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Physics Astrophysics

astro-ph Watch Astrophysics

Sunday 22 March

High Energy Astrophysical Phenomena

On the origin of the strong internal magnetic fields of central compact objects

Kaz{\i}m Yavuz Ekşi and İrem Bak{\i}r

Central compact objects are radio-quite young neutron stars associated with supernova remnants. They have relatively small dipole fields, $B_{\rm p} \sim 10^{10}\,{\rm G}$ as inferred from their spin parameters. X-ray observations and theoretical arguments imply the presence of stronger internal magnetic fields. We argue that the dipole fields of these objects are very close to what they had inherited from the core of the progenitor by flux conservation and their small initial rotation frequency does not allow for the $\alpha$-process to enhance their poloidal fields. Although a full-fledged dynamo process can not proceed, relatively strong toroidal magnetic fields, $B_\phi \sim 10^{13}\,{\rm G}$, can be generated from the seed poloidal fields via the $\Omega$-effect in the proto-neutron star stage. We present a simplistic model for these processes and further speculate that the reason why these objects are born relatively slow-rotating is that they were not spun-up by acquiring angular momentum from the fallback matter.
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High Energy Astrophysical Phenomena

Distributed accelerators in the jet of Centaurus A: the origin of the spectral hardening of very high energy gamma-rays

Y. S. Honda and M. Honda

We propose the synchrotron self-Compton (SSC) scenario coupled with filamentary jet model, to reproduce the very high energy $\gamma$-ray emissions from Cen A. With reference to self-similarity of knot-like features in the jet, we assume nonuniform magnetic field associated with current filaments having various transverse sizes. For energetic electron production, the diffusive shock acceleration at sites distributed over the kiloparsec-scale jet is considered. We show that maximum Lorentz factor of the electron steadily exceeds $10^{8}$ due to suppression of synchrotron loss of the electrons trapped in weak magnetic field of the thin filaments, and inhomogeneous SSC in the inner jet can dominantly contribute to establishment of the pronounced hardening of $\gamma$-ray flux detected by the H.E.S.S. It is also suggested that the spectral contribution from diffuse regions of the outer jet potentially amounts to the observed Fermi fluxes.
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Saturday 21 March

Solar and Stellar Astrophysics

High-resolution near-IR spectroscopy of the B[e] supergiant LHA 115-S 18: discovery of hot water vapor emission

M. L. Arias, A. F. Torres, M. Kraus et al. (+1 more)

The post-main-sequence evolution of massive stars involves phases of intense, often eruptive mass loss, including the B[e] supergiant phase. These hot stars are surrounded by cool, dense circumstellar disks that host complex chemistry, producing both molecules and dust. Understanding the mass-loss history of B[e] supergiants is essential for constraining stellar evolution models, particularly regarding their final stages. Near-infrared CO band emission serves as a key tracer of disk dynamics, typically arising from the inner edge of the molecular disk or ring. However, the oxygen-rich environments of these stars also favor the presence of other molecules which trace regions complementary to those probed by CO. In this work, we present high-resolution near-infrared spectra of the Small Magellanic Cloud B[e] supergiant LHA 115-S 18. Our analysis reveals rotationally broadened CO emission consistent with a Keplerian molecular ring, alongside strong hydrogen wind features in both H and K bands and numerous metallic emission lines. Notably, we report the first detection of hot water vapor emission in a B[e] supergiant. This finding indicates the existence of extended cool and dense regions in a harsh environment. A radial velocity offset between molecular and Pfund line emission further supports a binary system, with the molecular gas potentially being circumbinary. The discovery of hot H2 O around the B[e] supergiant star LHA 115-S 18 challenges classical models on evolution and chemistry of massive binary stars and provides critical insight into mass-loss processes and molecular enrichment of the ISM.
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All authors M. L. Arias, A. F. Torres, M. Kraus, L. S. Cidale

Cosmology and Nongalactic Astrophysics

Redshift Dipoles from Non-Geodesic Observer Congruences in Covariant Cosmology

Erick Pastén

Recent analyses of large-scale structure and redshift surveys have reported significant dipolar anisotropies in the local Universe that are not straightforwardly attributable to a kinematical boost. When interpreted within standard frameworks, these signals may correspond to coherent bulk flows that have been reported to exhibit tension with $\Lambda$CDM expectations. On the other hand, signals inferred from different astrophysical probes are not always consistent with the Cosmic Microwave Background (CMB) dipole, challenging the assumption of dipoles that are pure kinematical in origin. In more general cosmological scenarios, the congruence associated with cosmological observers need not be geodesic. Within a fully covariant framework, we show that a non-geodesic observer congruence introduces an additional contribution to the propagation of redshift along the past light cone, proportional to the line-of-sight projection of the observer four-acceleration. This generates an anisotropic modulation in the redshift itself, which could propagate to any observable defined in redshift space. We discuss different physical mechanisms that may produce a non-geodesic observer congruence, including interactions within the dark sector, modified theories of gravity, and relative motion between cosmological frames in tilted cosmologies.
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Earth and Planetary Astrophysics

Pre-perihelion observations of comet P/2023 JN16 (Lemmon) at the 2024 apparition

Serhii Borysenko, Alexander Baransky, Christopher A. Onken et al. (+1 more)

We present an analysis of the photometric data of new main belt comet P/2023 JN16 (Lemmon) observed with the 1.35-m SkyMapper telescope at Siding Spring Observatory in 2024 during July - September. The faint object showed dusty activity during a long period. Some photometric parameters, such as SkyMapper r band magnitudes, Afrho parameters, and absolute magnitude were estimated. We estimate the nuclear radius for comet P/2023 JN16 to be less than 0.5 km. The activity of the object is possible driven by the release of large, slow-moving particles.
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All authors Serhii Borysenko, Alexander Baransky, Christopher A. Onken, Iryna Kulyk

Astrophysics of Galaxies

The Extinction Distance of Supernova Remnants in Combination with the CO Line Measurements

