2024

Multi-source connectivity as the driver of solar wind variability in the heliosphere
S. L. Yardley et. al (including CfAR member David M. Long) 
Published in Nature Astronomy
The ambient solar wind that fills the heliosphere originates from multiple sources in the solar corona and is highly structured. It is often described as high-speed, relatively homogeneous, plasma streams from coronal holes and slow-speed, highly variable, streams whose source regions are under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify solar wind sources and understand what drives the complexity seen in the heliosphere. By combining magnetic field modelling and spectroscopic techniques with high-resolution observations and measurements, we show that the solar wind variability detected in situ by Solar Orbiter in March 2022 is driven by spatio-temporal changes in the magnetic connectivity to multiple sources in the solar atmosphere. The magnetic field footpoints connected to the spacecraft moved from the boundaries of a coronal hole to one active region (12961) and then across to another region (12957). This is reflected in the in situ measurements, which show the transition from fast to highly Alfvénic then to slow solar wind that is disrupted by the arrival of a coronal mass ejection. Our results describe solar wind variability at 0.5 au but are applicable to near-Earth observatories.

Observation of Alfvén Wave Reflection in the Solar Chromosphere: Ponderomotive Force and First Ionization Potential EffectM. Murabito et. al (including CfAR member David M. Long) 
Published in Physical Review Letters
We investigate the propagation of Alfvén waves in the solar chromosphere, distinguishing between upward and downward propagating waves. We find clear evidence for the reflection of waves in the chromosphere and differences in propagation between cases with waves interpreted to be resonant or nonresonant with the overlying coronal structures. This establishes the wave connection to coronal element abundance anomalies through the action of the wave ponderomotive force on the chromospheric plasma, which interacts with chromospheric ions but not neutrals, thereby providing a novel mechanism of ion-neutral separation. This is seen as a “first ionization potential effect” when this plasma is lifted into the corona, with implications elsewhere on the Sun for the origin of the slow speed solar wind and its elemental composition.

Identifying Plasma Fractionation Processes in the Chromosphere using IRIS
David M. Long (CfAR), Deborah Baker, Andy S. H. To, Lidia van Driel-Gesztelyi, David H. Brooks, Marco Stangalini, Mariarita Murabito, Alexander W. James, Mihalis Mathioudakis, and Paola Testa
Published in Astrophysical Journals
The composition of the solar corona differs from that of the photosphere, with the plasma thought to fractionate in the solar chromosphere according to the first ionization potential (FIP) of the different elements. This produces a FIP bias, wherein elements with a low FIP are preferentially enhanced in the corona compared to their photospheric abundance, but direct observations of this process remain elusive. Here, we use a series of spectroscopic observations of active region AR 12759 as it transited the solar disk over a period of 6 days from 2020 April 2–7 taken using the Hinode Extreme ultraviolet Imaging Spectrometer and Interface Region Imaging Spectrograph (IRIS) instruments to look for signatures of plasma fractionation in the solar chromosphere. Using the Si x/S x and Ca xiv/Ar xiv diagnostics, we find distinct differences between the FIP bias of the leading and following polarities of the active region. The widths of the IRIS Si iv lines exhibited clear differences between the leading and following polarity regions, indicating increased unresolved wave activity in the following polarity region compared to the leading polarity region, with the chromospheric velocities derived using the Mg ii lines exhibiting comparable, albeit much weaker, behavior. These results are consistent with plasma fractionation via resonant/nonresonant waves at different locations in the solar chromosphere following the ponderomotive force model, and indicate that IRIS could be used to further study this fundamental physical process.

