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Physics Astrophysics

astro-ph Watch Astrophysics

Saturday 14 March

Solar and Stellar Astrophysics

The Historical Lightcurve of the R Coronae Borealis Star, V854 Cen, from 1890 to 2026

Geoffrey C Clayton

The R Coronae Borealis (RCB) Star, V854 Cen, was not discovered until the 1980's even though it is 7th magnitude at maximum light. This is because it was in a faint state due to the presence of thick circumstellar dust clouds for nearly a century. RCB stars are known for having deep declines of up to 9 magnitudes at irregular intervals. The declines are caused by dust clouds which block the light from the star. The historical lightcurve of V854 Cen before discovery was investigated by examining plates taken by Harvard College Observatory and other observatories beginning in 1889. These observations show that V854 Cen was well below 7th magnitude from 1890 to 1980, often as faint as 16th or 17th magnitude.
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Solar and Stellar Astrophysics

The Eccentric Disk Model for Superhumps

Stephen H. Lubow

An important goal of the disk instability model is to explain the superhump phenomenon. Superhumps are features found in the light curves of binary systems, characterized by a period slightly different from the binary orbital period. In cases where the superhump period is longer than the orbital period (positive superhumps), they have been interpreted as arising from an eccentric, precessing disk. This paper reviews the theory and simulations that indicate that the disk's eccentricity originates from a dynamical instability at the 3:1 resonance. The instability is described by a mode-coupling process involving the interaction of the disk eccentricity with the binary tidal potential. This instability provides critical constraints on the nature of the disk turbulence that enables the disk to reach this resonance.
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Earth and Planetary Astrophysics

Spin Parameters and Shape Models of Near-Earth Asteroids (4660) Nereus, (21088) Chelyabinsk, (66146) 1998 TU3, and (297418) 2000 SP43

Javier Rodríguez Rodríguez, Enrique Díez Alonso, Santiago Iglesias Álvarez et al. (+8 more)

We present our shape and rotational characterization of four near-Earth asteroids observed as part of the Visible NEAs Observations Survey. This work includes 61 new light curves obtained between 2020 June and 2024 September for asteroids (21088) Chelyabinsk and (66146) 1998 TU3 and the potentially hazardous asteroids (4660) Nereus and (297418) 2000 SP43. We combine these observations with archival data to derive their shape models, spin parameters, and refined rotation periods using a light-curve inversion method. Our derived rotational periods are consistent with previously published values for all the objects. We present constant-period models for each asteroid, while for (66146) 1998 TU3 we detect a possible Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) acceleration of $\upsilon \simeq 2.05 \times 10^{-8} \text{ rad day}^{-2}$, potentially adding it to the short list of asteroids known to experience the YORP effect.
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All authors Javier Rodríguez Rodríguez, Enrique Díez Alonso, Santiago Iglesias Álvarez, Saúl Pérez Fernández, Alejandro Buendia Roca, Julia Fernández Díaz, Javier Licandro, Miguel R. Alarcon, Miquel Serra-Ricart, Amadeo Aznar Macías, Francisco Javier de Cos Juez

Earth and Planetary Astrophysics

HAT-P-32 b: what can be deduced from transit observations in H{\alpha} and He I lines?

Shaikhislamov I.F., Sharipov S.S, Khodachenko M.L. et al. (+4 more)

HAT-P-32 b is the first exoplanet for which absorption in hydrogen and helium lines has been measured simultaneously. In addition to the relatively large maximum depth of ~5% in both lines, observations have revealed very long pre-transit signatures. In this paper, we apply a 3D aeronomy model to simulate the detailed spectrally resolved absorption profiles at mid-transit, formed in the upper atmosphere, as well as the integral transit curves formed by atmospheric material accumulating around the star. By fitting the observations, we derive key atmospheric characteristics, including the atmospheric composition and metallicity, and constrain the stellar XUV, hard X-ray, and Ly{\alpha} fluxes, as well as the intensity of the stellar plasma wind. We show that the presence of metals crucially affects the absorption in hydrogen and helium lines by accelerating the dissociation of H2. We also demonstrate that several processes not previously included in the modeling of HAT-P-32 b are important for the interpretation of the observations, such as the 3D asymmetric structure of the atmosphere, heating and cooling by excited states of hydrogen and metals, and the stellar VUV flux.
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All authors Shaikhislamov I.F., Sharipov S.S, Khodachenko M.L., Miroshnichenko I.B., Rumenskikh M.S., Golubovsky M.P., Berezutsky A.G

High Energy Astrophysical Phenomena

Comparative analysis of BL Lacertae in flaring and non-flaring states: timing and spectral studies

A. Priyana Noel, Alicja Wierzcholska and Raj Prince

BL Lacertae is a blazar known for its high flux variability and occasional broadband flares of unknown origin. It was in an extended flaring state from July 2020 until the end of 2021, making it an ideal candidate to study spectral and temporal properties during different flux states. We analysed five XMM–Newton EPIC observations of BL Lacertae taken up to the end of 2021. Temporal properties were investigated using fractional variability, minimum variability timescale, and the discrete correlation function. Detailed spectral modeling was performed on the two most variable observations, including correlation analysis between the soft (0.3–2.0 keV) and hard (2.0–10.0 keV) bands. Two of five observations were found to be highly variable with $F_{\mathrm{var}} = 19.16 \pm 0.32$ and $6.27 \pm 0.43$. The 2021 observation corresponds to the highest flux state. The shortest variability timescale in the 0.3–10 keV band is 1.24 ks. Assuming synchrotron-dominated X-ray emission, this timescale constrains the emission region size. Under equipartition between the magnetic field and radiating particles, this implies $B \approx 0.4\,\mathrm{G}$. A softer-when-brighter spectral trend was found, as commonly seen in blazars. Spectra were modeled with single power-law, log-parabola, and broken power-law models; the broken power-law gave the best fit by Akaike Information Criterion in most cases, with a strong break energy–flux correlation. A thermal blackbody component showed a positive temperature–flux correlation in some observations. The spectral break, interpreted as the synchrotron cooling break, shifts to higher energies with increasing flux. The source consistently showed softer-when-brighter behavior. Only one observation showed significant soft–hard band correlation. The data suggest the synchrotron peak moves into or across the X-ray band as the source brightens.
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc

Multi-Field Dilaton Screening Beyond the Thin-Shell Mechanism

Philippe Brax, Carsten van de Bruck, Anne-Christine Davis et al. (+1 more)

