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Duncan R. Lorimer

Publications and source records attributed to Duncan R. Lorimer.

At least 19 recordsLinked to original sources
arXiv2026

Discovery of Hidden Extragalactic Pulsars in the Parkes Archival Data

Just over 1% of the known radio pulsar population resides in the Large and Small Magellanic Clouds (MCs), the satellite galaxies that are 50-62 kpc distant from the Milky Way. These pulsars are important for constraining the peak of the pulsar luminosity function, and may give insights into neutron star populations formed from stars of different metallicities than the Milky Way. Using search techniques that have proven highly effective at discovering a large number of pulsars in archival data by folding candidates near the noise floor at high harmonic folds, we reprocessed the original Parkes Multibeam MC surveys and discovered six pulsars. Five of these pulsars are located in the Large Magellanic Cloud (LMC), including one with a spin period of 3.8s, making it the slowest pulsar known in the MCs. The remaining pulsar was detected toward the Small Magellanic Cloud (SMC), and is associated with the Milky Way foreground. Four of the newly discovered pulsars exhibit scintillation, with one showing clear nulling and others showing possible nulling behavior. These discoveries bring the total number of radio pulsars known in the LMC to 49. A luminosity function and duty cycle analysis of all current MC pulsars shows that they are consistent with Galactic canonical pulsars. Population synthesis simulations suggest that deeper surveys would reveal many more pulsars in the MCs, including up to handful of millisecond pulsars, based on the adopted upper limits for their parent populations. Finally, this reprocessing demonstrates the continued importance of reanalyzing archival data, both to improve the completeness of pulsar surveys and detect scientifically valuable objects.

astro-ph.HE↗
arXiv2026

Evidence for Distinct One-Off and Repeating Subpopulations in CHIME/FRB Catalog 2

The Canadian Hydrogen Intensity Mapping Experiment (CHIME) has published its second catalog of 3,641 fast radio bursts (FRBs). While this sample includes 981 bursts from 83 repeating sources, only 2.3% of CHIME FRBs are observed to repeat. This raises the question of whether the FRB population truly consists of a single repeating population or includes a distinct subpopulation of one-off sources. We apply Simulation Based Inference (SBI), a likelihood-free machine learning framework, to model the CHIME/FRB Catalog 2 dataset, testing eight FRB population models, half of which include a subpopulation of truly one-off sources. The current catalog strongly and decisively favors models including such a subpopulation, with the best-fitting model combining a log-normal burst rate distribution, a Poissonian wait-time distribution, and a one-off subpopulation. This preference is corroborated by an independent random forest classifier and by the ability of one-off models to naturally reproduce the hyperactive repeating sources present in the catalog without having been trained on them. We place upper limits on the potentially observable CHIME/FRB population of 36,000 repeating sources and 19 one-off sources per day in the CHIME sky. Models with a one-off subpopulation naturally account for the hyperactive repeating sources present in the catalog without having been trained on them, providing an independent consistency check on our results. We predict the repeater percentage will fall below 2% in the next five years, eventually declining to ~0.5% as the sample saturates with one-off detections.

astro-ph.HE↗
arXiv2026

The NANOGrav 15 yr Dataset: Modified Functional Forms for Profile-Evolution Time Delays in Pulsar Timing Models

Radio pulsars exhibit frequency-dependent variations in the shape of their pulse profiles that introduce systematic delays in the observed pulse times of arrival (TOA) across an observing band. The North American Nanohertz Observatory for Gravitational Waves (NANOGrav) models these delays using a frequency-dependent (FD) log-polynomial function whose coefficients are fit to TOA measurements at different radio frequencies. However, FD parameters are prone to absorbing power from other chromatic effects, such as interstellar dispersion, leading to fitted FD values that overestimate profile evolution and vary significantly across datasets. To separate these effects, we introduce two new mathematical formulations of profile evolution: a monomial expansion (IFD) and a Legendre polynomial expansion (LIFD). We test these models on observations of 11 pulsars in the NANOGrav 15-year dataset and on simulated data, and also compare their performance to that of frequency-resolved pulse templates. We find that Legendre-based models generally predict timing delays that more closely replicate the true profile evolution, reducing the residual offset relative to FD by as much as 85% for the simulated data. Additionally, we find that the choice of profile evolution model can bias the fitted dispersion model, with FD-based models overestimating the injected DM by 0.013 pc cm^-3 compared to 0.0002 pc cm^-3 for LIFD. These results support the use of Legendre bases to mitigate covariances between chromatic effects, directly benefiting targeted timing studies of these effects and the development of advanced noise-modeling techniques for nanohertz gravitational-wave detection.

