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Physics Astrophysics

astro-ph Watch Astrophysics

Saturday 8 November

High Energy Astrophysical Phenomena

A New Phase of Optical Activity of BL Lacertae in the Fall of 2024: Intra-Night Flux and Polarization Variations

Rumen Bachev, Milen Minev, Anton Strigachev et al. (+1 more)

BL Lacertae is not only archetypical of an entire class of jet-dominated active galactic nuclei, blazars, but also one of the most active and rapidly changing objects in this class. In the fall of 2024 (September–November), BL Lacertae underwent another episode of strong optical activity, reaching an R-band magnitude of about 12 and showing extremely rapid and large-amplitude inter- and intra-night flux and polarization variations. During this period, the object was monitored over 40 nights using telescopes with an aperture of up to 2 m at three observatories: Rozhen and Belogradchik in Bulgaria and Skinakas in Greece. The results from this study include some of the most spectacular intra-night variability episodes detected in a blazar. These rapid variations, combined with high photometric accuracy and high time resolution, allowed for confirmation of consistency between different optical bands with zero time delays, down to a minute scale. Unlike previous activity reports, polarization was relatively stable on these short time-scales. Possible connections between polarization, flux, and intra-night variability were explored in order to better model or constrain the physical processes and emission mechanisms in the relativistic jets.
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All authors Rumen Bachev, Milen Minev, Anton Strigachev, Alexander Kurtenkov

Astrophysics of Galaxies

Radio AGN feedback sustains quiescence only in a minority of massive galaxies

Huiling Liu, Yan Lu, Hui Hong et al. (+11 more)

Radio active galactic nuclei (AGNs) eject a huge amount of energy into the surrounding medium and are thought to potentially prevent gas cooling and maintain the quiescence of massive galaxies. The short-lived, sporadic, and anisotropic nature of radio activities, coupled with the detection of abundant cold gas around some massive quiescent galaxies, raise questions about the efficiency of radio feedback in massive galaxies. Here we present an innovative method rooted in artificial intelligence to separate galaxies in which radio feedback is effective (RFE), regardless of current radio emission, from those in which radio feedback is ineffective (RFI), according to their optical images. Galaxies categorized as RFE are all dynamically hot, whereas quiescent RFI (RFI-Q) galaxies usually have extended cold-disk components. At given stellar mass, dark matter halos hosting RFE galaxies are between four to ten times more massive than those of RFI-Q galaxies. We find, for the first time, that almost all RFE galaxies have scant cold gas, irrespective of AGN activity. In contrast, many RFI-Q galaxies are surrounded by substantial amounts of condensed atomic gas, indicating a different evolutionary path from RFE galaxies. Our finding provides direct and compelling evidence that a radio AGN has gone through about 300 on-off cycles and that radio feedback can prevent gas cooling over a timescale much longer than that of radio activity. Contrary to general belief, our analysis shows that only a small fraction of massive galaxies are influenced by strong radio AGNs, suggesting that current galaxy formation models need serious revision.
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All authors Huiling Liu, Yan Lu, Hui Hong, Huiyuan Wang, Houjun Mo, Jing Wang, Wanli Ouyang, Ziwen Zhang, Enci Wang, Hongxin Zhang, Yangyao Chen, Qinxun Li, Hao Li, Mengkui Zhou

Solar and Stellar Astrophysics

Absolute Parameters of the Southern Detached Eclipsing Binary DG Mic

Derya Sürgit, Mücahit Kuz, Volkan Bak{\i}ş et al. (+2 more)

As part of an ongoing programme of observing detached eclipsing binary stars in the southern sky, we present the first analysis of spectroscopic observations of the Algol-type binary system DG Mic. A spectroscopic analysis of mid-resolution spectra allowed us to constrain the effective temperature of the primary component and to test the consistency of the system parameters with its spectral energy distribution (SED). Combined solutions of mid-resolution spectra and TESS, ASAS and WASP light curves imply a system of two almost identical components ($q$ = 0.99) in circular orbits. Our final model shows that the system is a detached binary star. The masses and radii of the primary and secondary components of DG Mic were derived to be 1.65($\pm$0.12) M$_\odot$, 1.64($\pm$0.18) M$_\odot$ and 1.63($\pm$0.10) R$_\odot$, 1.91($\pm$0.13) R$_\odot$, respectively. According to Geneva evolution models, both components of the system are main-sequence stars and their age is approximately 713 Myr.
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All authors Derya Sürgit, Mücahit Kuz, Volkan Bak{\i}ş, Chris Engelbrecht, Fred Marang

High Energy Astrophysical Phenomena

On the numerical convergence of MRI simulations

Thomas Jannaud and Henrik N. Latter

The magnetorotational instability (MRI) plays a crucial role in the evolution of many types of accretion disks. It is often studied using ideal-MHD numerical simulations. In principle, such simulations should be numerically converged, i.e. their properties should not change with resolution. Convergence is often assessed via the MRI quality factor, $Q$, the ratio of the Alfvén length to the grid-cell size. If it is above a certain threshold, the simulation is deemed numerically converged. In this paper we argue that the quality factor is not a good indicator of numerical convergence. First, we test the performance of the quality factor on simulations known to be unconverged, i.e. local ideal-MHD simulations with zero net-flux, and show that their $Q$s are well over the typical convergence threshold. The quality-factor test thus fails in these cases. Second, we take issue with the linear theory underpinning the use of $Q$, which posits a constant vertical field. This is a poor approximation in real nonlinear simulations, where the vertical field can vary rapidly in space and generically exhibits zeros. We calculate the linear MRI modes in such cases and show that the MRI can reach near-maximal growth rates at arbitrarily small scales. Yet, the quality factor assumes a single and well-defined scale, near the Alfvén length, below which the MRI cannot grow. We discuss other criticisms and suggest a modified quality factor that addresses some, though not all, of these issues.
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Cosmology and Nongalactic Astrophysics · Cross-listed from physics.hist-ph