We analyse screening in multi-field scalar-tensor theories, focusing on systems with a dilaton coupled to matter and an axion with a dilaton-dependent kinetic term, in the presence of both planetary and stellar density profiles. Using analytic arguments and fully coupled numerical solutions, we identify a regime in which full screening for a dark-energy-light, effectively unpinned string-dilaton, can occur without fine-tuning. The backreaction of the dilaton's partnered axion field can suppress the exterior scalar charge by selecting a minimum-energy configuration (the BBQ mechanism), yielding robust screening for generic axion gradients. In this regime screening is achieved by cancelling the dilaton's gradient rather than localising it. This reduces the exterior scalar charge and allows for gravity tests in the solar system to be passed. We then show that the more familiar thin-shell intuition need not apply in the multi-field setting. Axion surface gradients can drastically reshape the dilaton profile and drive a more localised transition without generically suppressing the fifth force. The exterior charge can remain essentially unchanged or even be enhanced as the shell is made thinner by a kinetically coupled field. Multi-field two-derivative dynamics therefore decouple localisation in thin shells from screening, evade single-field no-go arguments, and reopen viable parameter space for cosmologically light dilaton-like scalars with strong couplings to matter.
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All authors Philippe Brax, Carsten van de Bruck, Anne-Christine Davis, Adam Smith

Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ex

Dark Matter Search with the DEAP-3600 Detector using the Profile Likelihood Ratio Method

DEAP Collaboration: P. Adhikari, R. Ajaj, M. Alpízar-Venegas et al. (+121 more)

We present here a search for WIMP dark matter using 790.8 live-days of data collected with 3269 kg of liquid argon (1266 kg fiducial) by the DEAP-3600 detector at SNOLAB, using the Profile Likelihood Ratio method. The likelihood model is based on three parameters: estimated energy, pulse-shape discrimination parameter, and reconstructed position within the detector. Using this method, the expected signal sensitivity of DEAP-3600 benefits from an increased fiducial volume and improved event selection acceptance. Alpha-decays from a small number of dust particulates circulating within the liquid argon target are the dominant source of background events and limit the sensitivity of this search. This result provides improved exclusion upper limits on the WIMP-nucleon spin-independent cross section on liquid argon for WIMP masses between 20 GeV/$c^{2}$ and 100 GeV/$c^{2}$. At 100 GeV/$c^{2}$ the observed limit is 3.4 $\times$ 10$^{-45}$ cm$^2$ at 90% confidence level.
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All authors DEAP Collaboration: P. Adhikari, R. Ajaj, M. Alpízar-Venegas, P.-A. Amaudruz, J. Anstey, D. J. Auty, M. Baldwin, M. Batygov, B. Beltran, A. Bigentini, C. E. Bina, W. Bonivento, M. G. Boulay, J. F. Bueno, P. M. Burghardt, A. Butcher, M. Cadeddu, B. Cai, M. Cárdenas-Montes, S. Cavuoti, Y. Chen, S. Choudhary, B. T. Cleveland, R. Crampton, S. Daugherty, P. DelGobbo, P. Di Stefano, G. Dolganov, L. Doria, F. A. Duncan, M. Dunford, E. Ellingwood, A. Erlandson, S. S. Farahani, N. Fatemighomi, G. Fiorillo, R. J. Ford, D. Gahan, D. Gallacher, A. Garai, P. García Abia, S. Garg, P. Giampa, A. Giménez-Alcázar, D. Goeldi, P. Gorel, K. Graham, A. Grobov, A. L. Hallin, M. Hamstra, S. Haskins, J. Hu, J. Hucker, D. Huff, T. Hugues, A. Ilyasov, B. Jigmeddorj, C. J. Jillings, A. Joy, G. Kaur, A. Kemp, M. Khoshraftar Yazdi, M. Kuźniak, F. La Zia, M. Lai, S. Langrock, B. Lehnert, J. LePage-Bourbonnais, M. Lissia, L. Luzzi, I. Machulin, P. Majewski, A. Maru, J. Mason, A. B. McDonald, T. McElroy, J. B. McLaughlin, C. Mielnichuk, L. Mirasola, A. Moharana, J. Monroe, A. Murray, M. Needs, C. Ng, G. Oliviéro, M. Olszewski, S. Pal, D. Papi, B. Park, M. Perry, V. Pesudo, T. R. Pollmann, F. Rad, C. Rethmeier, F. Retière, I. Rodríguez García, L. Roszkowski, R. Santorelli, F. G. Schuckman II, N. Seeburn, S. Seth, V. Shalamova, P. Skensved, T. Smirnova, N. J. T. Smith, K. Sobotkiewich, T. Sonley, J. Sosiak, J. Soukup, R. Stainforth, M. Stringer, J. Tang, P. Taylor, R. Turcotte-Tardif, E. Vázquez-Jáuregui, G. Vera Díaz, S. Viel, B. Vyas, M. Walczak, J. Walding, M. Ward, S. Westerdale, R. Wormington, A. Zuñiga-Reyes

Cosmology and Nongalactic Astrophysics

Smoking-gun signatures of bounce cosmology from echoes of relic gravitational waves

Mian Zhu and Yi-Fu Cai

We report a novel feature of relic gravitational waves (GWs) in non-singular bounce cosmologies that is testable in light of GWs astronomy. In non-singular bounce cosmologies, the effective potential $M_p^2 a^{\prime \prime}/a$ that governs the evolution of primordial GWs contains two peaks due to the existence of contraction phase prior to the standard expansion phase. Accordingly, relic GWs interference between the two peaks in the effective potential. This interference results in a distinctive oscillatory feature in the energy density spectrum of GWs, analog to the resonant tunneling effect in quantum mechanics. As a result, the GWs spectrum exhibits an oscillatory patterns on high frequency regime, distinctive to other cosmological scenarios such as inflation. We show that the amplitude of GWs spectrum is high enough to reach the sensitivity of current and forthcoming GWs instruments, making our predictions falsifiable. Hence, our finding offers a promising way to experimentally test the non-singular bounce scenarios and search for new physics in early universe cosmologies.
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Solar and Stellar Astrophysics

