Instrumentation and Methods for Astrophysics
Numerical Model Simulation of the Carruthers GCI Images
Heather Filippini, Alex Zhang, Evan Widloski et al. (+7 more)
The Carruthers Geocorona Observatory, launched in September 2025, is NASA's first mission devoted to investigating the fundamental nature of Earth's exosphere from its distant vantage in
halo orbit around the Earth-Sun Lagrange (L1) point. Its primary payload, the GeoCoronal Imager, consists of two coaligned photometric imagers that measure the radiance of ultraviolet emission at 121.6 nm (Lyman-$\alpha$, or Ly-$\alpha$) from exospheric hydrogen atoms simultaneously at wide and narrow fields of view. In order to validate the calibration and hydrogen density
retrieval algorithms used in the Carruthers data processing pipeline, we developed a comprehensive numerical simulator to produce realistic images similar to those collected by the actual imagers on orbit. This paper details the
algorithms used to simulate the exospheric emissions, background scene components, and instrument measurement model necessary to produce synthetic raw images.
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All authors Heather Filippini, Alex Zhang, Evan Widloski, Jason McPhate, Lara Waldrop, Thomas Immel, John Clarke, Pratik Joshi, Michal Ondrejcek, Martin M. Sirk
Cosmology and Nongalactic Astrophysics
Higher-Order Analytical Expansion of Thawing Dark Energy with an Exponential Potential
Naoto Maki and Kazunori Kohri
Motivated by recent DESI results suggesting dynamical dark energy, we investigate the thawing scenario in quintessence with an exponential potential, $V=V_0e^{-\lambda\phi/m_{\mathrm{pl}}}$, by analytically expanding the deviation of the equation of state parameter $w_{\phi}$ from $-1$ in powers of $\lambda$. In addition to the previously known leading-order result at $O(\lambda^2)$, we derive the $O(\lambda^4)$ correction as a function of the density parameter $\Omega_\phi$. We show that a consistent determination of the
redshift dependence of $w_\phi$ through $O(\lambda^4)$ requires corrections to the background expansion. We obtain the required correction by expanding $\Omega_\phi$ in powers of $\lambda$ around its $\Lambda\mathrm{CDM}$ value. Comparison with numerical solutions demonstrates that the $O(\lambda^4)$ expansion provides a more accurate approximation than the leading-order result. Our analytical approximation, which consistently incorporates the $O(\lambda^4)$ correction, will provide a potentially useful tool for distinguishing the exponential quintessence model from other dark energy models in future observations.
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Earth and Planetary Astrophysics
No Helium Detected in LHS 1140 b from Four JWST NIRISS/SOSS Transits
Katherine A. Bennett, Carlos Gascón, Jacob Lustig-Yaeger et al. (+13 more)
In the effort to determine which low-mass
exoplanets have atmospheres, LHS 1140 b remains one of the most favorable targets. Its large size (5.6 $\rm M_{\oplus}$ and 1.7 $\rm R_{\oplus}$) and relatively long orbital period (24.7 days) imply an atmosphere may be likely, and notably, recent interior models favor either a hydrogen-dominated "mini-Neptune" or a "water world" over a true terrestrial
planet. Another possibility is that it has a helium-rich atmosphere. This hypothesis is supported by recent ground-based observations that detected the metastable helium triplet during transit. These observations indicated there may be current helium escape from the
planet's upper atmosphere, yet the signal was not detected during a subsequent observation, suggesting time-variable escape. Here we present four observations of LHS 1140 b with JWST NIRISS/SOSS, which covers the metastable helium triplet, obtained between 2023 and 2026. These observations span the epoch of the ground-based measurements, and although none were contemporaneous with the ground-based transits, all four are sensitive to helium absorption at the previously reported level. However, we detect no helium absorption in any visit. We reject the best-fit ground-based model at $>3\sigma$ in each visit, and find no clear trend in mass-loss with time. Our results suggest the reported ground-based detection may be spurious, although variability cannot be excluded if detectable helium absorption occurs in $\lesssim50\%$ of transits. The nature of LHS 1140 b thus remains a mystery until future transmission and emission analyses are complete.
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All authors Katherine A. Bennett, Carlos Gascón, Jacob Lustig-Yaeger, Guangwei Fu, David K. Sing, Kevin B. Stevenson, Jonathan Brande, Munazza K. Alam, Jeff A. Valenti, Mercedes López-Morales, Sten J. Vermeiren, Megan Weiner Mansfield, Sarah E. Moran, Kristin S. Sotzen, Jegug Ih, Sarah Peacock
Earth and Planetary Astrophysics
Strict Limits on Helium Absorption from LHS 1140 b from Four JWST NIRISS Transits
Michael Radica
Orbiting in the habitable zone of its host
star, the 1.7 $R_\oplus$, 5.6 $M_\oplus$
planet LHS 1140 b is a target of great interest. Recently Cherubim et al. (2026) published a detection of metastable He escaping from the atmosphere of LHS 1140 b, simultaneously providing the first concrete inference of an atmosphere on this
planet and indicating that the atmosphere is He-rich and H-poor as would be expected due to Gyrs of fractionated mass loss. In this work, we analyze four archival transits of LHS 1140 b, spanning Dec 2023 to Jul 2026, taken with the NIRISS instrument on JWST, for evidence of He absorption. Each of the four visits disfavours the presence of He absorption compared to a flat continuum with odds ratios ranging from 3.9–11.6:1. He absorption with an amplitude and width equivalent to that observed by Cherubim et al. (2026) is strongly ruled out by the data with odds ratios from 300–8.6$\times$10$^4$:1 compared to a flat continuum — though it should be noted that none of the JWST transits are contemporaneous with the Cherubim et al. (2026) detection. We also fit the absolute out-of-transit
stellar spectra from these four visits, as well as an additional JWST NIRISS transit of
planet c, to search for evidence of
stellar variability, but find consistent photosphere and herterogeneity parameters in all five
datasets. In all, our work provides a set of strict limits on He escape from LHS 1140 b that will be valuable to future studies into the nature and
evolution of this intriguing world.
