Instrumentation and Methods for Astrophysics
Which is the best day of the week to submit to arXiv:astro-ph?
Chirag Sharma and Shantanu Desai
We examine whether the citations received by refereed astronomy papers vary systematically with the day of the week of their arXiv preprint release. We use NASA ADS citation data for all refereed articles published in 2020–2023 in six journals (MNRAS, ApJ, ApJL, ApJS, A&A and JCAP; 37,173 papers with astro-ph primary preprints), combined with version-1 submission timestamps from the arXiv API. We group papers both by submission weekday and by the day their announcement batch appears on arXiv, accounting for arXiv's weekday deadline and lack of weekend announcements. Given the heavy skew of citation distributions, our primary statistic is the median citations per group, with bootstrap confidence intervals. Papers submitted on weekends, all of which appear in the Monday listing, have median citations significantly lower than weekday submissions in five of the six journals, by 12–26 %; the sixth (JCAP) shows the same direction, but not significantly, consistent with its small weekend sample. Median citations are indistinguishable across the five weekdays. These results extend the recently reported weekend citation disadvantage in particle and
nuclear physics to astronomy. The link is correlational, consistent with either compositional variations in weekend submissions or reduced visibility in the enlarged Monday listings.
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Astrophysics of Galaxies · Cross-listed from gr-qc
A Dynamical-Photometric Phase Space for Spiral Galaxies: Probing the Local Coupling Between Light and Gravity
Aritra Sanyal and Farook Rahaman
The interplay between luminous matter distribution and the local gravitational field within disc
galaxies encodes physical information beyond that captured by global scaling relations. We introduce a dynamical–photometric phase space defined by the kinematic variable $X(R)=V(R)/R$ and the photometric variable $Y(R)=\mathrm{d}\ln I/\mathrm{d}\ln R$, placing the local gravitational scale and the logarithmic surface brightness gradient into direct pointwise correspondence at each galactocentric radius $R$. The quantity $X=V/R=\omega$ represents the angular frequency of circular motion and acts as a probe of the local mean mass density, while $Y$ measures the radial steepness of the
stellar light distribution. The
baryon-dominated inner disc is characterized by large negative $Y$, whereas the dark-matter-dominated outer region approaches $Y\rightarrow0$. This two-regime behaviour is described by the smooth sigmoid relation $Y=[a\ln X+b]/(1+\exp[k(X-X_{\rm trans})])$, which reduces to the logarithmic coupling $Y=a\ln X+b$ in the baryonic zone. We apply this framework to 136 late-type
galaxies from the SPARC database, spanning inclinations $20^{\circ}$–$89^{\circ}$, distances $1$–$130$\,Mpc, and five decades in
stellar mass. The median coefficient of determination is $R^{2}=0.930$. Statistical validation includes eight independent tests together with 5-fold cross-validation. The transition parameter $X_{\rm trans}$ identifies the onset of dark-matter dominance, corresponding to a median transition radius $R_{\rm trans}=5.40$\,kpc across the sample.
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Astrophysics of Galaxies
Antimatter in the universe and Milky Way
A.D. Dolgov
Theoretical model leading to a significant
Galaxy population by
primordial antimatter is described. Observational data confirming this "crazy" prediction are presented.
Instrumentation and Methods for Astrophysics
Closed-loop Atmospheric Dispersion Correction for High-Contrast Imaging with MagAO-X
Katie Twitchell, Sebastiaan Haffert, Jared R. Males et al. (+17 more)
Incoming starlight is refracted as it enters Earth's atmosphere from the
vacuum of space. The wavelength-dependence of atmospheric refraction causes elongation of the broadband PSF of ground-based
telescopes, especially in the visible spectrum. The result is degraded image quality alongside reduced coronagraph light-blocking efficiency, both of which limit high-contrast observations. An atmospheric dispersion corrector (ADC) is a dispersive optic used to compensate for this effect. Current methods for dispersion compensation use analytical models to anticipate dispersion strength based on parameters such as site altitude and
telescope zenith angle; however, dispersion strength is also dictated by a number of factors that cannot be measured, including instantaneous humidity, temperature, and pressure along the line of sight to the
star. This leads to constant over- or under-correction of the true atmospheric dispersion by the ADC. In this work, we use the Magellan extreme adaptive optics system MagAO-X at Las Campanas Observatory to measure and correct residual atmospheric dispersion in real-time. The amount of residual dispersion is encoded in the orientation of satellite spots generated by using MagAO-X's deformable mirror as a diffraction grating. We have used these real-time measurements as feedback for closed-loop control of the ADCs on-sky at visible and NIR wavelengths, reducing residual atmospheric dispersion down to sub-mas/$\mu$m levels. Active atmospheric dispersion correction on MagAO-X is a precursor to high-contrast imaging with Extreme AO for the upcoming Extremely Large
Telescopes, where high-precision dispersion compensation will be required to image
exoplanets in reflected light.
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All authors Katie Twitchell, Sebastiaan Haffert, Jared R. Males, Laird M. Close, Olivier Guyon, Kyle Van Gorkom, Alexander Hedglen, Parker T. Johnson, Maggie Y. Kautz, Jay K. Kueny, Joshua Liberman, Miles Lucas, Avalon McLeod, Matthijs Mars, Eden A. McEwen, Jialin Li, Joseph D. Long, Jhen Lumbres, Lauren Schatz, Elena Tonucci
Astrophysics of Galaxies
Scaling Relations of Galactic Outflows Across Cosmic Time: New Insights from Cosmic Noon
Tiffany Liou, Xinfeng Xu, Allison L. Strom et al. (+8 more)
Galactic outflows play a significant role in regulating
galaxy evolution. Scaling relations between
stellar mass ($M_\ast$),
star formation (SFR), and
outflow properties have been extensively studied at low
redshifts ($z<1$) but less so beyond $z \sim 2$. We construct a joint sample of 387
galaxies from $z \sim$ 0-9, including 98 new
Cosmic Noon
galaxies from the Keck Baryonic Structure Survey and the Keck Lyman Continuum Spectroscopic Survey. Using high signal-to-noise emission lines (SNR $>$ 50 for H$\alpha$ or [OIII] $\lambda5007$) from Keck/MOSFIRE spectra, we detect warm-ionized
outflows by decomposing lines into narrow and broad components. With the joint sample, we explore the
redshift evolution of
outflow scaling relations. On average,
outflows at
Cosmic Noon have higher maximum velocities than those at low$-z$ by up to a factor of 3 for a fixed $M_\ast$, SFR, or SFR surface density. They also have higher mass
outflow rates for a fixed $M_\ast$. Despite faster and stronger
outflows, there is no
evolution in the mass loading factor for a fixed $M_\ast$. We find evidence for
galactic fountains, as the majority of outflowing gas is recycled at a radius of $\sim$0.03 R$_\textrm{vir}$. We also constrain the overall
outflow occurrence rate in our
galaxy sample to be at least 30$\%$ when taking
galaxy orientation and
outflow geometry into account. By analyzing the largest sample of warm-ionized
outflows at
Cosmic Noon to date and compiling large
galaxy samples across all
redshifts, we present a comprehensive analysis of
galactic outflows throughout
cosmic time.
