Solar and Stellar Astrophysics
Early Planet Formation in Embedded Disks (eDisk). XXIV: Systematic Investigation of Disk Structures based on Visibility Analysis
Mayank Narang, Jerry Xu, Leslie W. Looney et al. (+11 more)
The dust continuum emission from young protostellar disks encodes key information about their mass distribution and early
evolution, yet uniform high-resolution comparative studies remain limited. We present a systematic uv-plane analysis of parametric intensity models applied to ALMA Band-6 (1.3 mm) observations of 23 disks (19 protostellar systems with 4 being in binary) from the eDisk sample, spanning Gaussian profiles to power-law cores with exponential tails (PLCT), including asymmetric extensions. Gaussian models generally fail to reproduce the centrally peaked emission and extended outer structure observed in most disks, whereas the PLCT framework provides a significantly improved description of radial brightness profiles. Incorporating azimuthal asymmetries further reduces residuals in 15 of 17 inclined disks, indicating that departures from axisymmetry are common at early stages. Only two disks, L1489 IRS and Oph IRS63, exhibit clear gap and ring substructures, while most appear smooth at the spatial resolution and sensitivity of our observations. These systems are among the most evolved in the sample, and the absence of flat-spectrum sources limits the evolutionary range probed, {suggesting that the detection of prominent gaps and rings is not common} in the earliest phases of disk
evolution. Using a uniform definition of disk radius based on the 95% enclosed flux, we find a positive correlation with stellar mass, $R_{\rm disk} \propto M_{\star}^{1.5 \pm 0.1}$, with disks in binary systems systematically smaller than those around isolated protostars. While the models capture overall morphology and large-scale asymmetries, distinguishing intrinsic structures from radiative transfer effects in optically thick regions remains challenging.
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All authors Mayank Narang, Jerry Xu, Leslie W. Looney, Nagayoshi Ohashi, Anika Khandavalli, Patrick Sheehan, Jonathan P. Williams, Shigehisa Takakuwa, Jes K. Jørgensen, Ilseung Han, Woojin Kwon, Zhi-Yun Li, Nguyen Thi Phuong, John J. Tobin
Solar and Stellar Astrophysics
ALMA high resolution observations of Betelgeuse: Persistent structure spanning the inner atmosphere
W.R.F. Dent, A.M.S. Richards, G.M. Harper et al. (+2 more)
The extended atmosphere of red supergiants (RSGs) forms an important link in the process of mass loss and the subsequent enrichment of the interstellar medium. Large-scale convection is thought to play a significant role, which is likely to result in irregularities in the surface. High resolution, high contrast sub-mm images of Betelgeuse - one of the closest RSGs - are used to probe the structure and temporal stability of the inner 1-2$R_\star$ of its atmosphere. Using ALMA in the longest baseline configuration, continuum emission and lines of SiO and CO and their isotopomers were observed at $\lambda$0.6-1.4mm, giving beamwidths down to 7mas at the shortest wavelengths. These were compared with a similar observation taken at 0.9mm approximately 7 years earlier. The observed continuum emission arises mostly from an optically-thick mm/sub-mm photosphere of radius 1.1-1.3$R_\star$ with a relatively constant temperature of $\sim$2300K, but with two hotter patches to the NE and SW. The brightest of these has a temperature enhancement of $\sim$800K, and its location and intensity appears relatively unchanged since the 2015 observation. The sub-mm photosphere shows deviations of up to $\pm$ 6% in radius, with weaker continuum extending out to $\sim$2.5$R_\star$ - similar to the extent of clumpy emission in SiO and CO. The hot regions of gas and deviations from radial
symmetry are thought to be associated with active shocks driven by underlying convective
cells, although their lifetimes appear longer than model predictions. They lie near the proposed poles of the
star, which might suggest enhanced and relatively stable polar convection. The present data show no clear evidence for stellar rotation in the extended line emission or absorption against the photosphere, although the structure of the gas emission has changed significantly since 2015.
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All authors W.R.F. Dent, A.M.S. Richards, G.M. Harper, L.D. Matthews, E. O'Gorman
Instrumentation and Methods for Astrophysics
Design, assembly, and initial test results of a cryostat for holographic characterization of microwave telescopes
Jon E. Gudmundsson, Miranda Eiben, Thomas J.L.J. Gascard et al. (+1 more)
We describe the design, fabrication, assembly, and room-temperature
vacuum qualification of a 1.4-m long cylindrical cryostat developed for holographic testing of cryogenic microwave
telescope optics. The system consists of a welded 6061-aluminum
vacuum vessel containing nested 45- and 4-K aluminum radiation shields, cooled by a two-stage pulse-tube cryocooler through commercial OFHC copper flexible thermal straps. The intermediate 45-K stage intercepts radiative, conductive, and wiring heat loads from room temperature, while the 4-K stage defines the volume used for optical testing. The cryostat includes a 38-cm aperture for a microwave-transparent
vacuum window and is sized to accommodate full-scale optical assemblies relevant to
cosmic microwave background instrumentation. We summarize the cryostat architecture, lightweighted radiation shields, G-10 support flexures, welded
vacuum-vessel fabrication, and room-temperature leak-checking campaign. Iterative helium leak checking and weld repair reduced the observed leak rate in the cryostat by over three orders of magnitude.
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All authors Jon E. Gudmundsson, Miranda Eiben, Thomas J.L.J. Gascard, Eve M. Vavagiakis
High Energy Astrophysical Phenomena
The intrinsic luminosity-decay correlation in subsamples of GRB X-ray afterglows
S. P. R. Shilling, S. R. Oates, J. L. Racusin et al. (+6 more)
The intrinsic luminosity-decay correlation in gamma-ray burst (GRB) afterglows, between the early-time luminosity and the average rate of decay past this time, has previously been observed in the
radio, optical/UV, X-ray and GeV wavebands and quantitatively shows that more luminous afterglows tend to have higher average rates of decay. We have compiled an updated sample of 427 X-ray afterglows with measured
redshifts, observed with Swift/XRT over 20 years. For each GRB, we measure the luminosity at 200 seconds in the rest frame, $L_{\mathrm{X,200s}}$, and the average rate of decay from this time, $\alpha_{X,>200s}$. We find these parameters are correlated with a Spearman's rank coefficient ($R_\mathrm{sp}$) of $0.54\pm0.04$ at a significance of $\geq3\sigma$ and a linear regression slope of $0.18\pm0.02$. We separate our sample into subsamples, including 395 long GRBs (LGRBs) and 32 short GRBs (SGRBs) and find evidence of the $L_{\mathrm{X,200s}}$-$\alpha_{X,>200s}$ correlation at a significance of $\geq3\sigma$ in LGRBs but not in SGRBs, consistent with previous studies. In a subsample of 102 LGRBs with well-sampled light curves and late end times, we find that scatter in the correlation is significantly reduced and the strength increases to $R_\mathrm{sp}=0.80\pm0.04$ whilst the slope remains consistent with the full sample. We discuss our results and, briefly, their potential implications on constraining the cause of the correlation. Possible causes include
geometric effects due to the angle between the observer and the jet-axis, or some mechanism that regulates the rate at which energy is released by the GRB central engine.