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Instrumentation and Methods for Astrophysics
JWST MIRI Medium Resolution Spectrometer Point Fixed Pattern Corrections: Cleaner and Higher Signal-to-Noise Spectra of Point Sources
Karl D. Gordon and David R. Law
The JWST Mid-Infrared Instrument Medium Resolution Spectrometer provides the capability to obtain spectra from 5-28 micron. The JWST data reduction pipeline removes the majority but not all of the instrument artifacts and the signal-to-noise (S/N) of the resulting spectra are limited by fixed pattern noise. Building on previous work, Point Fixed Pattern Corrections (PFPCs) are constructed using observations of O, A, and G
dwarf flux calibration
stars and asteroids taken using the default four point dither pattern. The PFPCs can be applied to spectra of point sources taken with target acquisition and the same dither pattern. They can be used alone or with the pipeline residual fringe correction depending on the sources spectral properties. Both narrow and broad artifacts are removed by the PFPCs improving the spectra regardless of their S/N. For higher S/N observations, the PFPCs significantly improve the S/N by up to factors of a few and S/N values of 1000 or more. The MRS-PFPC python package is provided to allow anyone to utilize the PFPCs for their own data.
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Solar and Stellar Astrophysics
The Production of Electron-Capture Elements in Thermonuclear Supernovae: Theory vs. Observations
S. Shiber, P. Hoeflich, T. Mera et al. (+9 more)
Type Ia
supernovae (SNe Ia) explosively destroy carbon-oxygen white
dwarfs (WDs) in multiple
stellar systems. They produce approximately 50% of the iron-group elements in the Universe, synthesize electron-capture (EC) elements, drive
nuclear physics experiments, and underpin high-precision cosmology. To first order, the outcome is governed by
nuclear physics, a property often described as
stellar amnesia. Recently, this
stellar amnesia has begun to be broken by the nearly universal detection of EC elements with JWST. These elements trace high-density burning, largely ruling out the currently popular helium-triggered, sub-Mch detonation models as the dominant channel. Instead, the ubiquitous presence of EC is shifting back the focus to dynamical and secular mergers, and near-Mch explosions similar to the deflagration model W7, but in which the
nuclear flame undergoes a deflagration-to-detonation transition. The early deflagration phase is especially important because spherical simulations identify the central WD density, and thus the WD mass, as a key parameter governing the explosion. Here, we present detailed magneto-hydrodynamical simulations. We find that small-scale, pre-existing
turbulence expected from the pre-explosion smoldering phase is essential for overcoming the fundamental challenges imposed by the intrinsic 3D physics. This
turbulence systematically reduces the production of EC elements by about a factor of two, implying the need for WD central densities closer to those associated with
accretion-induced collapse to a
neutron star. We also demonstrate the effect of
magnetic fields near the saturation field strength and highlight the need for higher-precision EC rates at low Ye.
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All authors S. Shiber, P. Hoeflich, T. Mera, E. Fereidouni, Z. Levy, D. Maci, C. Ashall, K. Medler, J. M. DerKacy, E. Baron, M. Shahbandeh, C. M. Pfeffer
Astrophysics of Galaxies
Widefield Arecibo Virgo Extragalactic Survey: II. Characterizing the HI properties and environment of the WAVES South region
V. Partík, R. Taylor and R. Minchin
Context.
Galaxy clusters are extreme environments where interactions with the hot intracluster medium drive rapid
galaxy evolution. These processes can result in the formation of optically dark gas clouds, as previously observed in Virgo and other clusters. Aims. We investigate the distribution and properties of neutral hydrogen (HI) in two large adjoining regions of the Virgo cluster to understand how the cluster environment influences
galaxy transformation. Specifically, we examine the gas content of both
star-forming and quiescent populations and search for evidence of gas-loss driven
evolution. Methods. We cataloged the 21cm HI Widefield Arecibo Virgo Extragalactic Survey (WAVES) South data using visual and automatic source extraction methods. By combining these results with an optically selected sample, we compared the HI properties of WAVES South with the previously studied VC1 region. To probe gas reservoirs below the nominal detection limit, we performed a stacking analysis of
radio spectra across the WAVES South, VC1 and VC2 footprints. Results. We detected 56 HI sources with a median root mean square (rms) noise of 0.8 mJy, including 50
galaxies, two gas clouds (one being optically dark), and the ALFALFA Virgo 7 complex. Our results reveal a significantly lower detection fraction in WAVES South compared to the VC1 region. Stacking showed no new HI detection at a 0.080 mJy rms with a maximum of 157 stacked objects from WAVES South, VC1, and VC2. Conclusions. The lower HI detection fraction suggests that WAVES South is a more dynamically relaxed and evolved environment than the VC1 region. The presence of residual HI in a small subset of early-type
galaxies supports a model of
dwarf irregular to
dwarf elliptical transformation via environmental stripping. Finally, we note a possible evolutionary link between optically dark clouds and recently discovered "blue blobs."
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Cosmology and Nongalactic Astrophysics
The Most Probable Outer Density Profile from Excursion Set Theory
Ericka Florio and Vasiliki Pavlidou
Measurements of the turnaround radius around
galaxy clusters can be used to break the degeneracy between measurements of the present day energy density of matter and dark energy. Korkidis & Pavlidou showed that the turnaround radius coincides with the first point of deviation between outer density profiles in N-body simulations and the analytic profile predicted by excursion set theory. However, their analytic profile relied on a number of simplifying assumptions, which may each introduce systematic error. We evaluate the effect of these assumptions on the shape of the analytic profile and its correspondence with simulated outer density profiles. We relax the key simplifying assumptions and re-derive the mode of the outer density profile from excursion set theory. We then numerically resolve the double distribution (DD) across a range of masses and clustering parameters, and compare the numerical mode estimate to the re-derived analytic profile. We find excellent agreement between our analytic profile and the numerically-realized DD. However, our analytic profiles diverge from N-body profiles, and this divergence grows as we relax successive assumptions. We relate this mismatch to the differing window functions used in the analytic and simulation-based approaches, which respectively yield Markovian and correlated density trajectories. We conclude that the analytic profile proposed by Korkidis & Pavlidou should only be used as a few-parameter effective description of the most-probable outer density profile, with parameters fitted to results of cosmological simulations.