Nearly forgotten results in development of physical cosmology

Alexander F. Zakharov

It would be reasonable to recall some critical issues in physical cosmology development. GR was created by A. Einstein in 1915. In 1917 Einstein proposed the first (static) cosmological model. Soon after the A. Eddington proved that the model is unstable therefore it can not be realizable in nature. In 1922 and 1924 A. A. Friedmann found non-stationary solutions for cosmological equations written in the framework of GR. In 1927 G. Lemaitre obtained very similar results and, in addition, he derived the Hubble law (E. Hubble obtained this law from observations). Unfortunately, G. Lemaitre published his paper in not very popular Belgium journal. In 1931 Lemaitre proposed the first version of hot Universe model (he called it hypothesis of the primeval atom). In his book Lemaitre predicted even a background radiation as a signature of his model. One of the important property of the Lemaitre – Gamow model was a prediction of CMB radiation with a temperature around a few K. It was recalled that the discovery of CMB radiation was done by T. Shmaonov in 1956 and his paper was published in 1957 (several years before Penzias and Wilson). In 1965, 1970 E. B. Gliner proposed vacuum like equation of matter which could correspond to exponential explosion of the Universe which was later called inflation. For decades in USSR, Friedmann's cosmological non-stationary models were treated as purely mathematical results without cosmologocal applications. On September 16, 1925 passed away untimely and it would be reasonable to remind today his great contribution in physical cosmology since the authors of book on Friedmann wrote that "similarly to Copernicus who forced the Earth to move Friedmann forced the Universe to expand".
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2511.06018 · 8 Nov · presented as a plenary talk at The XXVIth International Baldin Seminar on High Energy Physics Problems "Relativistic Nuclear Physics and Quantum Chromodynamics" (JINR, Dubna), minor misprints are corrected, references were added, accepted in Physics of Elementary Particles and Atomic Nuclei, 23 pages, 3 figures

Abstract PDF $VAC ×1

Earth and Planetary Astrophysics

Three New Light Curves and Updated Transit Timings of WASP-135 b

Kristine Kate Torres, Isabela G. Huckabee, Patrizia Phem Odo et al. (+14 more)

We present updated transit timing measurements for the hot Jupiter WASP-135 b using three new ground-based transit observations obtained with Leia, a 0.6-meter telescope operated by NASA's Exoplanet Watch at the Table Mountain Facility. These observations, conducted as part of Exoplanet Watch citizen science initiative, were analyzed with the EXOplanet Transit Interpretation Code (EXOTIC) pipeline to generate high-quality light curves and extract precise mid-transit times. By combining our new data with previously published observations, we refined the planet's ephemeris, reducing uncertainties in both the orbital period and mid-transit time. Our final mid-transit value is 2460585.6563426 +/- 0.00001908 BJD_TDB and the final period value is 1.4013776 +/- 0.0000002 days. Our updated timing solution demonstrates a 92% reduction in mid-transit time uncertainty compared to the original discovery paper and improves the precision of transit forecasts through 2030 which is critical to ensure efficient scheduling of future missions, such as ESA's Ariel. This work highlights the critical role of ongoing ground-based observations by students and citizen scientists in maintaining accurate ephemerides, which are essential for planning future space-based follow-up with facilities such as the Hubble and James Webb Space Telescopes. The work in this paper was done as part of the SEDS-PH (Students for the Exploration and Development of Space-Philippines) Upskill Groups, which provides opportunities for Filipinos to participate in space-related projects.
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All authors Kristine Kate Torres, Isabela G. Huckabee, Patrizia Phem Odo, Danielle Baldono, Riana Gabrielle Gamboa, Ma. Francelen Rose Molod, Michelle Dote, Dave Justine Bantilan, Juan Migelle Ferido, Zachary Lacuesta, Mark Erickson Calunod, Franchesca Margarette Visitacion, Jose Alexis Elimanco, Disney Gonzales, Robert Zellem, Heath Rhodes, Kyle Pearson

Astrophysics of Galaxies

Is M31 at the center of its satellite system ?

Amandine Doliva-Dolinsky, N. F. Martin and Michelle L. M. Collins

The arrangement of M31's dwarf galaxies exhibits anisotropy, with the majority located in the hemisphere between the Milky Way and the host galaxy. This study aims to investigate whether M31's present location is aligned with the center of its distribution of dwarf galaxies. We use forward modeling to infer the center of the M31 satellite 3D spatial distribution, folding in the completeness of dwarf galaxy searches. We observe a displacement of the center of the satellite distribution, relative to the center of M31, of approximately 10–50 kpc towards the Milky Way. Nonetheless, the center of M31 remains compatible with the center of the dwarf galaxy distribution given the broad constraints on its position, with the significance of the shift ranging from $\leq 1\sigma$ to $1.9\sigma$, depending on the assumed form of the volumetric spatial distribution of satellites. If M31 is truly offset from its satellite system, a quadrupling of the number of known satellites would be necessary to infer a significant ($3\sigma$) offset. Hence, expanding the number of known dwarf galaxies is crucial to deepen our understanding of the distribution of M31 satellites and further shed on its peculiar structure.
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc

Cosmologically Viable Solutions in Geometric Modified Gravity

P. A. G. Monteiro and C. J. A. P. Martins

The discovery of the accelerated expansion of the universe highlighted General Relativity's inability to naturally account for dark energy without invoking a finely tuned cosmological constant. In response, a wide range of alternative paradigms have been proposed. Among these, Teleparallel Gravity and Symmetric Teleparallel Gravity, which depart from the Riemannian framework of General Relativity and instead rely on torsion or non-metricity to describe gravitational interactions, have gained increasing attention in recent years. We explore extensions of these non-Riemannian approaches, aiming to replicate the observed late-time acceleration of the universe by emulating the cosmological constant's role. We also evaluate the consistency of these theories with local gravity constraints by studying their static, spherically symmetric solutions. We show that although some models can reproduce the desired cosmological behavior, they often fail to meet Solar System observational bounds, particularly through deviations in the predicted Eddington parameter. Our findings underscore the need for a unified approach that tests modified gravity theories across both cosmological and local scales.
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High Energy Astrophysical Phenomena

