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Physics Astrophysics

astro-ph Watch Astrophysics

Monday 2 March

Cosmology and Nongalactic Astrophysics

Role of Domain Walls in the Early Universe in the Context of Mode Matching

K.K. Venkataratnam

We study the role of domain walls and their relics in the very early Universe within the framework of the mode-matching technique. Domain walls formed during the spontaneous breaking of discrete symmetries are modelled as a short lived contribution to the background energy density, leading to a controlled deviation from standard slow-roll inflation. Solving the modified Friedmann equation, we obtain a smooth, time-dependent Hubble parameter that asymptotically approaches the standard inflationary value. We analyze the evolution of scalar perturbations using the gauge-invariant Mukhanov variable and perform mode matching across the transition between the domain wall affected phase and standard inflation. We find that only modes exiting the horizon near the transition experience a modified evolution, while modes far from the transition remain unaffected. As a result, the primordial scalar power spectrum exhibits localized, scale-dependent deviations from scale invariance, while preserving the overall success of inflation. These results demonstrate that unstable domain-wall relics can leave subtle imprints on primordial fluctuations, potentially providing a probe of early-Universe phase transitions.
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Instrumentation and Methods for Astrophysics

CosmicWeb-21cm array: A New Radio Observation Array Design for 21cm Cosmology

Jiancheng Wang, Jirong Mao, Xiangming Cheng et al. (+10 more)

This paper presents the CosmicWeb-21cm array, a novel radio interferometer designed to overcome the key challenges in 21 cm cosmology. Its core innovations include: (1) a multi-scale nested geometry combining a hexagonal core with logarithmic spiral arms for excellent UV coverage and calibration robustness; (2) an intelligent non-uniform frequency sampling strategy that adapts resolution to foreground and signal characteristics, reducing data volume while preserving information; and (3) a machine-learning-enhanced, physics-informed processing pipeline that achieves 99.7% foreground removal efficiency; (4) a dual-polarization crossed dipole integrated with a dielectric lens and cryogenically cooled LNA, achieving stable beam patterns and low noise temperature ($<35$ K) across 50-250 MHz. These co-designed advances enable high sensitivity mapping of the Epoch of Reionization, dark energy constraints and cosmic-web structure.
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All authors Jiancheng Wang, Jirong Mao, Xiangming Cheng, Yigong Zhang, Jie Su, Xiaogu Zhong, Min Wang, Zhigang Zhang, Qingwei Wang, Yonghua Xu, Zhixuan Li, Longhua Qin, Zhengjun Zhang

Astrophysics of Galaxies

LCEz4-M1: A Lyman Continuum Emitter Candidate at z = 4.444 in the MUSE Hubble Ultra Deep Field

Shuairu Zhu, Zhen-Ya Zheng, Fuyan Bian et al. (+5 more)

High-redshift Lyman continuum emitters (LCEs) are crucial for understanding how galaxies ionize the neutral hydrogen in the epoch of reionization. However, detected LCEs at $z>4$ are quite rare. Here we report an LCE candidate at $z = 4.444$, dubbed LCEz4-M1, which is one of the highest-redshift LCE candidates currently known. The redshift is determined from the Ly$\alpha$ emission line detected in the VLT/MUSE spectrum. The Lyman continuum (LyC) signal is detected independently in the Hubble Space Telescope (HST) F435W image and the VLT/MUSE spectrum at significances of $\simeq3.7~\sigma$ and $\simeq2.8-3.0~\sigma$, respectively. The LyC centroid is spatially consistent with the JWST/NIRCam continuum within the astrometric uncertainty. Adopting the maximum IGM transmission, we infer conservative lower-limit escape fractions of $f_{\rm esc}({\rm F435W}) = 0.82^{+0.13}_{-0.17}$ and $f_{\rm esc}({\rm MUSE}) = 0.75^{+0.18}_{-0.28}$. Using the combined JWST and MUSE data set, we characterize the physical properties and morphology of LCEz4-M1. In our fiducial JWST-only SED fit, the galaxy is compact but has a moderate current galaxy-integrated star formation surface density, $\Sigma_{\rm SFR}=0.38~M_{\odot}\,{\rm yr^{-1}\,kpc^{-2}}$, suggesting that it is not an extreme compact starburst under this fiducial interpretation. While we find no clear evidence for an ongoing major merger for LCEz4-M1, the presence of a faint companion ($\sim 0''5$) detected in the F277W band suggests a potential minor interaction. We also find that LCEz4-M1 may lie in a locally overdense region, although the environmental interpretation remains tentative. Finally, the low ${\rm SFR}_{10\,{\rm Myr}}/{\rm SFR}_{100\,{\rm Myr}}$ ratio, low Ly$\alpha$ EW, and relatively weak rest-frame optical emission lines of LCEz4-M1 may indicate a post-burst LyC-leaking phase.
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All authors Shuairu Zhu, Zhen-Ya Zheng, Fuyan Bian, Fang-Ting Yuan, Chunyan Jiang, Xiaer Zhang, Ruqiu Lin, Yucheng Guo

Astrophysics of Galaxies

Local Analogs of Little Red Dots: Optical Variability and Evidence for an Active Galatic Nucleus Origin

Ruqiu Lin, Zhen-Ya Zheng, Junxian Wang et al. (+9 more)

Little red dots (LRDs) draw extensive attention because of their unique observational characteristics and apparent overabundance in the early Universe, raising new insights into early black hole formation and growth. Early studies show that LRDs exhibit weak variability in broad-band photometry and emission-line fluxes, suggesting a preference for super-Eddington accretion or disfavouring an AGN origin. However, the cadence of the current data, and therefore, the resulting light curves for LRDs, is limited, preventing us from placing strong constraints on their variability. Based on Zwicky Transient Facility (ZTF) light curves with a baseline of $\sim6$ years, we here study the optical variability of seven previously reported local analogs of LRDs at $z \sim 0.3$, offering an insight into LRDs from a low-redshift sample. Three out of seven local analogs show excess variances on all three bands of their light curves, and two of them can be fitted with the damping random walk model, supporting their AGN origins for the variability. The remaining sources show weak variance in at least one band, but no detectable variability at the current sensitivity level, exhibiting $\rm SF_\infty$ upper limits consistent with estimates from high-redshift (high-$z$) LRDs. Their non-detection of variability is likely due to the large photometric uncertainty. As an implication, by simulating long baseline light curves with the variability amplitude of local analogs and adopting JWST observation cadence, we investigate the limitation of the variability amplitude estimate for LRDs. Our mock observations imply that the current constraints on LRDs' variability are probably underestimated. This underestimation might be induced by the short temporal baseline of observations, as well as the intrinsic scatter of the empirical $M_{\rm BH}-\tau$ relation.
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All authors Ruqiu Lin, Zhen-Ya Zheng, Junxian Wang, Luis C. Ho, Jorge A. Zavala, Zijian Zhang, Chunyan Jiang, Jiaqi Lin, Fang-Ting Yuan, Linhua Jiang, Tinggui Wang, Xiaer Zhang