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All authors S. P. R. Shilling, S. R. Oates, J. L. Racusin, B. Cenko, R. Gupta, P. Nuessle, M. Smith, G. P. Lamb, C. Turnbull
Earth and Planetary Astrophysics
Substructure evolution from protoplanetary to debris disks driven by mutually gravitating planetesimals and implications on Kepler resonances and free-floating planets
Yinuo Han, Konstantin Batygin and Fei Dai
Motivated by recent observations suggesting rings found in debris disks are wider than those in protoplanetary disks, we consider a picture in which planetesimals formed in radially narrow dust traps radially diffuse into debris rings via mutual scattering. Under this picture, evolving the fractional widths ($\Delta r/r$) of resolved debris rings back to a few Myr according to the theoretical $t^{1/5}$ evolutionary trajectory reproduces the protoplanetary ring distribution. We inferred the product of the ring mass and individual planetesimal mass required to reach the observed debris ring widths at their ages, finding that $M_\mathrm{disk}\times m$ ranges from $10^{-3}$ to $10^{3} \, M_\oplus^2$. The distribution of $M_\mathrm{disk} \times m$ appears to correlate with the stellar mass, peaking at 1.5 to 2 $M_\odot$, which resembles the stellar mass dependence of the giant
exoplanet occurrence rate. The population of resolved debris rings lie close to the $\Delta r / r = 10 \, h$ equipartition relation expected of a planetesimal ring that formed narrow, with typical resolved debris disks still expected to be broadening radially and vertically at present. If sufficiently massive ($\sim$10 $M_\oplus$), this radial broadening can send a few Mercurys to the terrestrial region within 10 Myr, making debris disks a plausible source of planetesimals disrupting resonant chains among Kepler
planets. Within Gyr timescales, outer planetesimal belts can also eject $\sim$1% of their mass into interstellar space if they consist of Moon-sized bodies or above, suggesting that the slow and steady intrinsic
evolution of massive debris disks could contribute to the interstellar free-floating population of terrestrial-
planet-sized bodies.
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Earth and Planetary Astrophysics
The Effects of M Star Age Dependent Ultraviolet Emission on Detecting and Interpreting Exoplanet Biosignatures
C. Evan Davis, Victoria S. Meadows, Evgenya L. Shkolnik et al. (+5 more)
Given their abundance and observational advantages, M
stars will arguably be the best candidates for characterizing and searching for biosignatures on terrestrial
exoplanets in the near future. However, photochemistry that can suppress or enhance key biosignature molecules in planetary atmospheres is primarily driven by UV flux from the host M
star, which is influenced by stellar activity that decreases with age. Here, we simulate Pre-Industrial Earth-like and Archean Earth-like atmospheres around M4 and M8
stars from 650 Myr to 5 Gyr old. We find that our Pre-Industrial Earth atmospheres around 5 Gyr M
stars have up to ten times more CH$_4$ than those around 650 Myr M
stars, producing 68% stronger methane bands in NIR transit spectroscopy. Additionally, photochemical shielding from O$_2$ in our Pre-Industrial Earth atmospheres reduces the impact UV-driven photochemistry on composition, while the Archean Earth exhibits larger compositional changes due to weaker shielding from CO$_2$. Lastly, enhanced CO$_2$ photolysis, driven by the strong net UV flux and high Far/Near-UV ratios of 650 Myr and 1 Gyr M
stars, cause our Archean Earth-like
planets to produce up to 5.4 dex more O$_3$ than when around 5 Gyr M
stars. The excess O$_3$ causes the Archean Earth to become half as reflective in the 0.2-0.3 $\mathrm{\mu}$m Hartley band feature in ultraviolet reflectance spectroscopy, which the Habitable Worlds Observatory may be sensitive to. Without the context of the
star's real-time, age-dependent UV radiation, this O$_3$ feature could be misinterpreted as a proxy for low, biogenic O$_2$.
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All authors C. Evan Davis, Victoria S. Meadows, Evgenya L. Shkolnik, Andrew P. Lincowski, Sarah Peacock, R. O. Parke Loyd, Adam C. Schneider, Travis Barman
Astrophysics of Galaxies
Serendipitous discovery of an almost-dark galaxy in the Virgo Cluster
Minh Ngoc Le, Ignacio Trujillo, Sergio Guerra Arencibia et al. (+9 more)
Analogues of extreme Local Group
galaxies with very low surface brightnesses and large effective radii must exist elsewhere, still hidden due to current detection limits. We report the serendipitous discovery of the low-mass almost-dark
galaxy TTT J1237327+143535 in the Virgo Cluster, observed using the Two-meter Twin
Telescope at the Teide Observatory. TTT J1237327+143535 has a central surface brightness of $27.9 \pm 0.2 \, \mathrm{mag\, arcsec}^{-2}$ in the $g'$ band, an effective radius of $0.9 \pm 0.1 \mathrm{kpc}$, and a total stellar mass of $(2.2 \pm 0.4) \times 10^6 \mathrm{M_\odot}$. Its effective radius and absolute magnitude are similar to those of
galaxies And XXI and And XXIII. The discovery of this extremely low-surface-brightness, extended, low-mass
galaxy suggests the existence of a significant population of almost-dark
galaxies in the Virgo Cluster. An in-depth analysis of the Next Generation Virgo Cluster Survey, as well as upcoming Rubin data releases and the 10-year Rubin Legacy Survey of Space and Time, is expected to reveal large samples of this extreme
galaxy population, which will offer insights into
galaxy formation in extreme conditions.