Formation of Binary Millisecond Pulsars with Helium White Dwarfs in a New Magnetic Braking Prescription

Xing-Peng Yang and Wen-Cong Chen

Magnetic braking (MB) mechanism plays a vital role throughout the evolution of low-mass X-ray binaries (LMXBs). Considering the standard MB prescription, the initial orbital periods of LMXBs that can evolve into binary millisecond pulsar (MSP) with He white dwarfs (WDs) and short orbital periods ($2-9~\rm hours$) are within an extremely narrow interval, which was named the fine-tuning problem. Employing the detailed binary evolution model, we investigate the evolution of LMXBs in both the standard and convection and rotation boosted (CARB) MB laws. In the standard MB case, it is difficult for donor stars to form a He core and exhaust H envelope through mass transfer at short orbital periods, making them semidetached systems. The CARB MB mechanism can drive LMXBs evolve toward compact detached MSP-WD systems in wide initial orbital periods, over which binary MSPs with long orbital periods will be produced. We obtain the initial parameter space of binary MSPs with He WDs in the initial orbital period and donor-star mass plane, which can be applied to future statistics study by population synthesis simulations. We also discuss a new relation between orbital period and WD mass, formation of persistent ultra-compact X-ray binaries with relatively long orbital periods, and detectability of compact MSP-WD systems as low-frequency gravitational wave sources.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-th

Symmetry of Bounce Solutions at Finite Temperature

Yutaro Shoji and Masahide Yamaguchi

The seminal work of Coleman, Glaser, and Martin established that, at zero temperature, any non-trivial solution to the equations of motion with the least Euclidean action is $O(D)$-symmetric. This paper extends their foundational analysis to finite temperature. We rigorously prove that for a broad class of scalar potentials, any saddle-point configuration with the least action is necessarily $O(D\!-\!1)$-symmetric and monotonic in the spatial directions. This result provides a firm mathematical justification for the symmetry properties widely assumed in studies of thermal vacuum decay and cosmological phase transitions.
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Astrophysics of Galaxies

AGN-Driven Biconical Outflows as the Origin of the Double-Peaked [O~iii] doublet in SDSS J134733.36+121724.27

PeiZhen Cheng, XingQian Chen, GuiLin Liao et al. (+4 more)

In this manuscript, we recheck the spectroscopic properties of SDSS J134733.36+121724.27 (4C+12.50), confirming the presence of the double-peaked [O~iii]$\lambda\lambda4959,5007$Å\ doublet and a broad H$\alpha$. The former likely results from AGN-driven biconical outflows, while the absence of a broad H$\beta$ supports a classification of the source as a Type-1.9 AGN. We analyze its high-quality Sloan Digital Sky Survey (SDSS) optical spectrum after robustly subtracting host galaxy and AGN continuum contributions through a simple stellar population fitting method employing 39 templates and a power-law continuum. Each narrow line of the [O~iii]$\lambda\lambda4959,5007$Å\ doublet is better described by two Gaussian components (blue-shifted and red-shifted) than by a single Gaussian, as confirmed by the F-test. Broad components are included for both H$\alpha$ and H$\beta$, but only H$\alpha$ reveals a significant detection, further supported by a comparison between the SDSS spectrum and that previously reported. These results support that the object is highly consistent with a Type-1.9 AGN classification, and the double-peaked [O~iii] profiles are most likely produced by AGN-driven biconical outflows rather than by a rotating narrow-line region or a dual AGN merger system. Additional observations are still needed to strengthen these conclusions.
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All authors PeiZhen Cheng, XingQian Chen, GuiLin Liao, Qi Zheng, Ying Gu, MuLin Chen, XueGuang Zhang

Astrophysics of Galaxies

Dissecting the Perseus-Pisces supercluster observed with CFHT-MegaCam: Investigating environmental effects on galaxy morphology

M. Mondelin, S. Codis, J-C. Cuillandre et al. (+4 more)

The discovery of the large-scale structure has transformed our view of galaxy formation and evolution. Filaments of the cosmic web provide key environments that channel the growth of structures. Guided by predictions from cosmological simulations, we study the morphological distribution of galaxies in the Perseus-Pisces Supercluster, a prominent filamentary complex at 70 Mpc. We focus on how galaxy morphology and structural disturbances relate to position within the filament network and to proximity to dense nodes. Our sample is built from a spectroscopic catalogue cross-matched with deep r-band CFHT/MegaCam imaging from UNIONS and additional time, enabling the detection of low-surface-brightness features and extended outer structures. Morphologies are determined both visually and through structural parameters extracted from surface-brightness profiles using AutoProf and AstroPhot. The 3D filamentary skeleton of Perseus-Pisces is reconstructed with the DisPerSE algorithm, providing distances from each galaxy to the nearest filament and to group or cluster centres. The 3D mapping reveals a network of interconnected sub-filaments converging around the Pisces cluster, forming a complex, multi-branched structure that likely shapes environmental effects on galaxy evolution. We observe clear morphological and stellar-mass segregation: massive early-type galaxies (E/S0) concentrate along filament spines and near dense nodes, while late-type and irregular systems are more broadly dispersed. About 10-13% of galaxies show strong signs of gravitational interaction, with stellar-halo asymmetries particularly common in filaments and groups. These findings underline the dual influence of filamentary environments, which both host evolved early-type systems and foster local tidal interactions and pre-processing that modify galaxy morphology.
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All authors M. Mondelin, S. Codis, J-C. Cuillandre, C. Laigle, A. Boselli, K. Kraljic, C. Stone

Astrophysics of Galaxies

An XMM-Newton View of the ANdromeda Galaxy as Explored in a Legacy Survey (New-ANGELS) II: Luminosity Function of X-ray Sources

Rui Huang, Jiang-Tao Li, Wei Cui et al. (+5 more)