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All authors Tiffany Liou, Xinfeng Xu, Allison L. Strom, Nathalie A. Korhonen Cuestas, Claude-André Faucher-Giguère, Tim B. Miller, Gwen Rudie, Ryan F. Trainor, Naveen A. Reddy, Charles C. Steidel, Yuguang Chen
Instrumentation and Methods for Astrophysics
windsoCC: reconstructing the wind-driven halo in MagAO-X images using wavefront sensor telemetry
Jay K. Kueny, Jared R. Males, Alycia J. Weinberger et al. (+16 more)
The wind-driven
halo (WDH) is a persistent, low spatial frequency noise artifact that arises due to the servo-lag error inherent to all adaptive optics (AO) instruments. Spatial filtering may be employed to overcome this artifact, however, filtering out the WDH while simultaneously preserving signal from an extended astrophysical object of interest is exceptionally challenging. Additionally, since the WDH changes in intensity and position angle through an observation, data-driven
algorithms (e.g., KLIP) that are commonly used to subtract the starlight need to be overly-aggressive to remove both the static and dynamic noise components. Since wavefront sensors (WFSs) continuously track the closed-loop residual wavefront error, WFS telemetry presents the ideal resource for combating this type of noise artifact through postprocessing. Using archival WFS telemetry from MagAO-X, which is the “extreme" AO instrument for the 6.5-meter Magellan-Clay
telescope, we demonstrate a novel workflow for WDH reconstruction and removal in individual coronagraphic science images. MagAO-X is equipped with a pyramid WFS capable of recording wavefront telemetry at a high-cadence which is saved during data acquisition. Given this, we detail how our WFS data processing pipeline, windsoCC, cross-correlates the recorded closed-loop wavefront to measure the wind vectors of several turbulent layers of the atmosphere above Las Campanas Observatory. We then make use of the wind parameters learned through windsoCC to reconstruct the WDH footprint by leveraging a parametric model. Notably, we demonstrate a dramatic improvement in object recovery using on-sky MagAO-X images of the disk around HR~4796A at visible wavelengths.
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All authors Jay K. Kueny, Jared R. Males, Alycia J. Weinberger, Laird M. Close, Joseph D. Long, Joshua Liberman, Sebastiaan Haffert, Eden McEwen, Maggie Y. Kautz, Olivier Guyon, Logan Pearce, Parker T. Johnson, Katie Twitchell, Jialin Li, Alex Hedglen, Avalon Gower, Warren Foster, Jhen Lumbres, Lauren Schatz
Instrumentation and Methods for Astrophysics
Lunar Reflective Interferometry
Peter W. Gorham, T. Joseph W. Lazio, Andrew Romero-Wolf et al. (+14 more)
We present the method of lunar reflection interferometry (LRI) in which a virtual interferometer can be formed by using a spacecraft-borne
antenna in lunar orbit that receives both direct rays and those reflected from the lunar surface. The technique exploits the method of images and is akin to the classic "sea cliff" interferometer, with the Moon's surface, primarily the lunar Maria, replacing the ocean surface. We describe the method in detail, demonstrate that significant portions of the Moon's surface are sufficiently smooth at low
radio frequencies, $\nu \lesssim 10\,\mathrm{MHz}$, for the technique to work, and outline a spacecraft instrument implementation. We describe potential systematic errors and how they could be mitigated. We present several astrophysics applications of the method.
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All authors Peter W. Gorham, T. Joseph W. Lazio, Andrew Romero-Wolf, Patrick S. Allison, Marin M. Anderson, Ali M. Bramson, Roman Burridge, Amy Connolly, Emily S. Costello, Cosmin Deaconu, Susan Lepri, Christian Miki, Eric Oberla, Sean Peters, Kathryn Plant, Julie Rolla, Matthew Siegler
Instrumentation and Methods for Astrophysics
Tabular foundation models for the estimation of probabilistic quasar photometric redshifts in S-PLUS
Raquel R. Valença, Lilianne Nakazono, Rafael Izbicki et al. (+6 more)
We assess whether tabular foundation models can be used as off-the-shelf probabilistic photometric-
redshift estimators for
quasars in the 12-band S-PLUS DR6 survey, where colour-
redshift degeneracies produce multi-modal posteriors and spectroscopic training sets are shifted relative to the photometric population. TabPFN 2.5, RealTabPFN 2.5, and TabICL are benchmarked against eight task-specific baselines, including linear conditional Gaussians, FlexZBoost, mixture-density networks, normalising flows, random forests, and gradient-boosted trees, with training sets from 500 to 121,626
quasars, using both density and point-prediction metrics, together with importance-weighted scores that approximate deployment on the photometric target sample. TabPFN 2.5 is best or statistically tied for best on all metrics except the unweighted CDE loss, on which the normalising flow is statistically tied and attains the lowest mean value; its largest gains occur for small training sets and in difficult regimes (very bright and faint sources, high
redshift), while retaining near-nominal calibration under
covariate shift. Its main practical cost is inference: with frozen weights, large support and target catalogues require substantial GPU/accelerator
memory, and full-catalogue deployment may need support-set subsampling or
distillation. SHAP attributions identify WISE W1/W2 as the strongest individual predictors, with UV and optical bands offering non-negligible refinements. We conclude that TabPFN 2.5 is a strong default for probabilistic
quasar photo-z estimation, particularly when training data are limited or when calibration under
covariate shift is critical.