astro-ph.HE↗
arXiv2026

Optimal Pulsar Timing Array Strategies with the Deep Synoptic Array

Pulsar timing array (PTA) experiments have seen evidence for a nanohertz-frequency gravitational wave background (GWB) through coordinated radio timing observations of millisecond pulsars. The significance of this evidence is expected to grow and the GWB's progenitor(s) uncovered with continued observations, especially as the next generation of radio telescopes comes online. We present a framework for simulating timing observations of a set of pulsars with a set of telescopes to predict the per-pulsar optimal instrument, observing frequency, and integration time. We apply this methodology to the NANOGrav source list of 85 pulsars observed with the Green Bank Telescope, Very Large Array, Canadian Hydrogen Intensity Mapping Experiment (CHIME), and the Deep Synoptic Array (DSA), a radio dish array under construction in Nevada. We discuss the dominant noise contributions to the timing precision of these pulsars and show that most are not dominated by intrinsic pulse phase jitter noise. We also determine which pulsars should be timed with DSA and CHIME or only DSA and show that an ab initio DSA PTA is more sensitive than one which uses current instruments. Finally, we solve for the optimal integration time per pulsar, subject to a fixed time budget, that maximizes the GWB signal-to-noise. We show that there is little benefit to optimizing over integration time for these pulsars observed with DSA. Through Monte Carlo realizations of the PTA, we show that the GWB sensitivity improves by $\sim 5\%$ for time-optimized observations compared to the equal-time-per-source scenario with an early-science, fixed source list.

astro-ph.HE↗
arXiv2026

Constraints on Supermassive Black Hole Binaries from the Lack of Resolvable Sources in the NANOGrav 15-yr Dataset

Pulsar timing arrays (PTAs) have found evidence of a gravitational wave background (GWB) consistent with a population of supermassive black hole binaries (SMBHBs), but have not yet resolved a continuous wave (CW) from an individual binary. We present the first SMBHB population constraints incorporating PTA upper limits on CWs, based on the NANOGrav 15-year (NG15) data. Using semi-analytic models to generate simulated populations, we calculate each sample's GWB likelihood by free spectral comparison and CW nondetection (nCW) likelihoods by (1) mapping each realization's highest CW signal-to-noise ratio (S/N) to a detection probability and (2) counting the fraction of realizations without a binary close enough that NG15 would have detected it. CW nondetection favors populations in which many lower-mass sources, rather than a few ultramassive ones, dominate the GWB. This information is complementary to that provided by the GWB amplitude, breaking the degeneracy between the masses and number of binaries required to reproduce the observed spectrum. Relative to GWB-only constraints, the joint posteriors favor higher galaxy merger rates, lower $M_\mathrm{BH}$-$M_\mathrm{bulge}$ scatter, shorter binary lifetimes, and steeper small-separation hardening. The most detectable sources in the S/N-weighted joint posterior have chirp masses $\sim 10^{9.6} M_\odot$, luminosity distances $\sim$1300 Mpc, and frequencies $\sim$6 nHz, while the nCW-only constraints favor lower frequencies, coinciding with the NG15 4 nHz candidate. These constraints will tighten if CW nondetection continues.

astro-ph.HE↗
arXiv2026

Generalized Non-linear Bayesian Pulsar Timing with Enterprise

In this study, we use the Bayesian methods in the Enterprise package to examine the fully general parameterization of pulsar timing models in tandem with noise. We investigate four pulsars, PSR J1600$-$3053, PSR J2043+1711, PSR J0740+6620, and PSR J1640+2224, through the lens of Bayesian timing. These four are selected as they are well-studied, but exhibit interesting characteristics under the lens of Bayesian timing. Our new pulsar mass constraints (medians and 68\% confidence intervals) for our fully general non-linear Bayesian timing models are $m_{\mathrm{p}}=1.6(1)~\mathrm{M}_{\odot}$ for PSR J2043+1711 and $m_{\mathrm{p}}=2.3^{+0.9}_{-0.7}~\mathrm{M}_{\odot}$ for PSR J1600$-$3053 both using the NANOGrav 12.5-yr data release, and $m_{\mathrm{p}}=2.06(6)~\mathrm{M}_{\odot}$ for PSR J0740+6620 using the data from Fonseca, et al., 2021. We investigate the effects on placing physical priors on timing model parameters, including restricting the upper limit on the pulsar mass for PSR J1640+2224, which has a mass often estimated to be greater than $3~\mathrm{M}_{\odot}$. We find \ark{that restricting the allowed sampling space of the pulsar mass for PSR J1640+2224 to} $m_{\mathrm{p}}<3~\mathrm{M}_{\odot}$ results in a pulsar mass of $m_{\mathrm{p}}=2.2(5)~\mathrm{M}_{\odot}$ for PSR J1640+2224 using the NANOGrav 12.5-yr data release. For the first time, we find evidence for intrinsic red noise in PSR J2043+1711. We show how fully general Bayesian timing can better model the interplay of the intrinsic noise and the timing parameters.