As part of the New-ANGELS program, we systematically investigate the X-ray luminosity functions (XLFs) of 4506 X-ray sources projected within a radius of 2.5 deg centering on M31. We construct XLFs for different regions in the disk and halo of M31, accounting for the incompleteness with an effective sensitivity map. Assuming that the halo regions contain (mostly) foreground stars and background active galactic nuclei, they are taken as "background" for deriving the XLFs of the sources in the disk. Through modeling XLFs, we decompose the X-ray sources into distinct populations for each region. We find that low-mass X-ray binaries are the dominant X-ray population throughout the disk of M31. The XLFs of M31 reveal a consistently lower integrated LMXB luminosity per stellar mass ($\alpha_\mathrm{LMXB}$) compared to other galaxies, likely due to M31's prolonged period of quiescent star formation. Variations in the XLF shape and $\alpha_\mathrm{LMXB}$ across different regions of M31 suggest that the relationship between integrated luminosity and stellar mass may vary within the galaxy. Additionally, the relatively low integrated luminosity observed in the inner-arm region provides crucial evidence for a rapid fading of M31's LMXBs around 1 Gyr, a finding consistent with recent observations of other nearby galaxies.
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All authors Rui Huang, Jiang-Tao Li, Wei Cui, Zhijie Qu, Joel N. Bregman, Xiang-Dong Li, Gabriele Ponti, Q. Daniel Wang

Astrophysics of Galaxies

Supermassive Black Hole and Broad-line Region in NGC 5548: 2023 Reverberation Mapping Results

Wen-Zhe Xi, Kai-Xing Lu, Jin-Ming Bai et al. (+6 more)

We present the results of the 2023 spectroscopic reverberation mapping (RM) campaign for active galactic nuclei (AGN) of NGC 5548, continuing our long-term monitoring program. Using the Lijiang 2.4-meter telescope, we obtained 74 spectra with a median cadence of 1.9 days. Through detailed spectral decomposition, we measured the light curves of the optical continuum at 5100~Å\ and the broad He~ii, He~i, H$\gamma$, and H$\beta$ emission lines. The time lags of these lines relative to the continuum are measured as $1.3^{+1.6}_{-0.6}$, $2.3^{+1.5}_{-2.1}$, $10.0^{+2.0}_{-1.8}$, and $15.6^{+2.6}_{-2.9}$ days (rest-frame), respectively. Velocity-resolved lag profiles for H$\gamma$ and H$\beta$ were constructed. Combined with data from previous seasons (2015$-$2021), we find that the radial ionization stratification of the broad-line region (BLR) is stable; the average virial mass of the supermassive black hole in NGC~5548 is $(2.6\pm1.1)\times 10^{8}M_{\odot}$, consistent with the $M_{\rm BH}-\sigma_*$ relation; the broad He~ii line exhibits the largest responsivity, followed by broad He~i (or H$\gamma$) and H$\beta$ lines; the BLR kinematics show significant temporal evolution, transitioning from virialized motions to signatures of inflow and outflow. Furthermore, an analysis of 35 years of historical data confirms a 3.5-year time lag between variations in the optical luminosity and the BLR radius, potentially implicating the role of radiation pressure or dynamical structure changes in the inner accretion disk. Long-term campaign demonstrates that the BLR in NGC 5548 is a robust yet dynamically evolving entity, providing crucial insights into AGN structure and accretion physics.
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All authors Wen-Zhe Xi, Kai-Xing Lu, Jin-Ming Bai, Zhang Yue, Weimin Yi, Liang Xu, Sha-Sha Li, Hai-Cheng Feng, Jian-Guo Wang

High Energy Astrophysical Phenomena

Probing Extragalactic Ultralight Axion Dark Matter with Decade-Long Blazar Optical Polarimetry of 1ES 1959+650

Qiu-Ju Huang, Bao Wang, Jun-Jie Wei et al. (+1 more)

Axions or axion-like particles (ALPs) are well-motivated dark matter (DM) candidates whose coupling to photons induces periodic oscillations in the polarization angle of astrophysical light. This work reports the first search for such a signature using 10 years of optical polarimetric monitoring of the blazar 1ES~1959+650. No statistically significant periodicity is detected, determined by a Lomb-Scargle periodogram combined with Monte Carlo analysis. Assuming a central DM density in the host galaxy, this null result places tight upper limits on the ALP-photon coupling constant at $g_{a\gamma}<(1.3\times10^{-13}-6.0\times10^{-10})\,\mathrm{GeV}^{-1}$ across a broad ALP mass range of $m_a \sim (1.4\times10^{-23}-5.2\times10^{-20})\,\mathrm{eV}$. Assuming a soliton-core DM density, we obtain upper limits of $ g_{a\gamma}< (2.5\times10^{-13}-6.2\times10^{-13})\,\mathrm{GeV}^{-1} $ over the same ALP mass range. Our constraints surpass those from Very Long Baseline Array polarimetry of active galactic jets and from polarimetric data of the European Pulsar Timing Array, and are competitive with those from long-term Galactic pulsar timing of PSR J0437-4715 over the same ALP mass window. These results establish long-term blazar polarimetry as a competitive and complementary approach for probing axion-like DM on extragalactic scales.
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All authors Qiu-Ju Huang, Bao Wang, Jun-Jie Wei, Xue-Feng Wu

Astrophysics of Galaxies

ALMASOP: Inner-Envelope Structures of Protostars Driving Nascent Jets

Somnath Dutta, Chin-Fei Lee, Naomi Hirano et al. (+15 more)

