalized by the host galaxy size, the offset of FRB 20240209A is comparable to that of FRB 20200120E, the only FRB source known to originate in a globular cluster. We consider several explanations for the large offset, including a progenitor that was kicked from the host galaxy or in situ formation in a low-luminosity satellite galaxy of the putative host, but find the most plausible scenario to be a globular cluster origin. This, coupled with the quiescent, elliptical nature of the host as demonstrated in our companion paper, provide strong evidence for a delayed formation channel for the progenitor of the FRB source.
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Submitted 30 October, 2024;
originally announced October 2024.
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The Massive and Quiescent Elliptical Host Galaxy of the Repeating Fast Radio Burst FRB20240209A
Authors:
T. Eftekhari,
Y. Dong,
W. Fong,
V. Shah,
S. Simha,
B. C. Andersen,
S. Andrew,
M. Bhardwaj,
T. Cassanelli,
S. Chatterjee,
D. A. Coulter,
E. Fonseca,
B. M. Gaensler,
A. C. Gordon,
J. W. T. Hessels,
A. L. Ibik,
R. C. Joseph,
L. A. Kahinga,
V. Kaspi,
B. Kharel,
C. D. Kilpatrick,
A. E. Lanman,
M. Lazda,
C. Leung,
C. Liu
, et al. (17 additional authors not shown)
Abstract:
The discovery and localization of FRB20240209A by the Canadian Hydrogen Intensity Mapping Fast Radio Burst (CHIME/FRB) experiment marks the first repeating FRB localized with the CHIME/FRB Outriggers and adds to the small sample of repeating FRBs with associated host galaxies. Here we present Keck and Gemini observations of the host that reveal a redshift $z=0.1384\pm0.0004$. We perform stellar po…
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The discovery and localization of FRB20240209A by the Canadian Hydrogen Intensity Mapping Fast Radio Burst (CHIME/FRB) experiment marks the first repeating FRB localized with the CHIME/FRB Outriggers and adds to the small sample of repeating FRBs with associated host galaxies. Here we present Keck and Gemini observations of the host that reveal a redshift $z=0.1384\pm0.0004$. We perform stellar population modeling to jointly fit the optical through mid-infrared data of the host and infer a median stellar mass log$(M_*/{\rm M_{\odot}})=11.34\pm0.01$ and a mass-weighted stellar population age $\sim11$Gyr, corresponding to the most massive and oldest FRB host discovered to date. Coupled with a star formation rate $<0.36\,{\rm M_{\odot}\ yr^{-1}}$, the specific star formation rate $<10^{-11.8}\rm\ yr^{-1}$ classifies the host as quiescent. Through surface brightness profile modeling, we determine an elliptical galaxy morphology, marking the host as the first confirmed elliptical FRB host. The discovery of a quiescent early-type host galaxy within a transient class predominantly characterized by late-type star-forming hosts is reminiscent of short-duration gamma-ray bursts, Type Ia supernovae, and ultraluminous X-ray sources. Based on these shared host demographics, coupled with a large offset as demonstrated in our companion paper, we conclude that preferred progenitors for FRB20240209A include magnetars formed through merging binary neutron stars/white dwarfs or the accretion-induced collapse of a white dwarf, or a luminous X-ray binary. Together with FRB20200120E localized to a globular cluster in M81, our findings provide strong evidence that some fraction of FRBs may arise from a process distinct from the core collapse of massive stars.
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Submitted 30 October, 2024;
originally announced October 2024.
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A Repeating Fast Radio Burst Source in a Low-Luminosity Dwarf Galaxy
Authors:
Danté M. Hewitt,
Mohit Bhardwaj,
Alexa C. Gordon,
Aida Kirichenko,
Kenzie Nimmo,
Shivani Bhandari,
Ismaël Cognard,
Wen-fai Fong,
Armando Gil de Paz,
Akshatha Gopinath,
Jason W. T. Hessels,
Franz Kirsten,
Benito Marcote,
Vladislavs Bezrukovs,
Richard Blaauw,
Justin D. Bray,
Salvatore Buttaccio,
Tomas Cassanelli,
Pragya Chawla,
Alessandro Corongiu,
William Deng,
Hannah N. Didehbani,
Yuxin Dong,
Marcin P. Gawroński,
Marcello Giroletti
, et al. (26 additional authors not shown)
Abstract:
We present the localization and host galaxy of FRB 20190208A, a repeating source of fast radio bursts (FRBs) discovered using CHIME/FRB. As part of the PRECISE repeater localization program on the EVN, we monitored FRB 20190208A for 65.6 hours at $\sim1.4$ GHz and detected a single burst, which led to its VLBI localization with 260 mas uncertainty (2$σ$). Follow-up optical observations with the MM…
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We present the localization and host galaxy of FRB 20190208A, a repeating source of fast radio bursts (FRBs) discovered using CHIME/FRB. As part of the PRECISE repeater localization program on the EVN, we monitored FRB 20190208A for 65.6 hours at $\sim1.4$ GHz and detected a single burst, which led to its VLBI localization with 260 mas uncertainty (2$σ$). Follow-up optical observations with the MMT Observatory ($i\gtrsim 25.7$ mag (AB)) found no visible host at the FRB position. Subsequent deeper observations with the GTC, however, revealed an extremely faint galaxy ($r=27.32 \pm0.16$ mag), very likely ($99.95 \%$) associated with FRB 20190208A. Given the dispersion measure of the FRB ($\sim580$ pc cm$^{-3}$), even the most conservative redshift estimate ($z_{\mathrm{max}}\sim0.83$) implies that this is the lowest-luminosity FRB host to date ($\lesssim10^8L_{\odot}$), even less luminous than the dwarf host of FRB 20121102A. We investigate how localization precision and the depth of optical imaging affect host association, and discuss the implications of such a low-luminosity dwarf galaxy. Unlike the other repeaters with low-luminosity hosts, FRB 20190208A has a modest Faraday rotation measure of a few tens of rad m$^{-2}$, and EVN plus VLA observations reveal no associated compact persistent radio source. We also monitored FRB 20190208A for 40.4 hours over 2 years as part of the ÉCLAT repeating FRB monitoring campaign on the Nançay Radio Telescope, and detected one burst. Our results demonstrate that, in some cases, the robust association of an FRB with a host galaxy will require both high localization precision, as well as deep optical follow-up.