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All authors Raquel R. Valença, Lilianne Nakazono, Rafael Izbicki, Marco Henrique de Almeida Inácio, Bruno Marcondes e Resende, Maycon Jorge Deláqua da Silva, Kiana Coimbra Buin Lins, Natanael M. Cardoso, Claudia Mendes de Oliveira
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
On the nature of oscillating modes of proto-neutron stars
Dimitra Tseneklidou, Alejandro Torres-Forne, Pablo Cerda-Duran et al. (+2 more)
Newborn proto-
neutron stars (PNS) are potential targets of gravitational wave asteroseismology, the study of the (inner) structure of
stars via their oscillation modes. To prepare for the eventual detection of such modes by current and future gravitational wave observatories, theoretical studies have obtained the possible spectrum of oscillations. However, there has been disagreement when it comes to identifying and classifying specific modes according to the physical mechanism that excites them. In this paper, we present a novel scheme to classify the oscillation modes of a newly born PNS surrounded by a stalled
accretion shock in core-collapse
supernovae (CCSNe). Our classification is physically motivated, as it is based on the energy of the restoring forces of the mode. We investigate the nature of the modes by considering the different regions of the CCSN that they stem from. We apply this scheme to a set of 28 non-rotating 1D, 2D and 3D CCSN simulations performed with two different numerical codes and using different progenitors and equations of state. In that way, we find that there are different families of f-, p- and g-modes in the system, living in different areas. More specifically, we identify two families of f- and p-modes associated with the PNS and the shock, respectively, and two families of g-modes originating from the two convectively stable regions, one in the PNS core and one near its surface. We also find that the dominant high-frequency emission mode is the f-mode of the PNS, associated with the strong density gradient at its surface. Our classification procedure is automatic, performs consistently for all the models considered, and paves the way to systematic studies of the dependence of the mode frequencies on the PNS properties, with direct application to parameter estimation from future observations of gravitational wave signals.
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All authors Dimitra Tseneklidou, Alejandro Torres-Forne, Pablo Cerda-Duran, Martin Obergaulinger, Jose Antonio Font
High Energy Astrophysical Phenomena
Astrophysical Constraints on Hadron–Quark Crossover in Hybrid Neutron Stars
Gábor László Kasza and György Wolf
We investigate astrophysical constraints on hybrid
neutron-
star equations of state constructed by combining an extended linear sigma model description of
quark matter with several representative hadronic equations of state through a smooth
hadron–
quark crossover. Four different hadronic models are examined in order to explore the model dependence of the resulting hybrid equations of state. After imposing stability, causality, perturbative QCD matching,
tidal deformability, and maximum-mass constraints, only the eLSM+GMSR(BSK16) construction remains fully consistent with current astrophysical observations. The surviving parameterizations are further constrained using
Bayesian inference based on NICER mass–radius measurements and the GW170817 gravitational-wave event. The posterior distributions favor a broad
hadron–
quark crossover occurring at relatively high
baryon densities, while the formation of extended pure
quark cores is strongly disfavored. Instead, the current observations favor
neutron stars containing an extended mixed
hadron–
quark transition region. We also investigate the implications of the inferred maximum-mass distribution for the secondary object of GW190814 and find that, within the present model and adopted observational constraints, its interpretation as a
neutron star is unlikely.
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Solar and Stellar Astrophysics
Astro+ database. I. Description and first results
K. Rübke, A. Marco, I. Negueruela et al. (+4 more)
The vast amounts of spectroscopic data for massive
stars provided by previous and existing instruments on ground-based and space-based
telescopes have saturated our capability to process them by human inspection routines. Consequently, there is a pressing need for fully automatic machine-assisted tools to help handle incoming data. To this end, we present the development of a massive
star spectroscopic interactive database, Astro+. We aim to provide users with a reliable, versatile, and user-friendly platform that will be significant for understanding massive
stars and set an important precedent for future open-access astrophysical research. This tool allows authorized users to upload their own spectra and, by using the fully automated tool HiLineThere, a Python-based program, it can homogeneously derive basic
stellar parameters, such as v_rad, v sin i, Teff and log g for massive OB-type
stars, using a
solar-
metallicity grid of FASTWIND models, and v_rad, [Fe/H], Teff and log g for red supergiant
stars, in a completely autonomous way. Here we present the first results of the tool HiLineThere on optical spectra for OB-type
stars and red supergiants. We compare the output of our analysis for OB-type
stars with literature values for a large sample of well-studied objects, finding differences within the expected error ranges: Teff ~ 800 K, log g ~ 0.1 dex, and v sin i ~ 10 km/s. Preliminary tests on early-B
stars also show consistent results during the transition to lower temperatures. For red supergiants, we find differences within 7 km/s in v_rad and ~300 K in Teff for two test samples.
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All authors K. Rübke, A. Marco, I. Negueruela, A. Herrero, S. Simón-Díaz, H. M. Tabernero, L. R. Patrick
Solar and Stellar Astrophysics
The Carbon Giant Population Revealed by Gaia DR3
Benjamin R. Roulston and Paul J. Green
Classical carbon
stars (atmospheric C/O >1) are asymptotic
giant branch (AGB)
stars that become carbon-rich through third dredge-up during the thermally pulsing AGB phase. However, carbon
stars also occur among red
giants and main-sequence
stars, where the carbon is thought to originate from binary mass transfer from a former AGB companion. Using the all-sky catalog of G<16.5 mag
Gaia DR3 carbon
stars from Roulston et al. (2025), we investigate a uniform, high-confidence sample of carbon
giants in the Milky Way, its globular clusters, and nearby Local Group
galaxies. We identify 6937 carbon
giants in the Large Magellanic Cloud, 2148 in the Small Magellanic Cloud, and 219 associated with the Sagittarius
dwarf spheroidal, nearly quadrupling the previously known sample in the latter. We identify several candidate carbon symbiotic
stars through their X-ray counterparts. The mean absolute C-AGB magnitude, $M^0_J=-6.30$ in the LMC and -6.15 in the SMC, agrees closely with the photometrically derived values of Ripoche et al. (2020), reinforcing the utility of carbon AGB
stars as distance indicators. From 4276
Galactic carbon
giants with $M_G<0$ and $|b|>5^\circ$, we measure a local disk space density of $n_0=11\pm0.5\times10^{-8},\mathrm{pc}^{-3}$ and a scale height of $H_z=257\pm4$ pc. Lower-luminosity carbon
giants exhibit significantly larger
Gaia DR3 RUWE values than C-AGB
stars, providing strong evidence that most are extrinsic post-mass-transfer systems, likely evolved
dwarf carbon
stars. C-AGB
stars are more tightly confined to the
Galactic disk and are rare inside $R\lesssim7$ kpc, consistent with
Galactic age and
metallicity gradients, whereas the lower-luminosity carbon
giants have a larger scale height and require an additional
halo component.