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All authors Minh Ngoc Le, Ignacio Trujillo, Sergio Guerra Arencibia, Ignacio Ruiz Cejudo, Junais, Mireia Montes, Johan H. Knapen, Željko Ivezić, Michael H.F. Wilkinson, Reynier Peletier, Miquel Serra-Ricart, Miguel R. Alarcon
Astrophysics of Galaxies
Detectable subhalo impacts in Milky Way streams
Junyang Lu, Elias Bernreuther, Tongyan Lin et al. (+3 more)
Dark matter subhalos leave gravitational imprints in the stellar streams of the Milky Way. Observing individual strong impacts of subhalos offers a compelling way to constrain and discover potentially dark subhalos down to $10^6 M_\odot$, allowing for new tests of the particle physics properties of dark matter. We develop a pipeline and statistical framework to forecast the expected number of detectable subhalo impacts on stellar streams, based on morphological and kinematic data from surveys such as LSST and Via. Starting from a catalog of confirmed stellar streams, we focus our efforts on 14 promising streams that are relatively well-modeled with a particle spray
algorithm. Our criteria for a detectable impact is a deviation at 95% CL from the best-fit
polynomial proxy model for the stream, which accounts for stream modeling uncertainties and regulates the effect of distant impacts that are degenerate with these uncertainties. Among the 14 streams studied, we find that 5 streams have an expected number of detectable impacts greater than 0.2. With LSST and Via data, the stream Jet has $5.15^{+1.10}_{-0.95}$ expected detectable impacts, followed by Orphan-Chenab ($1.40^{+0.62}_{-0.47}$), ATLAS-Aliqa Uma ($1.25^{+0.60}_{-0.44}$), GD-1 ($0.55^{+0.43}_{-0.28}$), and Palomar 5 ($0.40^{+0.39}_{-0.23}$), where error bars are the 95% containment on the Poisson mean. These values rely on the assumed subhalo population, which can give a factor of few systematic uncertainty in the predictions. We also consider effects of different particle dark matter models on the number of impacts, finding a suppression by a factor of $\sim 4$ for warm dark matter and fuzzy dark matter models at their current mass bounds and an $O(1)$ enhancement for a toy model of self-interacting dark matter.
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All authors Junyang Lu, Elias Bernreuther, Tongyan Lin, Vincent S. H. Lee, Ana Bonaca, Ethan O. Nadler
Astrophysics of Galaxies
Low Ly$\alpha$ Visibility in Galaxy Overdensities: Reionization Topology and Neutral-Fraction Ceilings from DIVER over $4.8<z<11$
Yongda Zhu, Xiaohui Fan, Laura C. Keating et al. (+19 more)
Ly-alpha emission is widely used to trace
cosmic reionization, but its interpretation depends on how Ly-alpha visibility varies with
galaxy environment. We use deep JWST/NIRSpec observations from Deep Insights into UV Spectroscopy at the Epoch of Reionization (DIVER) in GOODS-N to measure Ly-alpha visibility for 250
galaxies at 4.8<z<11. The sample contains 84 Ly-alpha detections, including 44 strong emitters with rest-frame Ly-alpha equivalent width W_Lyalpha>25 A. We combine these measurements with H-alpha and [O III] emitters from JWST/NIRCam wide-field slitless spectroscopy to map the density field around each DIVER
galaxy.
Galaxies with high Ly-alpha equivalent widths (W_Lyalpha>25 A) or high effective Ly-alpha escape fractions (f_esc,Lyalpha^eff>0.05) tend to lie farther from nearby H-alpha and [O III] emitters than
galaxies with lower Ly-alpha visibility. The clearest signal occurs near the prominent GOODS-N overdensity at z~5.2, where fewer than 15% of
galaxies show strong Ly-alpha emission. This trend is opposite to the simplest inside-out reionization expectation that overdensities produce larger ionized regions and enhance Ly-alpha visibility. Possible explanations include circumgalactic and local intergalactic opacity, dense absorbers, and gas kinematics. We also derive an empirical upper envelope for f_esc,Lyalpha^eff and calibrate it with reionization simulations. Interpreting this envelope as a limiting IGM-attenuation signal gives neutral-fraction ceilings of <x_HI>_max=0.36, 0.76, 0.74, 0.84, and 1.0 at z~5.2, 5.8, 6.7, 7.7, and 9.8, respectively. The z~8 ceiling disfavors an almost completely neutral IGM at this epoch. These results support patchy reionization already underway by z~8 and show that
galaxy Ly-alpha visibility encodes both large-scale ionization
topology and near-source gas structure.
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All authors Yongda Zhu, Xiaohui Fan, Laura C. Keating, George D. Becker, Eiichi Egami, Xiaojing Lin, Fengwu Sun, Christopher Cain, Marcia J. Rieke, Andrew J. Bunker, Sijia Cai, Francesco D'Eugenio, Jakob M. Helton, Xiangyu Jin, Mingyu Li, Zheng Ma, Roberto Maiolino, Pierluigi Rinaldi, Christopher N. A. Willmer, Yunjing Wu, Zihao Wu, Junyu Zhang
Astrophysics of Galaxies
The THESAN-ZOOM project: clumpiness of high-redshift galaxies and its connection to bursty star formation
Zihao Wang, Xuejian Shen, Rahul Kannan et al. (+12 more)
Recent JWST observations have revealed diverse high-
redshift galaxy morphologies, including a population with irregular and clumpy structures. The physical origin of these structures, and the extent to which observational biases shape their appearance, remain uncertain. We present a power-spectrum-based method for quantifying
galaxy clumpiness across spatial scales, using the radiation-hydrodynamic simulation suite THESAN-ZOOM, which employs a state-of-the-art
galaxy formation model that resolves the multiphase interstellar medium (ISM). Although the total stellar mass distributions in THESAN-ZOOM
galaxies are usually smooth, clumpy structures appear in the H$\alpha$, far-ultraviolet (FUV), and optical light distributions. Tracers sensitive to shorter-timescale
star formation exhibit more pronounced small-scale structure ($\sim10^{2}$–$10^{3}{\rm pc}$). The corresponding projected light spectra follow $P(k)\propto k^{-1}$ to $k^{-2}$, with progressively shallower slopes for tracers sensitive to more recent
star formation, reflecting enhanced small-scale power and greater spatial intermittency in young stellar populations. This behaviour is consistent with a highly compressible, shock-dominated ISM in which stellar feedback and outflows reorganise dense gas into filamentary and clumpy structures. We also find that
galaxy clumpiness depends on the treatment of stellar feedback. Weaker early stellar feedback enhances small-scale power in both the mass and light distributions. Clumpiness also varies strongly over the bursty
star formation cycle, implying that observed samples may be biased towards
galaxies caught in phases of elevated
star formation.
Galaxy clumpiness, therefore, could provide a complementary probe of the bursty
star formation in the early Universe.
