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Physics Astrophysics

astro-ph Watch Astrophysics

Monday 23 March

Astrophysics of Galaxies

The ALMA-QUARKS survey: Investigating Thermal Feedback of Massive Protostars in Hot Molecular Cores

Dezhao Meng, Tie Liu, Jarken Esimbek et al. (+33 more)

We identify a sample of 83 spatially resolved hot molecular cores (HMCs) in the QUARKS survey, aiming at investigating thermal feedback from massive stars. Using CH$_3$CN\,(12–11) line emission together with 1.3\,mm continuum data we derive the radial temperature, volume density and \ch3cn{} abundance profiles for the 83 HMCs. Based on the envelope temperature and density profiles, we compute the luminosities of the embedded massive protostars with \radmc{} radiation transfer model. The derived luminosities are comparable (within $\sim1$ dex) to the bolometric luminosities of their natal clumps and show strong correlations with several core-scale properties, including the HMC mass ($Log[ M_\mathrm{env}] = 1.01\,Log [L_\star] - 4.80$), the inner core radius (the flat radius of Plummer-like volume density profile) ($Log[a] = 0.46\,Log[L_\star] + 0.52$) and the central density $ (Log[n_c] = -0.55 Log[L_\star] +10.47) $. These empirical relations provide useful observational constraints for physical models of protostellar objects. Importantly, we find a strong positive correlation between the massive protostellar luminosity and the local thermal Jeans mass. The derived Jeans masses, $M_\mathrm{Jeans}$, exceed the HMC masses $M_\mathrm{env}$, with the average $M_\mathrm{Jeans}$ being two times larger than the average $M_\mathrm{env}$. This provides observational evidence that thermal feedback from massive protostars can effectively suppress further fragmentation of HMCs, thereby promoting massive star formation. In addition, the positive correlation between massive protostellar luminosity and natal clump mass suggests that more massive clumps preferentially host more luminous protostars, leading to stronger thermal feedback.
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All authors Dezhao Meng, Tie Liu, Jarken Esimbek, Yisheng Qiu, Jixing Ge, Neal J. Evans, Aina Palau, Guido Garay, Paul F. Goldsmith, Fengwei Xu, Sami Dib, Jeong-Eun Lee, Amelia M. Stutz, Xindi Tang, Xiaofeng Mai, Yankun Zhang, Wenyu Jiao, Jiahang Zou, Leonardo J. Bronfman, Swagat R. Das, Prasanta Gorai, J. W. Zhou, Pablo Garc'ia, L. Viktor Toth, Sheng-Yuan Liu, Patricio Sanhueza, Chang Won Lee, Kee-Tae Kim, Jianjun Zhou, Gang Wu, Dalei Li, Yuxin He, Dongting Yang, James O. Chibueze, Xunchuan Liu, Lei Zhu

High Energy Astrophysical Phenomena

Multimessenger Concordance for the Cygnus Region as the Source of the Cosmic-Ray Knee

Luis E. Espinosa Castro, Kotha Murase, Carlo Rizza et al. (+3 more)

The origin of the cosmic-ray (CR) knee remains one of the central open questions in particle astrophysics. Recent measurements by the Large High Altitude Air Shower Observatory revealed a pronounced feature in the proton spectrum at $\sim3-4$~PeV, while observations of diffuse gamma rays above $100$~TeV do not exhibit a corresponding spectral break. This apparent discrepancy challenges the standard interpretation, in which the local CR distribution is representative of the Galactic CR sea. Here, we investigate whether the CR knee can instead originate from the Cygnus region as a nearby PeVatron. By combining CR measurements at Earth with very-high-energy gamma-ray observations from LHAASO and the Tibet-AS$\gamma$ experiment, we identify an additional hard gamma-ray component in the inner Galaxy consistent with a source located in the Cygnus region. We show that our results provide a concordance multimessenger picture. The required properties are compatible with the PeVatron candidate detected by LHAASO in the Cygnus bubble and with the Galactic neutrino flux observed by the IceCube Neutrino Observatory.
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All authors Luis E. Espinosa Castro, Kotha Murase, Carlo Rizza, Francesco L. Villante, Vittoria Vecchiotti, Giulia Pagliaroli

Solar and Stellar Astrophysics

Investigating the propagation of small-scale flare energy in the lower and upper atmosphere of solar active region

Girjesh Gupta, Ananya Rawat, Helen Mason et al. (+1 more)

During solar flares, a considerable portion of the flare atmosphere becomes heated; however, the energy deposition process is still unclear, especially in the lower solar atmosphere. Here, we present spectroscopic and imaging observations of a small-scale transient of lifetime $<$1-min and further formation of a hot loop of lifetime $\approx$2-min in a solar active region. The observed transient shows the appearance of hot plasma $>$10 MK at the loop foot-point and the subsequent formation of a small-scale transient loop with a loop-top temperature $>$8 MK. The transient shows an enhancement in intensities in several AIA and IRIS passbands. Light curves obtained from several lower atmospheric passbands show consistent time lags in several peak intensities, which, to our knowledge, has never been reported before. Beneath the transient, associated HMI magnetogram shows evidence of flux emergence of both polarities. Using the IRIS \ion{O}{IV} line pair, we obtained the average electron number density of $10^{11.22}$ cm$^{-3}$ at the transient. IRIS transition region lines such as \ion{O}{IV} and \ion{Si}{IV} show a redshift of 10-15 km s$^{-1}$, whereas neutral lines such as \ion{C}{I} and \ion{S}{I} show a redshift of about 5 km s$^{-1}$. These Doppler shifts suggest a down-flowing warmer plasma in the lower atmosphere. The appearance of \ion{Mg}{II} triplets in emission is also observed. We interpret these enhancements in intensities in the lower atmosphere as a result of heating due to both non-thermal electrons and thermal conduction operating simultaneously.
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All authors Girjesh Gupta, Ananya Rawat, Helen Mason, Robertus Erdélyi

Solar and Stellar Astrophysics

Insights into the Exoplanet Radius Valley from Host-Star Ages, Activity, Chemistry, and Birth Radius

Xunzhou Chen, Tiancheng Sun, Yuxi Lu et al. (+2 more)