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Astrophysics of Galaxies
Electron temperature and emission measure of HII regions in the central molecular zone (CMZ) from H40 \alpha recombination line and continuum emissions by ALMA CMZ Exploration Survey - ACES -
Yoshiaki Sofue, Steven N. Longmore, Daniel Walker et al. (+40 more)
Star formation activity in the Central Molecular Zone (CMZ) directly manifests itself as
radio continuum free-free emission (Bremsstrahlung) and
radio recombination line emission from HII regions surrounding newly formed massive
stars. We derive the overall distribution of the HII regions and their fundamental properties: electron temperature ($\Te$) and emission measure ($EM$), and hence electron density in the form of two dimensional distribution maps over the CMZ by analyzing the ACES (ALMA CMZ Exploration Survey) \h40 (99.02 GHz) recombination line and 99.6 GHz continuum emission data with synthesized beam widths of $2''.45$ (0.097 pc at 8.2 kpc) and $2''.14$, respectively. We apply the 'TeEM' method ($\Te$–$EM$ mapping), which creates $\Te$ and $EM$ maps from input 2D maps of the continuum and integrated line intensity. The analysis covers the entire ACES field from $l\sim -0^\circ.6$ to $+0^\circ.8$ and from $b\sim -0^\circ.2$ to $+0^\circ.1$. The area analyzed is complete and includes previously known HII regions such as Sgr B2, Sgr B1, the Sickle, the Pistol, thermal filaments (Bridges), Sgr A HII regions, the Minispiral, and many other known HII regions. Sgr C is not included in the analysis due to the insufficient signal-to-noise ratio in the recombination line map. The mean electron temperature over the CMZ is determined to be $\Tcmz= 5872 \pm 78 ~{\rm (SE)} ~\pm 3682~{\rm (SD)}$ K (SE:standard error of the mean, SD: pixel-to-pixel standard deviation). Some HII regions, such as Sgr B2 Main and the Minispiral, exhibit large scatter and an internal $\Te$ gradient of several thousand K per parsec. The $EM$ distribution is more diverse, varying by orders of magnitude from $\sim 10^5$ to $\sim 3\times 10^8$ \emunit within the CMZ, as well as within individual HII regions.
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All authors Yoshiaki Sofue, Steven N. Longmore, Daniel Walker, Adam Ginsburg, Jonathan D. Henshaw, John Bally, Ashley T. Barnes, Cara Battersby, Laura Colzi, Paul Ho, Izaskun Jimenez-serra, Elizabeth Mills, Maya A. Petkova, Mattia C. Sormani, Jennifer Wallace, Robin G. Tress, Nazar Budaiev, Rojita Buddhacharya, Christoph Federrath, Zi-xuan Feng, Pablo García, Savannah Gramze, Christian Henkel, Pei-ying Hsieh, Fengwei Xu, Katharina Immer, Dani Lipman, Dariusz C. Lis, Álvaro Sánchez-Monge, Xing Lu, Mark R. Morris, Francisco Nogueras-Lara, JÜrgen Ott, Dylan M. Paré, Jaime E. Pineda, Víctor M. Rivilla, Jairo Armijos-Abendaño, Qizhou Zhang, 6Denise Riquelme-vásquez, Howard a. Smith, Marco Donati, Q. Daniel Wang, N. Bijas
Instrumentation and Methods for Astrophysics
The final design of GMagAO-X: high-contrast imaging at first-light of the GMT
Jared R. Males, Laird M. Close, Sebastiaan Y. Haffert et al. (+13 more)
GMagAO-X will be the first-light high-contrast imager on the 25 m
Giant Magellan
Telescope. The driving science case for GMagAO-X is characterization of the atmospheres of nearby rocky
exoplanets such as Proxima Centauri b. The revolutionary increase in spatial resolution and sensitivity provided by GMagAO-X will enable detailed study of such
planets for the first time. Additional science cases include: reflected light characterization of mature
giant planets; measurement of young extrasolar
giant planet variability; characterization of circumstellar disks at unprecedented spatial resolution; characterization of
benchmark stellar atmospheres at high spectral resolution; and mapping of resolved objects such as
giant stars and asteroids. These, and many more, science cases will be enabled by a 21,000 actuator extreme adaptive optics (ExAO) system, an integrated coronagraphic wavefront control system with dedicated deformable mirrors, and a suite of imagers and spectrographs. Science-driven performance requirements for GMagAO-X include achieving a Strehl ratio of 70% at 800 nm on 8th mag and brighter
stars, and
exoplanet characterization at
planet:
star flux-ratios of 1e-7 at 4 lambda/D (26 mas at 800 nm) separation. GMagAO-X has been added to the GMT project baseline plan and is in the final design phase, aiming to complete FDR in March, 2027. The instrument is on track to be ready at first-light of the GMT in the mid 2030s. We provide a brief update of the instrument designed to achieve our ambitious performance targets.
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All authors Jared R. Males, Laird M. Close, Sebastiaan Y. Haffert, Victor Gasho, Adam Fletcher, Joseph Boales, Dhruv Lakhani, Maggie Y. Kautz, Doug Kelly, Olivier Durney, Thomas Salanski, Peter Gray, Cody Nelson, Steven Cornelissen, Paul Bierden, Olivier Guyon
Solar and Stellar Astrophysics
Parametric Study of the Torus Instability Threshold
Jun Chen, Bernhard Kliem and Rui Liu
The
torus instability of an arched current channel has been suggested to initiate and drive major
solar and
stellar eruptions. Its threshold, given by the critical decay index of the
equilibrium external poloidal field (the so-called strapping field) at the position of the current channel, is insufficiently known. Here, we carry out a parametric numerical study of the threshold, employing the force-free Titov-Démoulin (TD)
equilibrium of a line-tied partial toroidal current channel and flux rope. This addresses the scatter of the threshold about its canonical value, $n_\mathrm{cr}=3/2$. Values scattering in the range $n_\mathrm{cr}\approx$\,1–2 are typically found in numerical and observational studies of flux rope eruptions on the Sun. For zero external toroidal (guide, or shear) field and approximately semicircular geometry (corresponding to minimal photospheric line-tying), we find the threshold to lie in the theoretically expected range of $\approx$\,1–1.5. An external toroidal field introduces a strong stabilizing effect on the instability, raising the threshold up to $\sim$\,2.5, which can explain observational and numerical results above the canonical value. Line-tying is found to act as a stabilizer as well. We also consider the approximate threshold based on the potential field and find a very good agreement with the exact numerical value, provided the horizontal component perpendicular to the flux rope axis is used to approximate the external poloidal field.