Zhe Zhang, Jun Li, Biwei Jiang et al. (+2 more)

Accurate distance measurements to supernova remnants (SNRs) are crucial for understanding their physical properties and evolution. We present a novel method that combines CO line observations with three-dimensional (3D) extinction maps to determine distances to SNRs (G93.7$-$0.2, G109.1$-$1.0, G156.2+5.7, and G166.0+4.3) through their associated molecular clouds. For each SNR, candidate CO velocity components corresponding to interacting molecular clouds are identified based on previous observational evidence with refinements: [$-$19, $-$3] km s$^{-1}$ for G93.7$-$0.2, [$-$51, $-$46] km s$^{-1}$ for G109.1$-$1.0, [$-$10, 0] km s$^{-1}$ for G156.2+5.7, and [$-$27, $-$15] km s$^{-1}$ for G166.0+4.3. By examining extinction-distance profiles along the sightlines and identifying extinction jumps that spatially coincide with CO emission features, we derive distances of 1.82$\pm$0.13 kpc for G93.7$-$0.2, 3.05$\pm$0.15 kpc for G109.1$-$1.0, 0.60$\pm$0.15 kpc for G156.2+5.7, and 3.44$\pm$0.23 kpc for G166.0+4.3. Our extinction-based distances are largely consistent with previous estimates while with better accuracy and robustness.
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All authors Zhe Zhang, Jun Li, Biwei Jiang, He Zhao, Fupeng Liu

Solar and Stellar Astrophysics

A turbulence index independent framework for deriving solar wind speed and coronal electron density from radio spectral broadening

Keshav Aggarwal, R. K. Choudhary, Abhirup Datta et al. (+3 more)

We present a turbulence index independent framework for simultaneously deriving solar wind velocity and coronal electron density in the near-Sun region using the spectral broadening of spacecraft radio signals. The formulation accommodates arbitrary turbulence spectral indices ($p$), providing a direct analytical link between the observed Doppler spectra and underlying plasma parameters without assuming a fixed turbulence regime. This generalization extends conventional radio occultation techniques and enables consistent interpretation across multiple radio frequencies. We apply the method to X-band ($\sim$ 8.41 GHz) radio occultation measurements from JAXA's Akatsuki spacecraft during the 2016 and 2022 Venus - Earth superior conjunctions, spanning heliocentric distances of 1.4 - 10 $R_{\odot}$ and sampling both equatorial streamer regions and mid-latitude coronal holes. The retrieved electron densities exhibit systematic trends consistent with empirical coronal models and in-situ observations. By coupling the measured spectral widths with a turbulence-based frequency-scaling relation, we obtain a compact expression that links spectral broadening, solar wind speed, and electron density, applicable for any turbulence index $p$. Fast-solar-wind intervals, characterized by nearly isotropic turbulence, yield speed estimates in close agreement with expectations, while the anisotropic nature of the slow solar wind introduces small but systematic deviations. Our results refine earlier work and demonstrate that explicit consideration of near-coronal turbulence anisotropy is essential for accurate solar-wind parameter retrievals.
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All authors Keshav Aggarwal, R. K. Choudhary, Abhirup Datta, Soumyaneal Banerjee, Takeshi Imamura, Hiroki Ando

Solar and Stellar Astrophysics

Rediscussion of Eclipsing Binaries. Paper XXX. The Slightly Evolved F-type System BK Pegasi

A.C. Kutluay and J. Southworth

BK Peg is a double-lined detached eclipsing binary containing two late-F stars in an orbit with small eccentricity. We use light curves from the Transiting Exoplanet Survey Satellite (TESS) and spectroscopic measurements from previous studies to measure the physical properties of the companions to a high precision. We obtain masses of $1.411 \pm 0.004$\Msun\ and $1.254 \pm 0.004$\Msun, and radii of $1.990 \pm 0.004$\Rsun\ and $1.460 \pm 0.004$\Rsun, which are among the most precise measurements made for these quantities in normal stars. These properties match theoretical stellar evolutionary models for a solar chemical composition and an age of 2.65~Gyr. We also present an updated ephemeris of the system, as a result of our TESS measurements and a collection of mid-eclipse times from previous studies.
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High Energy Astrophysical Phenomena

Modeling surface radiation of rotating neutron stars with Monk-NS

Wenda Zhang and Wenfei Yu

Neutron stars serve as unique laboratories for studying ultra-dense nuclear matter. The equation of state of neutron star matter can be effectively constrained by their masses and radii. Particular attention has been paid to rapidly rotating neutron stars, where strong relativistic effects leave imprints on their electromagnetic emission. To model the emission of rotating neutron stars in more realistic situations, especially when their surface emission is further re-processed by a scattering medium, we develop Monk-NS, a customized version of the general relativistic Monte-Carlo radiative transfer code Monk. We validate the code through a series of benchmarking tests, including computing the energy spectrum, pulse profile, and polarisation of rotating neutron stars, and comparing the results with those of the established codes in the X-ray timing community, yielding consistent outcomes. As an example to demonstrate Monk-NS's capabilities, we apply it to investigate various models proposed to explain the low pulsation amplitude of neutron star low-mass X-ray binaries. Our findings indicate that the dependence of the X-ray polarisation degree on the observer's inclination can serve as a key factor in distinguishing these models. We also find that complex hotspot morphologies yield polarisation properties different from those of circular hotspots.
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Cosmology and Nongalactic Astrophysics

Field-Level Inference of Primordial Non-Gaussianity with the Quijote Simulation Suite

Adam Andrews, Jens Jasche, Guilhem Lavaux et al. (+10 more)