The radius valley, a bimodal feature in the size distribution of close-in small exoplanets, is widely interpreted as a signature of atmospheric loss and therefore provides a key constraint on the formation and atmospheric evolution of these planets. We investigate its dependence on host-star properties using 769 planets orbiting 558 stars, for which we derive stellar ages, chromospheric activity, and Galactic birth radius, together with elemental abundances. We find that the radius valley is not fully established at ages $\sim 3$ Gyr and evolves over gigayear timescales, with its prominence strongly affected by stellar population mixing. The dependence on magnetic activity is non-monotonic: a clear valley is present even among magnetically quiet stars, while highly active systems do not show a systematically stronger depletion. The valley morphology also varies with stellar composition: the valley is strongest in metal-poor stars, weakens near solar metallicity, and partially strengthens again at the highest metallicities. In addition, the valley shows sensitivity to refractory element ratios such as [Mg/Si], while correlations with [C/O] are weaker, indicating a dependence on planetary interior structure. Our results are more consistent with a dominant role for core-powered atmospheric mass loss than with purely irradiation-driven photoevaporation. Finally, the radius valley also depends on the Galactic birth environment, with systems near the estimated solar birth radius $\sim 4.5$ kpc showing a high fraction of Earth-like planets and a well-defined bimodal structure, suggesting that the Solar System formed in a region with a well-developed Earth-sized planet population.
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All authors Xunzhou Chen, Tiancheng Sun, Yuxi Lu, Zixuan Lu, Lifei Ye

Astrophysics of Galaxies

Research on the central region of quasars based on variability and structure function

Xuan Wei, J.Tang, Yu Tao et al. (+1 more)

Quasars,asextremelyluminousanddistantspecialcelestialbodiesintheuniverse,aredrivenbyacomplexsystemcomposedof supermassiveblackholesandsurroundingaccretiondisks.Thispaperadoptsatime-domainobservationstrategyandcombines the analysis of light curves with the construction of structure functions to indirectly reveal the physical essence of the central regionofquasarsfromtheperspectiveofvariability.Theresearchdataarederivedfromthelargesampleobservationdataofthe SloanDigitalSkySurvey(SDSS).Throughextensivedatastatisticsandcorrelationanalysis,aseriesofimportantfindingshave been obtained: the characteristic parameters of the structure function of quasars show significant correlations with luminosity, black hole mass, and Eddington ratio. That is, quasars with higher luminosity, larger black hole mass, and larger Eddington ratiohavelargerstructurefunctions.Forquasarsofthesameluminosity,thelargertheEddingtonratio,thesmallerthestructure function. However, the correlation between the structure function and redshift or rest wavelength is not significant, indicating that the variabilitycharacteristicsofquasars aremainly determined bytheir own physical propertiesandareminimallyaffected by the cosmologicalredshifteffect.
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All authors Xuan Wei, J.Tang, Yu Tao, XiaoHan Zhang

Astrophysics of Galaxies

Chemical Abundance Ratios of Nitrogen Rich Galaxies Identified at $z\sim 6-12$: Observational Demographics and Models

Kuria Watanabe, Masami Ouchi, Kimihiko Nakajima et al. (+13 more)

We present chemical abundance ratios of 8 nitrogen-rich ([N/O]$>0.3$) galaxies at $z\sim 6-12$ identified by the first 4 years of the JWST observations, and compare these ratios with chemical evolution models. We reanalyze the JWST/NIRSpec data of these galaxies in the self-consistent manner for line fluxes and upper limits including those previously unconstrained. We derive the abundance ratios and constraints of [N/O], [C/O], [Ne/O], [Ne/C], [Ar/O], [S/O] and [Fe/O], characterizing the nebulae in the galaxies with the electron temperatures and densities measured with {\sc[Oiii]}$\lambda4363$ and {\sc[Oii]}$\lambda\lambda3727, 3729$ lines, respectively. We develop the chemical evolution models for the three major scenarios, Wolf-Rayet stars, supermassive stars, and tidal disruption events (TDEs) with the AGB star contribution, integrating the ejecta of the stars and core-collapse supernovae (CCSNe) over the age with yields calculated by numerical simulations. We compare the models with the [N/O] measurements and stellar ages, and find that all of the scenarios reproduce [N/O] as high as those of our galaxies. However, the time-scales of the high [N/O] ratios are too short to explain our galaxies in any of the scenarios, suggestive of very frequent failed supernovae that do not increase oxygen against nitrogen. We find that the three scenarios are distinguished in the plane of [Ne/C] vs. [N/O] due to Ne production outside CNO cycle, and that the observed abundance ratios are explained by the Wolf-Rayet models better than supermassive-star and TDE models. We argue that abundance ratios of various elements and time scales are clues for understanding nitrogen-rich galaxies.
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All authors Kuria Watanabe, Masami Ouchi, Kimihiko Nakajima, Nozomu Tominaga, Yuichi Harikane, Miho N. Ishigaki, Yuki Isobe, Minami Nakane, Moka Nishigaki, Ken'ichi Nomoto, Yoshiaki Ono, Masato Onodera, Akihiro Suzuki, Koh Takahashi, Yui Takeda, Hiroto Yanagisawa

High Energy Astrophysical Phenomena

Detection of a Molecular Cloud toward the Heartbeating Gamma-ray Source near the Microquasar SS 433

Tomoharu Oka, Ryo Ariyama and Tatsuya Kotani

We report the detection of a molecular cloud, CO+40.05-2.40, positionally coincident with the "heartbeating" GeV source Fermi J1913+0515 at the northern boundary of the SS 433/W50 system. Millimeter and submillimeter spectroscopy with the Nobeyama 45 m telescope and the James Clerk Maxwell Telescope shows that the cloud has physical properties typical of quiescent dark clouds in the Galactic disk, with no evidence of shock heating or enhanced excitation. We examine possible high-energy emission mechanisms and find that the observed GeV luminosity cannot be accounted for by electron bremsstrahlung or hadronic interactions driven by relativistic particles originating from SS 433 under reasonable energetic assumptions. As an alternative, we propose that the gamma-rays may arise from a compact object embedded within the cloud and powered by Bondi-type accretion. In this framework, the reported heartbeat-like variability may reflect periodic modulation of the accretion flow by density waves induced by the precessing equatorial outflow of SS 433.
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Solar and Stellar Astrophysics

Magnetic Field Measurements in the Solar Chromosphere Using the H$_{\beta}$ 4861Å~Line I: Forward Modeling Based on 1D Models

Jiasheng Wang, Wenxian Li, Xianyong Bai et al. (+3 more)