astro-ph.HE↗
arXiv2026

Pulsar Timing Array Sensitivity to Anisotropy: Empirical Sensitivity Curves, Scaling Relations, and the Multi-Resolution Pixel Basis

We quantify pulsar timing array (PTA) sensitivity to anisotropy in the gravitational wave background using the cross-correlation based Fisher information matrix in the pixel and spherical harmonic bases. We use a set of simulations to empirically determine scaling relations of a PTA's sensitivity to anisotropy with the number of pulsars $N_\mathrm{psr}$ in the array, the error $δt$ on the times of arrival, the frequency $f_\mathrm{GW}$ of the gravitational waves, and the angular scale $ΔΩ$ of the anisotropy. The sensitivity scales approximately as $N_\mathrm{psr}^{0.8}$, $δt^{-0.08}$, and $ΔΩ^{1.6}-ΔΩ^{2.1}$ (depending on the ranges of $\ell$ and $m$ under consideration). In addition, we use realistic simulations to project the NANOGrav PTA sensitivity to a 30-year baseline and quantify the growth in sensitivity at several timeslices. Except at the lowest frequencies, we find negligible effect on sensitivity through increasing the observation duration only. Finally, we introduce a multi-resolution pixel basis motivated by the large dependence of the sensitivity on sky location, and demonstrate the operation of the basis through a set of injections and recoveries.

astro-ph.IM↗
arXiv2026

Gamma-ray and radio populations of millisecond pulsars in globular clusters

The populations of millisecond pulsars (MSPs) across the Milky Way's globular cluster (GC) system serve as powerful diagnostics of neutron star evolution in a variety of dense stellar environments. Using properties of 118 Galactic GCs, we performed Monte Carlo simulations of their gamma-ray fluxes observed by Fermi. We compared two luminosity models: a 3D fundamental plane (model A) and a lognormal distribution (model B). Both models reproduce the observed gamma-ray fluxes and mirror the scaling law with the GC stellar encounter rate established for low-mass X-ray binaries and radio MSPs. Due to its lower average gamma-ray luminosities, model B predicts a 6-7 times larger MSP population ($5150^{+720}_{-710}$) than model A ($770\pm60$). Furthermore, both models accurately predict a population-wide expectation of roughly three clusters whose aggregate gamma-ray emission is dominated by a single bright MSP. Invoking a radio-to-gamma-ray luminosity scaling ($L_r \sim 3.5 \times 10^{-7} L_γ$), we find that model B predicts a mean radio pseudoluminosity ($\log L_{\rm pseudo} \sim -1.6$) that is fainter than canonical pulsars. This result is consistent with recent evidence attributing the apparent faintness of Galactic MSPs to geometric effects. In contrast, model A implies an intrinsically brighter population ($\log L_{\rm pseudo} \sim -0.3$) that lacks a clear physical basis and is inconsistent with the results found for Galactic pulsars. The larger underlying population of faint millisecond pulsars predicted by model B could be probed by sensitive surveys with emerging radio facilities to further constrain the evolutionary pathways of MSPs.

astro-ph.HE↗
arXiv2026

Evaluating the Fourier Approximation in Pulsar Timing Array Analysis

Pulsar timing arrays search for stochastic processes such as gravitational waves by comparing pulse time of arrival data for millisecond pulsars to expectations from a background with a given power spectral density (PSD). To make the analysis computationally tractable, the Bayesian likelihood is usually computed using an approximation in which the signal is taken to be a sum of Fourier modes appropriate to the total time of observation, even though the true signal is not periodic. We study the difference between likelihoods computed with this Fourier approximation method for power law spectra and those computed exactly (or using more-closely spaced frequencies as a proxy for the exact result) in the NANOGrav 15-year dataset. We find that the true marginal likelihoods for power-law PSDs are on average about half as large as the likelihoods computed using the Fourier approximation. This could lead to an error of a factor of two in model comparison. However, in the important comparison of uncorrelated vs. Hellings-Downs correlated models, a very similar correction appears in both, so the model comparison is essentially unaffected. We also compare parameter estimation results for power law PSDs, finding little difference between the methods. We briefly discuss spectra with sharper features, for which the approximation could be much worse.