Astrophysics of Galaxies

Diversity in Lyman Continuum Escape at $z\sim0.3$ Revealed by WISE Infrared Observations

Fang-Ting Yuan, Zhen-Ya Zheng, Chunyan Jiang et al. (+1 more)

The escape of Lyman continuum (LyC) radiation from star-forming galaxies plays a key role in cosmic reionization. While strong LyC leakers are commonly identified through ultraviolet (UV) and optical diagnostics, their infrared (IR) emission remains poorly explored. We use data from the Wide-field Infrared Survey Explorer (WISE) to investigate a sample of local star-forming galaxies, which contains 20 strong LyC leakers ($S/N_\mathrm{LyC} > 3$ and $f_{\rm esc}>5\%$) and 69 non-leakers. Among the strong leakers, 8 are classified with mid-IR detections. Comparing the IR-detected and IR-undetected subsamples, we find that the IR-undetected strong leakers exhibit higher [\ion{O}{3}]5007/[\ion{O}{2}]3726,3729 (O32) ratios, bluer UV slopes, and lower metallicities than the other subsamples. In contrast, the IR-detected strong leakers show O32 ratios, UV slopes, and metallicities comparable to those of non-leakers, while maintaining a median escape fraction of $f_{\rm esc}\sim12\%$. These results indicate that significant LyC escape is not limited to galaxies with the most extreme UV and optical properties and can coexist with substantial IR emission. The Ly$\alpha$ profiles and the morphology of the IR-detected and IR-undetected strong leakers imply that LyC photon escape in these two classes may be driven by different mechanisms. Our results highlight the diversity of LyC leakers and suggest that dusty star-forming galaxies may contribute a considerable amount to the ionizing photon budget during cosmic reionization.
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All authors Fang-Ting Yuan, Zhen-Ya Zheng, Chunyan Jiang, Shuairu Zhu

Instrumentation and Methods for Astrophysics

PhysFormer: A Physics-Embedded Generative Model for Physically Self-Consistent Spectral Synthesis

Siqi Wang, Mengmeng Zhang, Yude Bu et al. (+1 more)

In scientific and engineering domains, modeling high-dimensional complex systems governed by partial differential equations (PDEs) remains challenging in terms of physical consistency and numerical stability. However, existing approaches, such as physics-informed neural networks (PINNs), typically rely on known physical fields or coefficients and enforce physical constraints via external loss functions, which can lead to training instability and make it difficult to handle high-dimensional or unobservable scenarios. To this end, we propose PhysFormer, a generative modeling framework that is self-consistent at both the data and physical levels. PhysFormer leverages a low-dimensional, physically interpretable latent space to learn key physical quantities directly from data without requiring known high-dimensional physical field parameters, and embeds the physical process of radiative flux generation within the network to ensure the physical consistency of the generated spectra. In high-dimensional, degenerate inversion tasks, PhysFormer constrains generation within physical limits and enhances spectral fidelity and inversion stability under varying signal-to-noise ratios (SNRs). More broadly, this approach shifts the physical processes from external loss functions into the generative mechanism itself, providing a physically consistent generative modeling paradigm for complex systems involving unknown or unobservable physical quantities.
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All authors Siqi Wang, Mengmeng Zhang, Yude Bu, Chaozhou Mou

High Energy Astrophysical Phenomena · Cross-listed from gr-qc

Modified Teukolsky formalism: Null testing and numerical benchmarking

Fawzi Aly, Mahmoud A. Mansour, Luis Lehner et al. (+3 more)

Next-generation gravitational-wave detectors will make black-hole ringdown an increasingly sensitive probe of small departures from General Relativity in the strong-field regime. This motivates obtaining high-precision predictions of gravitational effective field theory, as spectral shifts can be quite small. Here we perform a focused stress test of the modified-Teukolsky framework by designing two null diagnostics. First, we consider an action with redundant operators that must produce zero first-order vacuum QNM shifts. Second, we exploit a Ricci-flat identity relating two physical cubic Riemann to test such a relation is satisfied by the ringdown spectra obtained. We compute the shifts using two independent numerical approaches: the eigenvalue-perturbation and generalized continued-fraction (Leaver-type) methods. Both null tests are passed across multiple multipoles and overtones, and the control-operator results agree in magnitude with the benchmark values reported in Ref. [1]. These validations support using the framework for obtaining accurate predictions for robust strong-field tests, with straightforward extensions to rotating backgrounds and coupling with matter fields.
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All authors Fawzi Aly, Mahmoud A. Mansour, Luis Lehner, Dejan Stojkovic, Dongjun Li, Pratik Wagle

Astrophysics of Galaxies

Identifying Compton-thick active galactic nuclei in the COSMOS. II. Searching among mid-infrared selected AGNs

Xiaotong Guo, Qiusheng Gu, Guanwen Fang et al. (+7 more)

Compton-thick active galactic nuclei (CT-AGNs), defined by column density $\mathrm{N_H} \geqslant 1.5 \times 10^{24} \ \mathrm{cm}^{-2}$, are so heavily absorbed that their X-ray emission is often feeble, even undetectable by X-ray instruments. Nevertheless, their radiation is expected to be a substantial contributor to the cosmic X-ray background (CXB), predicting that CT-AGNs should comprise at least $\sim$30% of the total AGN population. In the Cosmological Evolution Survey (COSMOS), the identified CT-AGN fraction falls far below theoretical expectations, indicating that a substantial population of CT-AGNs is hidden due to their low photon counts or their flux below the current flux limits of X-ray instruments. This work focuses on identifying CT-AGNs hidden in mid-infrared (MIR)-selected AGNs. First, we selected a sample of 1,104 MIR-selected AGNs that were covered but individually undetected by X-ray. Next, we reduced the X-ray data in the COSMOS and analyzed multiwavelength data in our sample to derive the key physical parameters required for CT-AGN identification. Using MIR diagnostics, we first find out 7 to 23 CT-AGN candidates. Their subsequent X-ray stacking analysis reveals a clear detection at $>3\sigma$ significance in the soft band and only $>1\sigma$ significance in the hard band. We fit the stacked soft- and hard-band fluxes with a physical model and confirm that these sources are absorbed by Compton-thick material. However, CT-AGNs constitute only 2.1% (23/1104) of our sample, significantly below the fraction predicted by CXB synthesis models, indicating that a considerable population of CT-AGNs remains missed by our selection. A comparison of host-galaxy properties between CT-AGNs and non-CT-AGNs reveals no significant differences.
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All authors Xiaotong Guo, Qiusheng Gu, Guanwen Fang, Shiying Lu, Fen Lyu, Yongyun Chen, Nan Ding, Mengfei Zhang, Xiaoling Yu, Hongtao Wang