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Cosmology and Nongalactic Astrophysics
Automatic detection of fast oscillations of dark matter scalar field and updated cosmological constraints on QCDM
Amin Aboubrahim and Pran Nath
It is well known that a scalar field dark matter with a quadratic potential undergoes fast oscillations when the time period represented by the mass scale in the Klein-Gordon equation becomes much smaller than that set by the Hubble parameter. This makes a solution to the equation numerically intractable. Many works in the literature have addressed the problem by either switching between solving the Klein-Gordon equation in the well-behaved regime to solving the fluid equations at the onset of oscillations, or by introducing a new set of variables that can absorb these oscillations. Despite being successful, these techniques rely on an estimate of when the oscillations start. For large scale scans of a model's parameter space, this can become cumbersome. Furthermore, the techniques have been used mainly for non-interacting dark matter models. In this work, we introduce an averaging technique with an automatic detection of the onset of oscillations, capable of capturing the non-interacting as well as the interacting dark matter scenarios. The technique, implemented in CLASS, is tested on the QCDM model and shows excellent detection and averaging abilities. We also update the cosmological constraints on the model using the most recent public data.
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High Energy Astrophysical Phenomena
Radio Monitoring of Classical Novae using the ASKAP Variable and Slow Transients Survey
Aishani Majumder, David L. Kaplan, Laura N. Driessen et al. (+3 more)
We present a search for
radio emission from classical novae at 887.5 MHz using data from the Australian SKA Pathfinder Variable And Slow Transient (VAST) survey. We cross-matched 43 optically discovered classical novae that erupted between 2021 September and 2025 November within the 1200-square-degree
Galactic survey footprint, and found three which show significant
radio emission: V6598 Sgr, V1716 Sco, and V1723 Sco. To analyse their
radio light curves, we use both thermal free-free and non-thermal synchrotron emission models. We fit the data using the Markov chain Monte Carlo (MCMC) method to constrain parameters, including the ejected mass and ejecta velocities for the thermal models, and mass-loss rate, explosion energy, wind velocity, and filling factor for the non-thermal model. All three novae show evidence of non-thermal synchrotron emission as the dominant emission mechanism at this frequency. We use a broken power law to describe the radial density structure of a non-uniform circumbinary material, which provides a better fit than a standard wind density profile. This strong early-time synchrotron emission is strong evidence of shock-driven particle acceleration, which may be related to detections of gamma-rays from all three novae as well. In contrast to earlier studies that used multi-frequency data to distinguish between emission models, our analysis is based on single-frequency
radio light curves, which can still provide useful constraints on the dominant emission mechanism when interpreted with physically motivated models
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All authors Aishani Majumder, David L. Kaplan, Laura N. Driessen, Ashna Gulati, Tara Murphy, Dougal Dobie
Solar and Stellar Astrophysics
JWST Detects a Dusty AGB-like Source Before the Type Ia-CSM Supernova 2026sqf
Tamás Szalai, Dan Milisavljevic, Noah Zimmer et al. (+22 more)
Supernova (SN) 2026sqf recently appeared in the nearby face-on spiral
galaxy NGC 3310 and has shown signs of strong interaction with a circumstellar medium (CSM). Such intense interaction, rare among nearby SNe, offers a valuable opportunity to reveal details on the origin and nature of its progenitor system. We analyzed the early-phase spectra and light curves (LCs) of SN 2026sqf. The general shapes of the observed spectra, the strengths of the emission lines, and the LC
evolution all suggest that SN 2026sqf belongs to the rare SN Ia-CSM subclass. If confirmed, this would be the closest known member of this class, at D~19 Mpc. We also report the first candidate progenitor system for a thermonuclear
supernova identified in JWST pre-explosion imaging, and the first evidence for a (probable) carbon-rich AGB donor to the exploding white
dwarf (WD). Our results are consistent with the expectation that SNe Ia-CSM emerge from a system consisting of a WD and an AGB
star undergoing a common-envelope phase. The CSM mass and
dust content are consistent with expectations for an AGB environment, but the narrow-line width exceeds superwind expansion velocities, favoring an episodic ejection. Binary interaction shortly before the explosion is a natural explanation, though the channel and timescale remain uncertain. Late-time follow-up, especially with JWST, will test the identification and the conclusions of our early-phase analysis.
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All authors Tamás Szalai, Dan Milisavljevic, Noah Zimmer, Braden Garretson, Thomas Moore, Schuyler D. Van Dyk, Anan Lu, Selcuk Topal, Ori D. Fox, Tuomas Kangas, Seppo Mattila, Andrea Reguitti, Uliana Pylypenko, Chuck Cynamon, Ting-Wan Chen, Amar Aryan, Dylan Caudill, Danielle Dickinson, Martin Bureau, Woorak Choi, Timothy A. Davis, Daryl Haggard, Thomas M. Reynolds, Maximilian Stritzinger, Patrick Wiggins
Astrophysics of Galaxies
Differential Reddening and Extinction Law Analyses of Galactic Open Clusters
Xiaohan Chen, Shu Wang and Xiaodian Chen
Extinction significantly affects open cluster parameters and their use in studies of
Galactic structure, yet homogeneous large sample measurements of open cluster extinction properties remain limited. Using
Gaia-era open cluster member samples combined with multi-band photometry and
stellar parameters, we derive color excesses of member
stars and provide the homogeneous characterization of the mean reddening, differential reddening, and color excess ratio (CER) at the cluster scale. Differential reddening increases systematically with mean reddening, with highly reddened clusters near the
Galactic plane showing stronger extinction variations.
Star-by-
star reddening corrections narrow color–magnitude diagram (CMD) sequences in 369 of 435 clusters (85%) with reliable CMD-width measurements, and cluster color excess maps reveal small-scale extinction structures. The median CER is compatible with the standard diffuse interstellar medium extinction curve, while the broad CER distribution and its large-scale variations across the
Galactic disk likely reflect differences in the dominant
dust environments sampled along different
Galactic sight lines.