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All authors Zihao Wang, Xuejian Shen, Rahul Kannan, Ewald Puchwein, Aaron Smith, Josh Borrow, Enrico Garaldi, Laura Keating, Mark Vogelsberger, Oliver Zier, William McClymont, Sandro Tacchella, Fangzhou Jiang, Hui Li, Lars Hernquist
Cosmology and Nongalactic Astrophysics
The Challenge of Observing Patchy Reionization with CMB Optical-Depth Fluctuations
Nick Takoudes, Hanjue Zhu and Nickolay Y. Gnedin
Spatial fluctuations in the Thomson optical depth encode information about the inhomogeneous nature of
cosmic reionization. We compute the optical-depth angular power spectrum, $C_\ell^{\tau\tau}$, using past lightcones constructed from five
Cosmic Reionization on Computers (CROC) radiation-hydrodynamical simulations. By decomposing the electron-density field into patchy and density components, we quantify the separate contributions of ionization-fraction and baryon-density fluctuations to the optical-depth anisotropy. Because the simulations end at $z\approx5$, we supplement the reionization-era signal with an analytic estimate of the fully ionized low-
redshift contribution. We find that baryon-density fluctuations dominate the high-
redshift signal over most angular scales, while the accumulated low-
redshift contribution exceeds the high-
redshift signal across the full multipole range considered. Our results demonstrate that a significant fraction of the optical-depth power is not uniquely associated with reionization morphology, implying that future interpretations of $C_\ell^{\tau\tau}$ must account for the density contribution in addition to patchy ionization.
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Solar and Stellar Astrophysics
Multi-lane type II radio bursts: Insights into shock propagation in the corona
Nadiya K., Divya Paliwal and Anshu Kumari
Type II solar
radio bursts are considered as the signatures of the coronal shocks. These bursts are generated from
plasma waves excited by magnetohydrodynamic (MHD) shocks, and then converted into
radio waves at the local
plasma frequency and/or its harmonics. Hence, these bursts often have fundamental-harmonic (FH) and band-splitting (SB) structures, which provide insights into shock generation and propagation in the corona, hence, in turn, the corresponding coronal conditions. In the present study, we analysed an unusual multi-lane type II burst observed with ground-based solar
radio spectrographs on May 29, 2024, between 14:24 and 14:43 UT. The start and end frequencies of the type II burst were 450 MHz and 25 MHz, respectively. By combining spectral information with
radio imaging data, we found that
radio waves were escaping from the corona via emissions from distinct shock regions. In addition, along with the traditional FH and SB, there were multi-lane structures in the type II bursts. Our analysis suggests complex, inhomogeneous shock dynamics near the leading edge (LE) of the coronal mass ejection (CME). This indicates that the
plasma material compresses more strongly in these forefront regions. This was confirmed by
radio imaging observations, which showed that the higher-frequency emission occurred at a higher altitude than the lower-frequency emission. Our results suggest that the shock geometry and
plasma inhomogeneity play an important role in the generation of type II bursts, leading to traditional fundamental-harmonic split-band (FH-SB) pairs with additional splitting in the type II bands.
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Astrophysics of Galaxies
Diffuse HI emission in the circumgalactic medium of NGC891 and NGC4565 - III: azimuthal profiles
Mary Rickel, Sanskriti Das, Nickolas M. Pingel et al. (+4 more)
Diffuse HI emission in the circumgalactic medium (CGM) of NGC891 and NGC4565 has been previously shown to trace an inflow along minor axes pointings and to co-rotate with the HI disk along major axes pointings out to ~100 kpc (Das2020b,Das2024a). To obtain a 360$^\circ$ view of the inner neutral CGM ($\rm < 25 kpc$ for NGC891, $\rm < 30 kpc$ for NGC4565), we perform deep stare observations with the Green Bank
Telescope (GBT) along the off-axes, 45$^\circ$ between principal axes, achieving a 5$\sigma$ column density sensitivity of $1.1-1.2 x 10^{17} \rm cm^{-2}$ over a 20 kms$^{-1}$ velocity width. While detecting HI emission in the inner CGM with single-dish
telescopes is common, separating the true CGM emission from disk contamination is extremely challenging and has so far been largely unsuccessful. To achieve that, we compare our single-dish detections to deep interferometric maps from the Westerbork Synthesis
Radio Telescope (WSRT) HALOGAS survey, and improve upon our previous methods by incorporating velocity offset corrections and channel-wise brightness-temperature scaling. We find that $30-38$ % and $18-28$ % of the emission detected by the GBT cannot be explained by WSRT in NGC891 and NGC4565, respectively, implying a true CGM detection. There is $4-6$ ($3-7$) times more HI along the off-axes than major (minor) axes, nullifying the common assumption of azimuthal
symmetry of the neutral CGM. The velocity profile of the diffuse inner CGM suggests a lagged co-rotation with the HI disk in both
galaxies. This exercise illustrates the power of deep observation and careful cross-instrument comparisons to characterize the diffuse HI in the CGM.
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All authors Mary Rickel, Sanskriti Das, Nickolas M. Pingel, D. J. Pisano, Adam Leroy, Smita Mathur, George Heald
Instrumentation and Methods for Astrophysics
Effects of manufacturing tolerances on the performance of metamaterial microwave anti-reflection coatings
Rustam Balafendiev, Miranda Eiben and Jon E. Gudmundsson
Metamaterial anti-reflection coatings (ARC) are used in a variety of applications, including: lenses, filters, and absorbers. Typically, the design of a given ARC is done within an infinite medium approximation, which presupposes that every unit
cell on the interface is identical. However, in realistic applications, the geometry of a given ARC usually has some degree of variability, be it due to the shape of the surface inherent to the application, like in a lens, or manufacturing tolerances. This variation may alter the performance of the optical element in unanticipated ways, by creating additional scattering, enabling diffractive maxima that would normally be absent and, most crucially, changing the transparency of the ARC as a function of frequency. In this work we utilize full-wave modeling of finite samples of plastic which are matched with free space using a metamaterial ARC on both of their interfaces. By adding a degree of randomness to the ARC geometry we attempt to characterize the extent to which a given variation affects the expected performance of an ARC.
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Astrophysics of Galaxies
Inferring the Dark from the Observable: Estimating Halo Masses Using Galaxy Properties
Alice Chen and Syeda Lammim Ahad
The formation and
evolution of
galaxies are interconnected with that of their host
halos. Given this closely related evolutionary history, it should follow that
galaxy properties are correlated with their host
halo mass. Previous works have shown that
star formation rates of
galaxies in cluster
halos differ systematically from those in field
halos, suggesting that host
halo mass plays a significant role in the history of
galaxy evolution. Here, we examine the correlations between observable
galaxy properties - such as stellar mass,
star formation rate, half-stellar radius, $r-$band magnitude, and color - and the underlying host
halo mass of
galaxies. Central
galaxy observables are used to probe host
halo mass, while satellite
galaxy properties are used to estimate subhalo mass. We perform this analysis using random forest, ordinary least squares (OLS), and symbolic regression. Random forest regression can assess the relative significance of different observable
galaxy properties, while OLS and symbolic regression can quantify their relationship with the host
halo mass. Our results show that gas mass is generally the most significant property in central
galaxies of all
halo mass ranges, followed by stellar mass and observed $r-$band magnitude. Adding parameters such as the colour and magnitude of
galaxies improves host
halo mass estimations compared to standard stellar-to-
halo mass relations. These results show that
halo mass likely has a multi-dimensional dependence on
galaxy properties and open the avenue of finding a simple way to constrain
halo mass based on what is directly observable in
galaxy surveys. Finding the observables that have the strongest correlation with
halo mass can also motivate future surveys on which areas to concentrate in detail.