Local primordial non-Gaussianity, parameterised as $f_{\rm NL}^{\rm local}$, will be stringently constrained using state-of-the-art methods applied to next-generation galaxy redshift survey data. In this paper, in preparation for the upcoming data sets, we demonstrate for the first time the joint field-level inference of $f_{\rm NL}^{\rm local}$, nuisance parameters, and the initial conditions in realistic halo catalogues, ones which are generated through full dark-matter-only $N$-body simulations. The field-level inference algorithm optimally constrains $f_{\rm NL}^{\rm local}$ through a Bayesian forward-modelling approach at the field level, which outperforms traditional methods by leveraging the full statistical power of the data at the scales considered. In addition, we assess its performance under various design choices in the forward model, including tests of the structure formation model and resolution. We demonstrate the robustness of our approach by applying it to a subset of the Quijote simulation suite, performing the inference at scales down to $k_{\rm max} \approx 0.1 h \rm{Mpc}^{-1}$. Compared with a power spectrum and bispectrum estimator, we find a $\sim1.3$ improvement in $\sigma(f_{\rm NL}^{\rm local})$ when applying \borg{}, while marginalising over the initial conditions and bias parameters. From the small-scale information sensitivity tests, we show that the constraints on $f_{\rm NL}^{\rm local}$ improve as we increase the resolution of the inference. These findings underscore the transformative potential of field-level inference to leverage the information available in ongoing surveys such as Euclid, providing accurate insights into the physics of cosmic inflation and the number of fields driving it.
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All authors Adam Andrews, Jens Jasche, Guilhem Lavaux, William Coulton, Francisco Villaescusa-Navarro, Marco Baldi, Drew Jamieson, Gabriel Jung, Dionysios Karagiannis, Florent Leclercq, Michele Liguori, Marco Marinucci, Benjamin Wandelt

High Energy Astrophysical Phenomena

X-Ray Polarization Study of Pulsar Wind Nebulae with eXTP: Simulation Results and Scientific Prospects

Kuan Liu, Fei Xie, Ming-Yu Ge et al. (+2 more)

X-ray polarization observations of pulsar wind nebulae (PWNe) provide crucial insights into magnetic field structures and particle acceleration mechanisms. While the Imaging X-ray Polarimetry Explorer (IXPE) has made significant contributions to PWN studies, its limited effective area restricts observations to only the brightest sources, leaving many fainter nebulae unexplored. We evaluate the polarization capabilities of the enhanced X-ray Timing and Polarimetry mission (eXTP) for studying PWNe and establish a methodology for simulating eXTP Polarimetry Focusing Array (PFA) observations using modified IXPEOBSSIM. We develop and validate a simulation framework with appropriate response functions and instrumental background models, conducting comprehensive simulations of twelve PWNe selected from the SNRcat catalogue across various evolutionary stages and brightness levels. Our simulations demonstrate that eXTP provides approximately a factor of 2 improvement in minimum detectable polarization at the 99% confidence level (MDP$_{99}$) compared to IXPE. For the brightest targets (N157B, G54.1+0.3, and Mouse), 1 Ms observations achieve MDP$_{99}$ values of 4-5%. The area with significant polarization detection for extended sources like Vela PWN is nearly twice as large as achievable with IXPE. These enhanced capabilities will significantly expand the sample of PWNe with robust X-ray polarization measurements, enabling systematic studies of magnetic field structures, particle acceleration mechanisms, and PWN-environment interactions across different evolutionary phases.
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All authors Kuan Liu, Fei Xie, Ming-Yu Ge, Wei Deng, En-Wei Liang

Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc

Non-local gravity effects in cosmological dynamics probed by IceCube/KM3NeT signals and dark matter relic abundance

Salvatore Capozziello, Gaetano Lambiase and Giuseppe Meluccio

Non-local gravity terms have a relevant role in determining the cosmological dynamics. Here we consider curvature- and torsion-based cosmological models where non-local terms can be “scalarised” and then reduced under the standard of scalar-tensor gravity. In this context, we study the role of non-local cosmology with regards to the recent results reported by the IceCube/KM3NeT experiments, which revealed high-energy astrophysical neutrino fluxes up to energies of $220$\,PeV. Specifically, we consider the four-dimensional operator $y_{\alpha\chi}\bar L_\alpha H\chi$ in order to explain both the neutrino rate result and the abundance of dark matter in the Universe, provided that the cosmological background evolves according to non-local gravitational field equations. We show that different dynamical systems representing the evolution of the Universe can be highly sensitive to the parameters of non-local gravity at energies probed by IceCube/KM3NeT. In particular, we adopt power law solutions inferred by the existence of Noether symmetries in non-local cosmological models.
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High Energy Astrophysical Phenomena

Measurement of the Orbital Parameters, Spin and Spectral Evolution During the Main High State of Her X-1 with Insight-HXMT

Wen Yang, Wei Wang and Qianhan Zhou

Based on Insight-HXMT observations, we present a detailed timing analysis and spectral evolution of a complete Main High state for Her X-1 in February 2020. We determine an accurate local ephemeris using the Rømer delay measured from five eclipses. We report the spin period of the neutron star at $P_{\rm spin}=1.23765212 \pm 0.00000026$ s with a spin period derivative of $\dot P_{\rm spin}=-(1.18\pm 0.04)\times 10^{-13}$ s\,s$^{-1}$. By combining the newly measured local values $T_{ecl}$ with those reported in the literature, we refine the orbital ephemeris of Her X-1, obtaining $T_{ecl} = 46359.871956 \pm 0.000010$ MJD and $P_{orb}=1.7001674990 \pm 0.0000000105$ day, then detect a continuous decrease in the orbital period with a rate of $\dot{P}_{\rm orb} = -(1.957 \pm 0.335)\times10^{-11}\,\mathrm{d\,d^{-1}}$. We also investigate the evolution of X-ray spectral parameters during the Main High state. The hydrogen absorption column density $N_{\rm H}$ increased monotonously during the phase, and the photon index kept nearly constant. The cyclotron absorption line was detected with a centroid energy around 38 keV, showing no significant evolution with luminosity. The spectral variations with the superorbital phase are discussed within the accretion disk precession scenario.
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Astrophysics of Galaxies