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Astrophysics of Galaxies
Radio Properties of Narrow-Line and Broad-Line Seyfert 1 Galaxies
K. É. Gabányi, S. Komossa, A. Mezősi et al. (+2 more)
Narrow-line Seyfert 1 (NLS1)
galaxies host active
galactic nuclei (AGN) with narrow optical emission lines of the broad-line region. This is often explained with a relatively lower mass of the central supermassive black hole and super-Eddington
accretion. We compared the
radio properties of large samples of NLS1 and broad-line Seyfert 1 (BLS1)
galaxies compiled from the Sloan Digital Sky Survey. We cross-matched the NLS1 and BLS1 samples with the Faint Images of the
Radio Sky at Twenty-Centimeters (FIRST) sky survey at 1.4 GHz and the first and second epoch data of the Very Large Array Sky Survey (VLASS) at 3 GHz. We calculated the
radio spectral indices, the 1.4-GHz
radio power, and the
radio loudness. We found lower 1.4-GHz
radio detection rates for the NLS1
galaxies. The median
radio loudness values, the fraction of
radio-loud AGN, and the median 1.4-GHz
radio power are also lower for the NLS1 sample. The median spectral indices imply a slightly steeper
radio spectrum for the NLS1 sample than for the BLS1 sample. Comparison of the
star formation rates estimated from the
radio data and the infrared measurements of the Wide-field Infrared Survey Explorer satellite indicated that more than half of the FIRST- and VLASS-detected NLS1 and BLS1
galaxies contain
radio-emitting AGN.
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All authors K. É. Gabányi, S. Komossa, A. Mezősi, E. Forgács-Dajka, S. Frey
High Energy Astrophysical Phenomena
X-ray Flaring and Variability in NGC 1275, the Heart of the Perseus Cluster
Sarah Ketchum, Jon M. Miller, S. W. Allen et al. (+6 more)
NGC 1275 is the central
galaxy in the Perseus Cluster. The active
galactic nucleus (AGN) within NGC 1275 is notable for its strong and variable
radio activity, tied to the production of
radio jets that inflate large bubbles in the hot intracluster medium (ICM). High spatial resolution X-ray imaging can separate the AGN from the bright ICM, but monitoring the mass
accretion rate onto the black hole and establishing disk-jet connections in NGC 1275 requires a high cadence. Here, we report on X-ray monitoring of NGC 1275 using data taken over 20 years with the Neil Gehrels Swift Observatory. Modeling the temporally constant ICM in each observation allows X-ray emission from
accretion onto the black hole to be traced reliably, with typical flux errors of $\sim 3\%$. X-ray flaring by a factor of $\sim2$ over mere days is detected starting on MJD 59956 (2023 Feb. 21). The
flares imply an emission region consistent with $r \leq 870~(10^{8}~M_{\odot}/M_{BH})~ GM/c^{2}$. The profile of the flaring is inconsistent with simple predictions for
tidal disruption events. A
flare appears roughly 300 days later in
radio monitoring data at 43 GHz. Overall, our results indicate that coordinated, moderate-resolution X-ray imaging and
radio monitoring could potentially trace disk-jet connections in the AGN that most vividly impact large-scale structure, and be extended to other sources that impact their hosts.
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All authors Sarah Ketchum, Jon M. Miller, S. W. Allen, Doyee Byun, Tianyin Hu, Missagh Mehdipour, Veronica Tananko, Xin Xiang, Irina Zhuravleva
Earth and Planetary Astrophysics
Stellar tidal systematics in apsidal-motion searches for circumbinary planets: CH Ind and SW CMa
Qunfeng Jiang
Thornton et al. (2026) reported 27 non-transiting circumbinary-
planet candidates from excess apsidal motion in TESS eclipsing-binary timings. The classical
stellar contribution is sensitive to target-specific radii, apsidal constants $k_2$, and rotation. We re-evaluate two evolved, double-lined eclipsing binaries in that sample: the pulsating system CH Ind and the Am system SW CMa. Their component masses and radii have been measured in dedicated binary studies, allowing the
stellar contribution to be calculated directly. For CH Ind, six independent TESS sector nodes give $\dot{\omega}_{\rm obs}=1.82^{+0.99}_{-0.94}\times10^{-3}\ {\rm deg\,cycle^{-1}}$, while a coeval fit to the measured binary components predicts $\dot{\omega}_{\rm stars}=2.05^{+0.43}_{-0.34}\times10^{-3}\ {\rm deg\,cycle^{-1}}$. For SW CMa, its measured dimensions raise the classical term by a factor of about 16; the published target-specific prediction, $0.670\pm0.020\times10^{-3}\ {\rm deg\,cycle^{-1}}$, agrees with the observed $0.690\pm0.050\times10^{-3}\ {\rm deg\,cycle^{-1}}$. Neither system shows a significant excess prograde component. The comparison shows that candidates from a bulk search require target-specific binary models before a third-body interpretation is assigned.