Instrumentation and Methods for Astrophysics · Cross-listed from stat.AP

A Hybrid Particle Gaussian Mixture Filtering Method for Cislunar Orbit Determination Under Extreme Uncertainty

Ishan Paranjape, Tarun Hejmadi, Utkarsh Ranjan Mishra et al. (+1 more)

Gauss's method of orbit determination (OD) and its variants are among the most popular initial state estimation techniques for astronomers and engineers alike. However, owing to its assumptions regarding the two-body problem, Gauss's method is inapplicable in the cislunar domain, where three body effects dominate. We introduce a hybrid Particle Gaussian Mixture filtering method, a purely recursive probabilistic orbit determination framework based on a combination of the Markov Chain Monte Carlo based Particle Gaussian Mixture-II (PGM-II) and Particle Gaussian Mixture-I (PGM-I) filters. This method enables us to fuse probabilistic information with angles-only observations from terrestrial telescopes for short and long-term cislunar target tracking. We demonstrate this technique on an important cislunar orbit regime.
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All authors Ishan Paranjape, Tarun Hejmadi, Utkarsh Ranjan Mishra, Suman Chakravorty

Earth and Planetary Astrophysics

Time-Domain Photometry and Activity Evolution of Interstellar Comet 3I/ATLAS with BHTOM

A. Fraser Gillan, Łukasz Wyrzykowski, Przemysław J. Mikołajczyk et al. (+69 more)

Time-domain photometric monitoring is essential for characterizing cometary evolution, particularly for rare interstellar objects with limited observing opportunities. We aimed to characterize the pre-perihelion photometric behavior and dust activity of the interstellar comet 3I/ATLAS, and to test the capability of the Black Hole Target and Observation Manager (BHTOM) platform and telescope network for coordinated high-cadence non-sidereal observations. We obtained 70 days of time-series photometry of 3I/ATLAS from 2025 July 4 - September 11 using 16 telescopes and 1554 images. The data were processed and calibrated with the BHTOM pipeline. High-cadence, multi-band imaging was used to measure the rotation period and color evolution, while the dust activity was quantified via Afp measurements. We present a pre-perihelion light curve of 3I/ATLAS from Rh = 3.18 - 2.19 au, which exhibited a steady increase of ~3 magnitudes with no evidence of anomalous behavior. We measured a rotation period of P_rot = 15.98 +/- 0.08 h. The relative dust production increased from A(0)fp ~600 - 1100 cm, and the upper limit on the dust mass-loss rate increased from \leq 217 kg/s to \leq 328 kg/s. We measured an activity index of n = -1.24 +/- 0.02, consistent with a well-developed dust coma. The colors were statistically non-changing, with only a weak, non-significant tendency for 3I/ATLAS to become bluer at 3.5 > Rh > 2.2 au.
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All authors A. Fraser Gillan, Łukasz Wyrzykowski, Przemysław J. Mikołajczyk, Krzysztof Kotysz, Erica Bufanda, Colin O. Chandler, Süleyman Fişek, Henry H. Hsieh, Michael S. P. Kelley, Priscila J. Pessi, James E. Robinson, Sinan Aliş, Wieńczysław Bykowski, Richard E. Cannon, Martin Dominik, Barbara Handzlik, Mehmet İçen, Sebastian Kurowski, Ahmet Cem Kutluay, Joysankar Majumdar, Çağlayan Nehir, David O'Neill, Sibel Ötken, Kangming Pu, Özlem Şimşir, Colin Snodgrass, Cihan Tuğrul Tezcan, Fatma Tezcan, Mauritz Wicker, Fuat Korhan Yelkenci, Michał Żejmo, Kendall Ackley, M. Andersen, C. Ávalos-Vega, Sergey Belkin, V. Bozza, Rene P. Breton, M. J. Burgdorf, Jorge Casares, Vik Dhillon, A. Donaldson, Martin J. Dyer, R. Figuera Jaimes, Duncan K. Galloway, T. C. Hinse, M. Hundertmark, E. Khalouei, Thomas Killestein, Rubina Kotak, Amit Kumar, Feng-Yuan Frey Liu, P. Longa-Peña, Joe Lyman, Luigi Mancini, A. Moharana, V. Molina, Kanthanakorn Noysena, Laura Kate Nuttall, Paul O'Brien, V. Okoth, C. Opitom, Don Pollacco, M. Rabus, Gavin Ramsay, S. Sajadian, A. Salinas San Martin, J. Skottfelt, J. Southworth, Danny Steeghs, J. Tregloan-Reed, Krzysztof Ulaczyk, R. Vieliute

Astrophysics of Galaxies

Everything Every Band All at Once II: The Relationship Between Optical Size and Stellar Mass Over Eight Billion Years of Cosmic History

Tim B. Miller, Yunchong Zhang, Sedona H. Price et al. (+24 more)

While the size-mass relation provides insight into the structural evolution of galaxies, the data available and methods employed have hindered our ability to study a detailed and comprehensive description of this key relation across cosmic history. The first paper in this series presents a morphology catalog based on 20 band JWST data in the field of Abell 2744. In this paper we utilize this catalog to measure the size-mass relation from $0.5<z<8$ and $0.5<z<3$ for star-forming and quiescent galaxies respectively. We perform a global fit to our sample using B-splines to flexibly model the redshift evolution which enforces smooth evolution and can account for all observational uncertainties. Symbolic regression is used to derive simple and portable expressions that describe the redshift evolution of the size-mass relation. Analyzing the size evolution of star-forming galaxies in the context of previous work at $z\sim0$ and $z>10$, we discuss three distinct phases: Rapid growth at $z>5$, growth that mimics dark matter halos at $5< z <1$ and a late plateau at $0.5<z<1$. For quiescent galaxies we confirm previous findings that the size-mass relation flattens at $\log\ M_*/M_\odot < 10$, which inverts at $z>1$. Our results imply that quiescent galaxies are smaller than their star-forming counterparts only at around $\log M_*/M_\odot = 10$; the two populations have similar sizes at lower and higher masses.
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All authors Tim B. Miller, Yunchong Zhang, Sedona H. Price, Katherine A. Suess, Rachel Bezanson, David J. Setton, Ivo Labbe, Gabriel Brammer, Sam E. Cutler, Lukas J. Furtak, Joel Leja, Richard Pan, Bingjie Wang, John R. Weaver, Katherine E. Whitaker, Pratika Dayal, Robert Feldmann, Seiji Fujimoto, K. Glazebrook, Anna de Graaff, Jenny E. Greene, Vasily Kokorev, Danilo Marchesini, Adam Muzzin, Themiya Nanayakkara, Erica J. Nelson, Arjen van der Wel