Protostellar jets provide valuable insight into the evolutionary stage and formation history of star-forming cores in their earliest phases. We investigated the inner envelope structures of three extremely young protostars, selected for having the shortest dynamical timescales in their outflows and jets. Our analysis is based on Atacama Large Millimeter/submillimeter Array (ALMA) observations of the N2D+, DCO+, DCN, C18O, CH3OH, and H2CO lines, along with 1.3 mm continuum data, obtained at two spatial resolutions of ~500 AU and 150 AU. By examining molecular depletion and sublimation patterns, emission extents at core-scale and outflow rotational temperatures, we assessed the relative evolutionary stages of the three sources. In G208.68-19.20N1, the absence of N2D+ toward the core-despite a semi-ring-like distribution-and the presence of bright DCN and DCO+ emission cospatial with C18O indicate a warmer envelope, possibly suggesting a more advanced evolutionary state. In contrast, G208.68-19.20N3 shows no dense central structures in C18O, DCN, DCO+, or N2D+, with emission instead appearing scattered around the continuum and along large-scale filaments, consistent with a likely younger stage than G208.68-19.20N1. The third source, G215.87-17.62M, exhibits compact C18O emission at the continuum peak, but spatially extended N2D+, DCN, and DCO+ along the continuum, pointing to a cooler envelope and likely the youngest stage among the three. This comparative analysis across three protostars demonstrates the effectiveness of molecular tracers for evolutionary staging, though variations in luminosity or accretion may also shape chemical morphologies. These results highlight the promise of broader surveys for advancing our understanding of early protostellar evolution.
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All authors Somnath Dutta, Chin-Fei Lee, Naomi Hirano, Doug Johnstone, Kee-Tae Kim, Yi-Jehng Kuan, James Di Francesco, Kenichi Tatematsu, Mika Juvela, Chang Won Lee, Alessio Traficante, Vivien Huei-Ru Chen, Manash Ranjan Samal, David Eden, Dipen Sahu, Shih-Ying Hsu, Tie Liu, Sheng-Yuan Liu

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

Chaotic Inflation RIDES Again

Venus Keus and Stephen F. King

Following the recent Atacama Cosmology Telescope (ACT) results, we revisit chaotic inflation based on a single complex scalar field with mass term $M^2 |\Phi|^2$, which usually predicts a spectra index $n_s\approx 0.96$ but a too-large tensor to scalar ratio $r\approx 0.16$. With radiative corrections, the potential $M^2 |\Phi|^2 \ln \left( |\Phi|^2/\Lambda^2 \right)$ induces spontaneous symmetry breaking near the scale $\Lambda$, yielding a Pseudo Nambu-Goldstone boson which can play the role of a quintessence field, hence radiative inflation and dark energy (RIDE). Including a non-minimal coupling to gravity $\xi |\Phi|^2 R^2$ reduces $r$, allowing a good fit of the RIDE model to Planck data. Allowing a small additional quartic coupling correction $\lambda |\Phi|^4$ increases both $n_s$ and $r$, with a good fit to ACT data sets achieved for $\xi \approx 1$.
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Astrophysics of Galaxies

The UV/optical Continuum Reverberation Mapping of Eight Active Galactic Nuclei with Swift: Further Evidence for the Outer Component

Chi-Zhuo Wang, Xue-Bing Wu, Yuanzhe Jiang et al. (+3 more)

In our previous work, we applied the ICCF-Cut method to the continuum reverberation mapping (CRM) of six active galactic nuclei (AGNs) based on the published Swift data. Extending this work, we perform a systematic AGN CRM study utilizing the Swift archive. We enlarge our sample with eight additional AGNs at $z<0.05$ with high-cadence ($<3$ days) and multiband photometric observations. Time series analysis of these light curves shows two main results: (1) The interband lags are broadly consistent with $\tau \propto \lambda^{4/3}$, while the average interband lags are larger than those predicted by the standard thin accretion disk model. (2) For most targets, there exists a $U$ band lag excess, which is probably due to the diffuse continuum emission from the broad-line region (BLR). We employ the ICCF-Cut method to extract the possible diffuse continuum component from the $U$ band light curves and calculate the diffuse continuum lags ($\tau_{\rm cut}$), which are generally consistent with the lags ($\tau_{\rm jav}$) derived by the JAVELIN Photometric Reverberation Mapping Model. Further analysis with our sample indicates a positive correlation between the diffuse continuum region size and the BLR size ($R_{\rm DCR}-R_{\rm BLR}$ relation), as well as another correlation with the luminosity ($R_{\rm DCR}-L$ relation). These findings provide further evidence for a significant contribution of diffuse continuum emission from the BLR to the AGN continuum lags.
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All authors Chi-Zhuo Wang, Xue-Bing Wu, Yuanzhe Jiang, Qinchun Ma, Huapeng Gu, Yuhan Wen

Solar and Stellar Astrophysics

Asteroseismology and Buoyancy Glitch Inversion with Fourier Spectra of Gravity Mode Period Spacings

Zhao Guo

We investigate the small, quasi-periodic modulations seen in the gravity-mode period spacings of pulsating stars. These “wiggles” are produced by buoyancy glitches – sharp features in the buoyancy frequency ($N$) caused by composition transitions and the convective-radiative interface. Our method takes the Fourier transform of the period-spacing series, $FT(\Delta P_k)$ as a function of radial order $k$. We show that $FT(\Delta P_k)$ traces the radial derivative of the normalized glitch profile $\delta N/N$ with respect to the normalized buoyancy radius; peaks in $FT(\Delta P_k)$ therefore pinpoint jump/drop locations in $N$ and measure their sharpness. We also note that the Fourier transform of relative period perturbations (deviations from asymptotic values), $FT(\delta P/P)$, directly recovers the absolute value of the glitch profile $|\delta N/N|$, enabling a straightforward inversion for the internal structure. The dominant $FT(\Delta P_k)$ frequency correlates tightly with central hydrogen abundance ($X_c$) and thus with stellar age for slowly pulsating B-stars, with only weak mass dependence. Applying the technique to MESA stellar models and to observed slowly pulsating B-stars and $\gamma$ Dor pulsators, we find typical glitch amplitudes $\delta N/N \lesssim 0.01$ and derivative magnitudes $\lesssim 0.1$, concentrated at chemical gradients and the convective boundary. This approach enables fast, ensemble asteroseismology of g-mode pulsators, constrains internal mixing and ages, and can be extended to other classes of pulsators, with potential links to tidal interactions in binaries.
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Friday 7 November