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High Energy Astrophysical Phenomena
The low luminosity end of Galactic HMXBs with eROSITA: Establishing a luminosity floor for accreting BeXRBs
Aafia Zainab, Philipp Thalhammer, Nico Zalot et al. (+18 more)
We present a first look at the
Galactic population of heretofore known HMXBs as observed by SRG/eROSITA during its first four surveys. eROSITA's sensitivity of $\sim10^{-13}\,\mathrm{erg}\,\mathrm{s}^{-1}\,\mathrm{cm}^{-2}$, translating to $10^{32}$-$10^{34},\mathrm{erg}\,\mathrm{s}^{-1}$ in luminosity for most known HMXBs in the Milky Way, has thus far never been reached by any wide-area survey instrument. We present the extended log N-log L distribution of known HMXBs reaching down to $10^{32}\,\mathrm{erg}\,\mathrm{s}^{-1}$ using eROSITA, and show the large scatter that can be induced by source intrinsic variability. We present sub-type resolved luminosity distributions, showing that the Supergiant X-ray binaries (SgXBs) and Be X-ray binaries (BeXRBs) occupy different parts of the overall distribution, and reanalyse RXTE/ASM data and MAXI for comparison to eROSITA. The luminosity regime uncovered by eROSITA allows a systematic study of the "transient" BeXRBs, which are typically below the detection threshold of monitors outside of outburst, and whose low luminosity behavior has been a longstanding question. Signatures of stable
accretion at low luminosities have been observed with pointed instruments for a fraction of the overall sample, so far. With the eROSITA results, we posit that
accretion outside of outburst is likely the norm, since a vast majority (> 80%) of BeXRBs are detected at luminosities at least an order of magnitude higher than expected for the most X-ray luminous Be
stars. We discuss the observed luminosity in the context of cold disk
accretion and the "propeller" mechanism. We highlight a small subpopulation of "isolated" Be-
stars that reach luminosities comparable to the least luminous BeXRBs, hinting at the presence of compact object companions.
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All authors Aafia Zainab, Philipp Thalhammer, Nico Zalot, Artur Avakyan, Jakob Stierhof, Ekaterina Sokolova-Lapa, Victor Doroshenko, Victoria Grinberg, Peter Kretschmar, Galina Lipunova, Nazma Islam, Matthias R. Schreiber, Christian Kirsch, Steven Hämmerich, Philipp Weber, Ralf Ballhausen, Alicia Rouco Escorial, Joel Coley, Richard Rothschild, Katja Pottschmidt, Joern Wilms
Instrumentation and Methods for Astrophysics
Optical concept model of the future cosmology project BISOU
Morgane Loquet Le Gall, Bruno Maffei, Pierre Guiot et al. (+2 more)
We present an optical analysis of BISOU (Balloon Interferometer for Spectral Observations of the
primordial Universe), an astronomical balloon-borne pathfinder spectrometer developed as part of a preparatory study for a future space mission aiming at measuring spectral distortions of the
cosmic microwave background (CMB). The BISOU optical system is based on a differential polarizing
Fourier Transform Spectrometer (FTS) that receives inputs from both a sky-facing
telescope and an internal calibration source. The FTS focal planes are equipped with bolometric detectors coupled to multimode feed horns, with distinct focal planes dedicated to the low (90 - 300GHz) and high (0.3 - 1.5THz) frequency bands. The optical analysis first relies on ray-tracing simulations to establish the overall configuration of the system, before proceeding to more advanced Gaussian beam and physical optics analyses.
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All authors Morgane Loquet Le Gall, Bruno Maffei, Pierre Guiot, Creidhe O'Sullivan, Neil Trappe
Earth and Planetary Astrophysics
Assessing Planetary Stability and Long-Term Habitability in Nearby Stellar Binaries: 70 Oph, 36 Oph, $\gamma$ Leo
Alyssa R. Jankowski, Juliette Becker, Catherine A. Clark et al. (+8 more)
Binary
stars are common and have the potential to host habitable
planets, which may reside in more complex habitable zones as compared to
planets orbiting single
stars. In this work, we use numerical simulations to assess the possibility that bright, nearby
stellar multiples 36 Oph, 70 Oph, and $\gamma$ Leo could host habitable
planets. We find that for the 36 Oph A/B system and for the 70 Oph A/B system, the
stars can support
planets residing in permanently habitable zones with low ejection rates and moderate eccentricity oscillations. The habitable zones around the red
giants in the $\gamma$ Leo system exhibit severe dynamical instability due to the high binary eccentricity, eliminating the habitable zones around both
stars. In these two systems, we find that
planets in the habitable zone with orbits coplanar to that of the binary become uninhabitable due to interactions with the binary only 1.5% - 1.8% of the time, while
planets with orbits 45 degrees misaligned to the plane of the binary experience larger oscillations in orbital eccentricity and as a result become uninhabitable 4.8% - 5.4% of the time. Our results identify 36 Oph and 70 Oph as promising targets for future missions such as the Habitable Worlds Observatory and SHERA, while suggesting that the
stars in $\gamma$ Leo are unlikely to host any habitable
planets. Our methods can be applied more generally to other binary
stellar systems to refine target lists for upcoming habitable
planet searches.
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All authors Alyssa R. Jankowski, Juliette Becker, Catherine A. Clark, Eric E. Mamajek, Jessie L. Christiansen, Yiting Li, Eduardo Bendek, Daniella Gagliuffi, Mark R. Giovinazzi, Simone Lilavois, Ryan Purviance
Instrumentation and Methods for Astrophysics
Optical development of the BISOU breadboard
Morgane Loquet Le Gall, Creidhe O'Sullivan, Bruno Borgo et al. (+4 more)
BISOU (Balloon Interferometer for Spectral Observations of the
primordial Universe) is an astronomical balloon-borne pathfinder developed as part of a preparatory study for a future space mission aimed at measuring spectral distortions of the
cosmic microwave background (CMB). A laboratory breadboard of the instrument is being developed at the Institut d'Astrophysique Spatiale (IAS), enabling the characterization of subsystems and instrument systematic effects, particularly in the optical system. The optical system is based on a differential polarizing
Fourier Transform Spectrometer (FTS) that receives inputs from both a sky-facing
telescope and an internal calibration source. The FTS focal planes include sub-K detectors coupled to multimode feed horns. The full spectral band, spanning between 90 and 1500 GHz, is sub-divided into two frequency sub-bands, thanks to the use of a dichroic. The optical analysis first relies on ray-tracing simulations to establish the overall configuration of the system, before proceeding to more advanced Gaussian beam and physical optics analyses.