Formation and rising phase of a flux rope through data-constrained simulations

M. V. Sieyra, A. Strugarek, A. Prasad et al. (+8 more)

Context. Data-constrained models incorporate observed photospheric magnetic fields. However, due to the lack of magnetic field information in the rest of the solar atmosphere, models rely on extrapolations that, in most cases, neglect the Lorentz force. Nevertheless, this force is present in the lower atmosphere and may play a key role in destabilising the equilibrium configuration and triggering eruptions. Aims. This study seeks to understand and reproduce a solar eruption SOL2014-12-18T21:41 that occurred in active region NOAA 12241, preceded by an M6.9 flare, and to investigate the impact of relaxing the initial force-free assumption. Methods. The resistive and compressible magnetohydrodynamic simulation is initiated using a non-force-free magnetic field extrapolated from a photospheric vector magnetogram taken minutes before the flare. The simulation includes a stratified atmosphere and non-ideal effects such as thermal conduction and radiative cooling. Results. A flux rope forms and rises in the simulation, carrying away dense material from the lower solar atmosphere. Its formation results from the non-zero Lorentz force acting on the initial sheared arcade, without assuming pre-existing flux ropes or photospheric driving motions. The flux rope is then deflected toward regions of low magnetic pressure, escaping the domain at 350 km/s with approximately constant acceleration. Conclusions. A robust numerical framework for modelling flaring active regions was applied to the eruption of NOAA AR12241 as a case study, assuming a realistic non-force-free magnetic field near the flare onset. It exemplifies how an initial Lorentz force imbalance can successfully trigger a flux rope formation that later escapes the simulation domain. It also enables comparison with real observations through the addition of a stratified atmosphere spanning from the photosphere to the corona.
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All authors M. V. Sieyra, A. Strugarek, A. Prasad, A. Wagner, P. Démoulin, F. Moreno-Insertis, A. J. Finley, R. Joshi, A. Blaise, A. S. Brun, E. Buchlin

Solar and Stellar Astrophysics

Time-Series Photometric Detection and Physical Characterization of Variable Stars in Four Intermediate- to Old-Age Galactic Open Clusters

K. Belwal, D. Bisht, Ing-Guey Jiang et al. (+4 more)

We present a ground-based time-series photometric study of stellar variability in four intermediate- to old-age open clusters NGC 2192, NGC 2266, NGC 2509, and IC 1369 based on high-cadence Cousins R-band observations obtained with the 0.6 m VASISTHA telescope at the IERCOO observatory. The monitoring campaign comprises more than 34 h of time-series data, providing sensitivity to short-period variability on timescales of 0.02-2 d. We identified between 190 and 290 probable members in each cluster using a Gaussian Mixture Model. Structural parameters were derived from radial density profiles fitted with King models. Fundamental parameters were further constrained using color-magnitude diagram analysis with PARSEC isochrones, yielding ages of 0.3-1.6 Gyr and distances of 2.5-3.9 kpc. From the time-series photometry, we identify four new variable stars and seven previously uncharacterized periodic variables, including {\delta} Scuti and {\gamma} Doradus pulsators, as well as rotational variables. The detected variables exhibit periods between 0.12-0.90 d, with R-band amplitudes ranging from 0.01 to 0.20 mag. Periods were determined using Lomb-Scargle analysis of calibrated light curves. For a subset of variables, spectral energy distribution fitting was performed to derive effective temperatures (4300-10 000 K), radii (1.3-46 R_{\odot}), and luminosities (2-100 L_{\odot}), enabling reliable placement on the Hertzsprung-Russell diagram. We present PHOEBE light-curve modelling of the W UMa-type eclipsing binary Gaia DR3 2164531610149292288 in IC 1369, deriving its physical parameters and providing the first detailed characterization beyond its previously reported variability. These results demonstrate that combining dense-cadence ground-based observations with Gaia astrometry provides a reliable approach for identifying and characterizing variable stars in OCs.
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All authors K. Belwal, D. Bisht, Ing-Guey Jiang, Mohit Singh Bisht, A. Raj, S. K. Chakrabarti, D. Bhowmick

Earth and Planetary Astrophysics

Mass Production of 2023 KMTNet Microlensing Planets. II: Two Planets and A Brown Dwarf

Zhixing Li, Hongyu Li, Weicheng Zang et al. (+63 more)

To expand the homogeneous microlensing planetary sample of the Korea Microlensing Telescope Network (KMTNet), we investigate six planetary candidates identified by the AnomalyFinder search in the 2023 prime-field data, namely KMT-2023-BLG-1592, OGLE-2023-BLG-0766, KMT-2023-BLG-0332, KMT-2023-BLG-0486, KMT-2023-BLG-0792, and OGLE-2023-BLG-1043. Light-curve modeling indicates that the first two events have planetary mass ratios of $\log q \sim -3.0$ and $-2.6$, while the third exhibits a brown dwarf mass ratio of $\log q \sim -1.4$. The remaining three events show the well-known degeneracy between the binary-lens single-source (2L1S) and single-lens binary-source (1L2S) interpretations. A Bayesian analysis yields companion masses of about 0.6 and 1.2 Jupiter masses for the two planetary systems, likely orbiting beyond the snow lines of M- or K-dwarf hosts. A review of the KMTNet planetary sample shows that candidates discovered by AnomalyFinder are significantly more likely to exhibit the 2L1S/1L2S degeneracy, consistent with the tendency of AnomalyFinder to detect subtler planetary signals.
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All authors Zhixing Li, Hongyu Li, Weicheng Zang, Yoon-Hyun Ryu, Andrzej Udalski, Takahiro Sumi, Hongjing Yang, Yuchen Tang, Jiyuan Zhang, Shude Mao, Michael D. Albrow, Sun-Ju Chung, Andrew Gould, Cheongho Han, Kyu-Ha Hwang, Youn Kil Jung, In-Gu Shin, Yossi Shvartzvald, Jennifer C. Yee, Sang-Mok Cha, Dong-Jin Kim, Seung-Lee Kim, Chung-Uk Lee, Dong-Joo Lee, Yongseok Lee, Byeong-Gon Park, Richard W. Pogge, Przemek Mróz, Michał K. Szymański, Jan Skowron, Radoslaw Poleski, Igor Soszyński, Paweł Pietrukowicz, Szymon Kozłowski, Krzysztof A. Rybicki, Patryk Iwanek, Krzysztof Ulaczyk, Marcin Wrona, Mariusz Gromadzki, Mateusz J. Mróz, Fumio Abe, Ken Bando, David P. Bennett, Aparna Bhattacharya, Ian A. Bond, Akihiko Fukui, Ryusei Hamada, Shunya Hamada, Naoto Hamasak, Yuki Hirao, Stela Ishitani Silva, Naoki Koshimoto, Yutaka Matsubara, Shota Miyazaki, Yasushi Muraki, Tutumi Nagai, Kansuke Nunota, Greg Olmschenk, Clément Ranc, Nicholas J. Rattenbury, Yuki Satoh, Daisuke Suzuki, Sean Terry, Paul J. Tristram, Aikaterini Vandorou, Hibiki Yama