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Earth and Planetary Astrophysics
No Persistent Helium Absorption in LHS 1140 b: Four JWST/NIRISS SOSS Transits and Multi-epoch Stellar He I Variability
Amélie Gressier, Charles Cadieux, René Doyon et al. (+4 more)
The search for atmospheres on temperate terrestrial
planets is important for understanding how these objects form and evolve, and their potential habitability. Recent transit observations of LHS 1140 b, a temperate ($T_{\rm eq}=226$ K)
planet straddling the radius valley ($R_{\rm p}\approx1.7 R_\oplus$), with the WINERED high-resolution spectrograph yielded a detection of planetary atmospheric escape through the measurement of excess absorption ($1.24\pm0.23\%$) in the metastable helium triplet, although a later second visit resulted in a non-detection. We analyze four transits of LHS 1140 b and two of LHS 1140 c observed with JWST/NIRISS SOSS. We find no evidence of helium absorption in either
planet, with all amplitudes consistent with zero within $1\sigma$. For LHS 1140 b, we derive $3\sigma$ upper limits of $0.72$–$1.21\%$. Individual visits disfavor the reported WINERED absorption at $2.6$–$3.7\sigma$, while their joint constraint disfavors a persistent signal at $4.5\sigma$. We find that the stellar He I line of LHS 1140 varies substantially between NIRPS and WINERED epochs, with both its strength and fractional variability consistent with the behavior of other M dwarfs. We also identify a moderate correlation between the 2024 He I depth and seeing, suggesting a possible seeing-dependent instrumental contribution. If the high-resolution detection is indeed planetary, the rate of such atmospheric loss events must be relatively low ($f=22_{-12}^{+17}\%$). Alternatively, stellar He I variability may contribute to the reported excess absorption. Additional high-resolution observations, both in and out of transit, are required to distinguish between these scenarios.
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All authors Amélie Gressier, Charles Cadieux, René Doyon, Louis-Philippe Coulombe, Romain Allart, Étienne Artigau, François Bouchy
Instrumentation and Methods for Astrophysics · Cross-listed from physics.ins-det
Identifying Cost-Favorable Locations for Cosmic Explorer
Laurence Datrier, Geoffrey Lovelace, Tooba Ansar et al. (+19 more)
Cosmic Explorer (CE) is a proposed next-generation gravitational-wave observatory that aims to extend our gravitational-wave
vision to the edge of the observable universe. With a foundation of technology proven by the National Science Foundation's
Laser Interferometer Gravitational-Wave Observatory (LIGO), CE will observe black holes and
neutron stars across
cosmic time, explore the nature of extreme matter with high fidelity, and probe the nature of
gravity and fundamental physics. CE's reference design consists of two widely separated L-shaped detectors to be located in the conterminous United States, one with 20 km arms and one with 40 km arms. As of 2026, CE is in its design and site evaluation phase, with plans to begin observing in the early 2040s together with the Einstein
Telescope in Europe. The size of CE observatories—up to an order of magnitude larger than the 4 km LIGO observatories—presents a significant challenge for identifying suitable candidate sites where CE will achieve its science goals, be built within cost boundaries, attract and retain a workforce, and align with community values. In this paper, we report on the design and use of a Python package, the
Cosmic Explorer Location Search (CELS) package, to identify cost-favorable sites for CE. For a specified detector location and L-shaped geometry in the conterminous United States, CELS estimates site-preparation costs associated with excavation, land clearing, and land acquisition, while accounting for the scientific effects of detector tilt, arm length, and arm opening angle. After describing the package's methods, we present results for a national-level cost and positioning analysis that complements a recent national suitability analysis. We also discuss how future improvements to CELS will allow deeper, more local studies as the
Cosmic Explorer team narrows its list of potential locations.
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All authors Laurence Datrier, Geoffrey Lovelace, Tooba Ansar, Lance Blagg, Warren Bristol, Matthew Evans, Chris Lukinbeal, Vuk Mandic, Kiet Pham, Jocelyn Read, Sarmad Rameez, Amber Romero, Oscar Romero, Babatunde Isaac Rotimi, Joshua B. Russell, Andrew Saenz, Francois Schiettekatte, Robert Schofield, David H. Shoemaker, Bretton Simpson, Bram J.J. Slagmolen, Joshua R. Smith
Instrumentation and Methods for Astrophysics
Real-Time RFI Mitigation in SPOTLIGHT: A Two-Stage Approach for Transient Searches
Raghav Wani, Jayanta Roy, Harshavardhan Reddy et al. (+10 more)
Radio Frequency Interference (RFI) remains one of the primary challenges limiting the sensitivity and reliability of modern
radio transient surveys, particularly for real-time searches of fast
radio transients. The SPOTLIGHT system is a commensal real-time transient search backend operating at the upgraded Giant Metrewave
Radio Telescope (uGMRT), where robust and computationally efficient RFI mitigation is essential for sustained operations. We present the real-time two-stage RFI mitigation framework developed for SPOTLIGHT, comprising an
antenna-level voltage-filtering module (VOLT) operating prior to correlation beamforming and the SPOTLIGHT Time-domain RFI Processing Engine (STRIPE), a statistical RFI-filtering framework applied to beamformed data. Together, these complementary techniques mitigate a broad spectrum of RFI, ranging from broadband impulsive interference mitigated by VOLT to narrowband spectrally confined spurious signals mitigated by STRIPE, while remaining computationally efficient enough to satisfy the stringent requirements of real-time processing. The framework is evaluated using routine commensal GMRT observations, controlled 76
pulsar observations, and benchmarking against PRESTO's rfifind. The deployed system reduced the false detection rate by 98%. The recovered astrophysical pulses exhibit a 2.7x improvement in S/N after the two-stage filtering compared with the unfiltered data. These improvements enhance SPOTLIGHT's detection efficiency, sensitivity, and operational reliability, strengthening its capability to discover
radio transients with the uGMRT.