Radiative Compression of Dense Cores in the Pillars of Creation as Revealed by JWST Extinction Mapping

Jun Li, Bingqiu Chen, He Zhao et al. (+2 more)

The Pillars of Creation in M16 represent an iconic star-forming region where stellar feedback shapes molecular cloud evolution. We present a detailed investigation of dust extinction and density structure in the Pillars of Creation using multiband photometric observations from JWST NIRCam. A high-resolution (2\arcsec) extinction map reaching depths of $A_V\sim 100$ mag has been constructed using NIRCam filters F090W, F200W, F335M, and F444W. This map clearly reveals the intricate structure of dense gas within the molecular cloud in the Pillars of Creation region. Analysis of the column density probability distribution function (N-PDF) exhibits a characteristic lognormal distribution at intermediate extinctions ($A_V\approx10-30$\,mag), which transitions to a power-law tail at high extinctions ($A_V\gtrsim$ 30\,mag) where star-forming cores reside. The power-law slope $\alpha$ displays significant spatial variation, steepening from $\alpha\approx 2.0$ at the pillar tips facing the NGC 6611 cluster to $\alpha\approx$4.0 in regions distant from the cluster. This systematic gradient demonstrates that stellar feedback not only disperses molecular clouds but can also locally enhance the formation of dense, self-gravitating structures through radiative compression.
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All authors Jun Li, Bingqiu Chen, He Zhao, Jian Gao, Xi Chen

Cosmology and Nongalactic Astrophysics

Probing the stochastic signal from primordial gravitational waves with pulsar timing arrays

Jun Li, Guanghai Guo and Pengfei Yan

In this study, we investigate the scenario in which the stochastic signal arises from primordial gravitational waves. Within this framework, we consider two distinct possibilities: one in which the pulsar timing arrays (PTAs) signal corresponds to a stochastic gravitational-wave background (SGWB), and one in which it does not. Primordial gravitational waves can generate an SGWB spanning an exceptionally broad frequency range and are also a source of B-mode polarization in the cosmic microwave background (CMB). We combine CMB B-mode polarization data from BICEP/Keck (BK18), Planck (Planck18), and baryon acoustic oscillation (BAO) measurements with SGWB limits from PTAs to derive updated constraints on the tensor spectral index of the primordial power spectrum. Under the assumption of no detection of an SGWB from PTAs, the allowed parameter space excludes a large portion of the positive region. The constraint within PTA limits is $n_t= -0.165^{+1.20}_{-1.56}$ at $95\%$ confidence level, which are consistent with those obtained from the combined BK18+Planck18+BAO dataset, leading to tighter constraints on the tensor spectral index. Conversely, if the PTA signal is interpreted as an SGWB, the likelihood distribution for the tensor spectral index favors positive values, with $n_t= 2.39^{+1.46}_{-1.35}$ at $95\%$ confidence level, providing evidence for a blue-tilted primordial gravitational-wave power spectrum. In this case, the allowed parameter space excludes the negative region.
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High Energy Astrophysical Phenomena

Southern eROSITA bubble as a forward shock and the low-metallicity CGM. South-east side story

E.Churazov, I.I.Khabibullin, A.M.Bykov et al. (+4 more)

Unlike the complicated X-ray and radio structure observed in the North Polar Spur area, the South-Eastern part of the eROSITA bubbles can be reasonably well described as a propagating forward shock, plausibly created by the transient energy release at the Galactic Center. In this model, the physical radius of the bubble is $R_{\rm b}\sim 7-8\,{\rm kpc}$ and the age of the outburst is $t_{\rm age}\sim 5-8\,{\rm Myr}$. The latter quantity is plausibly a lower limit on the true age. The visible segment of the shock front (located at a distance of $\sim 10-12\,{\rm kpc}$ above the Galactic Disk and at a similar distance from the Sun) is currently expanding with the velocity $\sim 700\,{\rm km\,s^{-1}}$ through the gas with density $n_e\sim 3\times 10^{-4}\,{\rm cm^{-3}}$, and the abundance of heavy elements in this gas is low $Z\sim 0.1-0.2 \times Z_\odot$ (depending on the adopted reference Solar abundances). Unlike constraints derived from the line-of-sight-integrated quantities, these are effectively in situ measurements of the circumgalactic medium (CGM) properties. Given the simplifying assumptions used in deriving the density and abundance, we assign a factor of 2 systematic uncertainty to the final estimates. An eventual decisive test for the shock properties can be provided by the velocity measurements of the X-ray-emitting gas with soft X-ray bolometers. The extended forward shock propagating through low-metallicity gas is a favorable site to accelerate very high-energy cosmic rays, which might contribute to the recently discovered proton-rich Galactic cosmic ray component at PeV energies impinging on the Earth's atmosphere.
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All authors E.Churazov, I.I.Khabibullin, A.M.Bykov, N.N.Chugai, R.A.Sunyaev, V.P.Utrobin, I.I.Zinchenko

High Energy Astrophysical Phenomena

Synchrotron Self-Absorption Spectral Modeling Reveals a Magnetically Driven Shock-in-Jet Scenario in Blazar 1156+295

Wancheng Xu, Lang Cui, Tao An et al. (+6 more)

Unveiling the launching and driving mechanisms of powerful jets in active galactic nuclei (AGNs) is crucial for understanding the co-evolution of supermassive black holes (SMBHs) and their host galaxies. 1156+295 is a blazar at a redshift of z=0.729 and exhibits significant variability in long-term radio monitoring. Using multi-frequency Effelsberg single-dish flux density data from 2007 to 2012, we performed synchrotron self-absorption (SSA) spectral modeling and extracted the turnover frequency and turnover flux density. By combining SSA spectral modeling with the core size and brightness temperature from quasi-simultaneous very long baseline interferometry (VLBI) images, we estimated the jet magnetic-field strength and magnetic flux, and investigated their temporal evolution in 1156+295. The evolution of radio flux density, spectral shape, and jet structure is consistent with the shock-in-jet framework. The inferred magnetic flux reaching or exceeding the magnetically arrested disk (MAD) threshold, together with evidence that magnetic energy release precedes the radio flares, supports a magnetically driven jet scenario. Overall, our results place magnetic-field measurements, spectral evolution, and inner-jet structural changes on a common timeline, providing observational constraints on their coupled evolution during flares.
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All authors Wancheng Xu, Lang Cui, Tao An, Sándor Frey, Xin Wang, Yuanqi Liu, Ning Chang, Liang Chen, Yingkang Zhang