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Submitted 22 October, 2024;
originally announced October 2024.
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Investigating the sightline of a highly scattered FRB through a filamentary structure in the local Universe
Authors:
Kaitlyn Shin,
Calvin Leung,
Sunil Simha,
Bridget C. Andersen,
Emmanuel Fonseca,
Kenzie Nimmo,
Mohit Bhardwaj,
Charanjot Brar,
Shami Chatterjee,
Amanda M. Cook,
B. M. Gaensler,
Ronniy C. Joseph,
Dylan Jow,
Jane Kaczmarek,
Lordrick Kahinga,
Victoria M. Kaspi,
Bikash Kharel,
Adam E. Lanman,
Mattias Lazda,
Robert A. Main,
Lluis Mas-Ribas,
Kiyoshi W. Masui,
Juan Mena-Parra,
Daniele Michilli,
Ayush Pandhi
, et al. (9 additional authors not shown)
Abstract:
Fast radio bursts (FRBs) are unique probes of extragalactic ionized baryonic structure as each signal, through its burst properties, holds information about the ionized matter it encounters along its sightline. FRB 20200723B is a burst with a scattering timescale of $τ_\mathrm{400\,MHz} >$1 second at 400 MHz and a dispersion measure of DM $\sim$ 244 pc cm$^{-3}$. Observed across the entire CHIME/F…
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Fast radio bursts (FRBs) are unique probes of extragalactic ionized baryonic structure as each signal, through its burst properties, holds information about the ionized matter it encounters along its sightline. FRB 20200723B is a burst with a scattering timescale of $τ_\mathrm{400\,MHz} >$1 second at 400 MHz and a dispersion measure of DM $\sim$ 244 pc cm$^{-3}$. Observed across the entire CHIME/FRB frequency band, it is the single-component burst with the largest scattering timescale yet observed by CHIME/FRB. The combination of its high scattering timescale and relatively low dispersion measure present an uncommon opportunity to use FRB 20200723B to explore the properties of the cosmic web it traversed. With an $\sim$arcminute-scale localization region, we find the most likely host galaxy is NGC 4602 (with PATH probability $P(O|x)=0.985$), which resides $\sim$30 Mpc away within a sheet filamentary structure on the outskirts of the Virgo Cluster. We place an upper limit on the average free electron density of this filamentary structure of $\langle n_e \rangle < 4.6^{+9.6}_{-2.0} \times 10^{-5}$ cm$^{-3}$, broadly consistent with expectations from cosmological simulations. We investigate whether the source of scattering lies within the same galaxy as the FRB, or at a farther distance from an intervening structure along the line of sight. Comparing with Milky Way pulsar observations, we suggest the scattering may originate from within the host galaxy of FRB 20200723B.
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Submitted 9 October, 2024;
originally announced October 2024.
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A search for persistent radio sources toward repeating fast radio bursts discovered by CHIME/FRB
Authors:
Adaeze L. Ibik,
Maria R. Drout,
Bryan M. Gaensler,
Paul Scholz,
Navin Sridhar,
Ben Margalit,
Casey J. Law,
Tracy E. Clarke,
Shriharsh P. Tendulkar,
Daniele Michilli,
Tarraneh Eftekhari,
Mohit Bhardwaj,
Sarah Burke-Spolaor,
Shami Chatterjee,
Amanda M. Cook,
Jason W. T. Hessels,
Franz Kirsten,
Ronniy C. Joseph,
Victoria M. Kaspi,
Mattias Lazda,
Kiyoshi W. Masui,
Kenzie Nimmo,
Ayush Pandhi,
Aaron B. Pearlman,
Ziggy Pleunis
, et al. (3 additional authors not shown)
Abstract:
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 localizat…
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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.