Astrophysics of Galaxies

Three-dimensional reddening maps of the Magellanic Clouds constructed by RR Lyrae stars

Shunxuan He and Yang Huang

We present the first three-dimensional reddening maps of the Large and Small Magellanic Clouds (LMC and SMC) constructed using fundamental-mode RR Lyrae stars from the OGLE-IV survey. By applying a period-amplitude-color relation and a period-luminosity-metallicity calibration in the OGLE photometric system, we derive intrinsic colors, color excess $E(V-I)$, and photometric distances for more than 20,000 RRab stars in the LMC and 3,000 in the SMC. Spatial variations in reddening are modeled using an adaptive quadtree scheme, where robust reddening-distance relations are fit within each partition and distances are iteratively updated to achieve self-consistency. The resulting maps reveal resolved dust structures across both galaxies, including steep reddening gradients in the central LMC and flatter profiles in the SMC. The construction of the three-dimensional reddening maps further reveals that high-extinction regions exhibit reddening behavior inconsistent with a uniform extinction law, implying localized variations in dust properties. The final maps comprise 205 partitions for the LMC and 67 partitions for the SMC, and are released together with a Python-based query tool and GeoJSON data products. These 3D maps provide a foundation for distance-dependent reddening corrections and for probing the structure and physical conditions of the Magellanic interstellar medium, and future high-precision and cadence RR Lyrae sample from Gaia DR4 will support higher-resolution mapping and deeper exploration of dust substructure.
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High Energy Astrophysical Phenomena

Discovery of a millisecond pulsar with a CO white dwarf companion

Jie Zhang, Zerui Wang, Lei Zhang et al. (+13 more)

We report the discovery and characterization of PSR J1810-0623, a fully recycled millisecond pulsar with a spin period of 4.55 ms, discovered with the Five-hundred-meter Aperture Spherical radio Telescope (FAST) and followed up with FAST and the Green Bank Telescope (GBT). A phase-connected timing solution spanning over 6.5 years reveals a 15.4-day binary orbit with extremely low eccentricity (about 1.5E-5). Assuming a neutron star mass of 1.4 Msun, the inferred companion median mass (about 0.64 Msun) is consistent with a carbon-oxygen white dwarf, indicating an evolutionary origin in an intermediate mass Xray binary. The system's properties closely resemble those of other massive white dwarf binaries thought to form via Case A Roche lobe overflow, suggesting a prolonged accretion phase during which the neutron star was efficiently recycled. Polarimetric analysis of FAST data yields a moderate degree of linear polarization and a rotation measure of 86.6 pm 0.6 rad/m^2, offering constraints on the Galactic magnetic field. The inferred characteristic age (about 32 Gyr) and low surface magnetic field (about 1E8 G) indicate a highly recycled pulsar. Proper-motion measurements imply a modest transverse velocity, consistent with those of recycled millisecond pulsars in the Galactic field. Although the proximity of the globular cluster Pal 7 raises the possibility of a dynamical origin, discrepancies in dispersion measure and proper motion argue against a physical association. PSR J1810-0623 adds to the rare class of long-orbital period MSP-COWD systems and provides a valuable laboratory for studying pulsar recycling, binary evolution, and Galactic structure.
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All authors Jie Zhang, Zerui Wang, Lei Zhang, Yulan Liu, Alessandro Ridolfi, Meng Guo, Di Li, Ryan S. Lynch, Cong Wang, Pei Wang, Mengmeng Ni, Jiale Hu, Mengquan Liu, Zhie Liu, Bo Han, Chenchen Miao

Instrumentation and Methods for Astrophysics

A Hybrid Framework for Kilonova Anomaly Detection using Single-Epoch SEDs from the 7-Dimensional Telescope

Gregory S. H. Paek, Myungshin Im, Seo-Won Chang et al. (+2 more)

We develop a hybrid framework to identify kilonovae (KNe), using single-epoch, medium-band spectral energy distributions from the 7-Dimensional Telescope (7DT). The framework integrates an unsupervised anomaly classifier (Isolation Forest) to flag unusual events with a supervised multi-class classifier (XGBoost) that characterizes eight common transient types. Trained on realistically simulated 7DT photometry accounting for per-filter sensitivity, the classifier achieves macro $F_{1}\sim0.80$ ($\sim0.82$) with 20 (40) filters across eight classes, Type~Ia/Ibc/II SNe, SLSNe, TDEs, AGN, stellar variables, and asteroids. Without direct training, the anomaly detector recovers $>$90% of simulated and observed optically detectable KNe (AT~2017gfo) with a low contamination fraction, with a caveat of limitations of the training sample such as limited redshift range of SNe ($z < 0.15$), and a relatively small number of early non-KNe spectra. A SHAP-based feature analysis reveals that only $\sim$40–50% of the most informative filters are sufficient to retain near-baseline performance, while red-end filters contribute little. Combining the top-ranked half of the 40 7DT filters with a single LSST band reproduces the full-model accuracy within 1–2%, suggesting practical follow-up strategies. These results demonstrate that 7DT's medium-band system enables rapid, interpretable classifications and reliable anomaly alerts from single-epoch data – promising for gravitational-wave follow-up, Rubin alert stream filtering, and serendipitous transient discovery in the 7DT survey.
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All authors Gregory S. H. Paek, Myungshin Im, Seo-Won Chang, Hyeonho Choi, Ji Hoon Kim

High Energy Astrophysical Phenomena

Ultra-compact X-ray Binaries: A Review

Bo Wang, Dongdong Liu, Yunlang Guo et al. (+3 more)