Astrophysics of Galaxies · Cross-listed from gr-qc

Generalized JMN Naked Singularity Models

Jay Verma Trivedi and Pankaj S. Joshi

We construct a generalized class of Joshi-Malafarina-Narayan (JMN) naked singularity spacetimes that arise as equilibrium end states of gravitational collapse with non-vanishing tangential pressure. The generalization introduces density inhomogeneity through a radially dependent mass function $F(r)=(M_0+M_n r^n)r^3$, leading to a two-parameter family of solutions matched smoothly to an exterior Schwarzschild spacetime. The observational properties of the spacetime are then examined through shadow formation and thin accretion disk emission. We find that when the photon sphere lies in the exterior Schwarzschild region, the shadow is identical to that of a Schwarzschild black hole. Accretion disk spectra show enhanced high-frequency emission compared to Schwarzschild, while deviations from the original JMN model remain small due to strong constraints on the inhomogeneity parameter. These results indicate that the generalized model effectively serves as a small perturbation of the JMN spacetime, demonstrating the robustness of JMN-type naked-singularity geometries.
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Astrophysics of Galaxies

Observations of DNC and DCO$^+$ toward the $\int$-shaped Filament and Starless Cores in the Orion Molecular Clouds

Ken'ichi Tatematsu, Atsushi Nishimura, Hideo Ogawa et al. (+25 more)

Although the deuterium fraction is known to be a powerful evolutionary tracer, its variation within individual molecular cloud cores is still poorly understood. The northern $\int$-shaped filament and 20 individual starless cores in the Orion A and B clouds were mapped in the deuterated molecules of DNC and DCO$^+$ with the Receiver 7BEE installed on the Nobeyama 45~m radio telescope. In a ~ 5' X 30' map of the northern $\int$-shaped filament in the Orion A cloud, the DNC emission is detected over the filament, whereas the DCO$^+$ emission is localized toward OMC-3, the northernmost region of the filament. The difference in distribution between DNC and DCO$^+$ can be attributed to that between N- and C-bearing molecules as previously suggested by Tatematsu et al. High DNC/HN$^{13}$C column density ratios were observed in OMC-2 and OMC-3, and low ratios in OMC-1. It seems that OMC-2 and OMC-3 still contain molecular gas close to the onset of star formation. In 3' X 3' maps of the individual starless cores in Orion, the column density ratios of DNC/HN$^{13}$C and DCO$^+$/H$^{13}$CO$^+$ are found to be rather constant locally within each core, although the core-to-core variation is not small. Similar timescales of deuterization, depletion, and dynamical evolution might explain the locally constant ratio.
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All authors Ken'ichi Tatematsu, Atsushi Nishimura, Hideo Ogawa, Nami Sakai, Takeshi Sakai, Kazuki Tokuda, Yutaka Hasegawa, Yasumasa Yamasaki, Toshikazu Onishi, Naomi Hirano, Sheng-Yuan Liu, Tie Liu, Somnath Dutta, Dipen Sahu, Chin-Fei Lee, Kee-Tae Kim, Gary A. Fuller, Shih-Ying Hsu, Hee-Weon Yi, Sho Masui, Shimpei Nishimoto, Chieko Miyazawa, Toshikazu Takahashi, Jun Maekawa, Alvaro Gonzalez, Takafumi Kojima, Keiko Kaneko, Ken Miyato

High Energy Astrophysical Phenomena

FAST Polarization Catalog of FRB 20240114A

Tian-Cong Wang, Jun-Shuo Zhang, Xiao-Hui Liu et al. (+60 more)

Polarization measurements of fast radio bursts (FRBs) probe the magnetized plasma surrounding their central engines. FRB~20240114A is an exceptionally active repeating source, with 17,356 bursts detected between 2024 January 28 and 2025 May 30 by FAST, enabling time-resolved polarimetric studies. In this work, we present a polarimetric catalog of 6,131 bright bursts (with a signal-to-noise ratio S/N $\geq$ 20, 35.3% of the total sample), including arrival time (MJD$_{\text{topo}}$), dispersion measure (DM), burst width (W$_{\text{eff}}$), bandwidth, Faraday rotation measure (RM), linear and circular polarization degrees (DOL, DOC), and intrinsic polarization angle (PA$_0$). We detect a clear temporal evolution of RM: after an initial stable phase, it decreases linearly by $\sim$200 $\rm rad\ m^{-2}$ over 200 days, forming a bimodal distribution, whereas DM remains stable at 528.9 $\rm pc\ cm^{-3}$. The linear polarization fraction is generally high, with the 3$\sigma$ lower bound around 76%, while circular polarization is low, with 1,157 of 17,356 bursts (6.67%) having DOC $\geq$10%. We perform a power-law fit between $|\textrm{V}|$/I and $|\textrm{RM}|$, which yields an index of $-2.98 \pm 0.80$. It is found that the combined 2D distribution of L/I versus V/I remains stable, implying that the emission mechanism is largely invariant. Our PA$_0$ measurements show a broad, non-uniform distribution, implying a complex emission geometry. These results suggest that FRB~20240114A resides in a dynamically evolving magneto-ionic environment. This catalog provides a foundation for studies of repeating FRB progenitors and their environments.
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All authors Tian-Cong Wang, Jun-Shuo Zhang, Xiao-Hui Liu, Wei-Yang Wang, Pei Wang, He Gao, Di Li, Bing Zhang, Wei-Wei Zhu, Jin-Lin Han, Ke-Jia Lee, Ye Li, Dengke Zhou, Wan-Jin Lu, Jintao Xie, Jianhua Fang, Jin-Huang Cao, Chen-Chen Miao, Yu-Hao Zhu, Yunchuan Chen, Si-Lu Xu, Huaxi Chen, Xiao-Feng Cheng, Qin Wu, Shuo Cao, Long-Xuan Zhang, Shi-Yan Tian, Yong-Kun Zhang, Yi Feng, De-Jiang Zhou, Jia-Rui Niu, Heng Xu, Xuelei Chen, Yuan-Pei Yang, Dong-Zi Li, Fa-Yin Wang, Chao-Wei Tsai, Wen-Fei Yu, Chen-Hui Niu, Jia-Wei Luo, Rui Luo, E. Gugercinoglu, Zi-Wei Wu, Chun-Feng Zhang, Xiang-Lei Chen, Shuai Feng, Xiang-Han Cui, Qing-Yue Qu, Yuan-Hong Qu, Bo-Jun Wang, Yi-Dan Wang, Lin Lin, Ai-Yuan Yang, Yuan-Chuan Zou, Yu-Xiang Huang, Wei-Cong Jing, Jian Li, Yong-Feng Huang, Su-Ming Weng, Shi-Han Yew, Xue-Feng Wu, Lei Zhang, Ru-Shuang Zhao

Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc

Breaking the degeneracy among regular black holes with gravitational lensing

Hong Liu, Xiaolong Liao and Yi Zhang

We examine parameter degeneracies in Culetu, Bardeen and Hayward regular black holes across lensing, shadow and quasinormal mode regimes. Our analysis reveals that while Einstein ring data yield extremely loose constraints, with the regularization parameter $q$ exceeding $\mathcal{O}(10^3)$, they fail to improve the parameter estimation when combined with strong lensing observables. In contrast, the Event Horizon Telescope observations provide remarkably tight limits: $0 \leq q < 0.0466 <0.0847$ for Culetu, $0 \leq q < 0.5115 <0.6682$ for Bardeen and $0 \leq q < 1.0258 <1.1881$ for Hayward, which shows that the strong field regime alone dominates the available parameter space. Despite these bounds, leading order geometric observables remain highly degenerate, which masks the microscopic details of non-singular cores. To break this “macroscopic universality,” we identify high order signatures, such as the Lyapunov exponent and subleading time delays, as sensitive probes of near horizon curvature. Crucially, we discover that the brightness hierarchy of accretion induced intensity profiles undergoes a fundamental inversion when transitioning from lensing dominated static flows to dynamics dominated infalling flows. These results demonstrate that high resolution temporal and intensity profiles are essential for distinguishing between regular black hole geometries.
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Friday 20 March

Cosmology and Nongalactic Astrophysics

Improved dark matter measurements with flexible modeling of resolved strongly-lensed quasar narrow-line emission

Maria F. Perez Mendoza, Anna M. Nierenberg and Vardha N. Bennert

The relative brightnesses of strongly lensed quasar images, called flux ratios, respond to perturbations from low-mass dark matter halos, enabling tests of dark matter models. The quasar narrow-line region (NLR) is ideal for flux-ratio studies: large enough to be insensitive to stellar microlensing, yet compact enough to remain sensitive to dark matter halo substructure. While nuclear emission dominates NLR flux, many quasars show low surface brightness extended emission spanning kiloparsec scales that could bias measurements. To test this potential bias, we generated mock Keck OSIRIS AO observations of seven $z<1$, $L_\mathrm{bol}\sim10^{46}$ erg s$^{-1}$ quasars characteristic of sources. Only one system shows detectable extended emission after lensing. We introduce a new pipeline for simultaneously fitting point sources (nuclear) + Sérsic elliptical profiles (extended [O\,III]). We show that we recover the true flux-ratios to $<5\%$ even when the extended emission is boosted to 100 times its original flux. We also demonstrate that visual inspection of lenses reliably determines whether to use point-source-only or include extended emission modeling in the pipeline; both achieve $<5\%$ accuracy – which is below the typical spectral fitting precision. The new pipeline and fitting procedure ensures reliable flux-ratio measurements can be made of narrow-line flux ratios for the thousands of lenses which will be discovered by Euclid, Rubin and Roman Space Telescopes.
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High Energy Astrophysical Phenomena

A Physical Model of Pulsar X-ray Filaments

Jack T. Dinsmore and Roger W. Romani

We present a model for pulsar filaments - a class of narrow X-ray nebulae misaligned with the proper motion, powered by pulsar-generated $e^\pm$. We suggest that cosmic ray-enhanced turbulence drives pitch-angle scattering and dominates $e^\pm$ motion along the filament; highly amplified magnetic fields are not required. A simulation built on this picture, using analytic approximations for the turbulence growth and cosmic ray evolution, generates images and spectra matching observations of the three best-measured filaments. The model structure depends on interstellar medium properties, and fits to filament data require values similar to observed ISM values. In this model a substantial fraction of the filament $e^\pm$ escape, free-streaming for many pc, in contrast to the suppressed cosmic ray diffusion near pulsar TeV halos. Accordingly, nearby low-power filament-generating pulsars may make out-sized contributions to the local positron spectrum. Future X-ray observatories can make the sensitive spectral maps required to test this particle escape.
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2603.20532 · 20 Mar · This paper was not accepted to ApJ after several rounds of review. Referees viewed our turbulence growth and cascade rate modeling as not meeting the plasma community's accustomed rigor. Nevertheless, this heuristic model agrees with observations better than other published pictures. We thus encourage readers to consider it, while acknowledging that more rigorous treatment is likely needed

