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Physics Astrophysics

astro-ph Watch Astrophysics

Tuesday 21 July

Astrophysics of Galaxies

Bright Galaxies at Cosmic Dawn: A Cloud-Scale Star Formation Model Unifying Variable SFE, IMFs, and Stochasticity

Elie Cueto and Anne Hutter

To investigate the origins of the high abundance of UV-bright galaxies at z > 10, we present a new semi-analytic model that bridges the gap between small-scale star formation physics and large-scale galaxy evolution by explicitly tracking discrete star-forming clouds within smoothly evolving dark matter potentials. Unlike conventional semi-analytic models, our approach naturally captures the stochasticity of star formation, allowing us to isolate how cloud properties, star formation efficiencies (SFEs), and stellar initial mass functions (IMFs) shape the star-formation burstiness of early galaxies. Clouds are drawn sequentially from a cloud mass distribution, assigned an SFE and IMF depending on cloud mass, metallicity, and redshift, and evolve under the influence of short-timescale stellar feedback. We identify three distinct star formation regimes arising from the interplay between cloud masses, densities, and feedback timescales: a stochastic, feedback-limited regime in low-mass halos with long quiescent phases; a bursty regime regulated by the cloud mass distribution; and a smooth, continuous regime in massive halos. Our fiducial model adopts a dynamic IMF, an SFE linked to cloud properties and the IMF, and massive, moderately dense clouds. Varying assumptions reveals that top-heavy IMFs and enhanced SFEs in massive clouds amplify burstiness, while altering the upper cloud mass or density normalisation is secondary. Among model ingredients, the IMF most strongly impacts the UV luminosity function (LF), while switching to a constant SFE boosts the faint end, and reducing the maximum cloud mass decreases the bright end. These results demonstrate that cloud-scale physics critically shape early galaxy UV luminosity distributions.
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Solar and Stellar Astrophysics

KIC 6464285: A Solar-type Eclipsing Binary in a Hierarchical Triple System with Quasi-periodic Out-of-eclipse Modulations

Fang-Bin Meng, Li-Ying Zhu, Sheng-Bang Qian et al. (+10 more)

We present the first detailed analysis of the solar-type triple system KIC 6464285. Combining long-term, high-precision photometry from Kepler, TESS, and ZTF with low-resolution spectra from LAMOST and near-infrared high-resolution spectra from SDSS/APOGEE, we performed a joint analysis of the light curves, eclipse timing variations (ETVs), and radial velocities. Spectroscopic analysis reveals the system to be triple-lined, with the inner binary's primary being a G-type main-sequence star and a mass ratio of $0.627(7)$. Light curve modeling indicates that the inner binary is detached, with filling factors of approximately 26% and 11% for the primary and secondary, respectively, and a tertiary light contribution of about 27%. ETV analysis shows a significant light-travel-time effect (LTTE), consistent with the presence of the tertiary companion, whose minimum mass is estimated as $M_{3,\rm min}=0.74(1)~M_\odot$. The light curve exhibits a pronounced O'Connell effect and quasi-periodic variations, indicative of starspot activity modulating the photometry on a $\sim$131-day timescale. Kepler observations further reveal 30 superflares, each with total energies exceeding $10^{34}$ erg. This study presents detailed observational constraints on the orbital configuration, stellar properties, and magnetic activity of KIC 6464285, providing a benchmark for studies of hierarchical triple systems.
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All authors Fang-Bin Meng, Li-Ying Zhu, Sheng-Bang Qian, Ildar Asfandiyarov, Azizbek Matekov, Jaqsiliq Baltamuratov, Wen-Ping Liao, A-Li Luo, Wen Hou, Ping Li, Lin-Jia Li, Er-Gang Zhao, Jia-Jia He

High Energy Astrophysical Phenomena

Searching for $\gamma$-ray emission from a bona fide Compact Symmetric Object sample: a $\gamma$-ray signal near GB6 J0906+4124

Ying-Ying Gan, Kai Wang, Ji-Shun Lian et al. (+1 more)

As a particular subclass of active galactic nuclei (AGNs), compact symmetric objects (CSOs) have attracted significant attention due to potential role as young AGNs. Several $\gamma$-ray emitting CSOs have been detected with Fermi Large Area Telescope (Fermi-LAT), which motivates further searches for more $\gamma$-ray emitting CSOs. We perform a systematic search for $\gamma$-ray emission from a bona fide CSO sample using 16 yr Fermi-LAT observation data. No significant $\gamma$-ray signal is found to be firmly associated with any CSO. Only one $\gamma$-ray signal is detected near CSO GB6 J0906+4124 with TS = 28.7 ($\sim4.9\sigma$) in 0.1–300 GeV band. Within the 68% containment radius of Fermi-LAT average PSF at 3 GeV, GB6 J0906+4124 remains the plausible counterpart of the $\gamma$-ray signal, primarily due to its classification and broad spectral coverage. This work suggests that GeV emission from CSOs may either be uncommon or simply below the current Fermi-LAT detection sensitivity. Further multi-wavelength follow-up is needed to determine the origin of the $\gamma$-ray signal near GB6 J0906+4124.
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All authors Ying-Ying Gan, Kai Wang, Ji-Shun Lian, Run-Meng Wang

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

Domain Walls From Confining Bubbles: $SU(N_{c})$ Yang Mills at Finite $\theta$

Bruno Missoni, Enrico Morgante and Nicklas Ramberg

We study the confinement phase transition in SU($N_{c}$) pure Yang-Mills theory at finite $\theta \neq 0$ using the Improved Holographic QCD (IHQCD) model. We show that the critical temperature, as a function of $\theta$ for large but fixed $N_{c}$, is reduced, thus decreasing the amount of supercooling in the confinement phase transition. Upon completion of the confinement phase transition, a network of domain walls can be produced, owing to the multi-branched vacuum structure of Yang-Mills theory at finite $\theta$. We highlight the potential interplay between the produced domain walls and the confinement phase transition dynamics. We emphasize that DW production from bubble coalescence in strongly coupled non-conformal FOPTs is a dynamical process of vacuum assignment, hydrodynamics, and local reheating effects, all potentially affecting the approach towards the scaling regime. Lastly, we demonstrate the level of tuning necessary for potentially interesting imprints from gravitational waves through domain wall annihilation and its interplay with the confinement PT.
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Instrumentation and Methods for Astrophysics

Enhanced Astrometry of the Rapid ASKAP Continuum Survey: Mid and High Frequency Epochs

Akhil Jaini, Adam T. Deller, Yuanming Wang et al. (+3 more)