Ultra-compact X-ray binaries (UCXBs) are a subclass of low-mass X-ray binaries (LMXBs) characterized by ultra-short orbital periods, typically less than $60-80\,$min. They consist of a compact mass-accretor and a hydrogen-poor mass-donor, in which the mass-accretor could be a neuron star (NS) or even a black hole (BH). UCXBs play an important role in multiple areas of astrophysics. In particular, they are considered strong, continuous gravitational wave (GW) sources in the low-frequency band, making them key targets for future space-based GW observatories such as LISA, TianQin and Taiji. As the most compact binaries, the formation and evolution of UCXBs remain highly uncertain. In this article, we review four classic formation channels: the white dwarf donor channel, the He star donor channel, the evolved main-sequence donor channel, and the accretion-induced collapse channel. We also discuss recent progress in these channels, covering evolutionary scenarios, the initial parameter space for UCXB formation, and associated objects. A comparison between observed UCXBs and theoretical expectations is provided, along with a discussion on the observed BH-UCXB candidates. The origin of UCXBs can be constrained by the chemical composition of mass-donors and their locations in diagrams of mass-transfer rate and X-ray luminosity versus orbital period. We also examine the implications of UCXBs for several astrophysical fields, including GW astronomy, multi-messenger astronomy, binary evolution, and NS physics under extreme conditions. Further progress will depend on multi-wavelength observations, the discovery of more UCXB samples, and more detailed theoretical simulations.
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All authors Bo Wang, Dongdong Liu, Yunlang Guo, Hailiang Chen, Wencong Chen, Zhanwen Han

Cosmology and Nongalactic Astrophysics

Non-parametric estimation of the baryon gas fraction and the cosmological bias with clusters

Hyeon Kim, Raphaël Wicker, Benjamin L'Huillier et al. (+3 more)

X-ray observations of galaxy clusters allow us to estimate the gas fraction, and thus the baryon fraction, and its evolution over time. This offers an additional cosmological probe as well as a probe of the gas behaviour in massive halos at the end of structure formation. However, cosmological and astrophysical effects are degenerate, and both should be modeled in order to explain observations; otherwise, the chosen baryonic model can potentially bias the cosmological results. We propose to quantify this effect by adopting a model-independent framework. We utilize Type Ia Supernovae to reconstruct the cosmic expansion history and apply the iterative smoothing method to infer the mass and redshift evolution of the hydrostatic mass bias. Our results confirm previous findings and show that the bias should evolve with time to reproduce CMB cosmological constraints.
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All authors Hyeon Kim, Raphaël Wicker, Benjamin L'Huillier, Marian Douspis, Laura Salvati, Arman Shafieloo

Astrophysics of Galaxies

Blackbody Quasar and Radio Source (BBQSORS): A Candidate of Transitional Little Red Dots with a $T\sim10^4\ K$ Blackbody Spectrum

Yuxing Zhong, Xiaoyang Chen, Kohei Ichikawa et al. (+12 more)

We report Subaru/PFS spectroscopic follow-up of a radio-loud quasar at $z=1.715$ from the UNVEIL radio AGN catalog and with X-ray detections. The PFS spectrum displays a broad MgII emission line with an $\mathrm{FWHM}\gtrsim4000\ km/s$, accompanied by a narrow absorption feature. The spectrum reveals a characteristic $\Lambda$-shape over the rest-frame wavelength ranging $\sim1500-3500\ \r{A}$. This underlying UV continuum is too curved to be reproduced by simply applying dust extinction to the spectrum of typical unobscured quasars. Alternatively, it is well described by a blackbody spectrum with a temperature of $T\approx10000\ K$. This result is in good agreement with its UV to MIR photometry that can be well modeled by three blackbody components representing the SMBH envelope ($\mathit{T}\approx9700\ K$), dust torus ($T\approx1500\ K$), and host galaxy dust ($T\approx80\ K$). The source is marginally detected in the GALEX NUV, revealing a potential V-shaped spectral energy distribution around $1400\ \r{A}$, reminiscent of the spectral feature reported for recently discussed LRDs whose V-shapes occur around $3000-4000\ \r{A}$. This wavelength shift is broadly consistent with the temperature contrast between our blackbody component, with $T\sim10^4\ K$, and the lower effective temperature of $T\sim5000\ K$ expected for an optically thick photosphere surrounding the SMBH in LRDs. These properties suggest that this source might be caught in a transient evolutionary phase in which the dense gas envelope characteristic of LRD has begun to fragment, allowing us to witness the emergence of a quasar from an LRD-like state.
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All authors Yuxing Zhong, Xiaoyang Chen, Kohei Ichikawa, Youwen Kong, Kentaro Aoki, Satoshi Yamada, Tohru Nagao, Daisaburo Kido, Toshihiro Kawaguchi, Yoshiki Matsuoka, Toru Misawa, Shoichiro Mizukoshi, Masafusa Onoue, Ayumi Takahashi, Yoshiki Toba

Earth and Planetary Astrophysics · Cross-listed from physics.soc-ph

Measuring Primitive Accumulation: An Information-Theoretic Approach to Capitalist Enclosure in PIK2, Indonesia

Sandy Hardian Susanto Herho, Alfita Puspa Handayani, Karina Aprilia Sujatmiko et al. (+5 more)

Large-scale land enclosure for speculative mega-development constitutes a non-equilibrium spatial process whose velocity, topology, and irreversibility remain poorly quantified. We study the Pantai Indah Kapuk 2 (PIK2) coastal mega-development north of Jakarta, Indonesia, using eight years (2017–2024) of Sentinel-2 land-use/land-cover (LULC) data at 10-meter resolution. The landscape is projected onto a Marxian probability simplex partitioning terrestrial pixels into Commons, Agrarian, and Capital fractions. Fisher-Rao (FR) geodesic distances on this simplex identify a transformation pulse of $0.405$~rad/yr during 2019–2020, coinciding with major construction activity. Absorbing Markov chain analysis yields expected absorption times into the built environment of $46.0$~years for cropland and $38.1$~years for tree cover, with a pooled built-area self-retention rate of $96.4\%$. Percolation analysis reveals that a giant connected component containing $89$–$95\%$ of all built pixels persists at occupation probabilities $p \in [0.096, 0.162]$, far below the random percolation threshold $p_c \approx 0.593$, indicating planned rather than stochastic spatial growth. The box-counting fractal dimension of the urban boundary increases from $d_f = 1.316$ to $1.397$, consistent with increasingly irregular frontier expansion. These results suggest that information-geometric and statistical-mechanical tools can characterize the kinematic and topological signatures of capitalist spatial accumulation with quantitative precision.
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All authors Sandy Hardian Susanto Herho, Alfita Puspa Handayani, Karina Aprilia Sujatmiko, Faruq Khadami, Iwan Pramesti Anwar, Rusmawan Suwarman, Dasapta Erwin Irawan, Deny Juanda Puradimaja