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All authors Raghav Wani, Jayanta Roy, Harshavardhan Reddy, Sanjay Kudale, Ujjwal Panda, Karel Adamek, Wesley Armour, Kshitij Bane, Kaushal Buch, Jayaram Chengalur, Jyotirmoy Das, Sridhar Gajendran, SPOTLIGHT Collaboration
Earth and Planetary Astrophysics
Wet Removal and Cloud Enhancement: The Microphysics of Cloud-Haze Interactions on Sub-Neptunes
Vighnesh Nagpal, Maria Steinrueck, Diana Powell et al. (+3 more)
Aerosols are a near-ubiquitous feature of sub-Neptune atmospheres, yet their microphysical nature remains poorly understood. Both condensate clouds and photochemical hazes have been proposed to explain observations, but have largely been studied in isolation. Here we present a new bin-scheme microphysical model, adapted from CARMA, that couples cloud and haze formation through heterogeneous nucleation - the dominant mode of cloud formation in the Solar System - in which haze particles act as cloud condensation
nuclei (CCN). Applying this model to KCl clouds on GJ 1214 b-like warm sub-Neptunes, we find that the microphysical contact angle $\theta$ between cloud and haze particles governs distinct regimes of aerosol behavior: at moderate contact angles ($25^\circ \lesssim \theta \lesssim 70^\circ$), hazes are efficiently removed from the upper atmosphere through "wet removal" as they seed gravitationally-settling clouds; at small contact angles ($\theta \lesssim 25^\circ$), heterogeneous nucleation instead produces an enhanced population of mixed cloud-haze particles at high altitudes, dramatically increasing aerosol optical depth ("cloud enhancement"). These structural changes produce differences of up to four scale heights in transmission spectra, with strong effects at optical and near-infrared wavelengths relevant to JWST NIRISS/SOSS, while wavelengths beyond about 3 microns remain comparatively unaffected. We map these effects across orders of magnitude in
metallicity, haze production rate, and vertical mixing strength, establishing their generality across sub-Neptune parameter space. Because heterogeneous nucleation is a universal phase-change process, this framework extends naturally to other
exoplanet atmospheres and potentially any astrophysical environments where condensation onto foreign substrates may occur, including protoplanetary disks and stellar outflows.
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All authors Vighnesh Nagpal, Maria Steinrueck, Diana Powell, Peter Gao, Dominic Samra, Wolf Cukier
Solar and Stellar Astrophysics
Asteroseismology of the multiperiodic field SX Phe pulsator BL Camelopardalis
W. Szewczuk, J. Daszyńska-Daszkiewicz, P. Walczak et al. (+1 more)
BL Camelopardalis (BL Cam) is the most metal-poor SX Phoenicis
star known in the Galactic field, making it an excellent test bed for studies of Population II stellar structure and
evolution, as well as for investigating the formation channels of blue straggler
stars. We aim to constrain fundamental stellar parameters and pulsational properties of BL Cam and identify the nature of its observed oscillation modes. We analysed high-precision space-based data from the TESS mission and long-term ground-based observations from the Zwicky Transient Facility (ZTF) survey. The ZTF data were primarily used to derive the orbital parameters of the system, while the TESS light curves enabled us to extract a rich oscillation spectrum. We identified multiple pulsation frequencies and performed seismic modelling using a
Bayesian approach. We detected numerous pulsation frequencies, including a dominant radial mode and additional non-radial components. We predicted all fitted modes in our seismic models as excited. The models reproduced the two highest amplitude-independent frequencies (i.e. the radial fundamental mode and a dipole mode) and suggested the possible presence of additional radial overtones. The inferred stellar parameters confirm the extremely low
metallicity of BL~Cam. We also confirm its binary nature, with an orbital period of 144 days. BL Cam provides a valuable
benchmark for testing stellar models of metal-poor pulsators. The combination of space-based photometry and
Bayesian seismic modelling enables robust constraints to be placed on its internal structure and pulsation properties.
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All authors W. Szewczuk, J. Daszyńska-Daszkiewicz, P. Walczak, E. Rodríguez
Cosmology and Nongalactic Astrophysics
Dipolar power asymmetry in wide-angle correlations of galaxy density, velocity and ellipticity
Yusuke Mikura, Teppei Okumura, Ippei Obata et al. (+1 more)
The large-scale structure of the universe has the potential to probe anomalies suggested by observations of the
cosmic microwave background. In this work, we focus on a position-dependent dipolar modulation of the primordial power spectrum and develop a full-sky formalism for computing correlation functions of
galaxy density, velocity and ellipticity. By comparing the correlation functions obtained with and without the plane-parallel approximation, we show that wide-angle corrections become non-negligible for opening angles $\Theta \gtrsim 30^\circ$. Our results demonstrate that wide-angle corrections must be taken into account when testing the dipolar modulation with future large-scale structure surveys.
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All authors Yusuke Mikura, Teppei Okumura, Ippei Obata, Maresuke Shiraishi
Solar and Stellar Astrophysics
The Ultrafast Line-Driven Wind from the Double-Degenerate Merger Remnant WD J005311
Kazuma Kato and Kazumi Kashiyama
We systematically construct steady-state wind solutions for double-degenerate merger remnants consisting of a degenerate oxygen-neon core and an optically thick expanding envelope powered by carbon-shell burning, with winds accelerated by radiation pressure including line driving. For a given envelope composition, each solution is characterized by two
eigenvalues: the degenerate core mass, $M_{\rm WD}$, and the total envelope and wind mass, $\Delta M$. We find that wind solutions exist for $M_{\rm WD} \gtrsim 1.0\,M_\odot$. For a given $M_{\rm WD}$, the solutions transition with decreasing $\Delta M$ from slow, continuum-driven winds to ultrafast, line-driven winds, forming a sequence that can be interpreted as the temporal
evolution of a merger remnant. We apply these solutions to WD J005311, a Galactic double-degenerate merger-remnant candidate with an ultrafast wind of $v_{\rm w} \sim 0.05\,c$. Its luminosity, effective temperature, and mass-loss rate are consistently reproduced with $M_{\rm WD} \sim 1.15-1.25\,M_\odot$ and $\Delta M \sim (1.8-5.7)\times 10^{-3}\,M_\odot$. Combining our evolutionary analysis with observations of the surrounding nebula Pa 30 and historical records of SN 1181, we argue that WD J005311 began launching a continuum-driven wind $400-650$ yr after the putative merger and transitioned to the ultrafast-wind phase approximately $100$ yr ago. This phase is expected to continue for another $\sim 1000$ yr, during which the WD will remain below the Chandrasekhar mass and avoid collapse into a
neutron star. Before the continuum-driven wind phase, the remnant may have passed through a more bloated, hydrostatic giant phase with a slower but more massive wind. Future observations of the wind nebula could test this scenario by revealing signatures of interactions between the slow, massive wind and the ultrafast wind.