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All authors Morgane Loquet Le Gall, Creidhe O'Sullivan, Bruno Borgo, Clémence De Jabrun, Valentin Sauvage, Neil Trappe, Bruno Maffei
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Long-term 3+1 simulations of primordial black hole formation during radiation domination
Zhuan Ning, Rong-Gen Cai, Shao-Jiang Wang et al. (+1 more)
We develop an efficient three-dimensional numerical-relativity framework for
primordial black-hole (PBH) formation from superhorizon
curvature perturbations in a radiation-dominated Universe. We implement flux-conservative relativistic hydrodynamics in the adaptive-mesh-refinement code GRChombo and introduce a cosmologically scaled Gamma-driver that allows the
cosmic-time step to grow in proportion to the scale factor. For a representative long-term simulation, the scaled driver preserves the apparent-horizon mass
evolution and constraint behavior while reducing the number of coarse-level advances by a factor of approximately $94$ relative to the standard driver. We also construct a conformal-time version of the moving-puncture gauge as an independent check. Applying the framework to a spherical Gaussian
curvature profile, we find a collapse threshold $0.79578 < \mu_c < 0.79580$ and a critical exponent $\gamma \simeq 0.3559$, consistent with previous spherically symmetric results. We further fit the late-time PBH mass growth to the Zel'dovich–Novikov
accretion law, demonstrating that the code can follow both near-critical collapse and long-term post-formation
evolution in three dimensions. The framework provides a foundation for future studies of PBH formation beyond spherical
symmetry.
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All authors Zhuan Ning, Rong-Gen Cai, Shao-Jiang Wang, Chul-Moon Yoo
Instrumentation and Methods for Astrophysics
FOSSIL's preliminary thermal architecture
Valentin Sauvage, Clémence de Jabrun, Anaïs Besnard et al. (+6 more)
FOSSIL (FTS fOr CMB Spectral diStortIon expLoration) is a proposed ESA M8 mission tailored to measure the spectral distortions monopole of the
Cosmic Microwave Background (CMB) with a sensitivity three orders of magnitude beyond the COBE/FIRAS legacy measurement. Achieving this sensitivity demands an extraordinarily challenging cryogenic architecture: the scientific instrument must be maintained at 4.5 K, while the detector focal plane assembly operates at 50 mK. This paper presents an overview of the preliminary thermal architecture of the FOSSIL payload, from the spacecraft service module at 293~K down to the sub-kelvin detector stage. The design draws on heritage from the Planck and ARIEL missions and relies on a staged passive cooling chain comprising a multi-layer insulation blanket, three V-groove radiators (operating at approximately 130 K, 90 K, and 50 K), and a 25 K actively cooled shield fed by an ESA-provided 4 K mechanical cryocooler. Sub-kelvin temperatures are achieved via a multi-stage adiabatic demagnetisation refrigerator (ADR) developed for NewAthena/X-IFU, providing continuous cooling at 1.8 K and 350 mK, and 50 mK with an 80% duty cycle. The Focal Plane Assembly (FPA), housing four Kinetic Inductance Detector (KID) arrays at 50 mK, is thermally isolated from the 4.5 K bench via a carbon-fibre reinforced
polymer (CFRP) hexapod with staged heat interception. We outline the staged cooling concept and show that the architecture closes with positive thermal margins at every stage; the detailed steady-state thermal budget will be presented in a forthcoming dedicated paper.
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All authors Valentin Sauvage, Clémence de Jabrun, Anaïs Besnard, Bruno Borgo, Ivan Charles, Jean-Marc Duval, Bruno Maffei, Sylvain Martin, Nabila Aghanim
Cosmology and Nongalactic Astrophysics
Cosmography with DESI-DR1 Cosmic Chronometers: Direct H(z) measurements from Luminous Red Galaxy ages
Carlos A. Álvarez, Marcos M. Cueli, Balakrishna S. Haridasu et al. (+6 more)
Providing robust
redshift estimates for almost 3 million luminous red
galaxies (LRGs), the Dark Energy Spectroscopic Instrument (DESI) offers a unique opportunity to test the expansion rate of the Universe with independent approaches. We apply the
cosmic chronometer method to derive new, independent constraints on the Hubble parameter at 0.3<z<1.2 from the differential age
evolution of DESI LRGs. We select spectra applying spectroscopic cuts to ensure sample purity and remove contamination by
star-forming objects, then build a robust sample of
cosmic chronometers (CCs) by stacking to obtain stable, high signal-to-noise (S/N) spectra, which also serves as a democratic binning choice for the $t-z$ plane. Ages are estimated by measuring Lick indices on the stacked spectra and fitting them with a theoretical
stellar population model. We obtain $t-z$ relations from which we derive $H(z)$ constraints via two independent approaches: a fit with a pivotal-
redshift cosmography, and a direct estimate from the original CC method. The cosmographic fit yields posteriors for the kinematic parameters $\{H_{z_0}, q_{z_0}, j_{z_0}\}$ compatible with currently considered cosmologies, giving a precision-level estimate of $H(z)$. We provide the maximum-a-posteriori (MAP) $H(z)$ estimate, an array of the median confidence region in the $H-z$ plane, and its covariance
matrix. We also leverage the
redshift distributions of the $t-z$ relation for different velocity dispersion groups to obtain two independent local measurements using the discrete approximation $H(z) \approx -\Delta z/[\Delta t (1+z)]$; the one from the reddest envelope of CCs gives $H(z \approx 0.61) = 88.5^{+6.7}_{-12.6}$ (stat.) $\pm 8.1$ (syst.) km s$^{-1}$ Mpc$^{-1}$. Systematic uncertainties for both the cosmographic and discrete $H(z)$ measurements come from a comprehensive analysis of all methodological choices in the data treatment.