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Instrumentation and Methods for Astrophysics
Sensor fusion on MagAO-X: real time vibration control using accelerometers
Parker T. Johnson, Jared R. Males, Povilas Palunas et al. (+16 more)
Mechanical vibrations are a significant source of residual wavefront error (WFE) in adaptive optics (AO) systems, limiting the performance of high-contrast imaging instruments. We present the design and on-sky deployment of a low-cost, modular accelerometer telemetry system for the MagAO-X extreme AO instrument on the 6.5 m Magellan Clay
Telescope, consisting of piezoelectric accelerometers and a Raspberry Pi-based acquisition system that streams synchronized data to the real-time control computer with microsecond-level timing stability. The system is used to identify dominant
telescope vibration sources and quantify their coupling to AO telemetry, revealing that several narrow-band modes originate from subsystems including the primary mirror glycol pump, secondary mirror actuation system, and
telescope autofocus system. Coherence analysis between the synchronized accelerometer and wavefront sensor telemetry demonstrates that approximately one-third of the residual tip and tilt WFE is correlated with structural vibrations, indicating that accelerometer telemetry provides a promising foundation for future predictive control implementations. These results demonstrate that low-cost accelerometer telemetry provides a practical approach for vibration identification and a foundation for predictive control in current and future AO systems.
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All authors Parker T. Johnson, Jared R. Males, Povilas Palunas, Olivier Guyon, Sebastiaan Haffert, Joseph Long, Vincent Deo, Julien Lozi, Laird M. Close, Maggie Kautz, Jay Kueny, Jialin Li, Joshua Liberman, Miles Lucas, Matthijs Mars, Eden McEwen, Tiffany Nguyen, Elena Tonucci, Katie Twitchell
Instrumentation and Methods for Astrophysics
Wavelength Calibration Accuracy Across the STIS CCD: Pipeline Update and User Guidance
Matilde Mingozzi, Robert Jedrzejewski, Matthew Siebert et al. (+3 more)
We investigate the wavelength calibration accuracy of STIS CCD spectra as a function of detector position, focusing on the E1/E2 pseudo-apertures. Comparison between measured lamp line centroids and laboratory wavelengths shows that, while the standard calstis solution is stable at the detector center, significant offsets are present toward the CCD edges and increase with time. We used a test version of calstis in which the wavelength calibration step employs a row-selected cross-correlation, leading to improved wavelength calibration accuracy for edge extractions. Motivated by these results, we implemented an update to calstis4 that applies a row-selected wavecal procedure to observations taken with the E1/E2 pseudo-apertures, while preserving the standard procedure for nominal extractions. The updated pipeline was then used to reprocess the entire STIS archive in MAST. Validation tests confirm improved agreement between nominal and E1/E2 spectra without significant side effects for more than 97% of the
datasets in the MAST archive. The main exceptions are the majority of G230MB and a few G230LB and G430M
datasets, where the lower signal-to-noise at the CCD edge makes the lamp lines harder to detect and
cosmic-ray residuals can dominate the cross-correlation, leading to incorrect wavelength shifts. A Jupyter Notebook is also provided to enable similar corrections in case the cross-correlation fails, for extractions at positions other than E1/E2, or for multiple extractions along the slit. Finally, we discuss the potential impact of the wavelength calibration accuracy on science results.
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All authors Matilde Mingozzi, Robert Jedrzejewski, Matthew Siebert, Daniel Welty, Sean Lockwood, Joleen Carlberg
Astrophysics of Galaxies
The Rotation Curve of the Milky Way: State of the Art, the Keplerian Decline Debate, and Implications for Dark Matter
Alessandro Melchiorri and Ruchika
For four decades, the roughly flat rotation curve (RC) of the Milky Way (MW) stood as local evidence for an extended dark matter (DM)
halo.
Gaia DR3 has changed the picture: several analyses now find a velocity decline beyond R \approx 15\kpc, and the most radical interpretation \citep{jiao2023} claims a nearly Keplerian fall-off (\vc \propto R^{-1/2}) that excludes a flat RC at 3\sigma and implies a total dynamical mass of only \sim 2 \times 10^{11}\Msun—three to five times below pre-
Gaia estimates. Taken at face value, this would make the MW exceptional among comparable spirals and challenge both \Lambda-CDM and MOND. It would also alter predictions for direct-detection experiments, although the local DM density is not fixed by virial mass alone. The Keplerian claim rests on the delicate assumptions of axisymmetric Jeans modelling, while
stellar streams, globular clusters, satellite kinematics, and the Local Group timing argument generally favour a substantially heavier
halo, and cosmological simulations reveal potentially substantial biases in Jeans-inferred outer RCs. This review offers a self-contained, pedagogical account of the debate: we derive the full formalism from first principles—the Jeans equations, the asymmetric drift correction, the standard DM
halo and baryonic mass models, the MOND flat-RC prediction, and the timing argument—present an illustrative phenomenological MCMC fit and a Gaussian Process reconstruction of the RC, and critically assess which features of the decline can be regarded as established and which remain open.
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Astrophysics of Galaxies
Constructing X-ray Spectral Models of Galaxies: Varying Contributions from X-ray Binary Populations with Host Galaxy Properties
Emerson Gehr, Bret D. Lehmer, Antara R. Basu-Zych et al. (+7 more)
Recent work has shown that the emission from X-ray binary (XRB) populations in
galaxies varies with
stellar mass ($M_\star$),
star formation rate (SFR), and
metallicity ($Z$). Such scaling relations are widely used to predict the XRB contributions to
galaxy-integrated X-ray luminosities including studies focused on
dwarf active
galactic nuclei (AGN) and the X-ray radiation field during the epoch of heating in the early ($z \geq 8$) universe. However, as
galaxies approach low SFR and low $Z$, the relatively shallow slope of the XRB luminosity function (XLF) can yield very large
stochastic variations in the total X-ray luminosity expected from the XRB population, for fixed values of $M_\star$, SFR, and $Z$. We have created a procedure to statistically sample any XLF and model total X-ray spectra for XRB populations and their
stochastic uncertainties. We demonstrate the accuracy of this procedure using data for
galaxies ranging from high to low $M_\star$, SFR, and $Z$ and generating X-ray spectral models consistent with Chandra observations. For
galaxies that lie on the
galactic main-sequence, we can relate SFR and $Z$ to $M_\star$ using established $M_\star$-SFR and $M_\star$-$Z$ relations. Applying these relations, we construct main-sequence (MS) XRB spectral models, which provide typical XRB spectral shapes, normalizations, and uncertainties as a function of $M_\star$. The spectral model library associated with this work is available at https://doi.org/10.5281/zenodo.20126734.