Solar and Stellar Astrophysics

Asteroseismology of red giants in the globular cluster 47 Tuc using the HST

Dennis Stello, Timothy R. Bedding and Ronald L. Gilliland

Globular clusters provide unique opportunities to study stellar evolution – as the second brightest cluster, 47 Tuc is a prime target. Asteroseismology can be used to measure precise masses of stars and has recently been applied to red giants in globular clusters, but so far not for 47 Tuc. Here, we present a search for solar-like oscillations in red giants of 47 Tuc using 8.3 days of high-cadence Hubble Space Telescope data. We detect oscillations in two out of the five giants falling in the field of view. One is on the horizontal branch (HB) while the other is on the red giant branch (RGB) at a similar brightness. From the seismic signal, we measure the stellar masses to be $0.78\pm0.13\,$M$_\odot$ (HB) and $0.94\pm0.15\,$M$_\odot$ (RGB), and hence an inferred integrated mass loss along the upper RGB of $0.16\pm0.20\,$M$_\odot$. A mass uncertainty of less than 0.05M$_\odot$ would be required to obtain a useful estimate of the mass loss, while an uncertainty below 0.01M$_\odot$ would be required to measure the mass difference between the cluster's multiple chemical populations. The former would be attainable with observations of about 100 times more stars to form ensemble-averaged values, or alternatively a longer campaign observing fewer stars. Detecting mass differences between the chemical sub-populations, could be obtained with a 20-day campaign observing several hundreds of stars. Our clear detection of oscillations and the prospects presented here warrant dedicated high-cadence campaigns of 47 Tuc, which are possible with NASA's Roman mission and future missions like HAYDN.
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Astrophysics of Galaxies

Prevalent elongated galaxies in the early Universe evidenced by stellar kinematics

Bitao Wang, Yingjie Peng and Hua Gao

The Universe is now extensively populated by discy galaxies with coherent galaxy-wise stellar rotation. This disc prevalence has been deemed a late-time phenomenon because the penetrating cold gaseous streams in the early Universe ($z\gtrsim 2$) fuel the star formation in galaxies too intensively to allow for thin disc formation. However, recent images taken by the James Webb Space Telescope (JWST) unveiled a prominent population of low-mass galaxies at high redshifts with flattened shapes, widely interpreted as early significance of discs given the well-established connection between flattening and discy morphology seen in the local Universe. It is noticed, on the other hand, that these galaxies show far more flattened systems than can be accounted for by randomly oriented oblate discs, and the axial ratio distributions are better explained by elongated prolate ellipsoids, an extremely rare spindle-like configuration at low redshifts. The true morphological nature of these early low-mass galaxies is fundamental to understanding the structure evolution of their discy descendants we see today, including our Milky Way. In this work, we discriminate the oblate disc and prolate spindle scenario by a decisive experiment with stellar kinematics at its core. The result clearly supports the prolate spindle scenario, and evidences an early Universe widely inhabited by linear stellar systems contrasting the current era dominated by planar discy galaxies, which suggests a dimensional transition in galactic structure over cosmic time.
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Friday 13 March

Instrumentation and Methods for Astrophysics · Cross-listed from physics.optics

Dichroic Dual-Angle Refractor: Multi-Cell Huygens' Metasurface-Based Circuit Approximation

Georgios Kyriakou and Giampaolo Pisano

A dichroic dual-angle refractor based on a 2D Huygens' metasurface model is treated by means of resonant-circuit approximations of multiple cells. The whole parameter space of refraction angles is tested for the analytic approximations involved, whereas the realised refraction guides the choice of optimal such angles. Our results indicate the possibility of sythesising a rectangular array of a number of cells which eventually depends on the low-frequency band diffraction limit. Aberrations from the ideal performance are also examined and attributed to certain approximation caveats.
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Astrophysics of Galaxies

The Environments of Star-Forming Galaxies Detected in the SFACT Survey: Do Mergers and Interactions Drive the Star Formation?

Brooke Kimsey-Miller, John J. Salzer, Kristin N. Baker et al. (+3 more)

We conduct an environmental analysis around 167 star-forming galaxies (SFGs) detected by the Star Formation Across Cosmic Time (SFACT) survey over the redshift range 0.129 $\leq$ z $\leq$ 0.500. We use three environmental estimators to characterize the local galactic environments around the SFACT SFGs, on the scales of 100 kpc to several Mpc. We categorize these environments based on the relative clustering strength with respect to a deep environment comparison redshift sample. The SFACT SFGs tend to be less clustered than the environment comparison sample (ECS), with no significant change in relative clustering strengths over our redshift range. We find that any trends with the star-formation rates (SFRs) of the SFACT galaxies and their environments are likely related to their absolute magnitudes, a proxy for mass. Mergers and interactions with other luminous galaxies do not appear to be the primary driver of the star-formation activity seen within the SFACT SFGs.
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All authors Brooke Kimsey-Miller, John J. Salzer, Kristin N. Baker, Samantha W. Brunker, David J. Carr, Jennifer Sieben

High Energy Astrophysical Phenomena

Pulsar timing arrays: the emerging gravitational-wave landscape

C. M. F. Mingarelli, J. A. Casey-Clyde, Y. T. Chang et al. (+8 more)

Pulsar Timing Array (PTA) experiments have entered a new era with evidence for a nanoHertz gravitational wave background (GWB). This review describes the physics of detection, detailing the noise models and cross-correlation techniques required to isolate the Hellings-Downs curve. We discuss astrophysical implications, arguing that the perceived tension between current amplitudes and standard merger models is largely resolved by new insights into supermassive black hole binary populations. Beyond the stochastic background, we review the framework for multi-messenger continuous gravitational-wave searches, highlighting targeted search campaigns and rigorous detection protocols. We also examine the potential to probe New Physics, including cosmic strings and ultralight dark matter. Critical challenges are addressed, including small-scale leakage bias in anisotropy searches and the separation of deterministic signals from the GWB and pulsar noise. Finally, we outline the field's future, from rapid data combination strategies to the sensitivity gains expected from the Square Kilometre Array Observatory (SKAO) and DSA-2000.
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All authors C. M. F. Mingarelli, J. A. Casey-Clyde, Y. T. Chang, E. Eisenberg, F. Hutchison, N. Khusid, B. Larsen, A. Moran, F. Semenzato, L. Willson, Q. Zheng

Cosmology and Nongalactic Astrophysics

Projected Sensitivity of Paleo-Detectors to Dark Matter Effective Interactions with Nuclei

Dionysios P. Theodosopoulos, Katherine Freese, Chris Kelso et al. (+1 more)