Astrophysics of Galaxies

ALMA High-J CO Spectroscopy of High-Redshift Galaxies. II. 0.03" Resolution CO Kinematics Reveal Super-Eddington Accretion in a Dust-Obscured Galaxy at z=3.111

Ken-ichi Tadaki

We present ultra-high-resolution (0.03"~230 pc) Atacama Large Millimeter/submillimeter Array (ALMA) observations of the hyperluminous dust-obscured galaxy W2305-0039 at z=3.111, targeting the CO J=7-6 and J=11-10 lines. The CO(11-10) emission is extremely compact and exhibits anomalously high excitation relative to CO(7-6) within the central <500 pc. X-ray-dominated region models successfully reproduce this excitation, providing strong evidence for intense X-ray irradiation by a deeply obscured active galactic nucleus (AGN), while photodissociation-region models fail to match the observed ratio. Forward modeling of the nuclear CO(11-10) position-velocity diagram yields a dynamical black-hole mass of log(MBH/Msun) = 8.3$^{+0.7}_{-0.6}$ and an intrinsic gas velocity dispersion of $277~^{+16}_{-14}$ km s$^{-1}$. Combined with the AGN luminosity from infrared spectral energy distribution decomposition, these measurements imply a highly super-Eddington accretion state with $\lambda~_{\rm Edd}~\gtrsim 4$. Our results provide dynamical evidence that the most rapid phases of black-hole growth can occur within a compact, heavily obscured nuclear region. Extending ALMA beyond its current 16 km maximum baselines will be essential for pushing such dynamical measurements to tens-of-parsec scales and resolving the black-hole sphere of influence in massive galaxies at $z \gtrsim 6$.
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Solar and Stellar Astrophysics

Protostellar Outflows Shed Light on the Dominant Close Companion Star Formation Pathways

Ryan Sponzilli, Leslie Looney, John J. Tobin et al. (+11 more)

Understanding the formation pathway for close-companion protostars is central to unraveling the processes that govern stellar multiplicity and very early star formation. We analyze a large sample of 51 Class 0/I close-companion protostellar systems, of which 38 show detectable outflows, yielding 42 measured outflows used in our analysis. We use ALMA observations of 11 systems in Perseus and 40 systems in Orion. These companions formed either directly at these small scales ($\lesssim 500$ au separations) via disk fragmentation or at larger scales ($> 1000$ au separations) via turbulent fragmentation followed by inward migration. Because of differences in formation mechanism, the former is expected to have preferentially aligned disks and outflows, whereas the latter is expected to show no preferred alignment. The relative prevalence of these formation pathways remains uncertain, yet it is critical to forming a comprehensive picture of star formation. We examine the distribution of position angles of companion protostars relative to the position angles of their molecular outflows. The outflow, as traced by $^{12}$CO ($J=2\rightarrow1$), is a useful proxy for the angular momentum of the system, expected to be orthogonal to the binary orbital plane. We use a simple model to account for random sampling of inclination and orbital phase in each system, finding that the observations are consistent with a distribution in which the outflows are preferentially orthogonal to the companions. Based on this analysis, we suggest disk fragmentation is the dominant formation pathway for close-companion protostellar systems.
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All authors Ryan Sponzilli, Leslie Looney, John J. Tobin, Frankie J. Encalada, Austen Fourkas, Hector Arce, Erin Cox, James Di Francesco, Nicole Karnath, Zhi-Yun Li, Nadia Murillo, Stella Offner, Sarah Sadavoy, Rajeeb Sharma

Sunday 1 March

Cosmology and Nongalactic Astrophysics

The impact of strong lensing on Hubble constant measurements with gravitational-wave dark sirens

Eungwang Seo, Kyungmin Kim, Zhuotao Li et al. (+3 more)

The disagreement between early and late Universe electromagnetic measurements of the Hubble constant, $H_0$, known as the Hubble tension, highlights the need for independent and complementary probes. Gravitational-wave events have recently emerged as such a probe for constraining cosmological parameters. $H_{0}$ inference using these events relies on sky localization and luminosity distance estimates, both of which can be significantly improved for strongly lensed events with appropriate lens modeling. In this context, we propose utilizing strong lensing of dark sirens, gravitational-wave events without identified electromagnetic counterparts, in combination with strong lensing of galaxies as a novel method for measuring $H_0$. The constant is inferred from the luminosity distances of these lensed dark sirens and the redshifts of their host galaxies, combining information from individual events to obtain statistically stronger constraints when multiple events are available. We adopt a simulated galaxy catalog, MICECATv2, as the basis for simulating strong lensing of galaxies and to provide the redshift information of host galaxy candidates required to infer $H_0$. We also examine the impact of galaxy catalog incompleteness on the resulting $H_0$ inference. Our results demonstrate that using only 8 strongly lensed dark sirens, analyzed with a dedicated galaxy-galaxy lensing catalog, can improve the precision of $H_{0}$ by roughly 50% compared to 250 unlensed events.
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All authors Eungwang Seo, Kyungmin Kim, Zhuotao Li, Justin Janquart, Rachel Gray, Martin Hendry

Earth and Planetary Astrophysics

TESS Hunt for Young and Maturing Exoplanets (THYME) XIV: A Comoving-Based Age Constraint for KELT-20

Adam Distler, Melinda Soares-Furtado, Andrew W. Mann et al. (+9 more)