gr-qc↗
arXiv2026

A pulsar escaping an ancient open cluster via tidal stripping

Open clusters are the primary birthplaces of stars in the Milky Way disk, yet their neutron star progeny are rarely found within them, presumably due to supernova-induced kicks that eject them at birth. Here we report the arcsec-level localization of the pulsar PSR J1921+3745 to the tidal tail of NGC 6791, one of the oldest and most massive open clusters. Our N-body simulation shows that more than 95% of neutron stars formed in such clusters have been ejected. This pulsar's location in the tidal tail indicates it was retained for billions of years before being stripped by Galactic tides. This long-term retention requires low natal kicks, consistent with formation via electron-capture supernova. Our findings capture a rare snapshot of a neutron star transitioning into the Galactic field, identifying tidal stripping of ancient clusters as a verified source of the Galactic neutron star population.

astro-ph.HE↗
arXiv2026

The NANOGrav 15 yr Data Set: Impacts of Customized Chromatic Noise Models on Gravitational Wave Analyses

We report updated nHz gravitational wave (GW) significance, characterization, and interpretations using the customized chromatic-noise models (CNMs) developed in Larsen, Baier et al. (2026). for the NANOGrav 15-year data set. We find increased evidence for the Hellings-Downs (HD) correlation signature of the stochastic gravitational wave background (GWB), with a Bayes factor of $1571\pm14$ for HD-correlations over a common uncorrelated red-noise process using a power-law model with $14$ Fourier modes. We find this $\sim8\times$ increase in Bayes factor from Agazie et al. (2023a) is a result of improved noise mitigation. Assuming an analytic null distribution for the frequentist interpulsar correlation statistic, this corresponds to a slightly more significant measurement from $3.16σ$ to $3.32σ$ against the no-correlation scenario. Spectral inference with CNMs brings the power-law GWB amplitude down to $A_{\rm GWB} = 2.1^{+0.6}_{-0.5}\times10^{-15}$ at fixed $γ_{\rm GWB} = 13/3$. In a varied-$γ$ analysis, the spectral index increases to $γ_{\rm GWB}=3.5^{+0.7}_{-0.6}$. We report updates on an all-sky continuous gravitational wave (CW) search as well as select targeted searches and calculate a $3.2\times$ larger detection volume for the NANOGrav detector. With CNMs, we find reduced evidence for a non-Einsteinian, scalar-transverse mode of gravity. Finally, we reinterpret the GWB first with the assumption of an astrophysical background sourced by SMBHBs and then assuming the more exotic origins of cosmic inflation, a first-order cosmological phase transition, and stable cosmic strings. Under both the SMBHB hypothesis and the cosmological hypotheses, we see only marginal shifts in model parameter posteriors which are consistent with the slightly quieter and steeper power-law GWB spectrum.

astro-ph.CO↗
arXiv2026

The NANOGrav 15 yr Data Set: Customized Chromatic Noise Models

Pulsar timing arrays conduct low-frequency gravitational wave searches, which require comprehensive accounting of various noise sources to achieve robust results. Interstellar propagation effects (e.g., dispersion and scattering) are especially complex noise sources, introducing chromatic delays that can reduce sensitivity to gravitational waves and bias their inference if left unmodeled. These delays also strongly depend on the line of sight properties to each individual pulsar. To address this, we present customized chromatic noise models for 67 pulsars in the NANOGrav 15 yr dataset. These models are selected from an expanded suite of Gaussian processes to simultaneously characterize multiple types of chromatic delays and are tailored to each pulsar's dataset. Alongside probing the interstellar medium, we use these models to infer the solar wind electron density over the course of $\sim 1.5$ solar cycles. We also find evidence for non-dispersive chromatic delays in 21 out of 67 NANOGrav pulsars. After applying our chromatic models, we observe significant impacts on the inference of achromatic noise in 19 out of 67 pulsars, finding in several cases that a previously significant achromatic noise process can be partially or entirely described as chromatic. These results demonstrate that refined noise modeling is essential to enhance the sensitivity and accuracy of low-frequency gravitational wave searches with pulsar timing arrays.

astro-ph.HE↗
arXiv2026

Gravitational Wave Measurement of the $M_\mathrm{BH}$-$M_\mathrm{bulge}$ Intrinsic Scatter at High Redshift