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Submitted 7 November, 2024; v1 submitted 17 September, 2024;
originally announced September 2024.
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A VLBI Calibrator Grid at 600MHz for Fast Radio Transient Localizations with CHIME/FRB Outriggers
Authors:
Shion Andrew,
Calvin Leung,
Alexander Li,
Kiyoshi W. Masui,
Bridget C. Andersen,
Kevin Bandura,
Alice P. Curtin,
Jane Kaczmarek,
Adam E. Lanman,
Mattias Lazda,
Juan Mena-Parra,
Daniele Michilli,
Kenzie Nimmo,
Aaron B. Pearlman,
Mubdi Rahman,
Vishwangi Shah,
Kaitlyn Shin,
Haochen Wang
Abstract:
The Canadian Hydrogen Intensity Mapping Experiment Fast Radio Burst (CHIME/FRB) Project has a new VLBI Outrigger at the Green Bank Observatory (GBO), which forms a 3300km baseline with CHIME operating at 400-800MHz. Using 100ms long full-array baseband "snapshots" collected commensally during FRB and pulsar triggers, we perform a shallow, wide-area VLBI survey covering a significant fraction of th…
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The Canadian Hydrogen Intensity Mapping Experiment Fast Radio Burst (CHIME/FRB) Project has a new VLBI Outrigger at the Green Bank Observatory (GBO), which forms a 3300km baseline with CHIME operating at 400-800MHz. Using 100ms long full-array baseband "snapshots" collected commensally during FRB and pulsar triggers, we perform a shallow, wide-area VLBI survey covering a significant fraction of the Northern sky targeted at the positions of compact sources from the Radio Fundamental Catalog. In addition, our survey contains calibrators detected from two 1s long trial baseband snapshots for a deeper survey with CHIME and GBO. In this paper, we present the largest catalog of compact calibrators suitable for 30-milliarcsecond-scale VLBI observations at sub-GHz frequencies to date. Our catalog consists of 200 total calibrators in the Northern Hemisphere that are compact on 30-milliarcsecond scales with fluxes above 100mJy. This calibrator grid will enable the precise localization of hundreds of FRBs a year with CHIME/FRB-Outriggers.
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Submitted 17 September, 2024;
originally announced September 2024.
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Contemporaneous X-ray Observations of 30 Bright Radio Bursts from the Prolific Fast Radio Burst Source FRB 20220912A
Authors:
Amanda M. Cook,
Paul Scholz,
Aaron B. Pearlman,
Thomas C. Abbott,
Marilyn Cruces,
B. M. Gaensler,
Fengqiu,
Dong,
Daniele Michilli,
Gwendolyn Eadie,
Victoria M. Kaspi,
Ingrid Stairs,
Chia Min Tan,
Mohit Bhardwaj,
Tomas Cassanelli,
Alice P. Curtin,
Adaeze L. Ibik,
Mattias Lazda,
Kiyoshi W. Masui,
Ayush Pandhi,
Masoud Rafiei-Ravandi,
Mawson W. Sammons,
Kaitlyn Shin,
Kendrick Smith,
David C. Stenning
Abstract:
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…
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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 $η_{\text{ x/r}} = F_{\text{X-ray}}/F_{\text{radio}}$, this corresponds to $η_{\text{ x/r}} < 7\times10^{6}$. 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 $η_{\text{ x/r}}$ to date, $η_{\text{ x/r}} < 2\times10^6$, 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 $η_{\text{ x/r}}$ of $8\times10^5$, which is only 3 times the observed value of $η_{\text{ x/r}}$ for SGR 1935+2154.
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Submitted 21 August, 2024;
originally announced August 2024.