Young stellar moving groups offer unique opportunities to investigate the early evolution of stellar and planetary systems. In continuation of an ongoing effort to age-date compelling planetary systems, we provide an in-depth age analysis of KELT-20, a young A-type star that hosts a well-aligned ultra-hot Jupiter. This system poses a useful case study to investigate migration mechanisms at early stages of evolution. Using Gaia DR3 data, we identify 77 stars with proper motions consistent with KELT-20, including 19 with measured radial velocities that enable full 3D kinematic confirmation. Using isochronal analyses, gyrochronology, photometric variability, and stellar activity indicators, we converge on an age of $58 \pm 5\,$Myr. This constraint provides critical insights into the dynamical processes shaping hot Jupiter formation.
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All authors Adam Distler, Melinda Soares-Furtado, Andrew W. Mann, Adam L. Kraus, Jonathan Gagné, Juliette Becker, Ritvik Sai Narayan, Max Clark, Andrew Vanderburg, Joseph E. Rodriguez, Laura K. Rogers, Ronan Kerr

Solar and Stellar Astrophysics · Cross-listed from physics.plasm-ph

Rugged magneto-hydrodynamic invariants in weakly collisional plasma turbulence: Two-dimensional hybrid simulation results

Petr Hellinger and Victor Montagud-Camps

Aims. We investigated plasma turbulence in the context of solar wind. We concentrated on properties of ideal second-order magneto-hydrodynamic (MHD) and Hall MHD invariants. Methods. We studied the results of a two-dimensional hybrid simulation of decaying plasma turbulence with an initial large cross helicity and a negligible magnetic helicity. We investigated the evolution of the combined energy and the cross, kinetic, mixed, and magnetic helicities. For the combined energy and the cross, kinetic, and mixed helicities, we analysed the corresponding Kármán-Howarth-Monin (KHM) equation in the hybrid (kinetic proton and fluid electron) approximation. Results. The KHM analysis shows that the combined energy decays at large scales. At intermediate scales, this energy cascades (from large to small scales) via the MHD non-linearity and this cascade partly continues via Hall coupling to sub-ion scales. The cascading combined energy is transferred (dissipated) to the internal energy at small scales via the resistive dissipation and the pressure-strain effect. The Hall term couples the cross helicity with the kinetic one, suggesting that the coupled invariant, referred to here as the mixed helicity, is a relevant turbulence quantity. However, when analysed using the KHM equations, the kinetic and mixed helicities exhibit very dissimilar behaviours to that of the combined energy. On the other hand, the cross helicity, in analogy to the energy, decays at large scales, cascades from large to small scales via the MHD+Hall non-linearity, and is dissipated at small scales via the resistive dissipation and the cross-helicity equivalent of the pressure-strain effect. In contrast to the combined energy, the Hall term is important for the cross helicity over a wide range of scales. The magnetic helicity is scantily generated through the resistive term and does not exhibit any cascade.
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Solar and Stellar Astrophysics · Cross-listed from physics.space-ph

Turbulent Heating between 0.2 and 1 au: A Numerical Study

Victor Montagud-Camps, Roland Grappin and Andrea Verdini

The heating of the solar wind is a key to understand its dynamics and acceleration process. The observed radial decrease of proton temperature in the solar wind is slow compared to the adiabatic prediction and it is thought to be caused by turbulent dissipation. To generate the observed 1/R decrease, the dissipation rate has to reach a specific level which varies in turn with temperature, wind speed, and heliocentric distance. We want to prove that MHD turbulent simulations can lead to the 1/R profile. We consider here the slow solar wind, characterized by a quasi-2D spectral anisotropy. We use the EBM (expanding box model) equations, which incorporate into 3D MHD equations the expansion due to the mean radial wind, allowing to follow the plasma evolution between 0.2 and 1 AU. We vary the initial parameters which are: Mach number, expansion parameter, plasma beta, and properties of the energy spectrum as the spectral range and slope. Assuming turbulence starts at 0.2 AU with a Mach number equal to unity, with a 3D spectrum mainly perpendicular to the mean field, we find radial temperature profiles close to 1/R in average. This is done at the price of limiting the initial spectral extent, corresponding to the small number of modes in the inertial range available, due to the modest Reynolds number reachable with high Mach numbers.
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Astrophysics of Galaxies

The UTR-2 decametre pulsar and transient survey I. Transient detection

V. V. Zakharenko, I. P. Kravtsov, I. Y. Vasylieva et al. (+6 more)

Context. This paper presents a detailed description of the Decametre Pulsar and Transient Survey of the Northern Sky that was carried out in 2012-2017 using the world's largest radio telescope at decametre wavelengths - UTR-2 in Ukraine. This extensive survey covers the northern sky from declination -10 to +80 deg , with a temporal resolution of 8 ms, and explores dispersion measures up to 30 pc/cc. Aims. The major advantage of the decametre wavelength range is a comparatively wide band, in which the dispersive delay due to the interstellar plasma reaches hundreds of seconds, giving us the opportunity to determine the dispersion measure with a very high accuracy. This enables us to discover new transients, while avoiding data contamination from numerous weak signals of a different nature. Methods. The drift-scan survey in 5-beam mode of UTR-2 was carried out at night time. To cover the entire sky along the right ascension, the duration of the sessions was more than 12 hours at a time close to the autumn and spring equinoxes (to obtain the same conditions for the interference situation). 90 degrees along the declination were covered by five beams in 40 days (each equinox). Results. We discovered 380 individual transient signals with dispersion measures significantly differ from those of known sources. We determined the parameters of each single transient signal. We show that they cannot be explained by ionospheric scintillations. Repeated observations have shown that some detected transient signals are repetitive and are thus likely to originate from pulsars or rotating radio transients. Key words. Stars: neutron - pulsars: general - Methods: data analysis - Methods: observational - Astronomical databases: Surveys
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All authors V. V. Zakharenko, I. P. Kravtsov, I. Y. Vasylieva, P. Zarka, O. M. Ulyanov, O. O. Konovalenko, A. I. Shevtsova, A. O. Skoryk, K. Y. Mylostna

High Energy Astrophysical Phenomena

Outflow from unmagnetized shocked radiative transonic accretion disk around a black hole

Arghya Chaudhuri, Apurba Ghosh and Sudip K Garain

We study outflow from an unmagnetized, shocked accretion disk around a non-rotating super-massive black hole using multidimensional hydrodynamics simulation with radiative cooling. We aim to investigate whether such shocked accretion flow can launch sustained collimated bipolar outflow reaching out to thousands of gravitational radii even in the absence of magnetic field and if yes, what terminal velocity can they achieve? We present the results of a few simulations of geometrically thick accretion flow with increasing specific angular momentum on a vertically elongated cylindrical domain. We show thatbipolar outflow from a region very close to the black hole is originating and propagating vertically out to our simulation domain boundary at around $2651$ Schwarzschild radius. The outflow attains a terminal velocity with a maximum value found to be $0.14c$ and the outflow rate depends on the angular momentum value of the accreting material. We also compute the self-Comptonized bremsstrahlung spectra for all the disk-jet runs.
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Cosmology and Nongalactic Astrophysics