The observed GWB spectrum is higher in amplitude than model predictions by a factor of 2-3. Using a semi-analytic model, we evaluate the effect of a high-scatter supermassive black hole (SMBH) scaling relation ($M_\mathrm{BH}$-$M_\mathrm{bulge}$) on models of the nanohertz gravitational wave background (GWB). By implementing an intrinsic scatter of the $M_\mathrm{BH}$-$M_\mathrm{bulge}$ relation, which is larger at higher redshift, but matches local observations, we find that the amplitude of GWB models increases to be consistent with the low-frequency end of the GWB spectrum. This amplitude increase is not uniform across frequencies, a strongly evolving scatter preferentially increases the number density of the most massive SMBHs which, in the GWB spectrum, minimizes the strength of the low-frequency turnover. Our models with positively evolving intrinsic scatter can reproduce the electromagnetically observed overmassive SMBHs at $4 < z < 6$ without changing the $M_\mathrm{BH}$-$M_\mathrm{bulge}$ normalization though we find that including moderate normalization evolution marginally improves fits to the GWB data. We conclude that the $M_\mathrm{BH}$-$M_\mathrm{bulge}$ relation which best describes the available GWB and electromagnetic data sets has intrinsic scatter that evolves as $\varepsilon(z) = \varepsilon_0 + (0.56 \pm 0.4) \log_{10}(1 + z)$ and normalization that evolves as $α(z) = α_0 (1 + z)^{0.84 \pm 0.35}$. The results of this work imply that the $M_\mathrm{BH}$-$M_\mathrm{bulge}$ relation we see today is not universal throughout cosmic time and that a diversity of seeding models and growth mechanisms may be at play in the early stages of SMBH-galaxy evolution.

astro-ph.HE↗
arXiv2026

The NANOGrav 15-Year Data Set: A Case Study for Simplified Dispersion Measure Modeling for PSR J1455-3330 and the Impact on Gravitational Wave Sensitivity

Evidence for a low-frequency gravitational-wave background using pulsar timing arrays has generated recent interest into its underlying contributing sources. However, multiple investigations have seen that the significance of the evidence does not change with choice of pulsar modeling techniques but the resulting parameters from the gravitational wave searches do. PSR J1455-3330 is one of the longest-observed pulsars in the array monitored by the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) but showed no evidence for long-timescale red noise, either intrinsic or the common signal found among many pulsars in the array. In this work, we argue that NANOGrav's piecewise-constant function used to model variations in radio-frequency-dependent dispersive delay should not be used for this pulsar, and a much simpler physical model of a fixed solar wind density plus a linear trend in dispersion measure is preferred. When the original model is replaced, (i) the pulsar's timing parallax signal changes from an upper limit to a significant detection, (ii) red noise becomes significant, and (iii) the red noise is consistent with the common signal found for the other pulsars. Neither of these signals are radio-frequency dependent. While the same physical motivation will not apply to many of the pulsars currently used in pulsar timing arrays, we argue for careful physically-motivated timing and noise modeling of pulsars used in precision timing experiments.

astro-ph.HE↗
arXiv2026

The RRATalog: a Galactic census of rotating radio transients

Rotating radio transients (RRATs) represent a significant but poorly understood component of the Galactic neutron star population, characterized by sporadic emission first detectable only through single-pulse searches. We present the RRATalog, an up-to-date catalogue of 335 RRATs, and utilize a uniform sample of RRATs discovered in four Parkes telescope surveys to model their Galactic population. Accounting in detail for observational selection effects, we find a radial density profile similar to pulsars, but identify a significantly steeper luminosity function (power-law index $α\simeq -1.3$) than previously assumed. For sources beaming towards Earth, we estimate $34000 \pm 1600$ potentially observable RRATs above a peak luminosity of 30 mJy kpc$^2$. At these high luminosities, the RRAT population is comparable in size to that of canonical pulsars. Consistent with the observed distribution, the underlying period distribution is significantly shifted toward longer periods compared to canonical pulsars, suggesting RRATs represent a more evolved population. We find evidence for a turnover in the luminosity function below 30 mJy kpc$^2$, and predict that the total number of potentially observable RRATs is $\lesssim 70,000$. Applying the Tauris \& Manchester beaming model, we estimate the total Galactic RRAT population to be $\lesssim 400,000$. The implied birth rate of $\lesssim 1.4$ RRATs per century is consistent with the Galactic core-collapse supernova rate, suggesting RRATs can be reconciled with known progenitor rates without requiring a separate evolutionary origin. We provide predictions for RRAT discoveries in ongoing and future surveys.