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CHIME/FRB/Pulsar discovery of a nearby long period radio transient with a timing glitch
Authors:
Fengqiu Adam Dong,
Tracy E Clarke,
Alice Curtin,
Ajay Kumar,
Ryan Mckinven,
Kaitlyn Shin,
Ingrid Stairs,
Charanjot Brar,
Kevin Burdge,
Shami Chatterjee,
Amanda M. Cook,
Emmanuel Fonseca,
B. M. Gaensler,
Jason W. Hessels,
Victoria M. Kaspi,
Mattias Lazda,
Robert Main,
Kiyoshi W. Masui,
James W. McKee,
Bradley W. Meyers,
Aaron B. Pearlman,
Scott M. Ransom,
Paul Scholz,
Kendrick M. Smith,
Chia Min Tan
Abstract:
We present the discovery of a 421 s long period radio transient (LPT) using the CHIME telescope, CHIME J0630+25. The source is localized to RA=06:30:38.4$\pm1'$ Dec=25:26:24$\pm1'$ using voltage data acquired with the CHIME baseband system. A timing analysis shows that a model including a glitch is preferred over a non-glitch model with $dF/F=1.3\times10^{-6}$, consistent with other glitching neut…
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We present the discovery of a 421 s long period radio transient (LPT) using the CHIME telescope, CHIME J0630+25. The source is localized to RA=06:30:38.4$\pm1'$ Dec=25:26:24$\pm1'$ using voltage data acquired with the CHIME baseband system. A timing analysis shows that a model including a glitch is preferred over a non-glitch model with $dF/F=1.3\times10^{-6}$, consistent with other glitching neutron stars. The timing model suggests a surface magnetic field of $\sim1.5\times10^{15}$ G and a characteristic age of $\sim1.28\times10^{6}$ yrs. A separate line of evidence to support a strong local magnetic field is an abnormally high rotation measure of $RM=-347.8(6) \mathrm{rad\, m^{-2}}$ relative to CHIME J0630+25's modest dispersion measure of 22(1) pc cm$^{-2}$, implying a dense local magneto-ionic structure. As a result, we believe that CHIME J0630+25 is a magnetized, slowly spinning, isolated neutron star. This marks CHIME J0630+25 as the longest period neutron star and the second long period neutron star with an inferred magnetar-like field. Based on dispersion measure models and comparison with pulsars with distance measurements, CHIME J0630+25 is located at a nearby distance of 170$^{+310}_{-100}$ pc (95.4\%), making it an ideal candidate for follow-up studies.
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Submitted 7 August, 2025; v1 submitted 10 July, 2024;
originally announced July 2024.
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Magnetospheric origin of a fast radio burst constrained using scintillation
Authors:
Kenzie Nimmo,
Ziggy Pleunis,
Paz Beniamini,
Pawan Kumar,
Adam E. Lanman,
D. Z. Li,
Robert Main,
Mawson W. Sammons,
Shion Andrew,
Mohit Bhardwaj,
Shami Chatterjee,
Alice P. Curtin,
Emmanuel Fonseca,
B. M. Gaensler,
Ronniy C. Joseph,
Zarif Kader,
Victoria M. Kaspi,
Mattias Lazda,
Calvin Leung,
Kiyoshi W. Masui,
Ryan Mckinven,
Daniele Michilli,
Ayush Pandhi,
Aaron B. Pearlman,
Masoud Rafiei-Ravandi
, et al. (4 additional authors not shown)
Abstract:
Fast radio bursts (FRBs) are micro-to-millisecond duration radio transients that originate mostly from extragalactic distances. The emission mechanism responsible for these high luminosity, short duration transients remains debated. The models are broadly grouped into two classes: physical processes that occur within close proximity to a central engine; and central engines that release energy whic…
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Fast radio bursts (FRBs) are micro-to-millisecond duration radio transients that originate mostly from extragalactic distances. The emission mechanism responsible for these high luminosity, short duration transients remains debated. The models are broadly grouped into two classes: physical processes that occur within close proximity to a central engine; and central engines that release energy which moves to large radial distances and subsequently interacts with surrounding media producing radio waves. The expected emission region sizes are notably different between these two types of models. FRB emission size constraints can therefore be used to distinguish between these competing models and inform on the physics responsible. Here we present the measurement of two mutually coherent scintillation scales in the frequency spectrum of FRB 20221022A: one originating from a scattering screen located within the Milky Way, and the second originating from a scattering screen located within its host galaxy or local environment. We use the scattering media as an astrophysical lens to constrain the size of the lateral emission region, $R_{\star\mathrm{obs}} \lesssim 3\times10^{4}$ km. We find that this is inconsistent with the expected emission sizes for the large radial distance models, and is more naturally explained with 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 polarisation angle swing, supporting 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.
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Submitted 16 June, 2024;
originally announced June 2024.
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A VLBI Software Correlator for Fast Radio Transients
Authors:
Calvin Leung,
Shion Andrew,
Kiyoshi W. Masui,
Charanjot Brar,
Tomas Cassanelli,
Shami Chatterjee,
Victoria Kaspi,
Kholoud Khairy,
Adam E. Lanman,
Mattias Lazda,
Juan Mena-Parra,
Gavin Noble,
Aaron B. Pearlman,
Mubdi Rahman,
Pranav Sanghavi,
Vishwangi Shah
Abstract:
One major goal in fast radio burst science is to detect fast radio bursts (FRBs) over a wide field of view without sacrificing the angular resolution required to pinpoint them to their host galaxies. Wide-field detection and localization capabilities have already been demonstrated using connected-element interferometry; the CHIME/FRB Outriggers project will push this further using widefield cylind…
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One major goal in fast radio burst science is to detect fast radio bursts (FRBs) over a wide field of view without sacrificing the angular resolution required to pinpoint them to their host galaxies. Wide-field detection and localization capabilities have already been demonstrated using connected-element interferometry; the CHIME/FRB Outriggers project will push this further using widefield cylindrical telescopes as widefield outriggers for very long baseline interferometry (VLBI). This paper describes an offline VLBI software correlator written in Python for the CHIME/FRB Outriggers project. It includes features well-suited to modern widefield instruments like multibeaming/multiple phase center correlation, pulse gating including coherent dedispersion, and a novel correlation algorithm based on the quadratic estimator formalism. This algorithm mitigates sensitivity loss which arises in instruments where the windowing and channelization is done outside the VLBI correlator at each station, which accounts for a 30 percent sensitivity drop away from the phase center. Our correlation algorithm recovers this sensitivity on both simulated and real data. As an end to end check of our software, we have written a preliminary pipeline for VLBI calibration and single-pulse localization, which we use in Lanman et al. (2024) to verify the astrometric accuracy of the CHIME/FRB Outriggers array.