Accurate radio astrometry is essential for reliable cross-identification of sources across wavelengths, precision localisation of transient events, and the construction of stable all-sky reference catalogues. In this work we extend our astrometric correction framework for the Rapid ASKAP Continuum Survey (RACS) to its mid- and high-frequency epochs (RACS-Mid1 and RACS-High1), building on our previous corrections to the low-frequency surveys. Using a hierarchical crossmatching strategy with high-precision external catalogues, we remove large-scale systematic positional errors that were present in the uncorrected data and significantly reduce the residual scatter across the sky. After correction, the median positional offsets are effectively eliminated, and the 68% confidence interval of the mean residuals of RACS source positions averaged over $~\sim1$~sq. deg. regions is reduced from $\gtrsim 0.4''$ to $\lesssim 0.18''$ over most of the survey area for both epochs. Independent validation against multiple external radio astrometric references confirms that individual corrected RACS source positions are accurate to a 1-$\sigma$ confidence level of $\sim 0.25''$ across the bulk of the sky, with slightly degraded performance within the Galactic plane. While motivated primarily by the need for improved localisation of ASKAP fast radio bursts, these corrections also benefit a wide range of science applications, including transient identification, multiwavelength host association, and studies of Galactic and extragalactic radio populations. Together with our previous work, this establishes RACS as the highest precision arcsecond-resolution all-sky astrometric reference in the southern hemisphere at decimetre wavelengths.
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All authors Akhil Jaini, Adam T. Deller, Yuanming Wang, Emil Lenc, Stefan W. Duchesne, Marcin Glowacki

High Energy Astrophysical Phenomena

Semi-Analytical Model for the Evolution of Stellar Binaries in the Empty Loss Cone of Massive Black Holes

Samuel McGuire, Evgeni Grishin, Ilya Mandel et al. (+1 more)

Binary star systems orbiting close to a supermassive black hole (SMBH) evolve through encounters with other stars, the SMBH's tidal forces, and the binary's internal dynamics, including general relativistic precession and tides. Many are driven onto highly eccentric inner binary orbits, potentially leading to stellar mergers; other possible outcomes include hypervelocity star ejections or tidal disruption events. We study the evolution of binaries in the empty loss cone regime, where the outer orbit's angular momentum change per orbit due to scattering off other stars is smaller than the outer angular momentum at the tidal separation radius. We build on the work of Hamers & Samsing to develop a computationally efficient semi-analytical model that captures the long term evolution of binaries in perturbative regimes where the ratio of the binary tidal separation radius to the pericenter around the SMBH is smaller than 0.15. Crucially, we apply corrections to preserve the orthogonality between the binary's eccentricity and angular momentum vectors, which prevents unphysical eccentricity growth. From these simulations, we find analytical fits for the probability distributions of the final orbital parameters of binaries approaching the SMBH. We find that general relativistic precession efficiently suppresses von-Zeipel-Lidov-Kozai-like eccentricity oscillations and reduces the fraction of merging binaries from $84\%$ with Newtonian physics only, to $3\%$ with precession included. Stellar tides further reduce the merger fraction to $0.4\%$.
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All authors Samuel McGuire, Evgeni Grishin, Ilya Mandel, Yuri Levin

High Energy Astrophysical Phenomena

The XMM-Newton Line Emission Analysis Program (X-LEAP) III: Earth's Magnetospheric X-ray Emission Revealed by 22-Year XMM-Newton Observations

Zeyang Pan, Zhijie Qu, Yuqi Gong et al. (+5 more)

The magnetosphere, protecting the Earth from intense solar activity, is also shaped by the solar wind, while its structure is still uncertain in observation. In this study, we map the X-ray emission in the magnetosphere, which is induced by the charge exchange between the highly-ionized solar wind and the neutral gas around the Earth, known as the magnetospheric solar wind charge exchange (SWCX). In particular, we extract the magnetospheric SWCX in the O VII line emission data adopted from the XMM Line Emission Analysis Program (X-LEAP). The observed magnetospheric SWCX shows an enhanced emission of approximately $I_{\rm OVII}^{\rm mag}\approx 2$ photons $\rm cm^{-2}~ s^{-1}~sr^{-1}$ toward the Sun, showing a consistent shape predicted by numerical simulations. Furthermore, this magnetospheric SWCX exhibits a dependence on the XMM pointing direction, which traces the path length of SWCX emission in the Earth's magnetosphere. Building on this directional dependence, we model the 3D magnetosheath structure using soft X-ray observations for the first time, constraining the averaged boundary geometry and SWCX emissivity distribution over 22 years. Finally, utilizing the XMM data, we derive an empirical O VII emission efficiency of $\alpha_{\rm OVII}=(2.1\pm0.4) \times 10^{-16}\ {\rm eV\,cm^{2}}$.
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All authors Zeyang Pan, Zhijie Qu, Yuqi Gong, Tianran Sun, Joel N. Bregman, Yingjie Zhang, Li Ji, Jifeng Liu

Astrophysics of Galaxies

Estimating stellar metallicities from Gaia DR3 XP data using LAMOST DR10

Divyansh Srivastava, Andrzej Niedzielski and Rodolfo Smiljanic

Gaia DR3 provides astrophysical parameters for hundreds of millions of stars, but the metallicities [M/H] from its GSP-Phot module suffer from systematic biases. We estimate stellar metallicities from Gaia DR3 data using the homogeneous spectroscopic iron abundances [Fe/H] of LAMOST DR10 as training labels. We cross-matched LAMOST DR10 with Gaia DR3 and trained a gradient-boosted decision-tree regressor (XGBoost) on 1.20 million AFGK stars using only Gaia-derived inputs and proxies. We validated the estimates on held-out LAMOST stars, GALAH DR4, APOGEE DR17, and 46 open clusters, and applied the model to measure the radial metallicity gradient of the Milky Way disk. On the held-out test set, the model achieves a mean absolute error of 0.052 dex and $R^2=0.94$ with negligible bias, compared with 0.242 dex for GSP-Phot on the same stars. The estimates transfer well to external surveys, with mean absolute errors of 0.066 dex for GALAH and 0.068 dex for APOGEE. For open clusters, the median difference between our estimated [Fe/H] and spectroscopic values is 0.041 dex, smaller than both GSP-Phot (0.248 dex) and a previous APOGEE-trained XGBoost model (0.067 dex). Applied to the Galactic disk, our model recovers a broken thin-disk radial gradient, with inner and outer slopes of $+0.119$ and $-0.058\,\mathrm{dex\,kpc^{-1}}$, respectively, and a break near 5.9 kpc, as well as an open-cluster gradient of $-0.066\,\mathrm{dex\,kpc^{-1}}$; both agree with previous high-resolution spectroscopic studies. Our [Fe/H] estimates are accurate to 0.05-0.07 dex for AFGK stars with $[\mathrm{Fe/H}]\gtrsim-2.5$; below this limit, the predictions should be treated as lower bounds. The catalogue and trained model are publicly available on Zenodo and are suitable for chemical studies of the Milky Way.
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High Energy Astrophysical Phenomena