Tracking the motion of a shock along a channel in the low solar corona
Jeremy Rigney, Peter T. Gallagher, Gavin Ramsay, J. Gerry Doyle, David M. Long (CfAR), Oleg Stepanyuk, Kamen Kozarev
Published in Astronomy and Astrophysics
Shock waves are excited by coronal mass ejections (CMEs) and large-scale extreme-ultraviolet (EUV) wave fronts and can result in low-frequency radio emission under certain coronal conditions. In this work, we investigate a moving source of low-frequency radio emission as a CME and an associated EUV wave front move along a channel of a lower density, magnetic field, and Alfvén speed in the solar corona.
Methods. Observations from the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory, the Nançay Radio Heliograph (NRH), and the Irish Low Frequency Array (I-LOFAR) were analysed. Differential emission measure maps were generated to determine densities and Alfvén maps, and the kinematics of the EUV wave front was tracked using CorPITA. The radio sources’ positions and velocity were calculated from NRH images and I-LOFAR dynamic spectra. The EUV wave expanded radially with a uniform velocity of ∼500 km s−1. However, the radio source was observed to be deflected and appeared to move along a channel of a lower Alfvén speed, abruptly slowing from 1700 km s−1 to 250 km s−1 as it entered a quiet-Sun region. A shock wave with an apparent radial velocity of > 420 km s−1 was determined from the drift rate of the associated Type II radio burst. The apparent motion of the radio source may have resulted from a wave front moving along a coronal wave guide or by different points along the wave front emitting at locations with favourable conditions for shock formation.

Acceleration and transport of relativistic electrons in the jets of the microquasar SS 433
The H.E.S.S. collaboration (including CfAR member R. Brose)
Published in Science
SS 433 is a microquasar, a stellar binary system that launches collimated relativistic jets. We observed SS 433 in gamma rays using the High Energy Stereoscopic System (H.E.S.S.) and found an energy-dependent shift in the apparent position of the gamma-ray emission from the parsec-scale jets. These observations trace the energetic electron population and indicate that inverse Compton scattering is the emission mechanism of the gamma rays. Our modeling of the energy-dependent gamma-ray morphology constrains the location of particle acceleration and requires an abrupt deceleration of the jet flow. We infer the presence of shocks on either side of the binary system, at distances of 25 to 30 parsecs, and that self-collimation of the precessing jets forms the shocks, which then efficiently accelerate electrons.

The radio to GeV picture of PSR B1259-63 during the 2021 periastron passage
M. Chernyakova (CfAR), D. Malyshev, B. van Soelen, S. Mc Keague (CfAR), S.P. O'Sullivan, D. Buckley.
Published in Monthly Notices of the Royal Astronomical Society
​PSR B1259-63 is a gamma-ray binary system with a radio pulsar orbiting an O9.5Ve star, LS 2883, with a period of ~3.4 yr. Close to the periastron the system is detected at all wavelengths, from radio to the TeV energies. The emission in this time period is believed to originate from the interaction of LS 2883 and pulsar's outflows. The observations of 4 periastra passages taken in 2010-2021 show strong correlation of the radio and X-ray lightcurves with two peaks just before and after the periastron. The observations of the latest 2021 periastron passage reveal the presence of the 3rd X-ray peak and subsequent disappearance of radio/X-ray flux correlation. In this paper we present the results of our optical, radio and X-ray observational campaigns on PSR B1259-63 performed in 2021 accompanied with the analysis of the publicly available GeV FERMI/LAT data. We compare the properties of different periastron passages, discuss the obtained results and show that they can be explained in terms of the 2-zone emission cone model proposed by us previously.
​
2023

Using machine learning to predict the correlation of spectra using SDSS magnitudes as an improvement to the Locus Algorithm
E. Hickey, O. Creaner (CfAR), K. Nolan, T. O’Flynn
Published in New Astronomy
The Locus Algorithm is a new technique to improve the quality of differential photometry by optimising the choices of reference stars. At the heart of this algorithm is a routine to assess how good each potential reference star is by comparing its SDSS magnitude values to those of the target star. In this way, the difference in wavelength-dependent effects of the Earth’s atmospheric scattering between target and reference can be minimised. This paper sets out a new way to estimate the quality of each reference star using machine learning. A random subset of stars from SDSS with spectra was chosen. For each one, a suitable reference star, also with a spectrum, was chosen. The correlation between the two spectra in the SDSS r band (between 550 nm and 700 nm) was taken to be the gold-standard measure of how well they match up for differential photometry. The five SDSS magnitude values for each of these stars were used as predictors. A number of supervised machine learning models were constructed on a training set of the stars and were each evaluated on a testing set. The model using Support Vector Regression had the best performance of these models. It was then tested on a final, hold-out, validation set of stars to get an unbiased measure of its performance. With an R² of 0.62, the SVR model presents enhanced performance for the Locus Algorithm technique.