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Submitted 26 March, 2024; v1 submitted 8 March, 2024;
originally announced March 2024.
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A pulsar-like swing in the polarisation position angle of a nearby fast radio burst
Authors:
Ryan Mckinven,
Mohit Bhardwaj,
Tarraneh Eftekhari,
Charles D. Kilpatrick,
Aida Kirichenko,
Arpan Pal,
Amanda M. Cook,
B. M. Gaensler,
Utkarsh Giri,
Victoria M. Kaspi,
Daniele Michilli,
Kenzie Nimmo,
Aaron B. Pearlman,
Ziggy Pleunis,
Ketan R. Sand,
Ingrid Stairs,
Bridget C. Andersen,
Shion Andrew,
Kevin Bandura,
Charanjot Brar,
Tomas Cassanelli,
Shami Chatterjee,
Alice P. Curtin,
Fengqiu Adam Dong,
Gwendolyn Eadie
, et al. (19 additional authors not shown)
Abstract:
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 (P…
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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.
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Submitted 14 February, 2024;
originally announced February 2024.
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CHIME/FRB Outriggers: KKO Station System and Commissioning Results
Authors:
Adam E. Lanman,
Shion Andrew,
Mattias Lazda,
Vishwangi Shah,
Mandana Amiri,
Arvind Balasubramanian,
Kevin Bandura,
P. J. Boyle,
Charanjot Brar,
Mark Carlson,
Jean-François Cliche,
Nina Gusinskaia,
Ian T. Hendricksen,
J. F. Kaczmarek,
Tom Landecker,
Calvin Leung,
Ryan Mckinven,
Juan Mena-Parra,
Nikola Milutinovic,
Kenzie Nimmo,
Aaron B. Pearlman,
Andre Renard,
Mubdi Rahman,
J. Richard Shaw,
Seth R. Siegel
, et al. (21 additional authors not shown)
Abstract:
Localizing fast radio bursts (FRBs) to their host galaxies is an essential step to better understanding their origins and using them as cosmic probes. The CHIME/FRB Outrigger program aims to add VLBI-localization capabilities to CHIME, such that FRBs may be localized to tens of milliarcsecond precision at the time of their discovery, more than sufficient for host galaxy identification. The first-b…
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Localizing fast radio bursts (FRBs) to their host galaxies is an essential step to better understanding their origins and using them as cosmic probes. The CHIME/FRB Outrigger program aims to add VLBI-localization capabilities to CHIME, such that FRBs may be localized to tens of milliarcsecond precision at the time of their discovery, more than sufficient for host galaxy identification. The first-built outrigger telescope is KKO, located 66 kilometers west of CHIME. Cross-correlating KKO with CHIME can achieve arcsecond-scale localization in right ascension while avoiding the worst effects of the ionosphere. This paper presents measurements of KKO's performance throughout its commissioning phase, as well as a summary of its design and function. We demonstrate KKO's capabilities as a standalone instrument by producing full-sky images, mapping the angular and frequency structure of the primary beam, and measuring feed positions. To demonstrate the localization capabilities of the CHIME -- KKO baseline, we collected five separate observations each for a set of twenty bright pulsars, and aimed to measure their positions to within 5~arcseconds. All of these pulses were successfully localized to within this specification. The next two outriggers are expected to be commissioned in 2024, and will enable subarcsecond localizations for approximately hundreds of FRBs each year.
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Submitted 29 May, 2024; v1 submitted 12 February, 2024;
originally announced February 2024.