Universal scaling between magnetar field and initial spin period for short gamma ray bursts

Qin-Mei Li, Qi-Bin Sun, Sheng-Bang Qian et al. (+5 more)

The $B_p$–$P_0$ correlation serves as a critical probe of magnetar engine physics. Although this scaling relation has been firmly established for long gamma-ray bursts (lGRBs), systematic investigations for short GRBs (sGRBs) remain absent, leaving the physical differences between the two populations poorly constrained. Here we analyze 33 Swift sGRBs exhibiting prominent X-ray plateaus from newborn millisecond magnetar spin-down, and derive their initial spin period $P_0$ and polar magnetic field $B_p$. sGRB magnetars span $P_0 \in [1.73,\,18.28]\ \mathrm{ms}$ and $B_p \in [0.06,\,2.82] \times 10^{17}\ \mathrm{G}$ ($\langle B_p \rangle = 7.05 \times 10^{16}\ \mathrm{G}$), significantly more magnetized than lGRB magnetars ($B_p \in [0.39,\,23.08] \times 10^{15}\ \mathrm{G}$; $\langle B_p \rangle = 3.69 \times 10^{15}\ \mathrm{G}$). For the first time, we derive consistent power-law $B_p$–$P_0$ correlations for GRBs : the scaling for sGRBs is $\log B_p = (0.84\pm0.07)\log P_0 + (15.79\pm0.07)$, whose slope is highly consistent with that of lGRBs, $\log B_p = (0.83\pm0.09)\log P_0 + (14.92\pm0.06)$. The near-identical slopes imply a universal magnetar spin-down mechanism, while the vertical offset between intercepts traces divergent progenitor channels. This scaling relation thus offers a new diagnostic to disentangle the formation pathways of GRB. Within the framework of the standard spin-up model, the mass accretion rates of sGRBs ($\dot{M} \sim 1 \times 10^{-1}$ to $3 \times 10^{-1}\,M_\odot\,\mathrm{s}^{-1}$) are substantially higher than those of lGRBs ($\dot{M} \sim 10^{-4}$ to $1 \times 10^{-1}\,M_\odot\,\mathrm{s}^{-1}$). Our work completes the missing $B_p$–$P_0$ statistics for sGRBs, quantitatively unifies their magnetar physics with lGRBs, and provides new observational constraints on the origin diversity of relativistic transients.
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All authors Qin-Mei Li, Qi-Bin Sun, Sheng-Bang Qian, Li-Yin Zhu, Fu-Xing Li, Si-Yuan Zhu, Ming Lian, Jing Li

Earth and Planetary Astrophysics

Azimuthal molecular variations in the AB Aur planet-forming disk

Haochang Jiang, Dmitry Semenov, Myriam Benisty et al. (+5 more)

Late infall episodes are emerging as an important driver of disk evolution. Observed as filamentary streamers in molecular lines and scattered light, such accretion perturbs disk structures, yet its chemical consequences remain unconstrained. We present NOEMA 1.2 mm observations of AB Aur, a structured young Herbig disk showing evidence for ongoing infall and planet formation. We detect azimuthal chemical diversity: SO emission is enhanced in the northern disk near the inferred streamer-disk interaction region, while C$_2$H peaks on the opposite southern side; CS forms a nearly axisymmetric ring. HCN and HCO$^+$ peak near the dust continuum overdensity in the dust ring. Rotational diagram analyses show higher SO rotational temperatures and column densities in the north, whereas CS remains axisymmetric with lower rotational temperatures, suggesting that the species probe different disk layers. For C$_2$H, temperature variations may contribute to but cannot fully explain the asymmetries. The HCO$^+$/H$^{13}$CO$^+$ line ratio indicates that HCO$^+$ is optically thick across the molecular ring, while the elevated ratio inside the cavity suggests enhanced gas-phase $^{12}$C/$^{13}$C, consistent with isotope-selective photodissociation. Comparison with chemical models favors gas-phase C/O ratios near or above unity, with higher effective C/O in the C$_2$H-bright sector. We discuss two origins for the chemical asymmetries: (i) infall-induced heating and desorption of O-bearing ices enhance SO and lower gas-phase C/O near the streamer's impact site, and (ii) planet-driven substructures and localized heating or enhanced UV irradiation promote hydrocarbon-rich chemistry in the southern disk. These results highlight that environmental accretion and planet formation can jointly imprint azimuthal variations in disk chemistry, with potential impacts on forming planets' compositions.
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All authors Haochang Jiang, Dmitry Semenov, Myriam Benisty, Vincent Piétu, Thomas Henning, Pablo Rivière-Marichalar, Lucas M. Stapper, Edwige Chapillon

Astrophysics of Galaxies

Examining the stellar-merger origin of the blue main sequence in the open cluster NGC\,3532 with N-body simulations

Khushboo K. Rao and Sambaran Banerjee

Extended main-sequence turnoffs, extended main sequences, and split main sequences observed in the colour-magnitude diagrams of young and intermediate-age star clusters are now widely interpreted as the consequence of a distribution of stellar rotation rates among their intermediate-mass (1.5-1.8~M$_\odot$) members. However, the origin of the slowly rotating population that occupies the blue main sequence (bMS) remains uncertain, and stellar mergers have been proposed as one possible pathway. We investigate whether stellar mergers can account for the observed bMS population in the 330-Myr Galactic open cluster NGC 3532. We perform fourteen direct NBODY7 simulations spanning different initial cluster masses, radii, binary fractions, and binary orbital distributions. The simulations are selected to reproduce the present-day properties of NGC 3532 within the observational uncertainties, allowing us to estimate the expected number of merger products among its intermediate-mass main-sequence (MS) members. The cluster hosts $\approx 37\%$ bMS members among its intermediate-mass MS population, which are predominantly slow rotators. Despite this large bMS population, our simulations produce only a handful of MS-MS merger products, due to the cluster's low density and substantial mass loss during its evolution. Stellar mergers are unlikely to be the dominant formation channel for the observed slowly rotating bMS population in NGC 3532 and other disperse open clusters. Our results instead favour angular-momentum loss mechanisms operating before or shortly after the zero-age main sequence, such as pre-main-sequence star-disk interactions or tidal synchronization in low-mass ratio binaries.
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Astrophysics of Galaxies

Morphology-spin connection in the SAMI Galaxy Survey

Youngmin Baek, Sree Oh, Sukyoung K. Yi et al. (+5 more)