Automation of MKID Simulations for Array Building With AEM (Automated Electromagnetic MKID simulations)
C. McAleer, O. Creaner (CfAR), C. Bracken, G. Ulbricht, M. De Lucia, J. Piercy, T. Ray
Microwave Kinetic Inductance Detectors (MKIDs) are photon detectors comprised of superconducting LC resonators with unique resonant frequencies corresponding to their geometrical structure. As each pixel has a unique resonance, simulations of every pixel in a kilo pixel array are impractical and current methods of interpolation across pixels are shown to lead to reduced pixel yield. We introduce a new software called AEM (Automated Electromagnetic MKID simulations) that automates the construction and simulation of every simulated MKID pixel in an array according to specified resonant frequencies and a Q c range. We show automated designs to have an increased pixel yield, accuracy in resonance frequency and Q c value when compared to interpolated structures. We also demonstrate a simulated trial of AEM for 100 MKIDs between 4–8 GHz to produce MKIDs with accuracies of±0.188 MHz with a runtime of 10 hours 45 minutes.

First dark matter search results from the LUX-ZEPLIN (LZ) experiment
Lux-Zeplin Collaboration (including CfAR member Oisin Creaner)
Published in Physical Review Letters
The LUX-ZEPLIN experiment is a dark matter detector centered on a dual-phase xenon time projection chamber operating at the Sanford Underground Research Facility in Lead, South Dakota, USA. This Letter reports results from LUX-ZEPLIN's first search for weakly interacting massive particles (WIMPs) with an exposure of 60 live days using a fiducial mass of 5.5 t. A profile-likelihood ratio analysis shows the data to be consistent with a background-only hypothesis, setting new limits on spin-independent WIMP-nucleon, spin-dependent WIMP-neutron, and spin-dependent WIMP-proton cross sections for WIMP masses above 9 GeV/c2. The most stringent limit is set for spin-independent scattering at 36 GeV/c2, rejecting cross sections above 9.2× 10-48 cm at the 90% confidence level.

The Eruption of a Magnetic Flux Rope observed by Solar Orbiter and Parker Solar Probe
D. M. Long (CfAR) et al.
Published in The Astrophysical Journal
Magnetic flux ropes are a key component of coronal mass ejections, forming the core of these eruptive phenomena. However, determining whether a flux rope is present prior to eruption onset and, if so, the rope's handedness and the number of turns that any helical field lines make is difficult without magnetic field modeling or in situ detection of the flux rope. We present two distinct observations of plasma flows along a filament channel on 2022 September 4 and 5 made using the Solar Orbiter spacecraft. Each plasma flow exhibited helical motions in a right-handed sense as the plasma moved from the source active region across the solar disk to the quiet Sun, suggesting that the magnetic configuration of the filament channel contains a flux rope with positive chirality and at least one turn. The length and velocity of the plasma flow increased from the first to the second observation, suggesting evolution of the flux rope, with the flux rope subsequently erupting within ~5 hr of the second plasma flow. The erupting flux rope then passed over the Parker Solar Probe spacecraft during its encounter (13), enabling in situ diagnostics of the structure. Although complex and consistent with the flux rope erupting from underneath the heliospheric current sheet, the in situ measurements support the inference of a right-handed flux rope from remote-sensing observations. These observations provide a unique insight into the eruption and evolution of a magnetic flux rope near the Sun.