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Polarization properties of 128 non-repeating fast radio bursts from the first CHIME/FRB baseband catalog
Authors:
Ayush Pandhi,
Ziggy Pleunis,
Ryan Mckinven,
B. M. Gaensler,
Jianing Su,
Cherry Ng,
Mohit Bhardwaj,
Charanjot Brar,
Tomas Cassanelli,
Amanda M. Cook,
Alice P. Curtin,
Victoria M. Kaspi,
Mattias Lazda,
Calvin Leung,
Dongzi Li,
Kiyoshi W. Masui,
Daniele Michilli,
Kenzie Nimmo,
Aaron Pearlman,
Emily Petroff,
Masoud Rafiei-Ravandi,
Ketan R. Sand,
Paul Scholz,
Kaitlyn Shin,
Kendrick Smith
, et al. (1 additional authors not shown)
Abstract:
We present a 400-800 MHz polarimetric analysis of 128 non-repeating fast radio bursts (FRBs) from the first CHIME/FRB baseband catalog, increasing the total number of FRB sources with polarization properties by a factor of ~3. 89 FRBs have >6$σ$ linearly polarized detections, 29 FRBs fall below this significance threshold and are deemed linearly unpolarized, and for 10 FRBs the polarization data a…
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We present a 400-800 MHz polarimetric analysis of 128 non-repeating fast radio bursts (FRBs) from the first CHIME/FRB baseband catalog, increasing the total number of FRB sources with polarization properties by a factor of ~3. 89 FRBs have >6$σ$ linearly polarized detections, 29 FRBs fall below this significance threshold and are deemed linearly unpolarized, and for 10 FRBs the polarization data are contaminated by instrumental polarization. For the 89 polarized FRBs, we find Faraday rotation measure (RM) amplitudes, after subtracting approximate Milky Way contributions, in the range 0.5-1160 rad m$^{-2}$ with a median of 53.8 rad m$^{-2}$. Most non-repeating FRBs in our sample have RMs consistent with Milky Way-like host galaxies and their linear polarization fractions range from <10% to 100% with a median of 63%. We see marginal evidence that non-repeating FRBs have more constraining lower limits than repeating FRBs for the host electron-density-weighted line-of-sight magnetic field strength. We classify the non-repeating FRB polarization position angle (PA) profiles into four archetypes: (i) single component with constant PA (57% of the sample), (ii) single component with variable PA (10%), (iii) multiple components with a single constant PA (22%), and (iv) multiple components with different or variable PAs (11%). We see no evidence for population-wide frequency-dependent depolarization and, therefore, the spread in the distribution of fractional linear polarization is likely intrinsic to the FRB emission mechanism. Finally, we present a novel method to derive redshift lower limits for polarized FRBs without host galaxy identification and test this method on 20 FRBs with independently measured redshifts.
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Submitted 2 May, 2024; v1 submitted 30 January, 2024;
originally announced January 2024.
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Updating the first CHIME/FRB catalog of fast radio bursts with baseband data
Authors:
The CHIME/FRB Collaboration,
:,
Mandana Amiri,
Bridget C. Andersen,
Shion Andrew,
Kevin Bandura,
Mohit Bhardwaj,
P. J. Boyle,
Charanjot Brar,
Daniela Breitman,
Tomas Cassanelli,
Pragya Chawla,
Amanda M. Cook,
Alice P. Curtin,
Matt Dobbs,
Fengqiu Adam Dong,
Gwendolyn Eadie,
Emmanuel Fonseca,
B. M. Gaensler,
Utkarsh Giri,
Antonio Herrera-Martin,
Hans Hopkins,
Adaeze L. Ibik,
Ronniy C. Joseph,
J. F. Kaczmarek
, et al. (36 additional authors not shown)
Abstract:
In 2021, a catalog of 536 fast radio bursts (FRBs) detected with the Canadian Hydrogen Intensity Mapping Experiment (CHIME) radio telescope was released by the CHIME/FRB Collaboration. This large collection of bursts, observed with a single instrument and uniform selection effects, has advanced our understanding of the FRB population. Here we update the results for 140 of these FRBs for which chan…
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In 2021, a catalog of 536 fast radio bursts (FRBs) detected with the Canadian Hydrogen Intensity Mapping Experiment (CHIME) radio telescope was released by the CHIME/FRB Collaboration. This large collection of bursts, observed with a single instrument and uniform selection effects, has advanced our understanding of the FRB population. Here we update the results for 140 of these FRBs for which channelized raw voltage ('baseband') data are available. With the voltages measured by the telescope's antennas, it is possible to maximize the telescope sensitivity in any direction within the primary beam, an operation called 'beamforming'. This allows us to increase the signal-to-noise ratio (S/N) of the bursts and to localize them to sub-arcminute precision. The improved localization is also used to correct the beam response of the instrument and to measure fluxes and fluences with a ~10% uncertainty. Additionally, the time resolution is increased by three orders of magnitude relative to that in the first CHIME/FRB catalog, and, applying coherent dedispersion, burst morphologies can be studied in detail. Polarization information is also available for the full sample of 140 FRBs, providing an unprecedented dataset to study the polarization properties of the population. We release the baseband data beamformed to the most probable position of each FRB. These data are analyzed in detail in a series of accompanying papers.
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Submitted 22 May, 2024; v1 submitted 31 October, 2023;
originally announced November 2023.