Solar and Stellar Astrophysics

The Triple System V1371 Tau: An Eclipsing Binary with an Outer Be Star

Danilo F. Rocha, Marcelo Emilio, Jonathan Labadie-Bartz et al. (+10 more)

Although triple systems are common, their orbital dynamics and stellar evolution remain poorly understood. We investigated the V1371 Tau system using TESS photometry, multi-epoch spectroscopy, and recent interferometric data, confirming it as a rare triple system consisting of an eclipsing binary orbited by a classical Be star, with a spectral classification of (B1V + B0V) + B0Ve. The eclipsing binary exhibits an orbital period of approximately 34 days, and the Be star orbits the inner pair on a timescale of a few years. Weak H$\alpha$ emission lines suggest the presence of a Keplerian disk with variability on a timescale of months around the Be star, and a nearly constant V/R ratio with no detectable asymmetry variations. Besides the eclipses, frequencies at 0.24 and 0.26 c/d dominate the photometric variability. Higher-frequency signals are present which appear associated with non-radial pulsation. The eclipsing pair ($i \approx 90^\circ$) shows projected rotational velocities of 160 and 200 km s$^{-1}$. The Be star's measured $v \sin i \approx 250$ km s$^{-1}$ implies a critical rotation fraction between 0.44 and 0.76 for plausible inclinations, significantly faster than the eclipsing components. The shallower eclipses in the KELT data compared to TESS suggest a variation in orbital inclination, possibly induced by Kozai-Lidov cycles from the outer Be star. The evolution analysis suggests that all components are massive main-sequence stars, with the secondary star in the eclipsing binary being overluminous. This study emphasizes the complexity of triple systems with Be stars and provides a basis for future research on their formation, evolution, and dynamics.
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All authors Danilo F. Rocha, Marcelo Emilio, Jonathan Labadie-Bartz, Coralie Neiner, Julia Bodensteiner, Tomer Shenar, Laerte Andrade, Michael Abdul-Masih, Felipe Navarete, Alessandro Melo, Eduardo Janot-Pacheco, Romualdo Eleuterio, Alan W. Pereira

Earth and Planetary Astrophysics

Finite Lifetime Fragment Model 4 for Striae Formation in the Dust Tails of Comets (FLM 4) Acceleration by Lorenz-force

Kimihiko Nishioka

The striations in the dust tails of comets are referred to as striae, and their origin has long been a mystery. We introduce a new dynamic model to describe the forms of the striae observed in comets Hale-Bopp (C/1995 O1), West (C/1975 V1), and Seki-Lines (C/1962 C1). Charged particles made of refractory materials, with radii less than 0.5micrometer, are expelled from the comet's nucleus and accelerated by Lorentz forces near the nucleus. These particles decay many times to form striae, which have a lifespan of less than about 100 days at a distance of 1 astronomical unit from the sun. Over time, they continue to decay and eventually disappear from view. The following dynamic model explains these material science processes. Particles expelled from the comet's nucleus are subjected to three forces: solar gravity, solar radiation pressure, and Lorentz forces near the nucleus. As these particles decrease in size, the Lorentz forces and radiation pressure cause fluctuations, increasing and decreasing to form striae. This model, which is less of a dynamic approximation than previous theories (FLM3), explains the structure of the striae, enables predictions of their luminosity, and clarifies their origin.
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Solar and Stellar Astrophysics

Simulations of the onset and dynamical evolution of inertial waves in solar/stellar interior

Mariane D. Souza-Gomes, Conrado S. Finotti, Gustavo Guerrero et al. (+4 more)

Inertial modes have been recently detected in the Sun via helioseismology, yet their origin, evolution, and role in the dynamics of the solar plasma and magnetic field remain poorly understood. In this study, we employ global numerical simulations to investigate the excitation mechanisms and dynamical consequences of inertial modes in the Sun and stellar interiors. We validate first our numerical setup by analyzing the evolution of sectoral and tesseral perturbations imposed on a rigidly rotating sphere. The results confirm that a perturbation of a given mode can excite neighboring modes with both smaller and larger wavenumbers along the dispersion relation of Rossby waves. Subsequently, we use a physically motivated forcing to impose differential rotation with varying shear amplitudes, and examine the spontaneous onset and nonlinear evolution of inertial modes. The simulations reveal that the growth of velocity perturbations is primarily driven by baroclinic instability. It gives rise to high-latitude inertial modes in the form of retrograde polar vortices whose properties depend on the imposed shear. Equatorial Rossby modes are also excited, albeit with lower intensity than their high-latitude counterpart. Perturbations with arbitrary azimuthal wavenumbers lead to the excitation of Rossby modes for all available wave numbers, sustained by both direct and inverse energy cascades. In simulations with stronger shear, the high latitude modes produce Reynolds stresses able to modify the imposed differential rotation and accelerate the rotation of the poles.
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All authors Mariane D. Souza-Gomes, Conrado S. Finotti, Gustavo Guerrero, Santiago A. Triana, Mausumi Dikpati, Piotr K. Smolarkiewicz, Eric S. Botelho

Instrumentation and Methods for Astrophysics

Fundamental Limits to Phase and Amplitude Estimation in the High-Strehl Regime

Jacob Trzaska and Amit Ashok

Context: Ground-based telescopes are susceptible to seeing, an atmospheric phenomenon that reduces the resolving power of large observatories to that of a home telescope. Compensating these effects is therefore critical to realizing the potential of upcoming extremely large telescopes, a challenging task that requires precise wavefront control. Ultimately, this precision is limited by one's wavefront sensor (WFS) and its capacity to accurately encode phase and amplitude aberrations. Aims: Our attention is on photon noise-limited wavefront sensing in the high-Strehl regime. In particular, we seek fundamental limits to phase and amplitude estimation in addition to a WFS that saturate these bounds. Methods: Information theory is employed for deriving minimum-achievable residual errors, as stipulated by a metric called the Holevo Cramer-Rao bound. Holevo's bound is closely related to another metric called the quantum Cramer-Rao bound, which has already been applied to phase estimation on nearly-corrected wavefronts. Results: We present a WFS that can perfectly extract and phase shift a telescope's piston mode. We show how this phase can be used to tune the apparatus' sensitivity to phase and amplitude, and provide a closed-form expression for the optimal phase shift. For circular apertures, this implementation saturates the fundamental limits, but it can be easily modified to work with arbitrary pupils. Moreover, our proposal uses optics that are manufactureable today and is readily achromatized with geometric phase shifters.
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High Energy Astrophysical Phenomena