​Multistage Reconnection Powering a Solar Coronal Jet
D. M. Long (CfAR) et al.
Published in The Astrophysical Journal
Coronal jets are short-lived eruptive features commonly observed in polar coronal holes and are thought to play a key role in the transfer of mass and energy into the solar corona. We describe unique contemporaneous observations of a coronal blowout jet seen by the Extreme Ultraviolet Imager (EUI) on board the Solar Orbiter (SO) spacecraft and the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO). The coronal jet erupted from the south polar coronal hole, and was observed with high spatial and temporal resolution by both instruments. This enabled identification of the different stages of a breakout reconnection process producing the observed jet. We find bulk plasma flow kinematics of ~100-200 km s-1 across the lifetime of its observed propagation, with a distinct kink in the jet where it impacted and was subsequently guided by a nearby polar plume. We also identify a faint faster feature ahead of the bulk plasma motion propagating with a velocity of ~715 km s-1, which we attribute to untwisting of newly reconnected field lines during the eruption. A differential emission measure (DEM) analysis using the SDO/AIA observations revealed a very weak jet signal, indicating that the erupting material was likely much cooler than the coronal passbands used to derive the DEM. This is consistent with the very bright appearance of the jet in the Lyα passband observed by SO/EUI. The DEM was used to estimate the radiative thermal energy of the source region of the coronal jet, finding a value of ~2 × 1024 erg, comparable to the energy of a nanoflare.

Understanding the Relationship between Solar Coronal Abundances and F10.7cm Radio Emission
A.S.H. To, D. M. Long (CfAR) et al.
Published in The Astrophysical Journal
Sun-as-a-star coronal plasma composition, derived from full-Sun spectra, and the F10.7 radio flux (2.8 GHz) have been shown to be highly correlated (r = 0.88) during solar cycle 24. However, this correlation becomes nonlinear during increased solar magnetic activity. Here we use cotemporal, high spatial resolution, multiwavelength images of the Sun to investigate the underlying causes of the nonlinearity between coronal composition (FIP bias) and F10.7 solar index correlation. Using the Karl G. Jansky Very Large Array, Hinode/EIS (EUV Imaging Spectrometer), and the Solar Dynamics Observatory, we observed a small active region, AR 12759, throughout the solar atmosphere from the photosphere to the corona. The results of this study show that the magnetic field strength (flux density) in active regions plays an important role in the variability of coronal abundances, and it is likely the main contributing factor to this nonlinearity during increased solar activity. Coronal abundances above cool sunspots are lower than in dispersed magnetic plage regions. Strong magnetic concentrations are associated with stronger F10.7 cm gyroresonance emission. Considering that as the solar cycle moves from minimum to maximum, the sizes of sunspots and their field strength increase with the gyroresonance component, the distinctly different tendencies of radio emission and coronal abundances in the vicinity of sunspots is the likely cause of saturation of Sun-as-a-star coronal abundances during solar maximum, while the F10.7 index remains well correlated with the sunspot number and other magnetic field proxies.

Global Hadamard form for the Green's function in Schwarzschild spacetime
M. Casals and B.C. Nolan (CfAR)
Published in Physical Review D
The retarded Green function of a wave equation on a 4-dimensional curved background spacetime is a (generalized) function of two spacetime points and diverges when these are connected by a null geodesic. The Hadamard form makes explicit the form of this divergence but only when one of the points is in a normal neighborhood of the other point. In this paper we derive a representation for the retarded Green function for a scalar field in Schwarzschild spacetime which makes explicit its complete singularity structure beyond the normal neighborhood. We interpret this representation as a sum of Hadamard forms, the summation being taken over the number of times the null wavefront has passed through a caustic point; the sum of Hadamard forms applies to the nonsmooth contribution to the full Green function, not only the singular contribution. (The term nonsmooth applies modulo the causality-generating step functions that must appear in the retarded Green function.) The singularity structure is determined using two independent approaches, one based on a Bessel function expansion of the Green function, and another that exploits a link between the Green functions of Schwarzschild spacetime and Plebański-Hacyan spacetime (the latter approach also yields another representation for the full Schwarzschild Green function, not just for its nonsmooth part). Our representation is not valid in a neighborhood of caustic points. We deal with these points by providing a separate representation for the Green function in Schwarzschild spacetime which makes explicit its (different) singularity structure at caustics of this spacetime.