Abstract PDF $PLSR ×5$CSMC ×3$TURB ×2$DIFF ×1 +3

Earth and Planetary Astrophysics

A New Method of Measuring Magnetic Field Strength in Highly Structured Protostellar Envelopes

Yisheng Tu, Xiaoyuan Yang and Zhi-Yun Li

Magnetic fields play a fundamental role in protostellar collapse and disk formation, yet direct measurements of magnetic field strength in deeply embedded protostellar envelopes remain difficult. We present a new method to estimate both the vertical and total magnetic field strength in collapsing, pseudodisk- or sheetlet-dominated protostellar envelopes, derived directly from the magnetohydrodynamic momentum equation. The method relates the magnetic field strength to two observationally accessible quantities: the projected gravitational acceleration toward the center of collapse and the face-on column density of the pseudodisk, and two dimensionless parameters, $a_{b, R}$ and $\gamma_{zR}$, which characterize magnetic contribution to the force balance and the field geometry, respectively, through $|B_z|=(2\pi a_{b,R}\gamma_{zR}g_R\Sigma)^{1/2}$. Using non-ideal magnetohydrodynamic simulations, we verify the assumptions underlying the method, justify the adopted approximations, and calibrate the two key dimensionless parameters. We provide canonical estimates of these two parameters, and show that they exhibit only weak spatial and temporal variations, allowing robust field strength estimates even when detailed gas kinematics or high-resolution polarization information is unavailable. We show that the method is applicable in both turbulent and non-turbulent envelopes and is insensitive to the ambipolar diffusion coefficient, making it robust against uncertainties in the local turbulence strength and ionization rate. We apply the method to the Class 0 source L1157, using column-density and gravitational-acceleration estimates from the literature to estimate the magnetic field strength for L1157. Our result is broadly consistent with previous estimates from independent methods, demonstrating the utility of this approach for constraining magnetic fields in embedded protostellar systems.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc

Singular structures and causality of the Schwarzschild Green's function in the frequency domain

Romeo Felice Rosato, Marina De Amicis and Paolo Pani

We study two singular spectral components of the Green's function of a Schwarzschild black hole and their interpretation in the frequency domain: (i) the low-frequency branch cut, which yields corrections to Price's law tails in the form of inverse power laws weighted by logarithmic terms; and (ii) the quasinormal-mode spectrum, which generates a redshifted response for sources extended toward the horizon. We show that the frequency-domain Green's function can be naturally interpreted in terms of greybody factors, providing the first analytical justification for recent phenomenological ringdown models based on these quantities. For sources localized outside the peak of the potential barrier, we identify two tail contributions activated with a time delay, arising from backscattering of the prompt response and of the ringdown signal. We show that corrections to Price's law can be relevant at intermediate times, when the ringdown still dominates the waveform. For sources localized inside the potential barrier peak, the tail is suppressed and the signal is instead dominated by quasinormal frequencies. In this regime, these spectral components produce both the ordinary quasinormal-mode ringdown and an infinite tower of exponentially decaying terms governed by the horizon surface gravity, the so-called redshift terms. We demonstrate that this component is not screened by geometric features of the background spacetime and persists up to late times, as supported by numerical investigations of perturbative waveforms. Our results provide a mathematical foundation for phenomenological modeling of the branch-cut contribution at intermediate times, which is relevant for prospective observations of tails, and strong evidence for the presence of redshifted components from intermediate to late times.
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Solar and Stellar Astrophysics

Magnetic white dwarfs from DESI

Larissa L. Amorim, S. O. Kepler and Alejandra D. Romero

A significant fraction of white dwarfs, the degenerate remnants of low- and intermediate-mass stars, host strong magnetic fields; yet, the origin and evolution of these magnetic fields remain poorly understood. Building a large, statistically robust sample of these magnetic white dwarfs (MWDs) is crucial for testing competing theories of field generation. We used the white dwarf candidates catalog from Gaia DR3 to select objects with spectra from the first data release of the Dark Energy Spectroscopic Instrument (DESI) survey. We identified candidate MWDs through visual inspection of their spectra, searching for the characteristic Zeeman splitting of absorption lines. After cross-matching with the literature, we present the discovery of 137 new MWDs. Follow-up analysis and atmospheric modeling were used to determine magnetic field strengths ranging from approximately 1 to nearly 500~MG. Our findings demonstrate the exceptional capability of large-scale spectroscopic surveys, such as DESI, to uncover rare stellar populations and advance our understanding of compact-object astrophysics.
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High Energy Astrophysical Phenomena

Circular polarization of gravitational waves from magnetorotational supernovae

Shota Shibagaki, Tomoya Takiwaki, Kei Kotake et al. (+2 more)

Context. Gravitational waves (GWs) provide a unique probe of the explosion mechanism of massive stars and the evolution of nascent proto-neutron stars (PNSs). Magnetorotational explosions are one of the promising noncanonical core-collapse supernova scenarios, possibly linked to magnetar formation and energetic supernova explosions. However, the GW signatures of such events remain incompletely understood. Aims. We investigate the origin and nature of GW polarization arising from a magnetorotational core-collapse model and examine its potential detectability by current GW observatories. Methods. We performed a 3D GRMHD simulation of a rapidly rotating, strongly magnetized 20 $M_{\odot}$ progenitor, including multi-energy neutrino transport. The GW signals were extracted using the standard quadrupole formalism, and their polarization states were analyzed with Stokes parameters. Results. Strong circular polarization emerges along the rotation axis during the early post-bounce phase ($\lesssim$ 230 ms). The characteristic GW spectrum peaks at ~90 Hz, consistent with the emission at twice the local angular velocity (~45 Hz) around the PNS surface at cylindrical radii of ~50 km. These features are attributed to the low-$T/\vert{}W\vert{}$ instabilities and nonaxisymmetric motions near the PNS and not to the MHD jets themselves. The polarization signals lie within the sensitivity bands of current detectors such as Advanced LIGO, Advanced Virgo, and KAGRA. Conclusions. Models launching magnetorotationally driven jets can produce circularly polarized GW signals originating from the inner PNS region. This provides an observational signature that complements previous findings from nonmagnetized rotating models. Thus, GW polarization is a promising diagnostic of noncanonical core-collapse supernovae. Future third-generation detectors will be crucial to fully exploit this potential.
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All authors Shota Shibagaki, Tomoya Takiwaki, Kei Kotake, Takami Kuroda, Tobias Fischer