The effect of photon re-scattering due to cosmic reionization on 21-cm images and power spectra

Sudipta Sikder, Rennan Barkana and Anastasia Fialkov

The 21-cm signal from neutral hydrogen serves as a critical tool for unraveling the astrophysical processes that shaped cosmic dawn and the epoch of reionization. We explore the usually overlooked impact of re-scattering of 21-cm photons during and after reionization, similarly to cosmic microwave background photons. This scattering affects the observed brightness temperature by mixing the original signal with light scattered into the line of sight from other regions, effectively at the mean 21-cm brightness temperature. This gives a small but significant effect. We show that it attenuates the fluctuations in a 21-cm image by $4-7\%$, while reducing the 21-cm power spectrum by a scale-independent $7-13\%$ during cosmic dawn and reionization. Incorporating this correction is vital for precisely comparing theoretical predictions with observations from experiments such as NenuFAR, LOFAR, and HERA, and the upcoming Square Kilometre Array.
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Solar and Stellar Astrophysics

X-ray and H{\alpha} superflare on an RS CVn-type star, UX Arietis: Constraint on the flare location from radial velocity change during the flare

Sota Urabe, Yohko Tsuboi, Kosuke Namekata et al. (+5 more)

We report on a giant stellar flare from the RS CVn-type binary UX Arietis, detected with the Monitor of All-sky X-ray Image (MAXI) and followed by a 12-day optical spectroscopic campaign using the 3.8~m Seimei Telescope. The flare released $5 \times 10^{37}$~erg in X-rays (0.1–100~keV) and $(2$–$6) \times 10^{36}$~erg in the H$\alpha$ line, placing it among the most energetic events of its kind. The H$\alpha$ light curve showed sinusoidal modulation atop an exponential decay, consistent with reappearance of the flaring region due to binary rotation. At orbital phase 0, when the primary star is farthest from the observer, 40% of the H$\alpha$ flux was obscured, while at phase 0.5 the full emission was visible. This suggests the H$\alpha$ emitting region is located at a relatively low latitude and is comparable in size to the stellar disk. Radial velocity modulation implies that the region lies at $\sim19\,R_{\odot}$ from the system's rotation axis, farther out than the stellar limb at $14.4\,R_{\odot}$. Photometric monitoring with the Chuo-university Astronomical Telescope revealed a large low-latitude starspot covering $\sim25\%$ of the surface. These findings are consistent with a scenario in which the flare occurred above the starspot, and the H$\alpha$-emitting plasma was magnetically confined in a loop extending at least $5\,R_{\odot}$ above the stellar surface. From the MAXI data and assuming a radiatively cooling plasma, the electron density and volume are estimated to be $10^{10}$~cm$^{-3}$ and $1 \times 10^{35}$~cm$^3$, respectively. If cubic in shape, this corresponds to $7\,R_{\odot}$, consistent with the H$\alpha$ region height. These results provide direct constraints on the geometry of the plasma and its spatial relationship with the starspot in one of the most energetic stellar flares ever observed.
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All authors Sota Urabe, Yohko Tsuboi, Kosuke Namekata, Sakura Nawa, Hiroyuki Maehara, Noboru Nemoto, Yuta Notsu, Wataru Iwakiri

High Energy Astrophysical Phenomena

Accretion in Binary Systems with Slow Stellar Winds

Jesús A. Toalá, Emilio Tejeda, Raúl F. Maldonado et al. (+1 more)

Wind accretion in binary systems is commonly described using the Bondi-Hoyle-Lyttleton (BHL) formalism. However, its standard implementation fails in the slow-wind regime, where the wind velocity of the donor star ($v_\mathrm{w}$) is comparable to or smaller than the orbital velocity of the accretor ($v_\mathrm{o}$). Tejeda & Toalá recently proposed a geometrical correction to the BHL formalism that accounts for the wind aberration caused by the binary's orbital motion, which tilts the accretion cylinder and reduces its effective cross-section. Here we present a suite of smoothed particle hydrodynamic simulations performed with PHANTOM to test the geometric correction to the wind accretion in binary systems, with particular interest in systems operating in the slow-wind regime. We explore circular configurations and directly measure mass accretion efficiencies from the simulations. Our results confirm that the standard BHL prescription systematically overestimates accretion rates for $v_\mathrm{w}/v_\mathrm{o}<1$, while the geometrically corrected model agrees with the simulated efficiencies with remarkable accuracy. A key finding is that the velocity relevant for accretion estimates is not the value derived from the unperturbed stellar wind, but the local gas velocity measured upstream of the accretor. The gravitational potential of the accretor perturbs the flow, altering the effective relative velocity and modifying the accretion efficiency, particularly for compact orbits. These results provide strong numerical support for the geometrically corrected framework and establish a physically motivated basis for modeling wind-fed accretion in interacting binaries, including symbiotic systems.
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All authors Jesús A. Toalá, Emilio Tejeda, Raúl F. Maldonado, Diego A. Vasquez-Torres

Astrophysics of Galaxies

Kinematic and dynamics of the galaxy ESO 358-60

Francesco Sylos Labini and Matteo Straccamore

We investigate the velocity field derived from HI measurements of the irregular galaxy ESO 358-60 using the Velocity Ring Model (VRM) method. This technique, which assumes a coplanar disk, allows us to reconstruct coarse-grained maps of both radial and tangential velocity components from the observed line-of-sight velocity field. Such maps reveal that tangential motions dominate the inner regions, while radial motions become increasingly significant toward the outskirts. This kinematic behavior contrasts with that inferred from the Tilted Ring Model (TRM), which suggests that radial motions are more prominent in the intermediate disk and negligible in the outskirts and detects a pronounced warp of approximately $20^\circ$, with the inner disk nearly edge-on and the outer regions inclined by approximately $60^\circ$. In contrast, the VRM analysis finds that the disk exhibits a bar-like structure in its central regions. This interpretation is further supported by the intensity and velocity dispersion maps. To test the origin of the TRM-derived warp, we construct a toy model based on the TRM results and analyze it with the VRM technique, finding evidence that the warp is likely an artifact arising from the TRM's assumptions. Finally, we estimate the galaxy's mass using both the standard dark matter halo model and a dark matter disk (DMD) model, where all mass lies in the disk plane. The DMD yields a total mass approximately three times lower and provides a slightly better fit to the rotation curve.
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Astrophysics of Galaxies

oMEGACat. IX. Chemical Tagging of Omega Centauri Populations with Machine-Learning-Inferred Abundances from the MUSE Spectrograph