Probing Jet Compositions with Extreme Mass Ratio Binary Black Holes

Hung-Yi Pu

Determining whether black hole jets are dominated by leptonic or baryonic matter remains an open question in high-energy astrophysics. We propose that extreme mass ratio binary (EMRB) black holes, where an intermediate mass secondary black hole (a "miniquasar") periodically interacts with the accretion flow of a supermassive black hole (SMBH), offer a natural laboratory to probe jet composition. In an EMRB, the miniquasar jet is launched episodically after each disk-crossing event, triggered by the onset of super-Eddington accretion. The resulting emissions exhibit temporal evolution as the jet interacts with the SMBH accretion disk. Depending on whether the jet is leptonic or hadronic in composition, the radiative signatures differ substantially. Notably, a baryonic jet produces a more pronounced gamma-ray output than a purely leptonic jet. By modeling the evolution of the multifrequency characteristic features, it is suggested that the gamma-ray-to-UV emissions may serve as a diagnostic tool capable of distinguishing between leptonic and baryonic scenarios. The resulting electromagnetic signals, when combined with multi-messenger observations, offer a powerful means to constrain the physical nature of relativistic jets from black holes.
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Astrophysics of Galaxies

EDGE-INFERNO: How chemical enrichment assumptions impact the individual stars of a simulated ultra-faint dwarf galaxy

Eric P. Andersson, Martin P. Rey, Robert M. Yates et al. (+6 more)

The chemical abundances of stars in galaxies are a fossil record of the star formation and stellar evolution processes that regulate galaxy formation, including the stellar initial mass function, the fraction and timing of type Ia supernovae (SNeIa), and nucleosynthesis inside massive stars. In this paper, we systematically explore uncertainties associated with modeling chemical enrichment in dwarf galaxies. We repeatedly simulate a single EDGE-INFERNO dwarf ($M_{\star} \approx 10^5 \, M_{\odot}$), varying the chemical yields of massive stars, the timing and yields of SNeIa, and the intrinsic stochasticity that arises from sampling individual stars and galaxy formation chaoticity. All simulations are high-resolution (3.6 pc), cosmological zoom-in hydrodynamical simulations that track the stellar evolution of all individual stars with masses $>0.5\,{\rm M}_{\odot}$. We find that variations in SNIa assumptions make the largest difference in mean abundance ratios and [Fe/H], highlighting the importance of detailed SNIa modeling even in such low-mass reionization-limited galaxies. In contrast, different massive star yields, accounting (or not) for stellar rotation, result in mean abundances comparable to those arising from stochasticity. Nonetheless, they significantly affect the shape of abundance trends with [Fe/H], for example, through the existence (or not) of a bimodality in the [X/Fe] - [Fe/H] planes, particularly in [Al/Fe]. Finally, we find that the variance arising from random sampling severely limits the interpretation of single galaxies. Our analysis showcases the power of star-by-star cosmological models to unpick how both systematic uncertainties (e.g., assumptions in low-metallicity chemical enrichment) and statistical uncertainties (e.g., averaging over enough galaxies and stars within a galaxy) affect the interpretation of chemical observables in ultra-faint dwarf galaxies.
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All authors Eric P. Andersson, Martin P. Rey, Robert M. Yates, Justin I. Read, Oscar Agertz, Alexander P. Ji, Jennifer Mead, Kaley Brauer, Mordecai-Mark Mac Low

High Energy Astrophysical Phenomena

Towards the Composition of sub-PeV Cosmic Rays at IceCube

Julian Saffer

With the implementation of a low-energy trigger, the surface array of the IceCube Neutrino Observatory is able to record cosmic-ray induced air showers with a primary energy of a few hundred TeV. This extension of the energy range closes the gap between direct and indirect observations of primary cosmic rays and provides the potential to test the validity of hadronic interaction models in the sub-PeV regime. Composition analyses at IceCube highly benefit from its multi-detector design. Combining the measurement of the electromagnetic shower component and low-energy muons at the surface with the response of the in-ice array to the associated high-energy muons improves the directional reconstruction accuracy and opens unique possibilities to extract the primary particle's mass. In this contribution, a new methodical approach for the analysis of these low-energy air showers is presented, including techniques for the identification of coincident background in the in-ice detector and a machine learning model based on convolutional neural networks to determine the elemental composition. The achieved performance in primary mass discrimination and energy reconstruction of air-shower events is discussed.
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Cosmology and Nongalactic Astrophysics

Grand Unification Higgs-$\mathcal{R}^2$ Inflation: Complementarity between Proton Decay and CMB Observables

Nilay Bostan, Rafid H. Dejrah and Anish Ghoshal

We propose a predictive $SO(10)$ Grand Unified Theory (GUT) framework for cosmic inflation in the Palatini $\mathcal{R}^2$ formulation of gravity. In this model, a GUT Higgs field both drives inflation and induces intermediate-scale symmetry breaking, thereby linking primordial cosmology, gauge unification, and topological defect formation. A partial inflationary phase of $N_I \sim 10$–$17$ $e$-folds following monopole formation can dilute magnetic monopoles to abundances $Y_M \sim 10^{-35}$–$10^{-27}$. The model yields Cosmic Microwave Background (CMB) predictions of $0.955 \lesssim n_s \lesssim 0.974$, accommodating the tensions between Planck-BICEP ($n_s \approx 0.965$) and Planck+ACT ($n_s \approx 0.971$) via $\phi < M$ and $\phi > M$ branches repectively. The predicted tensor-to-scalar ratio $r \lesssim 8\times10^{-4}$ lies within current observational constraints and is accessible to forthcoming experiments, including the Simons Observatory and LiteBIRD. The resulting correlations between the unification scale $M_U$, the inflationary observables $(n_s, r)$, and proton-decay lifetimes highlight a complementarity between CMB measurements and proton-decay searches, with regions of parameter space testable in forthcoming experiments such as Hyper-Kamiokande and DUNE.
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Astrophysics of Galaxies