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All authors Emerson Gehr, Bret D. Lehmer, Antara R. Basu-Zych, Konstantinos Kovlakas, Vianney Lebouteiller, Erik B. Monson, Izabela Pavel, Chris Richardson, Maxime Varese, Zachary Wilson
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
A parametrized test of general relativity for inspiralling eccentric binaries in LISA
Pankaj Saini, Sylvain Marsat, Lorenz Zwick et al. (+2 more)
The space-based detector
Laser Interferometer Space
Antenna (LISA) will observe inspiralling black hole binaries in the mHz band, many of which may retain orbital eccentricity. In contrast to quasicircular binaries, eccentric systems radiate through multiple orbital harmonics, while relativistic periastron precession introduces a secular phase structure in the waveform. We exploit this structure to develop a parametrized test of general relativity (GR) for eccentric bound orbits. We construct a frequency-domain eccentric waveform model in which a phenomenological deviation parameter $\delta\alpha$ modifies the GR prediction for the conservative azimuthal-to-radial frequency ratio, with $\delta\alpha=0$ corresponding to GR. We consider two parametrizations of this deformation. In the first, $\delta\alpha$ modifies only the explicit precession-dependent sideband structures of the waveform. In the second, the secular precession phase is assigned to the dominant lower-order angular carriers and retained in resummed form. The latter produces a substantially stronger response because the dominant waveform components coherently accumulate the modified phase. We implement both models within lisabeta and perform a
Bayesian analysis including the time- and frequency-dependent LISA response and associated time-delay-interferometry observables. We find that LISA can place stringent constraints on the parametrized deviation. For a binary with chirp mass $3000 M_{\odot}$, initial eccentricity $e_0=0.5$ observed for four years at an SNR of $50$, the second model yields a $90\%$ credible bound of $|\delta\alpha|\lesssim 10^{-4}$. Increasing eccentricity further sharpens the constraints by introducing additional harmonic structure and reducing degeneracies among the binary parameters. The framework developed here is general and can be extended to more complete eccentric waveform models.
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All authors Pankaj Saini, Sylvain Marsat, Lorenz Zwick, János Takátsy, Johan Samsing
Instrumentation and Methods for Astrophysics
CCD Rotation Rates From Regular Dispersion Solution Monitoring
Matilde Mingozzi and Matthew Siebert
It has been previously studied that the STIS CCD exhibits a slow rotation, evident from changes in spectral traces and flat-field
evolution. In this Instrument Science Report, we present an independent spectroscopic analysis of the CCD rotation angle and a comparison with previous studies. We describe the methodology used to derive rotation angles and rates across different gratings and central wavelengths, and report the corresponding median rotation rates over time. The results are broadly consistent within uncertainties with earlier measurements, indicating the CCD rotation has the same impact on all the CCD gratings. We also discuss key assumptions limiting our analysis. These findings contribute to the ongoing monitoring of STIS CCD rotation and its implications for calibration accuracy.
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Astrophysics of Galaxies
The Extended Mapping Obscuration to Reionization with ALMA (Ex-MORA) Survey: A Molecular Gas Line Search
V. Catán, J. González-López, M. Aravena et al. (+9 more)
Current investigations of cold gas in the interstellar medium face selection biases, as optical/near-infrared surveys favor massive, low-obscuration
galaxies and miss gas-rich passive or inefficient
star-forming systems. Overcoming this requires large-volume line surveys selected by molecular gas rather than
stellar luminosity. We present a molecular gas census across $0.5 < z < 5$ using ALMA Band 4 observations from the Extended Mapping of Obscuration to Reionization Survey (Ex-MORA), covering 577 arcmin$^2$. Combining an unbiased search for bright emitters with a targeted search using spectroscopic
redshift priors, we detect 52
galaxies in CO or \ci transitions (two showing two lines). Physical properties were derived via CIGALE with non-parametric
star-formation histories, and gas masses were estimated using
metallicity-dependent conversion factors. The sample is dominated by main-sequence (MS)
galaxies with high
stellar masses (median $\log M_*/\text{M}_{\odot} = 10.83$) and large gas reservoirs ($>10^{10}\,\text{M}_{\odot}$). Gas fraction ($\mu_{\text{gas}}$) increases with
redshift for active populations, though high-
redshift trends are influenced by a gas-rich protocluster at $z \approx 2.4$. Conversely, an overdensity at $z \approx 0.73$ mirrors the field population. Five Green Valley (GV)
galaxies exhibit a $\mu_{\text{gas}}$ peak at
cosmic noon, suggesting
stellar feedback may suppress
star formation by heating gas rather than rapidly depleting it in at least some transitional systems. Resolved kinematics show a prevalence of rotating disks. These results demonstrate that wide-area line searches effectively recover massive gas reservoirs across diverse evolutionary stages
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All authors V. Catán, J. González-López, M. Aravena, A.S. Long, C.M. Casey, D.L. Clements, E. da Cunha, M. Franco, A.M. Koekemoer, A. Man, J. Spilker, E. Treister
Cosmology and Nongalactic Astrophysics
CORN – Chronometers of Relic Nature I: The first estimate of the expansion rate of the Universe using compact relic galaxies
Krzysztof Lisiecki, Nicola Principi Cavaterra, Agnieszka Pollo et al. (+9 more)
Measuring the expansion rate of the Universe is a central challenge in cosmology. Independent and robust methods are essential to validate existing measurements and assess potential systematic effects. We employ the
cosmic chronometer (CC) approach, which uses the differential age
evolution of quiescent
galaxies to measure the Hubble parameter H(z) without assuming an underlying cosmological model. In contrast to previous CC studies, we restrict our analysis to relics – ultra compact massive
galaxies (UCMGs) hosting the oldest
stellar populations – thereby minimising uncertainties related to
star formation history and merger history. We select a sample of 189 relic
galaxies in the
redshift range 0.07< z <0.22 from the E-INSPIRE UCMGs catalogue. Using the D_n4000 spectral index of relic
galaxies and its
redshift evolution, combined with MILES
stellar population synthesis models, we derive the differential age relation required to infer H(z). We account not only for
metallicity effects but also for the impact of alpha-element enhancement, which has not been explicitly propagated into the systematic uncertainty budget of the D_n4000
cosmic chronometer method. We obtain an independent measurement of H(z=0.15) = 85\pm53 km/s/Mpc. The total uncertainty is dominated by statistical limitations. The systematic component is 13% (8.7% when alpha-enrichment is not propagated), among the tightest estimates in current CC studies. We find that alpha-enrichment plays a major role in the systematic error budget, particularly in the high
metallicity regime, and must be properly accounted for in future analyses. We demonstrate the proof of concept that relic
galaxies provide a promising pathway to reduce systematic uncertainties in the CC method. The statistical uncertainties, which dominate the error budget, can be significantly reduced by the increase of data volume expected during the next years.