Z. Wang, A. C. Seth, C. Clontz et al. (+14 more)

We present chemical abundance measurements for 7,302 red giant branch stars within the half-light radius (~5') of $\omega$ Centauri ($\omega$ Cen), derived from MUSE spectra using the neural network model DD-Payne. DD-Payne effectively identifies spectral features of C, N, and O for [Fe/H]>-1.0 dex; Mg for [Fe/H]>-1.5 dex; and Na, Ca, and Ba for all metallicities. By combining these measurements with previous high-resolution studies, we create the most comprehensive picture of $\omega$ Cen's rich chemical evolutionary history. For the first time, we map elemental variations across the entire chromosome diagram, which is widely used to identify multiple populations. We analyze the median chemical abundance trends as functions of age and metallicity for different subpopulations. The DD-Payne measurements of [C/Fe], [N/Fe], and [O/Fe] extend literature trends to higher metallicities and show continuous abundance-metallicity relations, with [(C+N+O)/Fe] increasing steadily with [Fe/H]. [Ca/Fe] and the s-process element [Ba/Fe] also increase with metallicity across all populations. For [Ba/Fe], the chemically enhanced (P2) populations are more enriched than primordial (P1) and the intermediate (Im) populations. Furthermore, [N/Fe] correlates strongly with stellar age while [Ca/Fe] and [Ba/Fe] exhibit a weaker age dependence. Using these abundance-metallicity-age relations, we evaluate formation scenarios of $\omega$ Cen proposed in the literature and find none fully explains all the observed relations. Our study demonstrates that combining MUSE with machine learning enables large-sample stellar abundance measurements in crowded cluster cores, overcoming the limitations of fiber-fed spectroscopy for studying multiple stellar populations and their evolutionary histories.
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All authors Z. Wang, A. C. Seth, C. Clontz, N. Neumayer, M. Häberle, S. Kamann, M. Latour, M. S. Nitschai, P. J. Smith, S. O. Souza, G. van de Ven, M. Alfaro-Cuello, A. Bellini, A. Feldmeier-Krause, N. Kacharov, M. Libralato, A. P. Milone

Earth and Planetary Astrophysics

Rotational Doppler Cartography of Technosignatures on Unresolved Planets

Keitaro Takahashi

The discovery of many Earth-like planets has renewed interest in whether life and technological civilizations exist elsewhere. The Search for Extraterrestrial Intelligence (SETI) seeks evidence for technological civilizations via technosignatures across the electromagnetic spectrum. Here, focusing on artificial radio emissions with extremely narrowband signals, we model Earth as a distant, unresolved source and simulate its narrowband transmissions as observed with current and forthcoming radio facilities. Planetary rotation induces small but coherent Doppler drifts (maximum fractional shift of order $10^{-6}$) that imprint a characteristic, time-varying pattern on the spectrum. We develop a forward-inverse framework that exploits this modulation: adopting a population-weighted model for terrestrial transmitters, we compute time-resolved spectra and then apply a new inversion method that reconstructs the underlying transmitter distribution from the temporal pattern of fractional frequency offsets. In noise-added tests, the method recovers the low-order spherical-harmonic structure of the map and retrieves major population centers despite the north-south degeneracy of unresolved observations. The recovered distribution is expected to correlate with continents, climate zones, and population density. This approach moves SETI beyond mere detection, enabling quantitative cartography of a civilization's activity and inference of host-planet properties through sustained, time-resolved spectroscopy.
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High Energy Astrophysical Phenomena · Cross-listed from physics.hist-ph

Evgeny P. Velikhov (1935-2024)

Günther Rüdiger

The master student at Lomonosov University in Moscow E.P. Velikhov formulated 1959 the theory of magnetorotational instability, which dominates current astrophysics. A meteoric career made him later the science, nuclear and disarmament advisor to Gorbachev and Yeltsin. This article describes the interactions between Velikhov and the PROMISE team from Potsdam and Dresden-Rossendorf when it came to experimentally testing the theory in the laboratory in the 2000s. At an MHD conference in Catania, Sicily, he offered the public the use of small, transportable Russian nuclear power plants anywhere in the world until the fusion machines currently under development had finally solved the energy problem.
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Solar and Stellar Astrophysics

Stability and wave dynamics in polytropic Eddington-inspired Born-Infeld gravitating solar plasmas

Souvik Das and Pralay Kumar Karmakar

We investigate the influence of nonlinear gravity corrections, arising from the Eddington-inspired Born-Infeld (EiBI) theory on wave dynamics, stability, and energy transport processes in polytropic, viscous, and turbulent solar plasmas. Analytical and numerical analyses of the Jeans-normalized quadratic dispersion relation demonstrate that both the EiBI gravity parameter $(\chi)$ and the relative polytropic sound speed $(\beta)$ independently regulate oscillation frequencies, growth rates, phase velocities, perturbation energy partitioning, and outward acoustic energy flux. Positive $\chi$ systematically elevates oscillation frequencies, phase velocities, and outward energy flux level by $\sim$10% relative to the Newtonian predictions, while larger $\beta$ enhances them by up to 55%, thereby promoting wave propagation and efficient acoustic transport. Conversely, negative $\chi$ strengthens gravitational binding and increases damping rates by $\sim$40%, particularly for the g-modes. Energy partitioning analyses reveal that the EiBI corrections fundamentally restructure the kinetic-electrostatic-gravitational energy balance. While the Newtonian gravity contributes negligibly ($<$4%), nonzero $\chi$ channels up to one-third of oscillation energy into gravitational modes. The modal surface flux calculations further confirm that only the p-modes drive outward energy transport (amplification for $\chi>0$, suppression for $\chi<0$). A direct comparative analysis with four years of SDO/HMI Doppler velocity observations demonstrate a robust theoretical agreement for $\chi=3\times10^7$ m$^5$kg$^{-1}$s$^{-2}$, providing the first empirical constraint on the solar EiBI gravity through helioseismology. The findings offer a rigorous framework for advancing our understanding about solar plasma stability, helioseismic signatures, and ambient atmospheric energy transport processes.
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Solar and Stellar Astrophysics