Continuum Reverberation Mapping of 18 AGN Over Four Years

Jake A. Miller, Edward M. Cackett, Misty C. Bentz et al. (+3 more)

Continuum reverberation mapping probes the size scale of the optical continuum-emitting region in active galactic nuclei (AGN). The source of this emission has long been thought to originate from the accretion disk, but recent studies suggest the broad line region (BLR) may significantly contribute to both the observed flux and continuum interband delays. We monitored 18 AGN over four years of observations to acquire high quality optical continuum light curves, measuring time lags between different photometric bands and determining continuum emission sizes for each AGN. We add this sample to existing lag measurements to test the correlation between continuum lags at $5100\r{A}$ ($\tau_{5100}$) and $5100\r{A}$ luminosity ($L_{5100}$). We observe that $\tau_{5100} \propto L_{5100}^{0.4}$, broadly consistent with the theoretical expectations of $\tau \propto L^{1/2}$ expected for continuum reverberation from either the accretion disk or the BLR.
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All authors Jake A. Miller, Edward M. Cackett, Misty C. Bentz, Michael R. Goad, Kirk T. Korista, Ian M. McHardy

Earth and Planetary Astrophysics

The Evolution in Coma Molecular Composition of Comet C/2017 K2 (PanSTARRS) Across the H$_2$O Sublimation Zone: ALMA Imaging of an H$_2$O-Dominated Coma

Nathan X. Roth, Stefanie N. Milam, Martin A. Cordiner et al. (+8 more)

We report a survey of molecular emission from cometary volatiles using the Atacama Large Millimeter/Submillimeter Array (ALMA) toward comet C/2017 K2 (PanSTARRS) carried out on UT 2022 September 21, 22, and 23 at a heliocentric distance ($r_H$) of 2.1 au. These measurements of HCN, CS, CO, CH$_3$OH, and H$_2$CO (along with continuum emission from dust) sampled molecular chemistry in C/2017 K2 at the inner edge of the H$_2$O sublimation zone, the region from $r_H$ = 2-3 au where H$_2$O begins vigorously subliming and increasingly dominating comet activity, discerning parent from daughter or extended source species. This work presents spectrally integrated flux maps, production rates, and parent scale lengths for each molecule. CH$_3$OH, CO, and HCN were produced within $\sim$250 km of the nucleus, potentially including contributions from sublimation of icy grains. CS was consistent with production from CS$_2$ photolysis, and H$_2$CO required production from extended sources in the coma. An ortho-to-para ratio OPR=$2.9\pm0.4$ for H$_2$CO was derived from simultaneously measured transitions of each spin species. The continuum was extended and spatially resolved, consistent with thermal emission from dust in the coma. Analysis of the continuum visibilities provided an upper limit on the nucleus diameter $d<6.6$ km and coma dust masses of $1.2-2.4\times10^{11}$ kg.
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All authors Nathan X. Roth, Stefanie N. Milam, Martin A. Cordiner, Anthony J. Remijan, Dominique Bockelee-Morvan, Nicolas Biver, Jeremie Boissier, Steven B. Charnley, Charles E. Woodward, Lillian X. Hart, Timothy N. Proudkii

Earth and Planetary Astrophysics

Are We There Yet? Challenges in Quantifying the Frequency of Earth Analogs in the Habitable Zone

Rachel B. Fernandes, Samson Johnson, Galen J. Bergsten et al. (+43 more)

Searching for life elsewhere in the universe is one of the most highly prioritized pursuits in astronomy today. However, the ability to observe evidence of Earth-like life through biosignatures is limited by the number of planets in the solar neighborhood with conditions similar to Earth. The occurrence rate of Earth-like planets in the habitable zones of Sun-like stars, $\eta_{\oplus}$, is therefore crucial for addressing the apparent lack of consensus on its value in the literature. Here we present a review of the current understanding of $\eta_{\oplus}$. We first provide definitions for parameters that contribute to $\eta_{\oplus}$. Then, we discuss the previous and current estimated parameter values and the context of the limitations on the analyses that produced these estimates. We compile an extensive list of the factors that go into any calculation of $\eta_{\oplus}$, and how detection techniques and surveys differ in their sensitivity and ability to accurately constrain $\eta_{\oplus}$. Understanding and refining the value of $\eta_{\oplus}$ is crucial for upcoming missions and telescopes, such as the planned Habitable Worlds Observatory and the Large Interferometer for Exoplanets, which aim to search for biosignatures on exoplanets in the solar neighborhood.
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All authors Rachel B. Fernandes, Samson Johnson, Galen J. Bergsten, Sakhee Bhure, Kiersten M. Boley, Alan P. Boss, Steve Bryson, William DeRocco, Jamie Dietrich, Alison Duck, Steven Giacalone, Arvind F. Gupta, Matthias Y. He, Michelle Kunimoto, Kristo Ment, Sheila Sagear, Michele L. Silverstein, Kendall Sullivan, Eliot Halley Vrijmoet, Kevin Wagner, Robert F. Wilson, Lucas Brefka, Ruslan Belikov, Aritra Chakrabarty, Jessie L. Christiansen, David R. Ciardi, Anne Dattilo, Evan Fitzmaurice, Eric B. Ford, Andrew Hotnisky, Sinclaire Jones, Aman Kar, Ravi Kopparapu, Nataliea Lowson, Eric E. Mamajek, Bertrand Mennesson, Michael R. Meyer, Sarah Millholland, Gijs D. Mulders, Susan E. Mullally, Arjun Murlidhar, Ilaria Pascucci, Darin Ragozzine, Paul Robertson, Karl Stapelfeldt, Jason Wright