Paleo-detectors are a proposed experimental technique for direct detection (DD) of dark matter (DM) via the read-out of DM-induced nuclear recoil tracks in natural minerals. The large detector mass required for the sensitivity of conventional DD experiments to rare events is replaced by the exposure of paleo-detectors to DM-induced nuclear recoils over geological timescales. In this paper, we extend previous theoretical predictions for canonical spin-independent coherent and spin-dependent scattering (proportional to $A^2$ and the spin of the nucleus, respectively). We estimate the sensitivity of paleo-detectors to interactions between weakly interacting massive particle (WIMP) DM and nuclei within the framework of a Non-Relativistic Effective Field Theory (NREFT), considering isoscalar couplings to nucleons for both elastic and inelastic scattering. Taking into account cosmogenic, astrophysical and radiogenic backgrounds, we project the 90% confidence-level (CL) upper limits on the isoscalar NREFT coupling constants for both scattering types. We consider representative read-out scenarios and examine several target minerals. The projected sensitivities of paleo-detectors are compared with the 90% CL limits from the XENON100, LUX-ZEPLIN, and PandaX-II experiments, as well as with the 95% Bayesian credible region of the 2D marginalized posterior distribution from SuperCDMS. For DM masses from 1 GeV-10 GeV, paleo-detectors are projected to have sensitivity superior to that of conventional experiments for WIMP-nucleus interactions via all NREFT operators, largely independent of read-out scenario or target mineral. For DM masses from 10 GeV-5 TeV, we find that the sensitivity of paleo-detectors is projected to be comparable to or better than that of conventional experiments for WIMP-nucleus interactions via several NREFT operators, depending on the read-out scenario and target mineral.
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All authors Dionysios P. Theodosopoulos, Katherine Freese, Chris Kelso, Patrick Stengel

Solar and Stellar Astrophysics

Line-driven Radiative Winds in B-Supergiants: Bridging the Gap between Fast and Slow m-CAK Solutions

Matías Montesinos, Emil Zabala-Arroyo, Juan José Castro-Salgado et al. (+2 more)

The modified Castor, Abbott, and Klein (m-CAK) theory predicts different wind regimes based on the line force parameter for changes in ionization ($\delta$) and the rotation parameter ($\Omega$). Stationary hydrodynamic studies have reported ”forbidden regions” or gaps in this parameter space where no steady-state solution exists, suggesting physical instabilities. We investigate the stability of wind solutions within these gaps for B-supergiants to determine if they correspond to physical instabilities or numerical artifacts. We perform 1D time-dependent hydrodynamic simulations, systematically exploring the full $(\Omega, \delta)$ space for three B-supergiant models ($T_{\rm eff}=15-25$ kK), adopting a fixed density boundary condition. Our simulations reveal stable stationary solutions continuously across the entire parameter space, effectively filling the reported gaps. The transition from fast to slow regimes is smooth but structurally complex. Within the gap, the velocity profile develops a distinct ”kink” or extended plateau in the supersonic flow, allowing the wind to reach a stable state. The mass-loss rate ($\dot{M}$) varies smoothly without artificial jumps. We find that the $\dot{M}$ gradient depends on the radiative driving strength ($k$): while $\dot{M}$ increases with $\delta$ for standard driving ($k \approx 0.32$), it decreases for the weak-driving regime ($k = 0.1$), consistent with stationary predictions. Moreover, in this regime, the final solution depends on the initial flow acceleration, confirming multiple hydrodynamic solutions. We conclude the m-CAK solution space is continuous; reported forbidden regions are artifacts of stationary methods. Time-dependent simulations effectively bridge the regimes, suggesting these transitions correspond to metastable states.
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All authors Matías Montesinos, Emil Zabala-Arroyo, Juan José Castro-Salgado, Michel Curé, Ignacio Araya

Earth and Planetary Astrophysics

The JWST Early Release Science Program for Direct Observations of Exoplanetary Systems. VII. Molecular Mapping Performance with JWST/MIRI MRS: VHS 1256 b as a case study

Mathilde Mâlin, Anthony Boccaletti, Benjamin Charnay et al. (+29 more)

VHS 1256 b was the first planetary-mass companion to be observed with the James Webb Space Telescope's Mid-Infrared Instrument (JWST/MIRI) using the Medium-Resolution Spectrometer (MRS). The MRS provides high-quality integral-field spectral data in the mid-infrared (IR) wavelengths from 4.9 to 18 um. This dataset serves as a testbed for applying cross-correlation techniques to characterize exoplanet atmospheres. We implement the so-called molecular mapping approach, which consists of performing a spectral cross-correlation between each spectral pixel and atmospheric model templates. We compare these results with those obtained from cross-correlation of the extracted spectrum. Using a self-consistent Exo-REM atmospheric model grid, we constrain the temperature, surface gravity, C/O ratio, and metallicity, finding values consistent with those obtained from other analysis methods. We detect CO (S/N $\sim$ 25) and H2O (S/N $\sim$ 76), with tentative detections of NH3 and CH4 (S/N$\sim$ 3). We test cross-correlation to measure trace-species abundances and isotopic ratios. We measure a volume mixing ratio of [NH3] =-5.73^{+0.15}_{-0.14} and an isotopic ratio $^{12}\mathrm{C}/^{13}\mathrm{C}=77.8^{+13}_{-10}$, both consistent with free-chemistry retrievals. The derived NH3 volume mixing ratio, combined with the measured temperature and radius, is consistent with VHS 1256 b having a mass above the deuterium-burning limit. These results demonstrate the diagnostic power of mid-IR spectroscopy and highlight cross-correlation as a robust method for characterizing directly imaged exoplanets, even in future higher-contrast regimes where spectral extraction becomes challenging. Future MIRI MRS observations across a wider range of temperatures and masses will further expand our understanding of planetary atmospheric chemistry.
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All authors Mathilde Mâlin, Anthony Boccaletti, Benjamin Charnay, Laurent Pueyo, Alexis Bidot, Polychronis Patapis, Sasha Hinkley, Simon Petrus, Niall Whiteford, Marshall Perrin, Beth A. Biller, Gabriele Cugno, Thayne Currie, Camilla Danielski, Thomas Henning, Kielan K. W. Hoch, Markus Janson, Jens Kammerer, Elisabeth C Matthews, Evert Nasedkin, Paulina Palma-Bifani, Isabel Rebollido, Matthias Samland, Andrew Skemer, Jordan M. Stone, Genaro Suárez, Ben J. Sutlieff, Motohide Tamura, Christopher A. Theissen, Johanna M. Vos, Zhoujian Zhang, Alice Zurlo