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All authors Krzysztof Lisiecki, Nicola Principi Cavaterra, Agnieszka Pollo, Chiara Spiniello, Laura Hunt, Charlie Rosen, Marek Biesiada, Darko Donevski, Patryk Matera, Giuliano Lorenzon, Katarzyna Małek, John Mills
Instrumentation and Methods for Astrophysics
The eXtreme Wavefront Control Toolkit: High-Contrast Imaging Instrument Control for Ground and Space-Based Coronagraphs
Jared R. Males, Joseph D. Long, Sebastiaan Y. Haffert et al. (+16 more)
We present the eXtreme Wavefront Control Toolkit (XWCTk) instrument control software system developed for the MagAO-X extreme adaptive optics (ExAO) instrument. The XWCTk is built on a foundation of the ImageStreamIO (ISIO) / MILK / CACAO low-latency image processing and high dimensional control tool chain. Instrument control is managed with the Instrument Neutral Distributed Interface (INDI). The application framework provides configuration, logging, and distributed IPC with INDI and low-latency IPC with ISIO. On MagAO-X, every detector is a potential wavefront sensor capable of sending commands to three separate DMs. MagAO-X utilizes a distributed control system, where multiple computers each manage low-latency wavefront control tasks but are capable of coordinated control. Implemented
algorithms include neural networks for nonlinear reconstruction at over 3 kHz. We have incorporated distributed raspberry pis for accelerometer data acquisition with low-latency streaming to the real-time computers for sensor fusion control. A core design principle of the XWCTk is that all data can be saved all the time. This includes full-rate WFS images, DM commands, as well as science data. To facilitate this we have implemented a custom lossless compression system capable of sustaining high data rates to disk. A python interface for scripting and experimentation, as well as a python application framework is provided which can be used for non-real-time tasks. Remote operations (e.g. from Tucson Arizona when the instrument is at LCO in Chile) are routine. The XWCTk is under continuous development for the MagAO-X instrument, and will be adapted for GMagAO-X, the planned first-light ExAO coronagraph for the
Giant Magellan
Telescope. XWCTk is the baseline for a space high contrast imaging instrument, and as such ongoing development is focused on automation for robust operation in flight.
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All authors Jared R. Males, Joseph D. Long, Sebastiaan Y. Haffert, Kyle Van Gorkom, Parker Johnson, Rico Landman, Eden McEwen, Olivier Guyon, Vincent Deo, Miles Lucas, Irina Stefan, Katie Twitchell, Jay Kueny, Joshua Liberman, Adam K. Taras, Adam Schilperoort, Matthijs Mars, Ewan S. Douglas, Laird M. Close
Instrumentation and Methods for Astrophysics
Freezing the speckles: focal plane wavefront sensing with the spatially-clipped self-coherent camera
Joshua Liberman, Sebastiaan Y. Haffert, Jared R. Males et al. (+8 more)
The next generation of Extremely Large
Telescopes (ELTs) and the Habitable Worlds Observatory (HWO) require active speckle suppression to directly image exo-Earths. Focal plane wavefront sensing and control allows us to detect and remove time-varying speckles through measurements of the electric field. Wavefront sensing approaches include pairwise probing (PWP) and the self-coherent camera (SCC). However, the PWP technique is time-consuming, requiring at least 4 images and reducing the speed at which aberrations can be eliminated. The classical SCC modifies a standard coronagraph design, creating a reference electric field that interferes with speckles in the final focal plane, forming Fizeau fringes. However, this design only works over small spectral bandwidths and requires significantly oversized optics, limiting its effectiveness. We demonstrate a new SCC variant, the Spatially-Clipped SCC (SCSCC). The SCSCC utilizes a pinhole placed close to the Lyot stop, reducing the overall beam footprint and boosting the sensor's spectral bandwidth by factors of 3, respectively. A beamsplitter and knife edge downstream of the Lyot stop splits the light into 2 channels: fringed and unfringed, enabling wavefront sensing with a single exposure. Time-varying speckles are frozen in place, making them easy to remove. We present the SCSCC optical design combined with the
photon resolving Hamamatsu Orca-Quest 2 camera. Furthermore, we demonstrate high speed wavefront control with the SCSCC, minimizing speckle intensity by 2x within a 5-11 lambda/D dark hole region on the Comprehensive Adaptive Optics and Coronagraph Test Instrument (CACTI) at the University of Arizona. These lab tests are in preparation for an on-sky demonstration of the SCSCC with the MagAO-X instrument. Our results make the SCSCC a valuable wavefront sensor for upcoming missions, including the
Giant Magellan
Telescope and HWO.
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All authors Joshua Liberman, Sebastiaan Y. Haffert, Jared R. Males, Aditya Khandelwal, Stephanie Rinaldi, Joseph D. Long, Katie M. Twitchell, Jay K. Kueny, Ewan S. Douglas, Lauren Schatz, Jhen Lumbres
Solar and Stellar Astrophysics
A Pre-Main Sequence Binary Viewed Through its Circumbinary Disk: A New Phase for KH 15D
Catrina M. Hamilton, Adi B. Chacko, George A. Carson et al. (+16 more)
The binary T Tauri system, KH 15D, is poised to provide unprecedented detail of gas and ices located between $\sim$3-5 AU of its circumbinary disk over the next few years. We analyze for the first time a complete set of ground-based time series photometry of the KH 15D system for which the 2022 October - 2025 April data have never been presented. By combining the latest $I$-band data with historical measurements, we show that the era of large amplitude photometric variability has ended. We define a revised photometric period of $P$ = 48.365 $\pm$ 0.005 days, which accurately phases data over a time span of seventy-five years. We adopt magnitudes and colors for the
stars that define the epochs when either
star A (1995-2008) or
star B (2010-2012) is the primary source of the out-of-eclipse brightness of the system. We determine for the first time the effective optical depth for the system between 2002 and 2025 assuming gray extinction. The current out-of-eclipse system color is consistent with a combination of the light from both
stars, supporting the previously suggested model in which the trailing edge of the circumbinary disk is more transparent than the leading edge. We continue to see evidence for “clumps” and variable transparency along ingress and egress when the
stars are probing the occulting material and suggest that observations made during these phases should permit studies of the physical and chemical nature of the
planet-forming zone with the circumbinary disk.