astro-ph.HE↗
arXiv2026

The NANOGrav 15 yr and 20 yr Datasets: Timing Events and Pulse Shape Changes

The average pulse shape of a pulsar is typically stable over decadal timescales, enabling estimation of pulse times of arrival to better than a small fraction of the pulse width using matched filtering techniques. However, in North American Nanohertz Observatory for Gravitational Waves (NANOGrav) observations of PSR J1713+0747, three discrete timing events that depart from the prevailing timing model have been seen in the last 20 yr. All three correspond to morphological changes in pulse shape. Using principal component analysis, we analyze the pulse profiles of nine NANOGrav pulsars, including seven with profiles from the 15 yr dataset and two with additional profiles from the forthcoming 20 yr dataset. We recover the three known pulse shape change events in PSR J1713+0747 and another previously known event in PSR J1643$-$1224. We implement a ranking metric for candidate events and address four highly ranked candidates in this nine-pulsar sample. We also recover known slow pulse shape variations in PSR J1643$-$1224, PSR J1903+0327, and PSR B1937+21 and report an unexpected recurrence after ~10 yr of one such variation in PSR B1937+21.

astro-ph.HE↗
arXiv2026

Searching for Exotrojans in Pulsar Systems

Trojan asteroids are found in the equilateral triangle Lagrange points of the Sun-Jupiter system in great number, though they also exist less prolifically in other parts of the Solar System. Despite up to planetary mass Trojans being predicted in extrasolar systems (i.e. exotrojans), they remain unconfirmed, although strong candidate evidence has emerged recently. For the first time, we extend the search for exotrojans to radio pulsars with low-mass ($\sim0.01\,\rm{M}_\odot$) companions using accurately measured pulse times of arrival. With techniques developed for detecting the reflex motion of a star due to a librating Trojan, we place $\sim 1\,\rm{M}_\oplus$ upper mass constraints on potential exotrojans around eight pulsars observed in the NANOGrav 15-year data set. We find weak evidence consistent with $\sim2$--4$\,\rm{M}_{\rm J}$ exotrojans in the PSR~J0023+0923 and PSR~J1705$-$1903 binary systems, though the signals likely have a different, unknown source. We also place a libration-independent upper mass constraint of $\sim8$\,M$_{\rm J}$ on exotrojans in the PSR~J1641+8049 system by looking for an inconsistency between the times of superior conjunction as measured by optical light curves and those predicted by radio timing. These results offer initial observational constraints on the existence of exotrojans around pulsars, while their possible formation mechanisms remain unexplored.

astro-ph.HE↗
arXiv2026

CHIME-o-Grav: Wideband Timing of Four Millisecond Pulsars from the NANOGrav 15-yr dataset

Wideband timing of the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) datasets, where a single time-of-arrival (TOA) and a single dispersion measure (DM) are measured using the entire bandwidth of each observation, was first done for the 12.5-year dataset, and proved to be invaluable for characterizing the time-varying dispersion measure, reducing the data volume, and for improving the overall timing precision. The Canadian Hydrogen Intensity Mapping Experiment (CHIME) Telescope has been observing most NANOGrav millisecond pulsars (MSPs) at nearly daily cadence (compared to roughly monthly cadence for other NANOGrav observations) since 2019 with the objective of integration into future pulsar timing array (PTA) datasets. In this paper, we show the results of integration of high-cadence, low-observing-frequency CHIME data with data from the NANOGrav experiment for an isolated MSP PSR J0645$+$5158 and three binary MSPs PSR J1012$+$5307, PSR J2145$-$0750, and PSR J2302$+$4442. Using a wideband timing pipeline which we also describe, we present updated timing results for all four sources, including improvements in measurements of relativistic post-Keplerian parameters for the three binary pulsars in this analysis. For PSR J2302$+$4442, we report an updated strong detection of Shapiro delay from which we measured a companion mass of $0.35^{+0.05}_{-0.04}\ M_{\odot}$, a pulsar mass of $1.8^{+0.3}_{-0.3}\ M_{\odot}$, and an orbital inclination of ${80^{\circ}}^{+1}_{-2}$. We also report updated constraints on the reflex motion for PSR J2145$-$0750 using a combination of Very Long Baseline Array astrometry and our updated measurement of the time derivative of the projected semi-major axis of the pulsar orbit as a prior.

astro-ph.HE↗