Renormalized stress-energy tensor for scalar fields in Hartle-Hawking, Boulware, and Unruh states in the Reissner-Nordström spacetime
J. Arrechea, C. Breen, A. Ottewill, P. Taylor (CfAR)
Published in Physical Review D
In this paper, we consider a quantum scalar field propagating on the Reissner-Nordström black hole spacetime. We compute the renormalized stress-energy tensor for the field in the Hartle-Hawking, Boulware and Unruh states. When the field is in the Hartle-Hawking state, we renormalize using the recently developed “extended coordinate” prescription. This method, which relies on Euclidean techniques, is very fast and accurate. Once, we have renormalized in the Hartle-Hawking state, we compute the stress-energy tensor in the Boulware and Unruh states by leveraging the fact that the difference between stress-energy tensors in different quantum states is already finite. We consider a range of coupling constants and masses for the field and a range of electric charge values for the black hole, including near-extreme values. Lastly, we compare these results with the analytic approximations available in the literature.

Energy-dependent periodicities of LS I +61°303 in the GeV band
M. Chernyakova (CfAR), D. Malyshev, A. Neronov, D. Savchenko
Published in Monthly Notices of the Royal Astronomical Society
LS I +61°303 is a rare representative of the gamma-ray binaries with a compact object known to be a pulsar. We report on the periodicity and spectral analysis of this source performed with more than 14 yr of Fermi/LAT data. The periodicity of LS I +61°303 is strongly energy dependent. Two periods P1 = 26.932 ± 0.004(stat) ± 0.008(syst) and P2 = 26.485 ± 0.004(stat) ± 0.007(syst) are detected only at E > 1 GeV and at E < 0.3 GeV correspondingly. Within 1σ (stat + syst) the periods are consistent with orbital (P2) and beat orbital/superorbital (P1) periods. We present the orbital light curves of the system in several energy bands and the results of the spectral analysis. We discuss the possible origin of the change in the variability pattern between 0.1 and 1 GeV energy.

On the nature of the energy-dependent morphology of the composite multi-TeV Gamma-Ray source HESS J1702-204
F. Aharonian, D. Malyshev, M. Chernyakova (CfAR)
Published in The Astrophysical Journal
HESS J1702-420 is a multi-TeV gamma-ray source with an unusual energy-dependent morphology. The recent H.E.S.S. observations suggest that the emission is well described by a combination of the point-like HESS J1702-420A (dominating at highest energies, ≳30 TeV) and diffuse (~0.°3) HESS J1702-420B (dominating below ≲5 TeV) sources with very hard (Γ ~ 1.5) and soft (Γ ~ 2.6) power-law spectra, respectively. Here, we propose a model that postulates that the proton accelerator is located at the position of HESS J1702-420A and is embedded into a dense molecular cloud that coincides with HESS J1702-420B. In the proposed model, the very-high-energy radiation of HESS J1702-420 is explained by pion-decay emission from the continuously injected relativistic protons propagating through a dense cloud. The energy-dependent morphology is defined by the diffusive nature of the low-energy proton propagation, transiting sharply to (quasi) ballistic propagation at higher energies. Adopting a strong energy dependence of the diffusion coefficient, D ∝ E β with β ≥ 1, we argue that HESS J1702-420 as a system of two gamma-ray sources is the result of the propagation effect. Protons injected by a single accelerator at a rate Q0≃1038(n0/100cm−3)−1(d/0.25kpc)−1ergs−1 can reasonably reproduce the morphology and fluxes of the two gamma-ray components.