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All authors Catrina M. Hamilton, Adi B. Chacko, George A. Carson, Aidan J. Pidgeon, C. Nicole Foley, Hillel Finder, Kyle Gimmy, Aleezah Ali, William Herbst, Dirk Froebrich, Brian A. Skiff, Bart Staels, Shawn Dvorak, Jochen Eislöffel, Teryn Huff, Gavin Frueh, Abigail Mead, Lia M. Gilmore, Robert J. Boyle
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Julian Heeck and Yu Zhi
Neutron stars have
baryon chemical potentials that can exceed the
neutron mass, providing favorable conditions to convert
neutrons to new particles carrying
baryon number, even if those processes are kinematically forbidden in
vacuum. We study the effect of GeV-scale scalars with
baryon number on
neutron stars' equation of state and show that non-perturbatively large repulsive self-couplings are required to support the observed two-
solar-mass
neutron stars. We also study potentials with attractive self-interactions, which can trigger scalar production even for masses above the chemical potential and resemble Coleman's Q-matter.
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Instrumentation and Methods for Astrophysics
The Carruthers Mission Concept and Performance
W. Craig, T. Immel, L. Waldrop et al. (+12 more)
The Carruthers Geocoronal Observatory (Carruthers), formerly GLIDE, is a NASA Heliophysics Science Mission of Opportunity implemented through the
Solar Terrestrial Probes (STP) Program and launched as a rideshare in September 2025. Carruthers is the first spaceflight mission edicated to continuous global imaging of Earth's hydrogen exosphere through observations of geocoronal Lyman-$\alpha$ emission at 121.6 nm. The observatory operates at distances of 1.3-1.7 million km in a
halo orbit about the Sun-Earth L1 point, enabling
retrieval of the three-dimensional distribution of atomic hydrogen, the dominant constituent of the exosphere, on hourly timescales and unprecedented spatial resolution. These new data provide the key to understanding processes governing atmospheric escape, geospace coupling, and
solar-wind interaction. Carruthers carries the GeoCoronal Imager (GCI), a dual-channel ultraviolet imaging instrument comprising the Narrow-Field Imager (NFI) for high-resolution observations of the inner exosphere and the Wide-Field Imager (WFI) for synoptic imaging of the extended hydrogen
halo. Along with a student-provided experiment, the instrument suite is the sole payload aboard a three-axis-stabilized spacecraft designed to support nadir viewing throughout the $\sim178$ day
halo orbit about L1. Observations also measure the interplanetary Lyman-$\alpha$ background, enabling separation of heliospheric and geocoronal emissions. The student-led experiment monitors
solar Lyman-$\alpha$ and extreme ultraviolet emission during portions of the orbit. Science data are returned through the Deep Space Network at data rates up to 1 Mbit s$^{-1}$. The two-year baseline mission begins in March 2026, with propellant reserves capable of supporting more than ten years of orbit maintenance and maneuvers.
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All authors W. Craig, T. Immel, L. Waldrop, J. Troeltzsch, E. Taylor, J. McPhate, K. Rider, A. Butterworth, D. Cosgrove, J. Thorsness, H. Filippini, K. Lee, S. Shomo, C. McGinn, C. Peterson
Cosmology and Nongalactic Astrophysics
Evaporation of Primordial Black Holes with Multimodal Mass and Extended Spin Distributions: Cosmological Imprints on the Effective Number of Relativistic Species
T. Toghrai, A. Daassou, Y. Ouchhaine et al. (+2 more)
Primordial black holes (PBHs) form through several distinct mechanisms, each imprinting a characteristic mass function that a single-mass treatment risks erasing. Building on the FRISBHEE code, we introduce FRISHBEE, implementing four mass functions–log-normal, power-law, critical collapse, metric preheating–in a
multimodal framework, with
spin modeled via Gaussian and Fishbach profiles. Crucially, each channel's weight is derived from the
primordial collapse probability rather than fitted, tying the mass function to the power-spectrum amplitude–a link between inflationary model-building and CMB observables. Solving the Friedmann-Boltzmann equations for $M_{\rm PBH}^{\rm in}=10^{7}$~g in the pre-BBN window, we compute $\Delta N_{\rm eff}$ for five distributions, three
spin configurations, and three weightings. Extended mass functions enhance $\Delta N_{\rm eff}$ over the monochromatic
benchmark by factors of $\sim\!1.03$ (critical collapse) to $\sim\!1.84$ (log-normal), preserving the hierarchy $LN > MM > PL > MP > CC$ across the mass window $\{10^{5},10^{7},10^{8}\}$~g. Near-extremal
spin ($a_{\star}=0.99$) and
spin-2 dark radiation invert this trend: superradiant
spin loss averages away faster in broad distributions than in a monochromatic population, letting the monochromatic approximation overestimate $\Delta N_{\rm eff}$. Against CMB-S4 and Simons Observatory sensitivities ($\sigma\simeq 0.06$ and $0.05$), the monochromatic
benchmark is undetectable for scalar dark radiation (sDR $=0$), while log-normal, power-law, and
multimodal distributions reach $\sim\!1.6$–$1.7\sigma$; for
spin-2 dark radiation the signal drops over an order of magnitude, with none detectable. The formation channel thus governs the magnitude and observational accessibility of the Hawking signal, establishing $\Delta N_{\rm eff}$ as a discriminant between single- and multi-channel PBH formation scenarios.
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All authors T. Toghrai, A. Daassou, Y. Ouchhaine, H. Laassiri, R. Benbrik
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Heavy neutral leptons beyond the BBN bound: probing the lepton asymmetry of the Universe
Kensuke Akita, Maksym Ovchynnikov and Vsevolod Syvolap
Hadronically decaying particles with lifetimes $\tau\gtrsim0.02\,{\rm s}$ are excluded by Big Bang Nucleosynthesis almost independently of their abundance: the
mesons from their decays convert
protons into
neutrons faster than the reverse, and helium is overproduced. For heavy neutral
leptons (HNLs), this blankets the couplings the upcoming accelerator searches can reach. We propose a scenario with large
lepton flavor asymmetries in which HNLs evade it. A Dirac HNL decays into $\pi^+$ and its antiparticle into $\pi^-$, so an asymmetry between the two populations injects an excess of $\pi^+$, which converts the
neutrons back to their standard abundance, while a cancellation between the asymmetries and the HNL decays keeps the shift in $N_{\rm eff}$ small. This opens the parameter space with $m_l+m_\pi\lesssim m_N\lesssim1\,{\rm GeV}$ and $\tau_N\lesssim1\,{\rm s}$, including a substantial region within the reach of SHiP. A discovery there, combined with the BBN and CMB observables, would fix the
primordial flavor asymmetries up to one remaining direction. The relic
neutrino background and a possibly first-order
cosmic QCD transition, a source of gravitational waves, may probe that direction, and with it the
lepton asymmetry of the Universe.
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