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Earth and Planetary Astrophysics
A Search for helium in the atmospheres of three sub-Neptunes and a super-Earth around M-dwarfs
Kiyoe Kawauchi, Norio Narita, Yuichi Ito et al. (+26 more)
Thousands of sub-Neptunes have been discovered mainly through space-based surveys such as Kepler and TESS. Their bulk compositions and internal structures are thought to reflect their formation and evolutionary pathways, and atmospheric observations provide constraints on these processes. The near-infrared helium triplet is a potential tracer of extended, escaping H/He atmospheres. Recent models that include
geometric effects suggest that
planets orbiting nearby late M dwarfs may offer favorable conditions for detecting this signal. Nevertheless, helium has been reported for only three
planets around M dwarfs to date. We conducted high-resolution transmission spectroscopy of three sub-Neptunes (TOI-2136b, TOI-654b, and LP 791-18c) and a super-Earth (TOI-1634b) orbiting M dwarfs with the InfraRed Doppler (IRD) spectrograph on the Subaru
Telescope. We find no statistically significant helium absorption in any target; accordingly, we derive 95% confidence upper limits on the helium line depth of 1.36%, 0.60%, 2.07%, and 3.00%, and on the equivalent width of 7.3, 2.1, 7.4, and 9.1 mÅ, for TOI-2136b, TOI-1634b, TOI-654b, and LP 791-18c, respectively. We further explored constraints on the upper-atmospheric temperature and mass-loss rate by comparing these results with isothermal Parker-wind models. While we have compared with self-consistent ATES models of primordial H/He atmospheres spanning a range of assumed X-ray luminosities, changes in the assumed XUV flux do not appear to account for the non-detections. The results suggest that these
planets have metal-enriched H/He primary atmospheres or non-primordial atmospheres, such as water-rich envelopes. Future observations of other absorption lines, such as Lyman-$\alpha$, H-$\alpha$, and H$_2$O, may provide further constraints on these atmospheres.
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All authors Kiyoe Kawauchi, Norio Narita, Yuichi Ito, Akifumi Nakayama, Teruyuki Hirano, Masayuki Kuzuhara, Mayuko Mori, Izuru Fukuda, Akihiko Fukui, Yuya Hayashi, Yasunori Hori, Masahiro Ikoma, Kai Ikuta, Taiki Kagetani, Yugo Kawai, Tadahiro Kimura, Vigneshwaran Krishnamurthy, Huan-Yu Teng, Noriharu Watanabe, Yujie Zou, Hiroki Harakawa, Klaus Hodapp, Tomoyuki Kudo, Takashi Kurokawa, Jun Nishikawa, Masashi Omiya, Motohide Tamura, Akitoshi Ueda, Sébastien Vievard
High Energy Astrophysical Phenomena
Quantifying uncertainty in the neutron-star equation of state using point estimates and posterior distributions
André Gonçalves da Silva and Ricardo Luciano Sonego Farias
We investigate uncertainty quantification for the
neutron-
star equation of state (EOS) by comparing point-estimation and distributional inference approaches using the same Chebyshev and piecewise-linear parameterizations. We combine
neutron-
star mass–radius and gravitational-wave tidal-deformability information within
Bayesian, multilayer-perceptron (MLP), and normalizing-flow frameworks. Although the methods yield similar mean EOS behavior, the deterministic MLP produces substantially narrower uncertainty bands at high densities. We show that this behavior is associated with the point-estimation objective, which maps degenerate solutions toward the conditional mean rather than representing the full parameter posterior. By contrast, the normalizing flow yields distributions more consistent with the
Bayesian inference. Our results demonstrate that reliable uncertainty quantification of the high-density EOS requires methods that represent conditional probability distributions rather than only point estimates.
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Astrophysics of Galaxies
The progenitors of $z\gtrsim10$ JWST galaxies in the COLIBRE simulations
Evgenii Chaikin, Andrew Pontzen, Carlos S. Frenk et al. (+4 more)
JWST has revealed a large population of luminous
galaxies ($M_{\rm UV}\lesssim -20$) at
redshifts $z \gtrsim 10$, widely interpreted as posing a challenge to models of
galaxy formation within the $\Lambda$CDM cosmology. Here, we search for counterparts of the JWST
galaxies in the COLIBRE simulations of
galaxy formation. Although these simulations have not been tuned to reproduce any $z > 0$ observations, we find a population of COLIBRE
galaxies with properties similar to those of the JWST
galaxies, and trace them to their earliest evolutionary phases, $z\simeq25$, to investigate the onset of
galaxy formation. We study the
evolution of
galaxy stellar masses, sizes,
star formation rates, UV magnitudes,
metallicities, central black hole masses, and molecular gas and dust content, finding good agreement with observationally inferred properties at $z > 10$, except for UV magnitudes and dust masses, which COLIBRE underpredicts and overpredicts, respectively. Our results indicate that the standard
galaxy formation physics and $\Lambda$CDM cosmology adopted in COLIBRE are sufficient to reproduce a broad range of properties of the most extreme $z > 10$ JWST
galaxies - including their compact sizes, stellar masses, gas content, and
metallicities. We show that the discrepancies with the UV magnitudes and dust masses can both be attributed to the uncertain rate of grain growth at high
redshift, possibly alongside a top-heavy stellar initial mass function. These findings provide strong evidence that the standard cosmological model can naturally explain even the most extreme
galaxies in the early Universe.
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All authors Evgenii Chaikin, Andrew Pontzen, Carlos S. Frenk, Joop Schaye, Shengdong Lu, Robert A. Crain, Anna Durrant
Instrumentation and Methods for Astrophysics
Physical Optics Analysis of Polarization Effects in SO LAT Reflectors
Xiaodong Ren, Patricio A. Gallardo and Jon E. Gudmundsson
We present a physical-optics analysis of the polarization response of the reflective optical of the Simons Observatory Large Aperture
Telescope (SO LAT). Far-field co-polar and cross-polar beam patterns are simulated for representative feedhorn positions, and the corresponding polarization-angle offsets are evaluated. The results show that the crossed-Dragone reflector system has good polarization performance. Off-axis feed positions introduce small, position-dependent offsets in the far-field polarization orientation, with a maximum value of 0.23 degrees, due to optical asymmetry. The relative polarization-angle offset under feedhorn polarization rotation, however, remains consistent with zero. No significant frequency dependence is found over the frequencies considered. These results provide a practical reference for polarization-angle calibration and for assessing reflector-induced polarization systematics in the SO LAT.