The chromosphere is a complex solar atmosphere that hosts a variety of transients and transports significant free energy to heat the corona. However, due to the limited sensitivity of polarization measurement and the influence of spectral line broadening, the basic magnetic field configuration in the chromosphere has not yet been fully revealed to correspond to the observed phenomena. In this work, we investigated the validity and application of the magnetic field inversion method for the H$_{\beta}$~4861~Å\ spectral line with non-local thermodynamic equilibrium approximations. We generated synthetic spectra by incorporating magnetic fields into semi-empirical FAL models for quiet Sun and sunspots, and then performed inversions to obtain the magnetic fields, which were then compared with the magnetic fields in the models. In addition, we evaluated the accuracy of the magnetic fields obtained using the weak field approximations and the impact of using the WFA results as the initial guess model for non-LTE inversion on the final results. Our work validates the effectiveness of the inversion method for the measurement of line-of-sight magnetic field components, which significantly improved the accuracy in both weak field (0 – 500~G) and strong field ($>$2000~G) regions, while maintaining accuracy in the intermediate field range of 500 – 2000~G. This demonstrates that the inversion techniques we employed are capable of resolving Zeeman-sensitive spectral lines in the chromosphere, which can be applied to the H$_{\beta}$ observational data from the new generation Solar Full-disk Multi-layer Magnetograph at GanYu Solar Station to provide full disk chromospheric magnetic field information.
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All authors Jiasheng Wang, Wenxian Li, Xianyong Bai, Yingzi Sun, Yuanyong Deng, Jiaben Lin

Astrophysics of Galaxies

Tracing Star Formation in Quasar Hosts via [O II] $\lambda$3727: A Kinematically Consistent Approach

Liang Wu, Jun-Xian Wang, Luis C. Ho et al. (+2 more)

Measuring star formation in quasar host galaxies is crucial for understanding the coevolution of supermassive black holes (SMBHs) and galaxies, yet remains observationally challenging due to severe contamination from active galactic nucleus (AGN) emission. In this work, we present a new method to robustly isolate the AGN contribution to the [O II] $\lambda$3727 emission line in quasars, based on a kinematically consistent decomposition of [O II] and the high-ionization [Ne V] $\lambda$3426 line. We find that the [O II] emission in quasars is primarily dominated by star formation, with only a weak AGN contribution, and thus can be reliably used as a tracer of star formation in quasar hosts. Applying this technique to a large sample of Sloan Digital Sky Survey quasars, we derive mean SFRs as a function of bolometric luminosity. We find a tight correlation between mean SFR and luminosity. Further analysis, assuming a constant dust extinction correction to [O II] emission, shows that luminosity is the primary parameter most strongly associated with star formation, rather than SMBH mass or Eddington ratio. This supports the scheme in which star formation and black hole accretion are closely linked through their common dependence on the cold gas supply.
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All authors Liang Wu, Jun-Xian Wang, Luis C. Ho, Junfeng Wang, Zhicheng He

Astrophysics of Galaxies

ASKAP EMU detection of an Odd Radio Circle (ORC) candidate: J094412-751016 (Anglerfish)

M. D. Filipović, Z. J. Smeaton, A. C. Bradley et al. (+33 more)

We report diffuse extended radio-continuum emission spatially coinciding with the IR source WISEA J094409.17-751012.8, and a semi-variable star, V687 Carinae. We use 944 MHz radio data from the large-scale Evolutionary Map of the Universe (EMU) survey to analyse this diffuse emission (EMU J094412-751016), which we nickname "Anglerfish". We investigate if the spatially correlated infrared (IR) source, WISEA J094409.17-751012.8, is physically related to Anglerfish. The IR colours of WISEA J094409.17-751012.8 are indicative of an elliptical galaxy, raising the possibility that Anglerfish may belong to the newly-discovered class of extragalactic radio sources known as Odd Radio Circles (ORCs) with WISEA J094409.17-751012.8 as the host galaxy. We also investigate the possibility that Anglerfish is physically related to the star, V687 Carinae, and whether it may be a remnant from a previous epoch of stellar mass-loss. We determine that a physical association between the radio emission and the star is unlikely due to the emission's non-thermal nature and the star's weak stellar winds compared to the theoretical expansion velocity of the 'shell'. It is possible that Anglerfish may be a Galactic high-latitude supernova remnant (SNR); however, we find that the observed size and luminosity are not consistent with this scenario. We also investigate the ORC scenario, which we deem the most likely scenario based on the Anglerfish's observed properties such as size, brightness, lack of other frequency detections, and spectral index. We therefore propose Anglerfish as an ORC candidate, but note that additional radio and optical observations are vital to further constrain the properties and confirm this classification.
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All authors M. D. Filipović, Z. J. Smeaton, A. C. Bradley, R. Kothes, E. J. Crawford, A. Ahmad, T. Akahori, L. Barnes, C. Bordiu, S. Dai, S. Duchesne, Y. A. Gordon, N. Gupta, A. M. Hopkins, B.s. Koribalski, S. Lazarević, D. Leahy, K. J. Luken, P. J. Macgregor, A. Mailvaganam, S. Mehmood, R. P. Norris, N. Novaretti, L. A. F. Park, S. Riggi, C. J. Riseley, G. Rowell, M. Sasaki, S. S. Shabala, S. Taziaux, N. F. H. Tothill, D. Urošević, V. Velović, T. Vernstrom, J. L. West, T. Zafar

Sunday 22 March

Instrumentation and Methods for Astrophysics

Orbital Debris in Earth Orbit: Operations, Stability, Control, and Market Formation

Slava G. Turyshev

Orbital debris is a nonlinear control problem in a stratified orbital environment, not a static inventory. This paper develops a reduced-order shell-and-size framework that connects collision-rate scaling, fragment-production gain, natural and controlled sinks, and orbital residence time to intervention ranking and procurement design. The formulation identifies three dominant control levers for near-term orbital sustainability: high-confidence disposal and short post-failure residence time for new spacecraft; reduced encounter-plane covariance for the high-risk conjunction tail; and retirement or deflection of the residual hazard stock of long-lived inactive bodies. A source-gain/sink stability margin separates shells that are operationally crowded but dynamically damped from shells that are dynamically amplifying. The analysis distinguishes the traffic-driven workload peak near 500–600 km from the persistence-driven hazard peak near $\sim$850 km, where inactive mass and long lifetime dominate future fragment production. Current public statistics report $\sim$44,870 tracked objects and more than 16,200 tonnes of material in Earth orbit, with model populations far larger below routine-catalog thresholds. The resulting intervention stack is rapid post-mission disposal, targeted covariance improvement for high-risk encounters, selective just-in-time collision avoidance or active removal of high-hazard derelicts. The appropriate procurement metric is not the number of objects removed, but verified reduction in time-integrated environmental hazard: verified disposal, verified reduction in ambiguous high-risk conjunctions, verified reduction in residual hazard stock.
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc

Cosmology with Logarithmic Corrected Horizon Entropy According to the Generalized Entropy and Variable-G Correspondence

Chen-Hao Wu and Yen Chin Ong

According to the GEVAG (Generalized Entropy Varying-G) framework, any modification to the Bekenstein-Hawking area law would also lead to a varying-$G$ gravity theory in which the effective gravitational constant $G_\text{eff}$ becomes area-dependent. Among a myriad of generalized entropy functions explored in the literature, of special interest is the logarithmic correction of quantum gravity. In this work, we apply GEVAG to investigate the effect of logarithmic correction on very early-time cosmology, including the conditions for inflation. We found that if the coefficient of the logarithmic correction term is negative, $G_\text{eff}$ becomes twice that of the current value; whereas, a positive coefficient leads to a very small value of $G_\text{eff}$, which may ameliorate the "arrow of time" problem. In fact, slow-roll inflation becomes more natural in the latter case. We make some comparisons with the constant-$G$ approach and reveal the advantages of the GEVAG approach. For example, it can evade the sudden singularity that could otherwise arise when the coefficient of the logarithmic correction term is negative. We also check the validity of the generalized second law and comment on the range of the various parameters.
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High Energy Astrophysical Phenomena

Transient narrowband radio bursts from the magnetar 1E 1547.0-5408

Marcus E. Lower, Paul Scholz, Fernando Camilo et al. (+5 more)

Radio-loud magnetars are well known for exhibiting radiative behaviors that are seldom seen among the wider pulsar population. Yet one form of emission that remains elusive among pulsars and magnetars is narrowband bursts of radio waves. Such emission is a hallmark of repeating sources of fast radio bursts (FRBs), intense radio flashes that originate from distant galaxies. Here, we report the detection of 84 narrowband radio bursts during observations of the magnetar 1E 1547.0-5408 by the Murriyang telescope. They were confined to a transient profile component that appeared between 2009 February 23 to 25, one month after its 2009 outburst. Their appearance coincided with both dramatic changes in the magnetar line-of-sight magnetic-field geometry, and an emergent pulsed hard X-ray component detected by the Rossi X-ray Timing Explorer. The leading edge of the hard X-ray emission was phase-aligned with the narrowband component. This may indicate the bursts originated from pair cascades along closed field lines, though open-field line emission remains valid. Our characterization of the bursts suggests they may represent a low-energy analogue of the repeating FRB mechanism, further linking FRB progenitors to young, highly magnetized neutron stars.
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All authors Marcus E. Lower, Paul Scholz, Fernando Camilo, David M. Palmer, John E. Reynolds, John M. Sarkissian, Lawrence J. Toomey, George Younes

Earth and Planetary Astrophysics

Modelling solar radial velocities and photometric variability with SOAPv4

Alba Barka, Eduardo Cristo, Ângela R. G. Santos et al. (+5 more)

Stellar activity remains one of the main limitations in the detection of Earth-like planets using radial velocity (RV) measurements. The Sun, as the only star for which surface features can be spatially resolved, offers a unique testbed for studying the impact of active regions on RV and photometric variability. Using SOAPv4, we modelled solar RV and photometric variability induced by spots and faculae over long timescales. Our goal is to verify whether present-day, state-of-the-art models of the cross-correlation function correctly reproduce the observed variability. Moreover, we aim to assess how the choice of input data and identification technique influences the agreement between simulated and observed signals. To simulate solar RV and photometric time series, we first identified active regions in SDO images. This was done using mathematical morphological (MM) transforms applied to SDO/HMI and AIA images. MM identification was validated against other state-of-the-art identification methods. Using these inputs, we ran SOAPv4 to simulate solar RVs and photometry, and we validated the results with HARPS-N RV observations, as well as with VIRGO/SPM photometric measurements. The simulations that use MM identification achieved the best match with the observed RV time series, yielding residuals with a measured standard deviation of ~0.91 m/s. Other state-of-the-art methods produced higher filling factors and, consequently, larger discrepancies. The photometric simulations reproduced the overall variability trends. We demonstrate that MM transforms accurately identify solar active regions. Using these inputs, SOAPv4 reproduces the observed solar RV variability with a measured standard deviation of the residuals of ~0.91 m/s. Photometric simulations capture the overall variability trends, confirming that SOAP can reliably model the impact of both spots and faculae on solar RVs and photometry.
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All authors Alba Barka, Eduardo Cristo, Ângela R. G. Santos, Nuno C. Santos, Khaled Al Moulla, Teresa Barata, Ricardo Gafeira, Michael Cretignier

Earth and Planetary Astrophysics

Iron isotope anomalies and the origin of the Earth

Timo Hopp, Shengyu Tian and Thorsten Kleine

Understanding the origin of the Earth requires determining the original formation location of its building material. Based on the similar Fe isotopic composition of Earth's mantle and Ivuna-type (CI) chondrites, a prior study has argued that Earth formed by accretion of sunward-drifting pebbles from the outer Solar System. Here, using new high-precision Fe isotopic data, we show however that CI chondrites and Earth's mantle have distinct Fe isotopic composition when the neutron-rich 58Fe is also considered. This observation rules out that the Fe in Earth's mantle derives from CI chondrite-like material and demonstrates that Earth did not form by accretion of sunwards-drifting pebbles. We show that the Fe in Earth's mantle instead derives from the inner Solar System, and has been partly or wholly delivered by bodies from the innermost disk that remained unsampled among meteorites. This provenance of terrestrial Fe is consistent with the classical model of Earth's formation by hierarchical growth among inner Solar System planetesimals and planetary embryos.
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High Energy Astrophysical Phenomena