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All authors Carlos A. Álvarez, Marcos M. Cueli, Balakrishna S. Haridasu, Michele Moresco, Martina Torsello, Alessandro Bressan, Lumen Boco, Luigi Danese, Andrea Lapi
Earth and Planetary Astrophysics
A Radon Transform Perspective on Exoplanet Transits
Shotaro Tada
Transit light curves are usually analyzed under the assumption that the transiting
planet has a circular sky-projected silhouette. However, planetary rotation, tides, rings, or atmospheric inhomogeneities can produce non-circular silhouettes. This raises the question of what information transit light curves can provide about the underlying two-dimensional attenuation map. In this paper, we show that, in a simple and transparent limit, the time derivative of the transit light curve during ingress or egress can be interpreted as a Radon-transform measurement of the planetary attenuation map, with the projection direction set by the local normal to the
stellar limb. This viewpoint makes the information content of a single transit clear. Ingress and egress provide at most two projection angles, so the data constrain the
Fourier transform of the attenuation map only along at most two radial slices, leaving a large null space. Physical constraints on the attenuation values and shape priors can reduce the range of viable solutions, but non-uniqueness generally remains. We further examine how realistic effects modify this picture. In particular, small
stellar-limb
curvature introduces weak sensitivity to transverse
Fourier-space structure around the ideal slices, a sensitivity that is absent in the strict Radon-transform limit. These results provide a framework for understanding what transit light curves can and cannot reveal about non-circular planetary silhouettes.
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Earth and Planetary Astrophysics
The atmospheric vertical structure of Uranus and Neptune from thermochemical models: the impact of model assumptions
Thomas Douçot, Ravit Helled, Daniel Kitzmann et al. (+2 more)
The composition and temperature-pressure profile of the atmospheres of Uranus and Neptune are not well-determined. As observational data are limited, we often rely on chemical
equilibrium computations to infer atmospheric abundances and cloud formation. The inferred atmospheric structures, however, strongly depend on several fundamental assumptions such as the elemental abundances and ratios, the condensation properties of the assumed species, or a reference temperature for the adiabatic structure. In this study we investigate the effects of different
metallicities (1 to 80
solar), element ratios (C/O and S/N, from 0.1 to 2 and 0.19 to 1.6) and 1 bar temperatures (66 to 86 K) on the vertical structure of ice
giant atmospheres. In particular, we use the chemical
equilibrium code FastChem to derive mixing ratios and cloud structures for CH$_4$, NH$_3$, H$_2$S, H$_2$O and NH$_4$SH. We find that the models are very sensitive to the assumed parameters, yielding drastically different possible atmospheric structures. For the cases considered here, we find that mixing ratios and cloud deck altitudes can vary by more than an order of magnitude. Additionally, thermal profiles can differ by several tens of kelvins due to composition and 1-bar temperature. We advise that future ground-based observations and a dedicated mission to Uranus and/or Neptune are required to better characterize the atmospheric structure and composition of ice
giants.
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All authors Thomas Douçot, Ravit Helled, Daniel Kitzmann, Ricardo Hueso, Audrey Vorburger
Cosmology and Nongalactic Astrophysics
Forecast for the detectability of patchy hydrogen reionization in WEAVE-QSO measurements of the Lyman-$\alpha$ forest power spectrum at redshift $z \geq 4$
Ke Ma, James S. Bolton, Vid Iršič et al. (+9 more)
We present the first detailed forecasts for the detectability of patchy hydrogen reionization in the one-dimensional Ly$\alpha$ forest power spectrum to be measured by the WEAVE-QSO survey. Using the Sherwood-relics reionization simulations and a WEAVE-QSO survey configuration, we generate mock spectra in four
redshift bins, $z=4.0,4.2,4.4,$ and $4.6$, in which relic ionization and temperature fluctuations from patchy hydrogen reionization enhance the Ly$\alpha$ forest power spectrum on large scales (i.e., at wavenumber $k\sim 10^{-3},\mathrm{s\,km^{-1}}$). Our Ly$\alpha$ forest pipeline forecasts the power spectrum covariance by considering sample size, spectral resolution, noise subtraction, continuum placement, metal contamination, and damping wings from high-column density absorbers. Applying our covariance forecast within a
Bayesian parameter inference framework, we find that the signature of patchy hydrogen reionization should be detectable at a significance of $\simeq 4.5\sigma$. The forthcoming WEAVE-QSO 1D power spectrum measurements should therefore be able to directly detect and characterize the large-scale relic imprint of patchy hydrogen reionization in the Ly$\alpha$ forest power spectrum at $z\geq 4$.
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All authors Ke Ma, James S. Bolton, Vid Iršič, Prakash Gaikwad, Matthew M. Pieri, Trystyn A. M. Berg, Rajeshwari Dutta, Matteo Fossati, Michele Fumagalli, Emanuel Gafton, Ignasi Pérez Ràfols, Francesco Pistis
Cosmology and Nongalactic Astrophysics
Cosmic Structures in CDM and SIDM
Sut-Ieng Tam
The standard $\Lambda$ Cold Dark Matter ($\Lambda$CDM) model has achieved remarkable success in explaining the formation and
evolution of
cosmic structures on large scales, supported by a wide range of observations, including the
cosmic microwave background, large-scale structure surveys, and
galaxy clusters. However, discrepancies between theoretical predictions and observations on small scales, have motivated the exploration of alternative dark matter models, including the self-interacting dark matter (SIDM) scenario. This review provides an overview of the theoretical foundations of CDM structure formation, the small-scale challenges, and the solutions proposed within the SIDM framework. We summarize recent theoretical developments in the SIDM framework and discuss current observational constraints on the dark matter self-interaction cross-section with particular emphasis on
galaxy clusters.
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High Energy Astrophysical Phenomena
Complex Energy-Dependent Behaviour of Quasi-Periodic Oscillation Observed in GRS 1915+105
Vaibhav Sharma, Ranjeev Misra, V. Jithesh et al. (+5 more)
We present complex energy-resolved properties of quasi-periodic oscillations (QPOs) in the black hole X-ray binary GRS 1915+105 using an observation from the LAXPC instrument onboard AstroSat. Power density spectra (PDSs) are constructed in multiple energy bands and modeled with multi-Lorentzian components to investigate the energy dependence of QPO properties. The QPO frequency shows a modest increase with energy. Dynamic PDS analysis does not reveal clear evidence for time-dependent
evolution of the QPO frequency, suggesting that the observed frequency shift is not primarily driven by temporal variability. We perform simultaneous fitting of energy-resolved PDSs and find that a model in which the QPO feature is described by two Lorentzian components provides a better fit. The two components exhibit different
evolution in fractional root mean square amplitude as a function of energy. We further examine the phase-lag properties by simultaneously modeling the PDS and the real and imaginary parts of the cross-spectrum and find distinct phase-lag behavior for the two components. Overall, these results indicate that the apparent energy-dependent
evolution of the QPO feature may be a result of the presence of more than one variability component.