H.E.S.S. Follow-up Observations of GRB 221009A
The H.E.S.S. collaboration (including CfAR member R. Brose)
Published in The Astrophysical Journal Letters
GRB 221009A is the brightest gamma-ray burst (GRB) ever detected. To probe the very-high-energy (VHE; >100 GeV) emission, the High Energy Stereoscopic System (H.E.S.S.) began observations 53 hr after the triggering event, when the brightness of the moonlight no longer precluded observations. We derive differential and integral upper limits using H.E.S.S. data from the third, fourth, and ninth nights after the initial GRB detection. The constraints derived from the H.E.S.S. observations complement the available multiwavelength data. The radio to X-ray data are consistent with synchrotron emission from a single electron population, with the peak in the spectral energy distribution occurring above the X-ray band. Compared to the VHE-bright GRB 190829A, the upper limits for GRB 221009A imply a smaller gamma-ray to X-ray flux ratio in the afterglow. Even in the absence of a detection, the H.E.S.S. upper limits thus contribute to the multiwavelength picture of GRB 221009A, effectively ruling out an IC-dominated scenario.

EMU Detection of a Large and Low Surface Brightness Galactic SNR G288.8-6.3
Filipović, Miroslav D. et al. (including CfAR member R. Brose)
Published in The Astronomical Journal
We present the serendipitous detection of a new Galactic supernova remnant (SNR), G288.8-6.3, using data from the Australian Square Kilometre Array Pathfinder (ASKAP) Evolutionary Map of the Universe (EMU) survey. Using multifrequency analysis, we confirm this object as an evolved Galactic SNR at high Galactic latitude with low radio surface brightness and typical SNR spectral index of α = - 0.41 ± 0.12. The angular size of the remnant is 1.°8 × 1.°6 (107.'6 × 98.'4), and we estimate that its intrinsic size is ~40 pc, which implies a distance of ~1.3 kpc and a position of ~140 pc above the Galactic plane. This is one of the largest in angular size and closest Galactic SNRs. Given its low radio surface brightness, we suggest that it is about 13,000 yr old.

Paper by CfAR researcher Prof. Masha Chernyakova features on RTE Brainstorm
The research reports on the sudden change of the periodicity in the gamma-ray binary LSI +61 303 in the GeV band.
The RTE article can be accessed here.
To read Prof. Chernyakova's scientific article, click here.

Paper by CfAR Director Prof. Turlough Downes features as a scientific highlight in the ALMA newsletter
The ALMA newsletter can be accessed here.
To read Prof. Downes scientific article, click here.

Length-scales and dynamics of Carina's Western wall
T. P. Downes (CfAR), P. Hartigan and A. Isella
Published in Monthly Notices of the Royal Astronomical Society
We analyse observations of a photo-dissociation region in the Carina Nebula (the so-called Western Wall). Through the use of well-known analysis such as Principal Component Analysis, as well as a new analysis involving wavelets developed for this work, we identify that the length-scale of 0.02 pc to 0.03 pc is important for the dynamics here. We suggest that this length-scale is engendered by the interplay between the turbulent cascade and self-gravity. Finally, we demonstrate that analysis of the shape of a photo-dissociation region can give important information about the density structures in the associated undisturbed molecular cloud.

2022

ALMA Data Cubes and Continuum Maps of the Irradiated Western Wall in Carina
P. Hartigan, M. Hummel, A. Isella and T. P. Downes (CfAR).
Published in Astronomical Journal
This paper presents ALMA observations of the Western Wall in Carina. We identify 254 distinct, possibly star-forming, cores which have a mass distribution similar to the stellar Initial Mass Function. We don't find any direct evidence for triggered star formation, despite the intense radiation field from nearly OB associations, although the densest part of the cloud lies closest to the photo-dissociation region which hints at this.