The spin parameter $\lambda_{\rm{R_e}}$ is a proxy for the specific stellar angular momentum of galaxies and is a useful metric for classifying kinematic morphology. This study aims to quantify the relative importance of galaxy properties in explaining $\lambda_{\rm{R_e}}$, using data from the Sydney-AAO Multi-object Integral-field spectrograph (SAMI) Galaxy Survey. We apply partial correlation analysis and partial least squares regression to assess the relative contributions of different parameters in explaining $\lambda_{\rm{R_e}}$. We find that morphology indicators, bulge-to-total ratio within one effective radius ($B/T_\rm{e}$) and ellipticity ($\varepsilon_\rm{e}$), show the strongest correlations with $\lambda_{\rm{R_e}}$ and play a leading role in the regression analysis. This result statistically confirms the established fast-rotator sequence, in which fast-rotating early-type galaxies form a continuous structural and kinematic sequence with spiral galaxies, with $\lambda_{\rm{R_e}}$ decreasing as bulge prominence increases. The light-weighted age and stellar mass also exhibit significant correlations, but their contributions are secondary to the morphology indicators in multivariate analyses. We also examine whether the observed trends in $\lambda_{\rm{R_e}}$ can be reproduced using galaxy properties alone. The morphology indicators (${B/T_\rm{e}}$, $\varepsilon_\rm{e}$) reproduce the overall distribution of observed $\lambda_{\rm{R_e}}$ with a scatter of about 0.12, while the inclusion of Age_LW and $M_\star$ provides only modest additional improvement. However, these relations do not reproduce the slow-rotator regime well. Overall, our results show that photometric structural parameters best explain $\lambda_{\rm{R_e}}$ and suggest that statistical inference of galaxy spin from non-IFS observables may become feasible with improved models and a broader set of parameters.
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All authors Youngmin Baek, Sree Oh, Sukyoung K. Yi, Scott M. Croom, Matthew Colless, Jesse van de Sande, Stefania Barsanti, Sam P. Vaughan

High Energy Astrophysical Phenomena

Time-Domain Axion Searches with Magnetic White Dwarfs

Hong-Yi Zhang, Heng Bian and Zhao-Yu Zuo

Magnetic white dwarfs can convert photons into axions in their strong magnetic fields, with the conversion probability modulating the light curve as the star rotates. However, this observable is degenerate with intrinsic stellar variability if the background is modeled too simplistically. We develop a controlled background-degeneracy framework that computes the axion-induced modulation from reconstructed stellar magnetic fields while fitting it simultaneously with a flexible Fourier model of the intrinsic light curve. Applying this framework to TESS observations of PG~1015+014 using two independent magnetic field reconstructions, we find that a sinusoidal stellar background can produce an apparent preference for nonzero axion-photon conversion. This preference is absorbed once the background light curve includes the second harmonic, indicating that higher-harmonic stellar variability is a leading degeneracy for precise photometric axion searches in magnetic white dwarfs. Interpreting the two-harmonic fit as a conservative baseline, we obtain competitive constraints for sub-$\mu\mathrm{eV}$ axions. We further derive an analytic target-ranking estimate for other TESS magnetic white dwarfs, identifying systems where phase-resolved magnetic modeling would be most valuable for competitive axion probes.
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc

Stochastic template banks for GW searches using low-discrepancy sequences

Tarun Kumar and Anand S. Sengupta

Matched filtering remains the most sensitive method for detecting gravitational waves from compact binary coalescences. The efficiency of such searches depends on how well a discrete template bank covers the underlying parameter space. Conventional geometric, stochastic, and hybrid placement methods can lead to uneven coverage and redundant templates in higher dimensions. Hybrid methods are generally the most efficient among these, while stochastic methods are simpler to implement, particularly when the parameter-space metric is difficult to compute. In practice, both approaches rely on uniform random sampling, which often requires a large number of proposal points to achieve adequate coverage. We find that stochastic template banks constructed using low-discrepancy sequences achieve comparable recovery fractions while requiring 27.5% fewer proposal points in two dimensions, about 12% fewer in three dimensions and 17% fewer in a four-dimensional eccentric equal-spin toy bank. The final template count is much less sensitive to the proposal sampling, consistent with the metric-volume constraints of the covering problem. We introduce a slab-wise coarse prefilter to accelerate candidate rejection for strongly anisotropic metrics. Applied to the 4D toy bank, it gives a total bank-construction speed-up of about $1.28\times$. The primary benefit of low-discrepancy sampling is therefore a reduction in the size of the initial proposal set, leading to lower memory usage and reduced bookkeeping during bank generation. These results show that low-discrepancy sampling provides a simple improvement to stochastic template-bank generation for current and future gravitational-wave searches.
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Solar and Stellar Astrophysics

A multiwavelength light curve analysis of the very fast nova V1723 Sco

Izumi Hachisu and Mariko Kato

We have analyzed multiwavelength light curves of the very fast nova V1723 Sco, based on our fully self-consistent nova explosion models. The time-stretching method gives the distance modulus in the $V$ band of $(m-M)_V = 15.3\pm 0.2$. Then the absolute $V$ magnitude reaches $M_{V,\rm max}= m_{V, \rm max} - (m-M)_V= 6.77 - 15.3\pm 0.2 = -8.5\pm 0.2$. Using our fully self-consistent nova outburst model combined with the optically thick winds on a $1.25 ~M_\odot$ white dwarf accreted by a mass accretion rate of $\dot{M}_{\rm acc}=1\times 10^{-9} ~M_\odot$ yr$^{-1}$, we successfully reproduce the overall $V$ light curve with a free-free emission model as well as the supersoft X-ray light curve with a blackbody approximation model. The epoch of the first GeV gamma-ray detection is almost coincident with the epoch of our model $V$ peak. This supports the shock formation mechanism that a strong shock arises soon after the optical $V$ maximum far outside the WD photosphere. We conclude that the shocked shell is optically thin.
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Monday 20 July

Astrophysics of Galaxies

Clarifying Dead Quasars and Downsizing through the Evolution of Star-Forming Galaxies and Active Galactic Nuclei

Shingo Sumie

From the catalogs of visible emission lines of galaxies measured by the Subaru Fiber Multi-Object Spectrograph (Subaru-FMOS) and the KECK Multi-Object Spectrograph For InfraRed Exploration (KECK-MOSFIRE), galaxies were classified into Star-Forming Galaxies (SFGs) and Active Galactic Nuclei (AGNs) based on the Baldwin-Phillips-Terlevich (BPT) diagram. In the redshift (z) range 0.8 <= z <= 2.6, z dependence of their number densities was examined, and it was found that SFGs dominate at lower redshifts, whereas AGNs are distributed at higher redshifts. Infrared analyses using the James Webb Space Telescope (JWST) NIRSpec and MIRI for galaxies up to z ~ 6.6 show similar trends, and the number densities of SFGs and AGNs were found to cross at z ~ 1-3. Combined with the fact that the luminosity of galaxies decreases monotonically with the age of the universe, these phenomena can be interpreted by an evolutionary scenario in which SFGs merged to form quasars in the early universe, whose activity weakened and they changed into SFGs later, and SFGs merged again to form Seyferts in the nearby universe. Within this framework, the longstanding issues of "dead quasars" and "downsizing" can be naturally explained.
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Solar and Stellar Astrophysics