Solar and Stellar Astrophysics

Refinement of Stellar Parameters for the Eclipsing Binary System KIC 8569819 using Stellar Modeling Approach

Dinesha Dharmathilaka, Janaka Adassuriya, Chandana Jayaratne et al. (+1 more)

Eclipsing binary systems with a Delta (${\delta}$) Scuti component serve a vital role in deriving precise fundamental stellar parameters and testing stellar evolution models. This study mainly focuses on the Kepler target KIC 8569819, a detached eclipsing binary system that consists of a ${\delta}$ Scuti pulsating component. The quarter 9 photometric data observed by the Kepler mission were used for the analysis. The binary nature of the KIC 8569819 system was modeled using the Wilson-Devinney (WD) code and extracted new set of stellar parameters. This comprehensive study mainly focuses on the application of the Differential Correction (DC2015) process after the initial fitting done by the Light Curve modeling (LC2015) process for the disentanglement of the binary nature from the observed light curve. Subsequently, an improved set of stellar parameters for both primary and secondary components of the KIC 8569819 system was determined. The DC2015 modeling process yielded an orbital inclination of $i=89.88\pm0.03$ degrees, primary component luminosity $L=10.911\pm0.005$ $L_{\odot}$, the effective temperature of the primary component of $T_{eff,1}=7155\pm9$ K and the effective temperature of the secondary component of $T_{eff,2}=5956\pm7$ K. Additionally, the values for the radius 1.790 $R_{\odot}$ and 0.986 $R_{\odot}$, bolometric magnitude $2.56$ mag and $4.65$ mag, and surface gravity $4.17$ $cm s^{-2}$ and $4.46$ $cm s^{-2}$, were found as refined stellar parameters for both primary and secondary components of the KIC 8569819 binary system respectively. These results not only deliver an updated and highly accurate stellar model for KIC 8569819 but also provide reliable input for the future analysis of mode identification of pulsation frequencies in the field of Asteroseismology.
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All authors Dinesha Dharmathilaka, Janaka Adassuriya, Chandana Jayaratne, Jordi Gutiérrez

Earth and Planetary Astrophysics

Coma Physics of an Interstellar Object: JWST Spatial-Spectral Mapping of 3I/ATLAS

Nathan X. Roth, Martin A. Cordiner, Stefanie N. Milam et al. (+17 more)

We report a survey of molecular emission from cometary volatiles using the James Webb Space Telescope (JWST) toward interstellar object 3I/ATLAS carried out on UT 2025 December 22 and 23 at a heliocentric distance ($r_H$) of $2.37-2.41$ au. These measurements of CO, CO$_2$, H$_2$O, CH$_3$OH, and CH$_4$ sampled molecular chemistry in 3I/ATLAS as it receded from its encounter with our Sun and entered the vicinity of the H$_2$O ice line – the region between $r_H$ = $2-3$ au where the temperature becomes too low for H$_2$O to vigorously sublime and CO and CO$_2$ begin to control the overall activity. CO was the most abundant molecule, followed by H$_2$O and CO$_2$, whose molecular abundances with respect to CO were $(40.5\pm3.1)\%$ and ($41.6\pm0.3)\%$, respectively. This work presents spatial-spectral maps of column density and rotational temperature as a function of distance from the nucleus for all detected species. The spatial distributions of both quantities were highly anisotropic for the apolar species in the coma of 3I/ATLAS, yet were more nearly symmetric for the polar molecules. These results demonstrate how volatiles were segregated in the nucleus ices of 3I/ATLAS and reveal heating and cooling mechanisms in its coma. Derived maps of the ortho-to-para ratio (OPR) for H$_2$O were flat with increasing distance from the nucleus and consistent with a coma-averaged value $\mathrm{OPR}=2.7\pm0.2$, slightly less than the expected equilibrium value of three.
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All authors Nathan X. Roth, Martin A. Cordiner, Stefanie N. Milam, Geronimo L. Villanueva, Steven B. Charnley, Nicolas Biver, Dominique Bockelee-Morvan, Dennis Bodewits, Steven J. Bromley, Jacques Crovisier, Maria N. Drozdovskaya, Sara Faggi, Davide Farnocchia, Kenji Furuya, Michael S.P. Kelley, Marco Micheli, John W. Noonan, Cyrielle Opitom, Megan E. Schwamb, Cristina A. Thomas

Instrumentation and Methods for Astrophysics

Astrophysics Research Organizations in the 21st Century: Database and Comparative Dashboards

Michael J. Kurtz, Carlolyn S. Grant, Matthew R. Templeton et al. (+1 more)

As many research papers in astronomy have been written since the beginning of the 21st century as had been written previously. This exponential growth has been accompanied by substantial changes in the structure of astrophysics research, which organizations perform it and where they are located. Using data from the Smithsonian/NASA Astrophysics Data System/Science Explorer (ADS/SciX) we have obtained an article number and citation based set of metrics as a function of the institutional affiliation of the first author; nearly every organization which has produced recent astronomy research is included. We use these data to examine changes in where astronomy research is being done. We demonstrate how to create custom rankings for the organizations. We develop a dashboard of key performance indicators (KPI) to examine the relative and absolute changes in the research performance for each of the 1949 organizations which have produced at least one first authored, refereed astronomy journal article since 1997. We also present KPI dashboards for 65 countries and three regions.
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All authors Michael J. Kurtz, Carlolyn S. Grant, Matthew R. Templeton, The ADS/SciX Team