Stellar versus Galactic: The intensity of energetic particles at the evolving Earth and young exoplanets
D. Rodgers-Lee, A. Vidotto, A. Taylor, P. Rimmer and T.P.Downes (CfAR)
Published in 37th International Cosmic Ray Conference
Energetic particles produced by a young Sun may have been important for the origin of life on Earth
by driving the formation of prebiotic molecules. In this work we calculate the intensity of energetic particles, both from
the Sun and from our Galaxy, on Earth at a time when life is thought to have begun. The model is also applied to a young,
warm Jupiter-like planet orbiting at 20AU from its host star (HR2562b).

Mode-sum prescription for the renormalized stress-energy tensor on black hole spacetimes
P. Taylor (CfAR), C. Breen and A.C. Ottewill.
Published in Physical Review D
In this paper, we describe an extremely efficient method for computing the renormalized stress-energy tensor of a quantum scalar field in spherically symmetric black hole spacetimes. The method applies to a scalar field with arbitrary field parameters. We demonstrate the utility of the method by computing the renormalized stress-energy tensor for a scalar field in the Schwarzschild black hole spacetime, applying our results to discuss the null energy condition and the semiclassical backreaction.

Response of an Unruh-DeWitt detector near an extremal black hole
A. Conroy and P. Taylor (CfAR).
Published in Physical Review D
We consider the response of an Unruh-DeWitt detector near an extremal charged black hole, modeling the near-horizon region of this extremal spacetime by the Bertotti-Robinson spacetime. The advantage of employing the Bertotti-Robinson limit is that the two-point functions for a massless scalar field are obtainable in closed form for the field in a number of quantum states of interest. We consider the detector coupled to a massless field in both the Boulware vacuum state and arbitrary thermal states, including the Hartle-Hawking state, and analyze the detector’s response for a broad range of trajectories. Particular attention is paid to the thermalization of the detector, the anti-Unruh and anti-Hawking effect.

Improved binary solution for the gamma-ray binary 1FGL J1018.6-5856
Published in Monthly Notices of the Royal Astronomical Society
B. van Soelen, S. McKeague (CfAR), D. Malyshev, M. Chernyakova (CfAR), N. Komin, N. Matchett, I.M. Monageng
Using new observations of 1FGL J1018.6-5856 with SALT, along with analysis of X-ray and GeV observations, an improved binary solution has been found for the system, starting with a refined periodicity based on searches made in the Fermi-LAT observational data.

Spin Hall effects and the localization of massless spinning particles
A.I. Harte (CfAR) and M.A. Oancea
Published in Physical Review D
The path of a light ray can be affected by its angular momentum. This is described in the optics community as the "spin Hall effect." It and related concepts, such as Wigner translations, are shown in this paper to be special cases of old results in the general relativistic theory of extended-body motion. This paper also demonstrates that light with angular momentum must have mass. In fact, massless spinning objects are shown to be impossible without violating energy conditions. If a massless spinning object did exist, it would have pathological properties: Reasonably-defined centroids could lie arbitrarily far from the object itself, invalidating any simple description for its motion. While light with angular momentum is "almost" massless, this is shown to be a delicate approximation which must be treated with care. 

The Faraday Rotation Measure Grid of the LOFAR Two-metre Sky Survey: Data Release 2
S. P. O'Sullivan (CfAR), T. W. Shimwell, M. J. Hardcastle, C. Tasse, G. Heald, E. Carretti, M. Brüggen, V. Vacca, C. Sobey, C. L. Van Eck, C. Horellou, R. Beck, M. Bilicki, S. Bourke, A. Botteon, J. H. Croston, A. Drabent, K. Duncan, V. Heesen, S. Ideguchi, M. Kirwan, L. Lawlor, B. Mingo, B. Nikiel-Wroczyński, J. Piotrowska, A. M. M. Scaife, R. J. van Weeren
Published in Monthly Notices of the Royal Astronomical Society (MNRAS)
Description paper of a publicly released catalogue of extragalactic Faraday rotation measure values, derived using data from the LOFAR radio telescope. This work is part of Data Release 2 from the LOFAR Two-metre Sky Survey (LoTSS), covering ~27% of the Northern sky. This catalogue is a valuable resource for the study of cosmic magnetism. 