The precessing jet axis of the supernova remnant 3C 397

Aleksei Klimov, Dmitry Shishkin and Noam Soker

We identify an S-shaped morphological feature in the enigmatic supernova remnant (SNR) 3C 397, which we attribute to the shaping by a precessing pair of jets during the explosion. We identify an S-shaped, faint region composed of two bubbles, located to the north and south of the center, between two X-ray-bright sides. We attribute the S-shape to a pair of precessing jets that were part of the explosion process. The identification of a main jet axis in SNR 3C 397 increases its similarity to the enigmatic SNR W49B. We discuss two possible scenarios for SNR 3C 397 and W49B. (1) The thermonuclear common-envelope-jet supernova scenario, which was suggested before for W49B, where a neutron star destroys a white dwarf and accretes part of the white dwarf's material via an accretion disk that undergoes a thermonuclear outburst and launches the jets. (2) The collapse-induced thermonuclear jet-driven explosion, which is a core-collapse supernova driven by jets, as in the majority of, or even all, core-collapse supernovae, and in addition, there is a thermonuclear outburst of a rare helium-oxygen mixed layer in the core, which is triggered by the core collapse. Our study emphasizes the primary role of jets even in the enigmatic SNR 3C 397.
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High Energy Astrophysical Phenomena

Analytical Framework for Expanding Bubbles in a Hot Circumgalactic Medium

Jiang-Tao Li

We develop an analytic framework for the evolution of feedback-driven bubbles expanding into a hot, volume-filling circumgalactic medium (CGM), where the ambient pressure and sound speed are non-negligible and radiative cooling is often inefficient. The evolution is organized into four stages – free expansion, Sedov–Taylor expansion, pressure-modified/transonic transition, and post-transonic relaxation – and we derive self-consistent scalings for the characteristic radii and timescales that delimit these stages. A central result is that, in hot halos, the end of the strong-shock evolution is frequently set by pressure confinement and transonicity rather than by the onset of catastrophic cooling, implying only a modest late-time overshoot beyond the pressure-balance/transonic point. We connect the dynamics to observable outcomes by estimating bubble sizes and lifetimes, order-of-magnitude band-limited X-ray luminosities, and high-ionization ion column densities, and we provide stitched numerical trajectories that contrast our pressure-modified model appropriate for hot CGM conditions with a classical Sedov–Taylor benchmark. We then discuss physically motivated extensions beyond the single-event baseline, including continuous or episodic energy injection relevant for AGN-driven bubbles and nuclear outflows, highlighting the much higher specific energy of AGN feedback compared to supernovae and the resulting dynamical differences in how bubbles are driven. We further outline how multiphase interaction, mass loading, anisotropic dissipation, intermittency, confinement, and non-thermal channels can increase the emergent X-ray radiation efficiency without requiring changes to the intrinsic feedback energy partition at the launching site. This framework provides a transparent bridge between idealized bubble theory and feedback signatures in hot galactic halos.
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Astrophysics of Galaxies · Cross-listed from gr-qc

Polytropes, logotropes, the universal value of the surface density of dark matter halos, and the value of the cosmological constant

Pierre-Henri Chavanis

We discuss the connection between logotropes and polytropes in astrophysics and cosmology. The logotropic equation of state $P=A\ln(\rho/\rho_P)$ may be seen as a degenerate form of the polytropic equation of state $P=K\rho^{\gamma}$ in the limit $\gamma\rightarrow 0$, $K\rightarrow\infty$ with $A=K\gamma$ fixed. The logotropic distribution function corresponds to the polytropic distribution function of index $\gamma=0$ for which the density is finite but the pressure diverges logarithmically. We show that the polytropic and logotropic distribution functions can be obtained in the nondegenerate limit of the Lynden-Bell theory of violent relaxation for a particular distribution of phase levels given by the $\chi$-squared distribution. This provides a justification of the Tsallis entropy from the Lynden-Bell entropy. The logotropic distribution function presents a power-law energy tail decreasing as $\epsilon^{-5/2}$. Interestingly, this “universal” power-law tail is predicted by recent kinetic theories of collisionless relaxation based on the coarse-grained Vlasov equation and on the secular dressed diffusion equation. When coupled to gravity, the associated density profile decreases as $r^{-1}$. This may explain the universal surface density of dark matter halos, or account for an effective NFW density cusp. This also accounts for the universal gravitational acceleration felt by a test particle and for the Tully-Fisher relation. The logotropic model can thus provide an alternative to the modification of Newtonian dynamics (MOND) theory. We recall how the logotropic model leads to a very accurate expression of the cosmological constant $\Lambda={G^2m_e^6}/{\alpha^6\hbar^4}=1.36\times 10^{-52}\, {\rm m^{-2}}$ in terms of the mass of the electron and the fundamental constants of physics.
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Astrophysics of Galaxies

Revisiting the Excess of Bar-like Structures in TNG50 Early-type Galaxies: Consistency and Tension with Observations

Hangci Du, Yougang Wang and Junqiang Ge

The IllustrisTNG simulation suite, particularly TNG50, was reported to have generated a notable population of elongated, bar-like structures within galaxies classified as Early-Type Galaxies (ETGs). In this work, we revisit the nature of these structures at $z=0$ using a morphology-agnostic census. We find that these features are ubiquitous ($f_{\rm bar} \sim 75-80\%$) in dispersion-dominated galaxies ($D/T < 0.2$) in TNG50-1. They are not prolate rotators (rotating around their long axis), but genuine non-axisymmetric instabilities characterized by coherent, albeit slow, pattern speeds. Unlike the fast bars found in Late-Type Galaxies, these bar-like structures in ETGs are physically longer ($\gtrsim 3$ kpc), rotate significantly slower ($\Omega_p \lesssim 20$ km s$^{-1}$ kpc$^{-1}$), and reside in red, gas-poor, dispersion-dominated systems. By tracing the evolutionary history of these systems, we demonstrate that such structures originate as typical fast bars in gas-richer discs at higher redshifts ($z \gtrsim 0.2$). They survive the galaxy quenching phase, undergoing secular deceleration and lengthening due to dynamical friction, ultimately appearing as slow, fossilized rotators in the $z=0$ red sequence. We conclude that the specific excess of bar-like structures in TNG50 ETGs likely reflects a combination of the imperfect baryonic physics of the simulation (over-producing these bar-like structures or their host ETGs) and a potential observational blind spot regarding long-lived, secularly evolved bars in hot stellar systems.
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Cosmology and Nongalactic Astrophysics

Closed-form approximations of fundamental quantities of Lemaitre-Tolman-Bondi cosmologies from Symbolic Regression: I. Results on the Garcia-Bellido-Haugbølle parameterization