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All authors Vaibhav Sharma, Ranjeev Misra, V. Jithesh, Shivani Chaudhary, Khushi Jirawala, J S Yadav, Pankaj Jain, N J Juris
Earth and Planetary Astrophysics
Revisiting gravitational instability in protostellar discs with improved radiative cooling models
Alison K. Young, Ken Rice, Richard Booth et al. (+1 more)
Young discs are expected to be significantly more massive than those observed at $>1$ Myr and it is at this earliest stage that
planet formation likely begins. Such massive discs may be susceptible to the gravitational instability (GI), therefore we need to determine the disc and
stellar properties for which the GI is active to understand its role in early disc
evolution and
planet formation. Prior work has been limited by model assumptions and inaccuracies due to the complex nature of the thermodynamics of protostellar discs so we now revisit this question using an improved method to approximate radiative cooling within hydrodynamics simulations. We have explored a wide parameter space, representative of young protostellar discs of 0.1 to 1 M$_{\odot}$ and include irradiation from the host
star. The parameters for which discs form spirals and fragment were found to differ to those obtained from earlier simulations. The outer regions of discs with radii of 50 au may be susceptible to fragmentation, meaning that GI-driven
planet formation is not restricted to only the most extended discs. The additional thermal support due to
stellar irradiation increases the disc mass that remains stable against GI: discs may reach up to $\gtrsim 0.4$ M$_*$ without fragmenting, providing a considerable quantity of material for building
planets. Large scale spiral arms only developed for $M_*\lesssim$ 0.3 M$_{\odot}$, except in the most compact discs. Furthermore, the long-lived spiral structures that form tend to be flocculent and compact, indicating that large-scale spiral arms should not be considered a typical outcome of GI.
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All authors Alison K. Young, Ken Rice, Richard Booth, Farzana Meru
Solar and Stellar Astrophysics
TIC 433545934: The first 2+2 type doubly eclipsing binary with extra, mutual eclipses
Tamás Borkovits, Saul A. Rappaport, Petr Zasche et al. (+5 more)
In this work we identify and photodynamically analyze TIC 433545934, the very first doubly eclipsing 2+2-type quadruple
stellar system, which shows outer eclipses, too. One such outer eclipse was discovered with TESS, which triggered a special interest in this system. Most of the data for this study come from TESS observations, but we also obtained supplemental ground-based photometric measurements for this quadruple system. The eclipse timing variation curves extracted from the TESS and ground-based follow-up data, the photometric light curves, and the spectral energy distribution are combined in a complex photodynamical analysis to yield the
stellar and orbital parameters of this dynamically interesting system. The periods of the two inner, eclipsing binaries were found to be $P_A=2.07$d and $P_B=1.41$d, while the outer period is $P_{AB}=224.5$d. The outer period alone makes this system the fifth most compact known 2+2-type quadruple. Moreover, what really makes TIC 433545934 unique is that TESS observed a triple-dipped extra eclipsing event when the
stars of binary B eclipsed the two components of binary A. We identified similar extra eclipsing events in the archival, ground-based data of ASAS-SN and ATLAS, as well. We found, however, that these extra events occur only once during an outer revolution, that is, binary A does not eclipse the
stars of binary B. This is in accord with our finding that the outer eccentricity is quite high, being $e_{AB}=0.62$. Our analysis reveals that binary A consists of two quite similar, but slightly evolved late A-type
stars ($q_A=0.92$), while in the case of binary B, the primary
star, whose mass is between the masses of the two
stars of binary A, is quite dominant, with $q_B=0.60$. The system was found to be substantially flat, with mutual inclination angles below $\approx2\degr$.
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All authors Tamás Borkovits, Saul A. Rappaport, Petr Zasche, M. Mašek, H. Kučáková, T. Mitnyan, V. B. Kostov, B. P. Powell
High Energy Astrophysical Phenomena
AT 2024qfm: a luminous fast blue optical transient at a redshift of z = 0.2267 identified by Lasair-ZTF
M. Fulton, S. J. Smartt, S. Srivastav et al. (+20 more)
Luminous fast blue optical transients (LFBOTs) emit from x-ray to
radio wavelengths, epitomised by the discovery of AT 2018cow in a host
galaxy at 65 Mpc. In the following eight years eleven more have been found, at
redshifts $0.075 \lesssim z \lesssim0.34$, plus one identified retrospectively from 2016. Here we present the discovery of AT 2024qfm, classified as an LFBOT in a host
galaxy at $z = 0.2267 \pm 0.0002$. Its ultraviolet-to-optical luminosity and rapid 13 day fade closely match AT 2018cow. We describe how the transient was identified in the Zwicky Transient Facility alert stream using a custom filter in the Lasair broker that flags flux gradients over time. Another LFBOT candidate was identified with the same methodology (AT 2024kth). The physical origin of LFBOTs remains debated with no firm consensus, and further progress requires more discoveries, host-
galaxy characterisation, and multi-wavelength analysis to constrain theory. We discuss this discovery in the context of Rubin Observatory's Legacy Survey of Space and Time (LSST), whose sensitivity will increase the effective LFBOT survey volume tenfold relative to ZTF, out to $z \lesssim 0.6$, and show that our FastFinder filter could recover such events. We highlight the challenge of detecting their fast
evolution with sufficiently low latency to trigger multi-wavelength follow-up that can constrain theoretical models.
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All authors M. Fulton, S. J. Smartt, S. Srivastav, J. H. Gillanders, J. W. Tweddle, M. E. Huber, M. Nicholl, C. R. Angus, K. W. Smith, K. C. Chambers, A. Lawrence, R. Williams, D. R. Young, K. Auchettl, T. de Boer, T.-W. Chen, C.-H. Lai, C. C. Lin, G. S. H. Paek, M. Pursiainen, S. I. Raimundo, R. Wainscoat, S. Yang