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Solar and Stellar Astrophysics
Quadrupole White-light Sources in an X1.2 Flare Observed by ASO-S/LST/WST and SDO/HMI
Zhichen Jing, Ying Li, Dechao Song et al. (+2 more)
We present observations of an X1.2 white-light
flare on 2023 January 6, which exhibits a rare quadrupolar white-light source configuration. This event was observed by the White-light Solar
Telescope (WST; 3600 Å) aboard the Advanced Space-based Solar Observatory and the Helioseismic and
Magnetic Imager (HMI; 6173 Å) aboard the Solar Dynamics Observatory. Four
flare-related footpoints (labeled as FP1–FP4) were nearly simultaneously identified in both WST 3600 Å\ and HMI 6173 Å\ continua, associated with a quadrupolar
magnetic configuration and a failed filament eruption. The inner sources of FP1 and FP2 showed a similar enhancement of $\sim$65%/10% in the WST/HMI continuum, while the outer sources of FP3 and FP4 exhibited weaker responses. The inner footpoints had earlier responses in UV and EUV bands and were spatially coincident with the hard X-ray (HXR) footpoint sources. The two southern footpoints (FP2 and FP4) showed stronger HXR and white-light emissions than their northern counterparts (FP1 and FP3), with FP4 uniquely exhibiting a distinct HXR emission above 60 keV, in contrast to the absence of such an emission at FP3. Notably, faint WST 3600 Å\ enhancements at FP4 were observed during the gradual phase, temporally consistent with the fallback of filament material. This X1.2
flare presents a novel quadrupolar white-light structure, enriching our understanding of the generation and
evolution of white-light
flares.
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All authors Zhichen Jing, Ying Li, Dechao Song, Qiao Li, Zhengyuan Tian
Cosmology and Nongalactic Astrophysics
Towards end-to-end Bayesian forward models in global 21-cm cosmology: surrogate modelling and marginalisation of beam uncertainty
Jacob L. Tutt, Dominic J. Anstey, John Cumner et al. (+3 more)
Robust statistical inference in global 21-cm cosmology requires end-to-end uncertainty quantification that jointly handles the highly degenerate cosmological signal, foreground emission, and instrumental response. Although electromagnetic simulations capture physical
antenna properties in a parametrised way, multi-hour runtimes make their integration within likelihood-based sampling frameworks infeasible. Most existing approaches therefore assume a single precomputed beam, a fragile assumption given our demonstration that realistic mismatches can severely bias the recovered cosmological and foreground parameters. To address this, we present an accelerated and differentiable
Bayesian framework that incorporates an informed surrogate representation of chromatic beam uncertainty directly into a forward-modelling pipeline. Treating the physical
antenna properties as nuisance quantities, we apply a two-stage decomposition directly to simulated directivity patterns, reducing the instrumental parameterisation by two orders of magnitude while retaining the angular and spectral structure required for accurate beam reconstruction. Exploiting the linearity of the resulting surrogate, we use analytical marginalisation to allow the continuous instrumental uncertainty to be propagated into the final posteriors and
Bayesian evidence without directly sampling the beam space. Testing the framework against a suite of unseen beams and cosmological signals, we recover the true inputs at approximately the instrumental-noise level. We further show that, for the uncertainty considered here, as few as 100 electromagnetic simulations are sufficient to construct an effective surrogate, substantially reducing the simulation burden for future analyses. This framework provides a scalable, statistically rigorous route towards hardware-accelerated uncertainty quantification in global 21-cm cosmology.
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All authors Jacob L. Tutt, Dominic J. Anstey, John Cumner, Harry T. J. Bevins, Jean Cavillot, Eloy de Lera Acedo
High Energy Astrophysical Phenomena
Constraining Cosmic-Ray Acceleration and Escape in Middle-Aged Supernova Remnants with GeV-TeV Gamma-Ray Observations
Siyu Chen, Bing Theodore Zhang, Yi Xing et al. (+2 more)
In this work, we perform a systematic, time-dependent study of the gamma-ray emission from four representative middle-aged SNRs (W51C, IC~443, W44, W28), incorporating both CRs within the remnant shells and escaped CRs interacting with surrounding molecular clouds. We compare our results with GeV–TeV gamma-ray observations from Fermi-LAT, H.E.S.S., MAGIC, and LHAASO, including a dedicated analysis of the Fermi-LAT data for regions A and B associated with W28. We find that the observed spectra favor steeper CR injection spectra with indices of \(\alpha\sim4.2\)–\(4.3\), maximum
proton energies of $\sim$ \(100\)–\(300\) TeV,
diffusion coefficients below the Galactic average, and CR acceleration efficiencies from a few to tens of percent. In particular, the VHE emission detected by LHAASO from W51C is more naturally explained by escaped CRs interacting with a nearby molecular cloud. We also investigate the contribution of escaped CRs to the VHE emission from IC~443, W44, and W28. We further demonstrate that escaped CRs can substantially enhance the TeV
neutrino flux from middle-aged SNRs, improving their prospects as potential
neutrino sources. These results provide new constraints on CR acceleration and escape in middle-aged SNRs and highlight the important role of escaped CRs in shaping their high-energy gamma-ray and
neutrino emission.
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All authors Siyu Chen, Bing Theodore Zhang, Yi Xing, Siming Liu, Xunxiu Zhou
Instrumentation and Methods for Astrophysics
Asgard/NOTT: Status of laboratory nulling performance
T. Mattheussen, R. Laugier, D. Defrère et al. (+26 more)
Nulling interferometry enables the direct detection of faint companions and circumstellar structures at angular separations unresolvable by classical, diffraction-limited imagers, whilst dramatically improving the measurable contrast. The Asgard/NOTT nulling instrument aims to achieve a contrast performance of 10^-5 in the L' wavelength band (3.5 - 4.0 {\mu}m), enabling observation and characterization of young giant
exoplanets near the snowline and hot exozodiacal dust. Previous studies have verified the nulling capabilities, of the chip in ambient conditions and of the test bench in cryogenic conditions. This work aims to add the first ambient performance assessment of the test bench with spectrally dispersed light. Necessary revisions are made to the data acquisition and calibration pipeline and fringe scans are carried out, modeled and fitted. The splitting ratios of the 4-
telescope nulling beam combiner, a photonic Gallium Lanthanum Sulfide (GLS) chip, are moreover characterized on the bench, showing tentative agreement with previous chip characterization. The null performance has worsened, the achieved contrast of ~ 10^-1 being one order of magnitude higher than what earlier characterized performance showed. Multiple future changes to the test bed and to the approach taken promise an improved characterization of performance. In particular, the input beam intensities will be deliberately mismatched to account for the imbalanced splitting ratios of the directional couplers. With the installation of the final cryostat and camera, the developed tools will be leveraged to re-assess the performance in ambient and cryogenic conditions.
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All authors T. Mattheussen, R. Laugier, D. Defrère, G. Garreau, P. Chingaipe, G. Raskin, M. Salman, K. Missiaen, B. Vandenbussche, W. Verstraeten, J. Morren, A. Kuriakose, M. Ireland, M.-A. Martinod, A. Sanny, S. Gross, L. Labadie, A. Bigioli, A. Jóo, S. Madden, A. Mazzoli, G. Medgyesi, S. Ertel, T. A. Stuber, J. P. Scott, S. Kraus, F. Martinache, X. Haubois, N. Schuhler