Stream-Driven Ignition of a Realistic Undisturbed Helium Shell on a White Dwarf

Nethra Rajavel, Dean M. Townsley and Ken J. Shen

The dynamically driven double degenerate double detonation (D$^6$) model has emerged as a promising progenitor scenario for Type Ia supernovae. In this model, a carbon-oxygen white dwarf (WD) in a close double WD binary undergoes a double-detonation triggered by dynamical mass transfer from its companion. The mass transfer stream directly impacts the surface of the primary WD, potentially igniting a helium detonation in the surface layer. The resulting shock converges in the core, triggering a carbon detonation that ultimately unbinds the star. While previous studies have demonstrated the viability of this mechanism, the conditions under which the helium shell ignites remain uncertain. We perform two-dimensional simulations using FLASH to study helium detonation ignition driven by stream impact on a carbon-oxygen WD with a realistic, unmixed composition profile left at the end of the previous helium-shell burning phase before the WD was formed. We model WDs with masses of 0.8, 0.9, and 1.0 $,M_\odot$ and vary stream properties for each case. We find that stream impact leads to helium ignition in all cases, with ignition occurring at varying distances from the impact point. Ignition consistently occurs near the core-shell transition, highlighting the importance of a realistic WD profile. However, the ignition mechanism differs between models and can arise from interactions of neighboring hot, mixed regions rather than a single point. Ultimately, all models but one sustain a propagating detonation capable of traversing the WD surface further reinforcing the viability of the D$^6$ model as a progenitor scenario for Type Ia supernovae.
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Earth and Planetary Astrophysics

Capture of interstellar objects during stellar encounters

Sean N. Raymond, Nathan A. Kaib and Matthew J. Hopkins

As they orbit within the Galaxy, stars swim through a vast population of interstellar objects (ISOs). In this paper, we use N-body simulations to show that a fraction of ISOs within $\sim$1 pc of the Sun (its tidal radius) may be captured during the flyby of another star – a mechanism that requires no planets. Capture is most efficient when the impulse imparted by the flyby is comparable to the escape speed at the widest stable orbit, which is roughly 0.1 km/s for the Sun. ISO capture is dominated by the few highest-impulse stellar flybys, typically involving relatively slow encounters with massive stars. Most ISOs are captured in the outer parts of the Oort cloud, with semimajor axes greater than $\sim$50,000 au. Using Monte Carlo simulations, we show that the Sun underwent only a small number of ISO-capturing flybys in its history (median [mean] of 1 [1.7]). Using the Ōtautahi-Oxford population model, we estimate that a few times $\sim$$10^{4}$ `Oumuamua-sized ISOs were likely captured by the Sun. This only represents a $\sim$$10^{-8\pm1}$ contribution to the total Oort cloud population, yet it contains roughly as many present-day captured ISOs as Jupiter-assisted capture provides. Given that flybys are unavoidable in the Galactic field, most stars should host sparse Oort clouds populated with ISOs captured during stellar flybys. Massive stars are both the main drivers of capture when they fly by a given star, and more efficient at capturing ISOs around themselves than low-mass stars.
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Cosmology and Nongalactic Astrophysics

The impact of Hawking radiation from primordial black holes on recombination and the Hubble tension

Adam Batten and Jeremy Mould

Primordial black holes (PBHs) evaporate through Hawking radiation, emitting high-energy photons and ionising their surrounding environment. As contributors to the density of dark matter, Omega_C, if 10^-18 solar mass PBHs are present in the Universe they delay recombination and move the surface of last scattering of the cosmic microwave background (CMB). We perform recombination simulations using the software Recfast, and calculate the PBH fraction of dark matter required to resolve the Hubble tension. We find that nominally a cosmic PBH energy density of Omega_PBH ~ 10^-3 Omega_C would cause an 8.9% increase in the value of H_0, enough to entirely reduce the tension between the early- and late-time observations. This PBH fraction is modified by Gray Body Factors affecting Hawking radiation. Furthermore, also fitting the CMB leaves the Hubble tension not fully relieved with our present PBH prescription. Until relevant non-gravitational properties of the dominant dark matter species are ruled out, we suggest that the hypothesis that the ionisation history of the universe matches the thermal history of the standard LCDM cosmology is too precarious to hang the expansion rate on, and that it is better to measure H_0 locally at z <~ 1.
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Earth and Planetary Astrophysics

Chondrite Parent Bodies as Escaped Satellites of Proto-Planetary Embryos

Harold F. Levison, Rogerio Deienno, Kevin J. Walsh et al. (+4 more)

Chondrites are composed of formerly partially molten material, known as chondrules, surrounded by fine-grained matrix. They date from the earliest times in Solar System history. However, their role in the formation of the planets is uncertain because, in part, it is not clear how they were produced. Here, we show a robust pathway for forming meteorite-producing asteroids that contain chondrules through embryo-embryo collisions during the late stages of terrestrial planet formation. Melted material from these impacts cool into chondrules and mix with unmelted material in embryo-centric disks that formed from the ejecta. This material accretes into numerous asteroid-sized satellites. These objects are later ejected onto heliocentric orbits because of gravitational encounters with other embryos, thereby becoming the parent bodies of chondrites. This mechanism provides a pathway to form chondrites in Solar System history at times commensurate with measured chondrule ages, while explaining many of their physical properties.
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All authors Harold F. Levison, Rogerio Deienno, Kevin J. Walsh, Brandon C. Johnson, Harold C. Connolly Jr., Shigeru Wakita, Robert E. Grimm

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

Modified Cosmology from Mass-to-Horizon Relation: Observational Bounds

Pranav Prasanthan, Hussain Gohar and Vincenzo Salzano

We constrain the class of modified cosmologies derived in Paper I [1] from a generalized mass-to-horizon relation (MHR) that enforces thermodynamic consistency between the Cai-Kim horizon temperature and generalized horizon entropies. The modified Friedmann equations depend on an entropy exponent $m$, an MHR coupling parameter $\gamma$, and an entanglement-correction amplitude $f_B$, with standard $\Lambda$CDM recovered in the appropriate limit. Using Pantheon$+$/SH0ES Type~Ia supernovae, cosmic chronometers, DESI DR2 baryon acoustic oscillations, and Planck 2018 CMB distance priors, we constrain eight physically motivated sub-cases via Markov chain Monte Carlo and compare models through the Bayesian log-evidence. The entropy exponent is tightly bounded, $|m-1|\lesssim O(10^{-4})$ when the MHR coupling is fixed ($\gamma=1$), relaxing to $O(10^{-3})$ along the $m$-$\gamma$ degeneracy, excluding any macroscopically significant departure from standard horizon thermodynamics. Freeing the MHR coupling parameter or the entanglement amplitude raises the inferred Hubble constant to $h\simeq0.70$-$0.71$, reducing the CMB-SH0ES tension from ${\sim}4\sigma$ to ${\sim}1.2$-$2.6\sigma$, but no scenario fully resolves it within a flat universe. The Bayesian log-evidence nevertheless disfavors every extension relative to $\Lambda$CDM in all dataset combinations ($-16\lesssim\Delta\ln Z \lesssim-1$): the improved fits obtained when the SH0ES calibration is included reflect an absorption of the Hubble tension by the additional parameters rather than genuine evidence for modified horizon entropy.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph

Detecting Cosmological Stasis with Future Gravitational Wave Observatories

Gabriela Barenboim and Anne-Katherine Burns

We map the observational predictions of cosmological stasis in the inflationary gravitational wave background onto the sensitivity bands of current and planned gravitational wave detectors. Using the closed-form piecewise spectral template derived in the companion paper, we generate detectability maps for four stasis scenarios: canonical, dynamical scalar, vacuum-energy/matter, and vacuum-energy/radiation across the frequency bands probed by NANOGrav, SKA, LISA, DECIGO, BBO, the Einstein Telescope, and Cosmic Explorer. For scenarios in which the spectrum is suppressed, $w_s < 1/3$, the stasis feature is detectable by BBO in the region of $(w_s,\Delta N)$ parameter space in which $w_s\gtrsim 0.2$ for tensor-to-scalar ratios close to the Planck upper limit, r = 0.036. For scenarios in which the spectrum is enhanced, $w_s > 1/3$, the stasis feature is detectable by BBO across the entire $(w_s,\Delta N)$ parameter space for tensor-to-scalar ratios of $O(0.01)$. We characterize the Standard Model (SM) $g_*$ fine structure of the IGWB, showing that SM phase transitions introduce spectral steps of $\approx 20\%$ (electroweak, at $\sim 2.6\times10^{-6}$~Hz) and $\approx 53\%$ (QCD, at $\sim 3.6\times 10^{-9}$~Hz). For stasis scenarios with end-of-stasis temperatures below the QCD scale these steps fall inside the stasis band and constitute additional spectral features that complement the primary signature. Finally, we model the finite-width end-of-stasis transition phenomenologically, demonstrating that the spectral break at $f_{end}$ is smoothed over a log-frequency window $\Delta N_\mathrm{trans}\times 3(1+w_s)/4$, and that the consistency relation $C^2=C^2(\alpha)$ remains testable provided $\Delta N_\mathrm{stasis}\gg \Delta N_\mathrm{trans}$, a condition easily satisfied for all scenarios of phenomenological interest.
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Cosmology and Nongalactic Astrophysics

Detection of cosmic strings by gravitational wave lensing. Predictions for Einstein Telescope

Jakub Szyndler and Tomasz Bulik

Cosmic strings are not yet confirmed, topological defects formed in the early Universe. They can bend light or gravitational waves, which causes an effect similar to the gravitational lensing. Our goal is to check whether cosmic string could be detected as a lenses of gravitational waves by the Einstein Telescope (ET). To do that the apparatus of wave optics had been applied. Firstly we explored the amplification factor strength and behaviour. Next the wave effects in SNRs and waveforms was examined for different inclinations of the source. Lastly we estimated the string tensions based on eight mergers from the StarTrack simulation, using the Bayesian Inference methods. The wave effects were easily to see in waveforms, SNR and characteristic strains. Also most of the events could be detected, based on their Signal to Noise Ratio values. Almost whole characteristic strain lies in the range of the ET. When it comes to mock observations, we had got estimated vale of a logarithm of the CS tension equal to $\bar{\log{G\mu}}=-9.80^{+0.49}_{-0.56} $, which were consistent with injected value equal to $-10$. At the end we conclude that CSs could be detected by the ET.
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Astrophysics of Galaxies

Vz-GAL Dusty Star-Forming Galaxies: Revisiting the CO-H2 Conversion Factor Tension

Prachi Prajapati, Axel Weiss, Dominik Riechers et al. (+17 more)

The CO luminosity-to-H$_2$ mass conversion factor ($\alpha_{CO}$) remains a debated uncertainty in determining molecular gas masses of high-redshift dusty star-forming galaxies (DSFGs). Dynamical mass constraints have often favored $\alpha_{CO}=0.8$~$M_{\odot}~{(K~km~{s}^{-1}~{pc}^{2})}^{-1}$, whereas dust- and radiative-transfer-based methods imply higher values. We revisit this “tension" using the largest homogeneous sample of 21 unlensed $z\sim1-4$ DSFGs, with securely measured \coonezero luminosities from the VLA \vzgal survey and resolved ($\sim{0.1}^{\prime\prime}$) ALMA 1~mm dust continuum imaging. For 12 galaxies with robust modeling constraints, we derive molecular gas masses using dust spectral energy distribution modeling and the TUNER LVG framework, adopting a solar-metallicity gas-to-dust mass ratio of 100. Although not fully independent due to shared assumptions on dust properties, these approaches yield mutually consistent gas masses corresponding to $\alpha_{CO}\sim1.5-11.5$, with a median near the Galactic $\alpha_{CO}=4.3$. Isotropic virial dynamical masses agree with these gas masses when realistic molecular gas sizes are adopted, while our proposed “mixed" (rotating, pressure-supported, thick-disk) estimator systematically underestimates dynamical masses, producing low $\alpha_{CO}$ limits. Using GN20 ($z=4.055$) as a case study, we show that resolved gas geometry and kinematics reconcile the discrepancy with LVG-derived $\alpha_{CO}$. Our results suggest that current data do not require $\alpha_{CO}=0.8$, and intermediate to near-Galactic values remain dynamically viable given uncertainties in gas geometry, dust properties, and gas-to-dust ratios. Further progress in calibrating $\alpha_{CO}$ in the early universe will require resolved molecular gas observations, physically motivated ISM modeling, and stringent constraints on dust properties.
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All authors Prachi Prajapati, Axel Weiss, Dominik Riechers, Tom J. L. C. Bakx, Leindert A. Boogaard, Diana Ismail, Pierre Cox, Andrew J. Baker, Roberto Neri, Matthew Lehnert, Chentao Yang, Emilio Romano-Diaz, Hiddo S. B. Algera, Stefano Berta, Edoardo Borsato, Kirsty M. Butler, Asantha Cooray, Bethany Jones, Amelie Saintonge, Paul van der Werf

High Energy Astrophysical Phenomena

Can We Find the Emission Mechanism Behind the Extremely Bright GRB 230812B?