A. Carvalho, A. Krone-Martins, A. Da Silva et al. (+2 more)

We introduce a novel set of analytic approximations for five fundamental functions in spherically symmetric, inhomogeneous Lemaitre-Tolman-Bondi (LTB) cosmologies, derived via Symbolic Regression (SR). Focusing on the constrained Garcia-Bellido-Haugboelle (GBH) parameterization, we sample the four-dimensional LTB parameter space using the bubble LTB numerical code and apply SR to reconstruct closed-form expressions for the radial and transverse scale factors A_parallel(r,t) and A_perp(r,t), the corresponding Hubble functions H_parallel(r,t) and H_perp(r,t), and the angular diameter distance D_A(z). Our best-fit formulas reproduce the numerical data with high precision: the relative mean error across all quantities remains below 0.3 percent, except for the radial Hubble function, where it reaches 1.4 percent. These compact expressions enable rapid evaluation of LTB predictions, supporting fast parameter scans, likelihood analyses, and model comparisons without time-consuming integrations. We provide explicit coefficients and discuss the domain of validity, demonstrating that SR-driven approximations can serve as robust surrogates for exact LTB solutions in both theoretical investigations and observational analyses.
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All authors A. Carvalho, A. Krone-Martins, A. Da Silva, J.P. Mimoso, C. Bœhm

Earth and Planetary Astrophysics

High-resolution spectroscopic atmospheric studies of 5 hot Jupiters across the edge of the Neptune desert

Zewen Jiang, Wei Wang, Shumei Jia et al. (+6 more)

Hot Jupiters (HJs), especially the Ultra-Hot Jupiters (UHJs), are ideal targets for robust atmospheric characterization, thanks to their high equilibrium temperatures and large atmospheric scale heights, which result from their proximity to their host stars and intense stellar irradiation. Here, we present atmospheric studies of five planets, namely WASP-50b, WASP-117b, WASP-156b, WASP-167b, and WASP-173Ab. These five planets include two UHJs, two classic HJs, and one hot Neptune, with four of them just on the upper and middle borders of the Neptune desert, providing an interesting sample for investigating the connection between planetary atmospheric composition and bulk properties. We have not detected any significant absorption signals exceeding 3$\sigma$ in the three less-inflated, relatively high-density HJs (WASP-50b, WASP-156b, and WASP-173Ab). We marginally detect H$\alpha$ and Li I with 3.2$\sigma$ and 3.1$\sigma$ in WASP-117b, respectively. In WASP-167b, we report tentative detection of H$\alpha$ and Fe I at 4.6$\sigma$ and $\sim3.4\sigma$, receptively. In addition, Fe I is significantly detected with a max SNR of 7.3 $\sigma$ using the cross-correlation technique, which exhibits a blue-shifted signal. For WASP-167b, we perform an atmospheric retrieval and yield the abundances of Fe, Mg, Ca, Ti, V, and equilibrium temperature of ${2479^{+193}_{-174}}$K. Comparing WASP-173Ab and WASP-167b, both are UHJ, but with quite different extents of atmospheric signals, we propose that there may be a transition in $T_{\rm eq}$ between 1900 and 2300K.
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All authors Zewen Jiang, Wei Wang, Shumei Jia, Yaqing Shi, Fei Yan, Li Zhou, Qianyi Zou, Xiang Ma, Yue Huang

High Energy Astrophysical Phenomena

First constraints on point-like astrophysical sources using Baikal-GVD muon neutrino events

Baikal-GVD Collaboration: V. A. Allakhverdyan, A. D. Avrorin, A. V. Avrorin et al. (+71 more)

Baikal-GVD is a new-generation neutrino telescope under final construction stages in Lake Baikal, Russia. With an instrumented volume already at 0.7 km$^3$, Baikal-GVD is currently the largest neutrino telescope in the Northern hemisphere. A sub-degree angular resolution, made possible thanks to high purity of Baikal water, further enhances Baikal-GVD sensitivity to cosmic neutrino sources. In this work, we employ track-like events collected from the partially completed detector between April 2019 and March 2024 to search for muon neutrino fluxes from 92 astrophysical objects of interest. For this, a $\chi^2$-based track reconstruction method is used along with a cut-based analysis. The analysis uses upward-going muons only, providing coverage for declinations between -90$^\circ$ and +38$^\circ$. No significant excess has been found, so upper limits are reported. The obtained limits are competitive with those set by ANTARES and KM3NeT. We briefly comment on a possible low-significance indication of an excess from the direction of Westerlund 1. This work sets a major milestone on the way to full-scale scientific exploitation of Baikal-GVD data.
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All authors Baikal-GVD Collaboration: V. A. Allakhverdyan, A. D. Avrorin, A. V. Avrorin, V. M. Aynutdinov, I. A. Belolaptikov, Z. Beňušová, E. A. Bondarev, I. V. Borina, N. M. Budnev, V. A. Chadymov, A. S. Chepurnov, V. Y. Dik, A. N. Dmitrieva, G. V. Domogatsky, A. A. Doroshenko, R. Dvornický, A. N. Dyachok, Zh.-A. M. Dzhilkibaev, E. Eckerová, T. V. Elzhov, V. N. Fomin, A. R. Gafarov, K. V. Golubkov, A. R. Gordeev, T. I. Gress, K. G. Kebkal, V. K. Kebkal, I. V. Kharuk, S. S. Khokhlov, E. V. Khramov, M. M. Kolbin, S. O. Koligaev, K. V. Konischev, A. V. Korobchenko, A. P. Koshechkin, V. A. Kozhin, M. V. Kruglov, V. F. Kulepov, A. A. Kulikov, Y. E. Lemeshev, M. V. Lisitsin, S. V. Lovtsov, R. R. Mirgazov, E. S. Morgunov, D. V. Naumov, A. S. Nikolaev, I. A. Perevalova, A. A. Petrukhin, D. P. Petukhov, E. N. Pliskovsky, M. I. Rozanov, E. V. Ryabov, G. B. Safronov, B. A. Shaybonov, A. S. Sheshukov, V. Y. Shishkin, E. V. Shirokov, F. Šimkovic, A. E. Sirenko, A. V. Skurikhin, A. G. Solovjev, M. N. Sorokovikov, I. Štekl, A. P. Stromakov, O. V. Suvorova, V. A. Tabolenko, V. I. Tretyak, G. V. Trubnikov, B. B. Ulzutuev, Z. Wang, Y. V. Yablokova, D. N. Zaborov, S. I. Zavyalov, D. Y. Zvezdov