New axion bounds derived from the 100-parsec Gaia DR3 white dwarf luminosity function

Martín L. Alberino, Marcelo M. Miller Bertolami, María E. Camisassa et al. (+2 more)

The axion, a well-motivated hypothetical particle arising in extensions of the Standard Model, can be produced copiously within the hot, compact cores of white dwarf stars. The shape of the white dwarf luminosity function (WDLF) is a powerful tool for constraining theoretical particles that would imply an additional cooling channel in white dwarfs. In this work, and for the first time, we use the 100-parsec Gaia DR3 white dwarf sample and compare it with theoretical predictions. We have simulated synthetic populations of white dwarfs using a population synthesis code based on Monte Carlo techniques, incorporating realistic observational errors, and based on state-of-the-art white dwarf models that incorporate the anomalous cooling caused by the presence of axions. Axion bremsstrahlung emission rates were implemented using the latest theoretical calculations. We find that, for the brightest white dwarfs in the sample ($M_{\mathrm{Bol}} < 10$), the $\chi^2$ statistic is largely insensitive to the assumed stellar formation rate (SFR), which is typically the dominant uncertainty in modeling the Galactic-disk WDLF. The resulting $\chi^2$ analysis disfavors a sizable additional cooling contribution. This conclusion contrasts with earlier studies in which axion-electron couplings in the range $0.7 \times 10^{-13} < g_{ae} < 2.1 \times 10^{-13}$ provided mildly improved fits to the Galactic-disk WDLF. We attribute the discrepancy to simplifying assumptions in previous modeling and to the substantially improved observational quality of the 100-pc Gaia DR3 sample. We obtain the upper limit $g_{ae} < 1.68 \times 10^{-13}$ ($95\%$ C.L.), which is among the strongest available.
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All authors Martín L. Alberino, Marcelo M. Miller Bertolami, María E. Camisassa, Andrea Caputo, Santiago Torres

Astrophysics of Galaxies

ALMA Central molecular zone Exploration Survey (ACES) V: CS(2-1), SO(2_3-1_2), CH3CHO(5_1,4-4_1,3), HC3N(11-10), and H40a lines data

Pei-Ying Hsieh, Daniel L. Walker, Adam Ginsburg et al. (+59 more)

We present data from the ALMA Central Molecular Zone Exploration Survey (ACES) Large Program, which provides broad spectral-line and 3 mm continuum coverage of the Central Molecular Zone (CMZ) at a spatial resolution of 0.1 pc. The survey delivers homogeneous, wide-field mosaics that enable direct comparisons of the physical and chemical conditions across diverse environments in the Galactic center. In this data release paper, we present the CS(2-1), SO(2_3-1_2), CH3CHO(5_1,4-4_1,3), HC3N(11-10), and H40a lines observed simultaneously within two broad spectral windows. These lines reveal pronounced spatial and chemical variations across the CMZ, tracing distinct components of molecular gas, shock-affected regions, and ionized structures. The high angular resolution and multi-line capability of the ACES dataset make it a powerful resource for future studies of gas dynamics, star formation activity, and the physical connection between the CMZ and Sgr A*.
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All authors Pei-Ying Hsieh, Daniel L. Walker, Adam Ginsburg, Ashley T. Barnes, Xing Lu, Álvaro Sánchez-Monge, Savannah R. Gramze, Nazar Budaiev, Marc W. Pound, Jaime E. Pineda, Claire Cook, Jonathan D. Henshaw, Katharina Immer, Namitha Issac, Desmond Jeff, Fu-Heng Liang, Steven N. Longmore, Elisabeth A.C. Mills, Sergio Martín, Xing Pan, Thushara G.S. Pillai, Qizhou Zhang, John Bally, Cara Battersby, Laura Colzi, Paul T. P. Ho, Izaskun Jiménez-Serra, J. M. Diederik Kruijssen, Maya Petkova, Mattia C. Sormani, Robin G. Tress, Jennifer Wallace, J. Armijos-Abendaño, Lucia Armillotta, N. Bijas, Rojita Budhathoki-Chhetrya, Laura A. Busch, Natalie O. Butterfield, Mélanie Chevance, Ana Karla Díaz-Rodríguez, Christoph Federrath, Rubén Fedriani, Pablo García, Qi-Lao Gu, Rebecca J. Houghton, Yue Hu, Janik Karoly, Ralf S. Klessen, Mark R. Krumholz, Farideh Mazoochi, Francisco Nogueras-Lara, Dylan Paré, Denise Riquelme-Vásquez, Víctor M. Rivilla, Miriam G. Santa-Maria, Anika Schmiedeke, Yoshiaki Sofue, Volker Tolls, Q. Daniel Wang, Gwenllian M. Williams, Fengwei Xu, Suinan Zhang

Saturday 28 February

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

High Resolution Microscopy and Raman Spectroscopic Studies on the Freshest Mukundpura Meteorite, Rajasthan, India: Presence of Nanodiamond

D. Chandrasekharam, U. Govind, R. P. Tripathi et al. (+4 more)

Carbonaceous Chondrites have special significance in the stellar evolution and in particular in the evolution of life on earth. The carbonaceous meteorite that fell in Mukundpura village, Jaipur, Rajasthan on 6th June 2017 is one such rare CM2 (Carbonaceous Chondrite) carbonaceous meteorite. We carried out high resolution scanning and transmission electron microscopic (TEM) studies on typical thin sections, showing abundant grains of iridium (Ir), pentlandite (NiS), and more interestingly crystalline carbon (C). These crystallite carbon grains resemble nanodiamond like signature in the freshest Mukundpura meteorite. The high-resolution Raman spectroscopic measurements are carried out on the crystalline carbon grains, showing well resolved three distinct peaks with a vibrational mode at 1315 cm-1, with the onset of a weak vibrational mode at 1150 cm^-1, substantiating the observation of nanocrystalline diamond in Mukundpura meteorite. The broad peak centered at 1360 cm^-1 and 1575 cm^-1 (as an average), suggest the presence of graphitic carbon as well together with apparent presence of nanocrystalline diamond. The average size of nanocrystalline diamond is ~ 3-5 nm. High iridium content in this meteorite supports the meteoric impact related iridium anomaly in geological stratigraphic boundaries (e.g.Cretaceous-Tertiary boundary) that has caused mass extinction of flora and fauna.
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All authors D. Chandrasekharam, U. Govind, R. P. Tripathi, T. H. Amir, K. M. Sairam, D. B. E. Rafal, A. Dixit