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A fast radio burst localized at detection to an edge-on galaxy using very-long-baseline interferometry
Authors:
Tomas Cassanelli,
Calvin Leung,
Pranav Sanghavi,
Juan Mena-Parra,
Savannah Cary,
Ryan Mckinven,
Mohit Bhardwaj,
Kiyoshi W. Masui,
Daniele Michilli,
Kevin Bandura,
Shami Chatterjee,
Jeffrey B. Peterson,
Jane Kaczmarek,
Chitrang Patel,
Mubdi Rahman,
Kaitlyn Shin,
Keith Vanderlinde,
Sabrina Berger,
Charanjot Brar,
P. J. Boyle,
Daniela Breitman,
Pragya Chawla,
Alice P. Curtin,
Matt Dobbs,
Fengqiu Adam Dong
, et al. (26 additional authors not shown)
Abstract:
Fast radio bursts (FRBs) are millisecond-duration, luminous radio transients of extragalactic origin. These events have been used to trace the baryonic structure of the Universe using their dispersion measure (DM) assuming that the contribution from host galaxies can be reliably estimated. However, contributions from the immediate environment of an FRB may dominate the observed DM, thus making red…
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Fast radio bursts (FRBs) are millisecond-duration, luminous radio transients of extragalactic origin. These events have been used to trace the baryonic structure of the Universe using their dispersion measure (DM) assuming that the contribution from host galaxies can be reliably estimated. However, contributions from the immediate environment of an FRB may dominate the observed DM, thus making redshift estimates challenging without a robust host galaxy association. Furthermore, while at least one Galactic burst has been associated with a magnetar, other localized FRBs argue against magnetars as the sole progenitor model. Precise localization within the host galaxy can discriminate between progenitor models, a major goal of the field. Until now, localizations on this spatial scale have only been carried out in follow-up observations of repeating sources. Here we demonstrate the localization of FRB 20210603A with very long baseline interferometry (VLBI) on two baselines, using data collected only at the time of detection. We localize the burst to SDSS J004105.82+211331.9, an edge-on galaxy at $z\approx 0.177$, and detect recent star formation in the kiloparsec-scale vicinity of the burst. The edge-on inclination of the host galaxy allows for a unique comparison between the line of sight towards the FRB and lines of sight towards known Galactic pulsars. The DM, Faraday rotation measure (RM), and scattering suggest a progenitor coincident with the host galactic plane, strengthening the link between the environment of FRB 20210603A and the disk of its host galaxy. Single-pulse VLBI localizations of FRBs to within their host galaxies, following the one presented here, will further constrain the origins and host environments of one-off FRBs.
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Submitted 4 November, 2024; v1 submitted 18 July, 2023;
originally announced July 2023.
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TONE: A CHIME/FRB Outrigger Pathfinder for localizations of Fast Radio Bursts using Very Long Baseline Interferometry
Authors:
Pranav Sanghavi,
Calvin Leung,
Kevin Bandura,
Tomas Cassanelli,
Jane Kaczmarek,
Victoria M. Kaspi,
Kholoud Khairy,
Adam Lanman,
Mattias Lazda,
Kiyoshi W. Masui,
Juan Mena-Parra,
Daniele Michilli,
Ue-Li Pen,
Jeffrey B. Peterson,
Mubdi Rahman,
Vishwangi Shah
Abstract:
The sensitivity and field of view of the Canadian Hydrogen Intensity Mapping Experiment (CHIME) has enabled its fast radio burst (FRB) backend to detect thousands of FRBs. However, the low angular resolution of CHIME prevents it from localizing most FRBs to their host galaxies. Very long baseline interferometry (VLBI) can readily provide the subarcsecond resolution needed to localize many FRBs to…
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The sensitivity and field of view of the Canadian Hydrogen Intensity Mapping Experiment (CHIME) has enabled its fast radio burst (FRB) backend to detect thousands of FRBs. However, the low angular resolution of CHIME prevents it from localizing most FRBs to their host galaxies. Very long baseline interferometry (VLBI) can readily provide the subarcsecond resolution needed to localize many FRBs to their hosts. Thus we developed TONE: an interferometric array of eight $6~\mathrm{m}$ dishes to serve as a pathfinder for the CHIME/FRB Outriggers project, which will use wide field of view cylinders to determine the sky positions for a large sample of FRBs, revealing their positions within their host galaxies to subarcsecond precision. In the meantime, TONE's $\sim3333~\mathrm{km}$ baseline with CHIME proves to be an excellent testbed for the development and characterization of single-pulse VLBI techniques at the time of discovery. This work describes the TONE instrument, its sensitivity, and its astrometric precision in single-pulse VLBI. We believe that our astrometric errors are dominated by uncertainties in the clock measurements which build up between successive Crab pulsar calibrations which happen every $\approx 24~\mathrm{h}$; the wider fields of view and higher sensitivity of the Outriggers will provide opportunities for higher-cadence calibration. At present, CHIME-TONE localizations of the Crab pulsar yield systematic localization errors of ${0.1}-{0.2}~\mathrm{arcsec}$ - comparable to the resolution afforded by state-of-the-art optical instruments ($\sim 0.05 ~\mathrm{arcsec}$).
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Submitted 25 April, 2023; v1 submitted 20 April, 2023;
originally announced April 2023.