Detection of magnetic fields in the circumgalactic medium of nearby galaxies using Faraday rotation
V. Heesen, S. P. O'Sullivan (CfAR), M. Brüggen, A. Basu, R. Beck, A. Seta, E. Carretti, M. G. H. Krause, M. Haverkorn, S. Hutschenreuter, A. Bracco, M. Stein, D. J. Bomans, R.-J. Dettmar, K. T. Chyży, G. H. Heald, R. Paladino, C. Horellou
Published in Astronomy & Astrophysics (A&A)
Using the Faraday rotation measure values from the catalogue of O’Sullivan et al. (2023), we find evidence for the existence of strong magnetic fields in the circumgalactic medium in a region extending from the minor axes of nearby star-forming galaxies. 

Magnetic field evolution in cosmic filaments with LOFAR data
E. Carretti, S. P. O'Sullivan, V. Vacca, F. Vazza, C. Gheller, T. Vernstrom, A. Bonafede
Published in Monthly Notices of the Royal Astronomical Society (MNRAS)
Here we compare the redshift evolution of the Faraday rotation measure associated with filaments of the cosmic web of structure with cosmological MHD numerical simulations. This allows us to rule out specific models for the origin of cosmic magnetic fields, in addition to indicating plausible magnetogenesis scenarios which are still consistent with the data. 

The redshift evolution of extragalactic magnetic fields
​Valentin Pomakov, Shane P. O'Sullivan, Marcus Bruggen, Franco Vazza, Ettore Carretti, George Heald, Cathy Horellou, Timothy Shimwell, Aleksandar Shulevski, Tessa Vernstrom
Published in Monthly Notices of the Royal Astronomical Society (MNRAS)
We use observations of close pairs of Faraday rotation measure values on the sky, in combination with a Monte Carlo model of extragalactic magnetic fields, to provide a robust upper limit on the strength of a uniform, primordial magnetic field. 

Frequency Domain Multiplexing for Microwave Kinetic Inductance Detectors: Comparing the Xilinx ZCU111 RFSoC with their new 2x2 RFSoC board
Baldwin, De Lucia, Bracken, Ulbricht, Creaner (CfAR), Piercy, Ray
Published in Journal of Low Temperature Physics 

A Next-Generation Liquid Xenon Observatory for Dark Matter and Neutrino Physics
The XENONnT Collaboration, The LUX-ZEPLIN (LZ) Collaboration, The DARWIN collaboration et al.
Published in Journal of Physics G

Cosmogenic production of 37Ar in the context of the LUX-ZEPLIN experiment 
The LUX-ZEPLIN (LZ) Collaboration
Published in Physical Review D

Repurposing ROACH-1 boards for prototyping of readout systems for optical-NIR MKIDs
O. Creaner (CfAR), C. Bracken, J. Piercy, G. Ulbricht, E. Baldwin, M. De Lucia, T. Ray
Published in X-Ray, Optical, and Infrared Detectors for Astronomy X 
Highly uniform superconducting Titanium Nitride – Titanium multilayers for MKIDs arrays for astronomical applications
M. De Lucia, J. D. Piercy, G. Ulbricht, E. Baldwin, O. Creaner (CfAR), C. Bracken and T. Ray
Published in X-Ray, Optical, and Infrared Detectors for Astronomy X

The Locus Algorithm: The design, implementation and performance characterisation of a software and grid computing system to optimise the quality of fields of view for differential photometry
O. Creaner (CfAR), E. Hickey, J. Walsh, K. Nolan
Published in Astronomy and Computing  
The Locus Algorithm: A technique for identifying optimised pointings for differential photometry
Creaner (CfAR), Nolan, Hickey and Smith
Published in Astronomy and Computing