Utkarsh Pathak, Sameer K. Patil, Hitesh Tanenia et al. (+23 more)

GRB 230812B is a bright long-duration GRB with a luminous, long-lived afterglow and an AstroSat/CZTI polarization measurement during the prompt phase, enabling a joint study of its prompt spectral evolution, polarization, and broadband afterglow. Time-resolved spectroscopy of the prompt emission shows that during the rising phase, the low-energy Band-function index exceeds the synchrotron line of death, favoring the presence of an additional thermal component. At later times, from $T_0+2$ s to $T_0+32$ s, the prompt spectra are consistent with predominantly non-thermal emission. Polarization analysis of the prompt emission in the $300$-$600$ keV band yields a marginal lower limit on the polarization fraction of $\Pi \gtrsim 50\%$ at the $1\sigma$ level. The long X-ray monitoring of the afterglow shows no jet break over the observed baseline. Multiwavelength afterglow modeling favors a wide jet with an inferred half-opening angle of $\theta_j = 15^{+6}_{-4}$ degrees observed close to the jet axis with a viewing angle of $\theta_v = 0.9^{+1.8}_{-0.6}$ degrees. The inferred circumburst density is low, $n_0 = 1.2^{+0.3}_{-0.1}\times10^{-4}\,\textrm{cm}^{-3}$, and the isotropic-equivalent kinetic energy of the jet is $E_{{\rm k}, iso} = 4.0^{+1.5}_{-0.8} \times 10^{53}$ erg. Taken together, the prompt spectral evolution favors an early phase with a thermal contribution followed by a later phase dominated by non-thermal emission. The polarization constraint in the late prompt phase is consistent with synchrotron emission, although a higher-significance polarization measurement will be required to robustly constrain the magnetic-field geometry and the relative contribution of photospheric emission.
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All authors Utkarsh Pathak, Sameer K. Patil, Hitesh Tanenia, Yashowardhan Rai, Viswajeet Swain, Anuraag Arya, Gaurav Waratkar, Anirudh Salgundi, Mehul Goyal, Varun Bhalerao, Igor Andreoni, Sarah Antier, G. C. Anupama, Sudhanshu Barway, Dipankar Bhattacharya, Tanmoy Chattopadhyay, Michael Coughlin, Anirban Dutta, Christoffer Fremling, Nidhal Guessoum, Mansi Kasliwal, Oliver J. Roberts, Gokul P. Srinivasaragavan, Rishabh Singh Teja, Santosh Vadawale, Peter Veres

Instrumentation and Methods for Astrophysics

First results for second generation SiSeRO CCD devices

Abigail Y. Pan, Declan O'Neill, Kevan Donlon et al. (+18 more)

The Astro2020 Decadal recommended the development of a suite of next generation astronomical observatories spanning the X-ray to near-IR spectrum. These programs require fast, extremely low noise detectors to fulfill their science goals. To address this technology gap, Stanford X-ray Astronomy and Observational Cosmology (XOC) group, MIT Lincoln Laboratory (MIT-LL), and MIT Kavli Institute (MKI) are advancing Single electron Sensitive Read Out (SiSeRO), a multiband detector technology capable of achieving substantially sub-electron noise via Repetitive Non-Destructive Readout (RNDR). We present initial results for our second generation SiSeRO CCDs. We also discuss our test bed, including a readout electronics system capable of accommodating all second-generation SiSeRO CCD variants utilizing the XOC-designed Multi-Channel Readout Chip (MCRC) ASIC.
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All authors Abigail Y. Pan, Declan O'Neill, Kevan Donlon, Peter Orel, Sven Herrmann, Steven Allen, Marshall W. Bautz, Tanmoy Chattopadhyay, Michael Cooper, Catherine E. Grant, Jill Juneau, Chris Leitz, Beverly LaMarr, Eric D. Miller, Glenn Morris, Tonya L. Peshel, Artem Poliszczuk, Gregory Prigozhin, Ilya Prigozhin, Haley R. Stueber, Keith Warner

Instrumentation and Methods for Astrophysics

Nancy Grace Roman Space Telescope Wide Field Instrument: Bright Point Source Saturation Response and Persistence Properties from Thermal-Vacuum Testing

Dana R. Louie, Robert F. Wilson, Thomas Barclay et al. (+19 more)

The Nancy Grace Roman Space Telescope's Wide Field Instrument (WFI) will observe hundreds of thousands of bright stars across its Core Community Surveys, particularly in the dense stellar fields of the Galactic Bulge Time Domain Survey (GBTDS). Sources brighter than ~17th magnitude will saturate WFI detector pixels in typical survey exposures, with the brightest stars deeply saturating large pixel regions and potentially producing persistence signals that may impact subsequent observations. Prior detector characterization did not explore the regime of deep point source saturation. To address this gap, we conducted a bright star saturation test during WFI's second Thermal Vacuum test campaign (TVAC2) at BAE Space & Mission Systems in Boulder, CO. Using the Stimulus of Ray Cones (SORC) telescope simulator, we projected nine in-focus point sources through the F146 filter onto two Sensor Chip Assemblies (SCAs), with fluxes tuned to approximate stellar magnitudes ranging from ~4 to ~18 in ~170 s exposures. We present analyses of the saturation response and persistence properties of these detectors. We find that the saturated region of a ~4 mag source grows to ~150 pixels in diameter after ~170 s of illumination, compared to ~15 pixels for a ~12 mag source. Pixels adjacent to the expanding saturation front exhibit pronounced non-linear behavior consistent with charge leakage from saturated neighbors. For persistence, we find that the median signal in the first post-illumination dark exposure is broadly consistent across source magnitudes spanning ~4 to ~17, and that persistence decays to detector background levels ($\lesssim$0.05 e$^{-}$ s$^{-1}$) within approximately 20 minutes, consistent with flat field persistence measurements from the same TVAC2 campaign. These pre-flight characterization results inform community understanding of WFI detector response to prepare for Roman science.
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All authors Dana R. Louie, Robert F. Wilson, Thomas Barclay, Joshua E. Schlieder, Nicholas Bond, Evan Bray, Mario Cabrera, Stephanie Cheung, Ami Choi, Analia Cillis, Nicholas Collins, Tyler D. Groff, Robert J. Hill, Jeffrey Kruk, Gregory Mosby, Jennie Paine, Bernard J. Rauscher, Timothy A. Reichard, Maxime Rizzo, Scott Rohrbach, Nicole Schanche, Eric R. Switzer

Astrophysics of Galaxies

The Next Generation Virgo Cluster Survey (NGVS). II. A Catalog of Galaxies in the Virgo Cluster

Laura Ferrarese, Patrick Cote, Lauren A. MacArthur et al. (+51 more)