Instrumentation and Methods for Astrophysics

Parallel adaptive reweighting importance sampling for Bayesian astrophysics

Miaoxin Liu and Alvin J. K. Chua

Efficient sampling from high-dimensional, multi-modal posteriors is a central challenge in Bayesian inference across the physical sciences. Gravitational-wave (GW) astronomy, where likelihood evaluations are computationally expensive and posteriors are complex, is one application motivating this work. Popular families of methods like Markov-chain Monte Carlo, nested sampling, and importance sampling all rely on proposal distributions to guide exploration. Because prior knowledge of the target is often limited, practitioners can adopt adaptive proposals that iteratively refine themselves using information gained from previously drawn samples. Traditional adaptive strategies, however, struggle in high-dimensional multi-modal settings: complex, non-linear correlations are hard to capture, and hyperparameters typically require tedious, problem-specific tuning. To address these issues, we introduce Parallel Adaptive Reweighting Importance Sampling (PARIS; descriptively, “seed sampling”). PARIS models its proposal as a Gaussian mixture whose component centers are the existing samples and whose component weights match the current importance weights. New draws from the proposal therefore concentrate around high-weight regions, while candidate points in unexplored areas receive intentionally inflated weights. As the algorithm continuously reweights all samples up to the latest proposal, any initial over-weighting self-corrects once additional neighbor samples are collected. To enable rapid reweighting, we present an efficient update scheme and evaluate PARIS on illustrative toy problems and more realistic gravitational-wave parameter estimation tasks. PARIS achieves accurate posterior reconstruction and evidence estimation with substantially fewer function evaluations than competing approaches, highlighting its promise for widespread use in astrophysical data analysis.
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Astrophysics of Galaxies

Q/W-band Observations toward Starless Cores in Orion (QWOSCO) I. Overview, Isotopologues, Isomers, and Complex Organics

Shih-Ying Hsu, Xunchuan Liu, Sheng-Yuan Liu et al. (+12 more)

Molecular inventories in starless cores are powerful tools for probing the physical and chemical structures at the earliest stages of star formation. Wide-band spectral scans are invaluable for obtaining a comprehensive view of the chemical composition. In this paper, we present the first results from the project Q/W-band Observations toward Starless Cores in Orion (QWOSCO), which uses the Yebes 40-m telescope to survey 23 starless cores in the Orion cloud at the Q (31.0–50.5 GHz) and W (71.1–91.4 GHz) bands with a total bandwidth of 40 GHz. We detect approximately 40 molecular species and derive their column densities, with each species exhibiting a characteristic spread of roughly one order of magnitude. The derived isomer and isotopologue column density ratios, including A/E, ortho/para, cyclic/linear, HNC/HCN, 12C/13C, 14N/15N, 16O/18O, 32S/34S, and D/H, are consistent with expectations for starless environments. Our results together with the literature suggest that the complex organic molecules (COMs) CH3OH and CH3CHO are both likely ubiquitous in starless cores. The column density ratio of CH3CHO with respect to CH3OH in starless cores are comparable or lower by a factor of around 25 than those in hot corinos at the protostellar stages if the CH3OH column density is directly derived or rescaled from that of 13CH3OH, respectively. Accordingly, we discuss the possible roles of methanol opacity and chemical mechanisms across the starless and protostellar stages.
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All authors Shih-Ying Hsu, Xunchuan Liu, Sheng-Yuan Liu, Tie Liu, Naomi Hirano, Mika Juvela, Kee-Tae Kim, Chin-Fei Lee, Shanghuo Li, Sheng-Jun Lin, Sheng-Li Qin, Dipen Sahu, Ken'ichi Tatematsu, Fengwei Xu, L. Viktor Toth

Astrophysics of Galaxies

No evidence of polarization in the $11.3\,\mu$m PAH emission line by independent analyses

Enrique Lopez-Rodriguez

Polycyclic aromatic hydrocarbons (PAHs) are commonly used as proxies for star formation, molecular gas content, and other interstellar medium (ISM) properties in our Galaxy and other galaxies. Given their abundance and brightness, polarization measurements of PAH features could, in principle, provide a probe of the ISM magnetic field and intrinsic PAH properties; however, the diagnostic power of PAH polarization remains to be established. Previous studies reported that the $11.3\,\mu$m PAH emission line in the northwestern nebula of the Herbig Be star MWC 1080 was polarized at $1.9\pm0.2$%. This level of polarization was explained via the paramagnetic relaxation process, which may allow the characterization of magnetic fields in the ISM. Using the same observations, here, we re-analyzed the $8-13\,\mu$m spectro-polarimetric observations taken with CanariCam on the 10.4-m Gran Telescopio CANARIAS (GTC), and we measure a polarization of $0.5\pm0.6$% within $11.3\pm0.2\,\mu$m, consistent with an unpolarized source, $0.6\pm0.2$% (instrumental polarization). We reproduce the previously reported polarized PAH emission line if the polarization fraction spectrum is oversubtracted by a constant instrumental polarization and the polarization uncertainties, which is inconsistent with the fundamentals of polarimetric data analysis. Thus, the published $8-13\,\mu$m spectro-polarimetric data taken with CanariCam/GTC provide no statistical evidence for a polarized $11.3\,\mu$m PAH emission line, in agreement with current dust models.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc

Causal Structure of Spacetime Singularities and Their Observable Signatures

Bina Patel, Jahnvi Mistry, Ayush Bidlan et al. (+1 more)

We analyze the causal structure of horizonless compact objects via the light-cone geometry and conformal compactification of the Joshi-Malafarina-Narayan (JMN-1) and Janis-Newman-Winicour (JNW) spacetimes. Penrose diagrams reveal that JMN-1 undergoes a transition from timelike $(0<M_0<2/3)$ to null $(2/3<M_0<4/5)$ singularities, while JNW remains timelike throughout, in contrast to the spacelike singularity of the Schwarzschild spacetime. We show that photon spheres exist in Schwarzschild and JNW, but arise in JMN-1 only in the null singularity phase, establishing a direct link between causal character and null geodesic trapping. We further demonstrate that radial timelike geodesics develop turning points for certain parameter regimes in both JMN-1 and JNW spacetimes, indicating the emergence of effective repulsive behavior in the strong field region. These features lead to distinct strong field lensing and shadow signatures, potentially testable by very long baseline interferometric observations such as those of the Event Horizon Telescope.
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All authors Bina Patel, Jahnvi Mistry, Ayush Bidlan, Parth Bambhaniya