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CHIME/FRB Discovery of 25 Repeating Fast Radio Burst Sources
Authors:
The CHIME/FRB Collaboration,
:,
Bridget C. Andersen,
Kevin Bandura,
Mohit Bhardwaj,
P. J. Boyle,
Charanjot Brar,
Tomas Cassanelli,
S. Chatterjee,
Pragya Chawla,
Amanda M. Cook,
Alice P. Curtin,
Matt Dobbs,
Fengqiu Adam Dong,
Jakob T. Faber,
Mateus Fandino,
Emmanuel Fonseca,
B. M. Gaensler,
Utkarsh Giri,
Antonio Herrera-Martin,
Alex S. Hill,
Adaeze Ibik,
Alexander Josephy,
Jane F. Kaczmarek,
Zarif Kader
, et al. (35 additional authors not shown)
Abstract:
We present the discovery of 25 new repeating fast radio burst (FRB) sources found among CHIME/FRB events detected between 2019 September 30 and 2021 May 1. The sources were found using a new clustering algorithm that looks for multiple events co-located on the sky having similar dispersion measures (DMs). The new repeaters have DMs ranging from $\sim$220 pc cm$^{-3}$ to $\sim$1700 pc cm$^{-3}$, an…
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We present the discovery of 25 new repeating fast radio burst (FRB) sources found among CHIME/FRB events detected between 2019 September 30 and 2021 May 1. The sources were found using a new clustering algorithm that looks for multiple events co-located on the sky having similar dispersion measures (DMs). The new repeaters have DMs ranging from $\sim$220 pc cm$^{-3}$ to $\sim$1700 pc cm$^{-3}$, and include sources having exhibited as few as two bursts to as many as twelve. We report a statistically significant difference in both the DM and extragalactic DM (eDM) distributions between repeating and apparently nonrepeating sources, with repeaters having lower mean DM and eDM, and we discuss the implications. We find no clear bimodality between the repetition rates of repeaters and upper limits on repetition from apparently nonrepeating sources after correcting for sensitivity and exposure effects, although some active repeating sources stand out as anomalous. We measure the repeater fraction over time and find that it tends to an equilibrium of $2.6_{-2.6}^{+2.9}$% over our total time-on-sky thus far. We also report on 14 more sources which are promising repeating FRB candidates and which merit follow-up observations for confirmation.
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Submitted 15 March, 2023; v1 submitted 20 January, 2023;
originally announced January 2023.
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An FRB Sent Me a DM: Constraining the Electron Column of the Milky Way Halo with Fast Radio Burst Dispersion Measures from CHIME/FRB
Authors:
Amanda M. Cook,
Mohit Bhardwaj,
B. M. Gaensler,
Paul Scholz,
Gwendolyn M. Eadie,
Alex S. Hill,
Victoria M. Kaspi,
Kiyoshi W. Masui,
Alice P. Curtin,
Fengqiu Adam Dong,
Emmanuel Fonseca,
Antonio Herrera-Martin,
Jane Kaczmarek,
Adam E. Lanman,
Mattias Lazda,
Calvin Leung,
Bradley W. Meyers,
Daniele Michilli,
Ayush Pandhi,
Aaron B. Pearlman,
Ziggy Pleunis,
Scott Ransom,
Mubdi Rahman,
Ketan R. Sand,
Kaitlyn Shin
, et al. (3 additional authors not shown)
Abstract:
The CHIME/FRB project has detected hundreds of fast radio bursts (FRBs), providing an unparalleled population to probe statistically the foreground media that they illuminate. One such foreground medium is the ionized halo of the Milky Way (MW). We estimate the total Galactic electron column density from FRB dispersion measures (DMs) as a function of Galactic latitude using four different estimato…
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The CHIME/FRB project has detected hundreds of fast radio bursts (FRBs), providing an unparalleled population to probe statistically the foreground media that they illuminate. One such foreground medium is the ionized halo of the Milky Way (MW). We estimate the total Galactic electron column density from FRB dispersion measures (DMs) as a function of Galactic latitude using four different estimators, including ones that assume spherical symmetry of the ionized MW halo and ones that imply more latitudinal-variation in density. Our observation-based constraints of the total Galactic DM contribution for $|b|\geq 30^\circ$, depending on the Galactic latitude and selected model, span 87.8 - 141 pc cm^-3. This constraint implies upper limits on the MW halo DM contribution that range over 52-111 pc cm^-3. We discuss the viability of various gas density profiles for the MW halo that have been used to estimate the halo's contribution to DMs of extragalactic sources. Several models overestimate the DM contribution, especially when assuming higher halo gas masses (~ 3.5 x 10^12 solar masses). Some halo models predict a higher MW halo DM contribution than can be supported by our observations unless the effect of feedback is increased within them, highlighting the impact of feedback processes in galaxy formation.
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Submitted 8 February, 2023; v1 submitted 9 January, 2023;
originally announced January 2023.