The Next Generation Virgo Cluster Survey (NGVS) is a deep, high resolution imaging campaign that used the 1 deg$^2$ MegaCam instrument on the Canada-France-Hawaii Telescope to carry out a comprehensive optical survey of the Virgo cluster, from its core to its virial radius. The NGVS covers a contiguous area of 104 deg$^2$ (8.63 Mpc$^2$ at the 16.5 Mpc distance of Virgo) in the $u^*$-,$g$-,$i$-, and $z$-band, with additional limited coverage in $r$. In this paper, we present the final catalog of Virgo galaxies across the entire NGVS area. The catalog includes 3680 galaxies considered to be $bona~fide$ members of the cluster, spanning a factor of 2.5 million in luminosity, from $g = 8.42$ mag to $g = 24.41$ mag ($M_g = -22.67$ mag to $M_g = -6.68$ mag). With 2100 previously uncataloged galaxies, the NGVS catalog augments the number of known Virgo members by a factor 2.3. The catalog is complete down to $g = 18.6$ mag ($M_g=-12.5$ mag, corresponding to a stellar mass $M_* \sim 1.6\times10^7~M_{\odot}$ for an old stellar population) and 50% complete at $g = 22.0$ mag ($M_g=-9.1$ mag, $M_* \sim 6.2\times10^5~M_{\odot}$), three magnitudes deeper than the venerable Virgo Cluster Catalog (VCC), which for over 40 years has served as the reference standard for Virgo. Photometric and structural parameters are derived for all NGVS galaxies and presented in a series of tables, alongside nuclear and morphological classification, as well as stellar masses and, when available, radial velocities.
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All authors Laura Ferrarese, Patrick Cote, Lauren A. MacArthur, Joel C. Roediger, John P. Blakeslee, Michele Cantiello, Jean-Charles Cuillandre, Puragra Guhathakurta, Stephen Gwyn, Max M. Kurzner, Eric W. Peng, Matthew Santos, Eleanore B. Todd, Elisa Toloba, Pierre-Alain Duc, Patrick R. Durrell, Nicholas Fantin, Yuting Feng, Ariane Lancon, Sungsoon Lim, Chengze Liu, Deborah Lokhorst, Alessia Longobardi, Simona Mei, J. Christopher Mihos, Sanjaya Paudel, Thomas H. Puzia, Anand Raichoor, Ruben Sanchez-Janssen, Kaixiang Wang, Hongxin Zhang, Alessandro Boselli, Michael L. Balogh, Samuel Boissier, Eric Emsellem, J.J. Kavelaars, Alan W. McConnachie, Cameron R. Morgan, Chelsea Spengler, James E. Taylor, Matthew A. Taylor, Toby Brown, Sebastien Fabbro, Raphael Gavazzi, Hendrik Hildebrandt, Rashi Jain, Andres Jordan, Rory Smith, Solveig Thompson, Haruka Yoshino, Wim van Driel, Ludovic van Waerbeke, Tyrone E. Woods, Jade Yeung

Earth and Planetary Astrophysics

Precise Determination of the Metallicity and C/O of WASP-39~b From a Single JWST Instrument Mode with Phase-Resolved Cross-Correlation Retrievals

Arjun B. Savel, Eliza M.-R. Kempton, Erin M. May et al. (+4 more)

Measuring atmospheric metallicities and C/O ratios is a key goal of JWST exoplanet science, given their proposed link to planet formation. Achieving this goal has previously been shown to require broad wavelength coverage ($\sim$1–5 $\mu$m), typically demanding multiple instrument modes to complete the molecular inventory. Here, we show that the multi-instrument requirement can be circumvented using phase-resolved cross-correlation retrievals at native pixel resolution – an approach more typically applied to ground-based high-resolution spectroscopy. By applying this novel analysis technique to an archival single-mode transit of the hot Jupiter WASP-39~b obtained with NIRSpec/G395H, we detect and obtain bounded abundances for all of its major carbon- and oxygen-bearing molecules: H$_2$O ($\Delta \ln(Z) = 67$), CO ($\Delta \ln(Z) = 25$), CO$_2$ ($\Delta \ln(Z) = 475$), and SO$_2$ ($\Delta \ln(Z) = 10$). Notably, while standard retrieval methods fail to detect CO in these same data ($\Delta \ln(Z) = 0.2$), our approach detects it decisively, confirming it as the dominant carbon carrier in WASP-39 b's atmosphere. From these abundances, we robustly derive a metallicity of $\rm [(C + O) / H] = 1.2 \pm 0.2$ and a C/O ratio of $0.68^{+0.10}_{-0.14} $, generally consistent with previous multi-instrument analyses. In comparison, traditional retrievals performed on the G395H data alone produce biased and inaccurate values of both parameters, driven primarily by the non-detection of CO as well as incomplete water band coverage. Our results establish phase-resolved cross-correlation retrievals as a powerful tool for extracting maximum atmospheric information from existing and future JWST data sets.
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All authors Arjun B. Savel, Eliza M.-R. Kempton, Erin M. May, Matthew C. Nixon, Jegug Ih, Katherine A. Bennett, Joost P. Wardenier

Earth and Planetary Astrophysics

Characterizing Microlensing Planetary System OGLE-2014-BLG-0676L with High-Resolution Image Constrained Light Curve Modeling

Asahi Idei, Naoki Koshimoto, Daisuke Suzuki et al. (+12 more)

We present an analysis that incorporates high-resolution Keck adaptive optics (AO) imaging into microlensing light-curve modeling for the planetary microlensing event OGLE-2014-BLG-0676. Using Keck AO observations obtained 6.3 years after the event, we directly resolved the lens and source. The Keck images reveal a tension, in that the $K$-band source flux is $0.52 \pm 0.22$ magnitudes brighter than predicted by previously reported light-curve models. By incorporating the Keck imaging constraints into the light-curve modeling, we find a host star mass of $M_{\rm host} = 0.60^{+0.17}_{-0.14}\,M_{\odot}$, a lens distance of $D_{\rm L} = 1.88^{+0.63}_{-0.35}$ kpc, a planet mass of $m_{\rm p} = 3.11^{+1.11}_{-0.63}\,M_{\rm J}$, and a projected separation of $a_{\perp} = 2.04^{+0.44}_{-0.35}$ au and $a_{\perp} = 3.72^{+0.92}_{-0.72}$ au for the close and wide solution, respectively. These results demonstrate the power of combining high-angular-resolution imaging with microlensing light-curve modeling to mitigate potential systematic effects and modeling degeneracies, enabling robust determinations of the physical properties of microlensing planetary systems. The results presented here can be confirmed by future observations from the Roman's Galactic Plane Survey.
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All authors Asahi Idei, Naoki Koshimoto, Daisuke Suzuki, Kansuke Nunota, David P. Bennett, Ian A. Bond, Jean-Philippe Beaulieu, Takahiro Sumi, Aparna Bhattacharya, Joshua W. Blackman, Ryusei Hamada, Tsutsumi Nagai, Takuto Tamaoki, Sean K. Terry, Aikaterini Vandorou