Cosmology and Nongalactic Astrophysics

Testing General Relativity on Galactic Scales via DESI-BAO and Strong Lensing: Circumventing Assumptions on the Hubble Constant, Sound Horizon, and Dark Energy

Hengyu Wu, Tonghua Liu and Chenggang Shao

We present a cosmological model-independent framework for testing general relativity (GR) on galactic scales by combining baryon acoustic oscillation (BAO) angular scale measurements with 120 galaxy-scale strong gravitational lensing systems. Using artificial neural networks (ANNs) and cubic spline reconstruction, we reconstruct the BAO angular scale from SDSS, BOSS, eBOSS, and DESI Data Release 2 (DR2), and infer the angular diameter distances to lenses and sources. Crucially, All the quantities used in the GR test are derived from observations and are independent of cosmological parameters such as the Hubble constant, the sound horizon, or the dark energy equation of state, minimizing potential biases from model-dependent distance priors. These distances are then incorporated into the strong lensing likelihood to constrain the parameterized post-Newtonian (PPN) parameter $\gamma_{\rm PPN}$ under two lens mass models: a constant-density-slope model ($P_1$) and a redshift-evolving model ($P_2$). For the $P_1$ model, the ANN reconstruction yields $\gamma_{\rm PPN} = 1.102^{+0.148}_{-0.125}$, consistent with GR at $1\sigma$ confidence level, while the cubic spline gives $\gamma_{\rm PPN} = 1.150^{+0.139}_{-0.118}$, consistent with GR at $2\sigma$ confidence level. For the $P_2$ model, the ANN reconstruction gives $\gamma_{\rm PPN} = 1.315^{+0.181}_{-0.155}$, compatible with GR at $2\sigma$, while the spline gives $\gamma_{\rm PPN} = 1.485^{+0.193}_{-0.168}$, showing mild tension at $\sim2.5\sigma$. The constraints exhibit a clear dependence on the adopted lens mass model, underscoring the critical role of lens modeling. No significant correlation is observed between $\gamma_{\rm PPN}$ and the Einstein radius. Overall, current galaxy-scale observations are consistent with GR, providing no evidence for deviations from Einstein's theory on kiloparsec scales.
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Cosmology and Nongalactic Astrophysics

Model-Independent Reconstruction of Quintessence Potential and Kinetic Energy from DESI DR2 and Pantheon+ Supernovae

Shengjia Wang, Tian-Nuo Li, Tonghua Liu et al. (+1 more)

We present a model-independent reconstruction of the quintessence scalar field's dynamics-both its potential and kinetic energy-directly from the latest cosmological observations. Our analysis combines DESI DR2 baryon acoustic oscillation measurements with the Pantheon plus Type Ia supernova compilation, employing Gaussian process with four distinct covariance kernels to avoid theoretical priors on the potential's functional form. Key findings reveal a monotonically decreasing potential with redshift, consistent with thawing quintessence, and a kinetic energy that crosses zero near $z\sim 1$, marking the dark energy-matter equality epoch. Notably, while apparent negative kinetic energy values emerge at intermediate redshifts (0.5<z<1.0), these are statistical artifacts within uncertainties, arising from error amplification in derivative reconstruction rather than new physics. Our results demonstrate the power of non-parametric methods to constrain dynamical dark energy and show minimal dependence on the choice of cosmological priors, whether from local (SH0ES) or early-universe (Planck) measurements.
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All authors Shengjia Wang, Tian-Nuo Li, Tonghua Liu, Guo-Hong Du

Astrophysics of Galaxies

Time-domain Radio-loudness of Active Galactic Nuclei: Intermittency, Memory, and Jet Escape

Tao An

The classical radio-loudness parameter $R \equiv f_\nu(5\,\mathrm{GHz})/f_\nu(4400\,\text{\AA})$ divides a radio flux density by an optical/UV accretion tracer, but the two terms do not probe the same clock. The radio numerator can blend compact-core emission from the current engine, lobe and relic plasma left by earlier jet episodes, and host-galaxy synchrotron emission. We introduce a time-domain radio-loudness (TDRL) description that keeps these contributions separate. The radio numerator is written as compact-core and extended-lobe terms, with recovered fractions set by observing frequency, angular resolution, and surface-brightness sensitivity. For a single intermittently jetted AGN population, a two-state duty cycle filtered by exponential lobe fading gives an exact stationary Beta distribution for the normalized extended-radio response. Its mean is $\fduty$, while its variance scales as $(1+\chi_\nu)^{-1}$, where $\chi_\nu\equiv\taunu/t_{\rm switch}$. In this reference limit, the familiar GHz valley near the classical radio-loud/radio-quiet boundary can arise from short radio memory alone, without requiring two intrinsic engine classes. Metre-wave surveys that recover diffuse emission and subtract the host contribution should therefore progressively fill the valley. In the $(\Rcore,\Rlobe)$ plane, a core–lobe mismatch index separates triggering, sustained, and remnant phases, provided orientation-dependent core beaming is modelled or controlled. A complementary two-barrier picture, involving horizon-threading magnetic flux and jet escape through the nuclear medium, separates jet launching from the formation of large-scale radio structure. This view makes radio loudness a probe of jet duty cycle, radio memory, and escape through the host environment.
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High Energy Astrophysical Phenomena

The First GeV Gamma-Ray Flares from the CSO-like Source 4C 76.03

Xiong Jiang, Hai Lei, Hao-Yi Huang et al. (+3 more)

We report the first detection of GeV gamma-ray flaring activity from the compact symmetric object (CSO)-like source 4C 76.03, based on 17 years of Fermi-LAT observations. Its long-term, time-averaged gamma-ray properties are consistent with the 4FGL-DR4 catalog. However, a time-resolved analysis with 100-day binning reveals two prominent flares occurring on timescales of approximately 30 days and 20 days, separated by about 2.5 years, with nearly identical fluxes, test statistic (TS) values, and photon indices. The short-timescale variability indicates localized and transient energy dissipation in the nuclear region, likely associated with newly injected jet components. Although the gamma-ray emission does not directly trace the long-term jet power responsible for building the observed radio structure, it demonstrates that the central engine remains active. In the context of CSO evolution, 4C 76.03 may represent a rare transitional case, where repeated energy injections allow the source to exceed the canonical 500 pc scale of most CSOs, providing key insight into the early stages of radio jet evolution.
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All authors Xiong Jiang, Hai Lei, Hao-Yi Huang, Wei Zhang, Yang-Ji Li, Da-Ming Wei