Instrumentation and Methods for Astrophysics · Cross-listed from nucl-ex

Direct Experiments of Neutron Capture on Stable and Unstable Isotopes for Stellar Nucleosynthesis Studies

Jorge Lerendegui-Marco, Javier Balibrea-Correa, Victor Babiano-Suárez et al. (+7 more)

Neutron-capture reactions provide essential nuclear-physics input for modeling the synthesis of heavy elements in stars. The growing precision of stellar spectroscopy and isotopic measurements in presolar SiC grains now demands cross sections with improved accuracy over the full energy range, and access to unstable nuclei relevant to slow (s-) process branchings and the intermediate (i-) process. This article reviews recent progress in direct neutron-capture measurements, focusing on time-of-flight (TOF) experiments at CERN n_TOF and complementary activation techniques. Substantial advances have been achieved for stable s-only and bottleneck isotopes, significantly improving constraints on s-process models. In parallel, the combination of high instantaneous neutron fluxes and advanced detector systems has facilitated first-time measurements of several radioactive branching-point nuclei. Feasibility studies, however, reveal current limitations related to sample availability, background conditions, and restricted energy coverage. In this context, the complementarity between TOF and activation emerges as a central strategy. Future developments, including high-flux facilities and novel inverse-kinematics experiments in ion storage rings, are expected to extend the boundaries of neutron-capture measurements, overcoming current limitation
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All authors Jorge Lerendegui-Marco, Javier Balibrea-Correa, Victor Babiano-Suárez, Cesar Domingo-Pardo, Gabriel de la Fuente-Rosales, Bernardo Gameiro, Ion Ladarescu, Ariel Tarifeño-Saldivia, Pablo Torres-Sánchez, the n_TOF Collaboration

Solar and Stellar Astrophysics

The Bochum Survey of the Southern Galactic Disk: III. Complete Data Release

Julia Blex, Moritz Hackstein, Christian Westhues et al. (+6 more)

The Southern Galactic Disk Survey (GDS) monitored a mosaic of 268 fields along a $6^\circ$-wide stripe in the southern Galactic disk with simultaneous observations in $r'$ and $i'$ ($7^\mathrm{m} \lesssim r', i' \lesssim 18^\mathrm{m}$) from September 2010 to September 2019. The survey design and data characteristics, as well as first results in $r'i'$, were presented by Haas et al. (2012; Paper I). Hackstein et al. (2015a; Paper II) extended the photometry and analysis process, and introduced the first catalogue including photometry of all 268 fields in $UBVr'i'z'$ and $r'i'$ light curves comprising up to 272 observations per field made between September 2010 and May 2015. Here we describe our custom-made observational scheduler and conclude the GDS with $r'i'$ light curves of up to 407 observations per field until September 2019 and $UBVz'$ light curves for a fraction of the fields. $113\,449$ distinct sources are identified as variables. Together with Paper II, we identified $77\,592$ variables that are not listed in either the International Variable Star Index (VSX) or the cross-match catalogue by Gavras et al. (2023). All emerging catalogues, comprising light curves, photometry, and reduced images, are made publicly available via the German Astrophysical Virtual Observatory (GAVO).
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All authors Julia Blex, Moritz Hackstein, Christian Westhues, Michael Ramolla, Markus Demleitner, Dominik J. Bomans, Kerstin Weis, Christofer Fein, Rolf Chini

Astrophysics of Galaxies

Implications of a contracted dark matter halo for the Milky Way's inferred virial mass

Diego Dado, Shaun T. Brown, Azadeh Fattahi et al. (+2 more)

We investigate how reliably the global properties of Milky Way-mass dark matter haloes can be recovered from dynamical data over a limited radial range, particularly $\lesssim 30~\mathrm{kpc}$ where observations are most sensitive but baryonic processes modify the halo structure. Using the ARTEMIS simulations, which produce varying degrees of baryon-induced contraction, we fit dark matter profiles over restricted radial ranges using commonly adopted parametric models. Assuming negligible observational uncertainties allows the systematic errors from these choices to be isolated. When fits are confined to inner radii, an NFW profile underestimates the virial mass by a factor of $\approx 2$ on average ($\approx 4$ for some systems), and the concentration by a factor of $\approx 2$. Einasto and generalised-NFW models provide excellent local fits but retain similar global biases. In contrast, the contracted halo prescription from Cautun et al. (2020) yields stable extrapolations and recovers unbiased halo mass estimates over all radii. The inferred mass improves systematically with increasing radial coverage, and tracers beyond $\gtrsim 50~\mathrm{kpc}$ largely eliminate the mean bias for all models. The local dark matter density at the Solar radius is recovered to within $\lesssim 5\%$ for all profiles other than NFW. These biases are sufficient to reconcile recent low Milky Way mass estimates derived from inner rotation-curve analyses with the canonical $\approx 10^{12}~\mathrm{M}_\odot$. We additionally find a halo-to-halo scatter of $\gtrsim 0.1$ dex ($\approx 25\%$) persists even under idealised conditions, setting a likely lower limit for the precision of halo mass estimates.
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All authors Diego Dado, Shaun T. Brown, Azadeh Fattahi, Andreea S. Font, Ian G. McCarthy

Solar and Stellar Astrophysics

Dust traps and gas kinematic signatures in a crescent structure of a planet-forming disk

Greta Guidi, François Menard, Daniel J. Price et al. (+2 more)

In the past few years, ALMA unveiled a variety of substructures (rings, spirals, crescents) in the continuum emission of most protoplanetary disks imaged at high spatial resolution. While the majority of disks presents axisymmetric ring-like structures in the dust brightness distribution, some sources display asymmetric morphologies (blobs, crescents) that have been often associated to vortices and/or mechanisms generated by the presence of one or more embedded planets. In this brief research report we present the analysis of the arc structure observed in the dust continuum emission of the disk around HD~163296, using high resolution ($\sim$8~au) matched continuum data from ALMA at four wavelengths. We characterize in detail the arc structures and present a kinematic signature observed in the CS(3-2) emission at the same location. Our results indicate that the crescent is caused by differential dust trapping in a local pressure maxima, for which plausible mechanisms can be the presence of a vortex or trapping in a Lagrangian point of the planet-star system.
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All authors Greta Guidi, François Menard, Daniel J. Price, Marion Villenave, Jie Ma