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Physics Astrophysics

astro-ph Watch Astrophysics

Friday 15 May

Solar and Stellar Astrophysics

Binarity at LOw Metallicity (BLOeM): massive star variability revealed using a novel software tool for point-spread function fitting of TESS images

Pieterjan J. Van Daele, Dominic M. Bowman, Roey Ovadia et al. (+12 more)

Massive stars, the progenitors of neutron stars and black holes, play a crucial role in shaping the chemical and radiative properties of entire galaxies through their winds and explosive deaths. Stellar pulsations are a common phenomenon in massive stars and asteroseismology – the study of such pulsations – provides crucial constraints on the physics of massive star interiors. The excitation of heat-driven pulsations in massive stars is expected to depend on a star's metallicity, but this remains largely uncalibrated in evolution models due to a lack of a sufficient observations. While TESS has dramatically improved the statistics for Galactic massive stars, obtaining TESS light curves for low-metallicity massive stars beyond the Milky Way is challenging, due to their faintness and heavy crowding. In this paper, we present a novel point-spread function (PSF) based light curve extraction method called Lemons, which overcomes these challenges. We also demonstrate the limitations of the often-used simple aperture photometry (SAP) method that can provide heavily contaminated light curves. With this new technique, accurate light curves of 91 SMC massive stars in the BLOeM sample are extracted. They reveal a variety of variability types including indications of binarity (e.g. eclipses and ellipsoidal modulation) and stellar pulsations. They also enable us to investigate stochastic low-frequency (SLF) variability for massive stars in the SMC. Furthermore we demonstrate how the morphology of SLF variability probes a star's location in the Hertzsprung–Russell diagram, which appears similar to Galactic massive stars thus indicating that the underlying physical mechanism could be insensitive to metallicity.
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All authors Pieterjan J. Van Daele, Dominic M. Bowman, Roey Ovadia, Zehava Katabi, Julia Bodensteiner, Tomer Shenar, Norbert Langer, Jan Henneco, Ankur Kalita, Paul A. Crowther, Maude Gull, Laurent Mahy, Lee Patrick, Daniel Pauli, Michał Pawlak

Instrumentation and Methods for Astrophysics

Forecasting megaelectron-volt electron flux in the Earth's outer radiation belt using supervised machine learning algorithms and a timeseries foundation model

Rungployphan Kieokaew, Ryad Guezzi, François Ginisty et al. (+1 more)

Accurate forecasting of megaelectron-volt (MeV) electrons in the outer Earth's radiation belt, which can pose significant risks to satellites, is essential for risk mitigation and spacecraft operations. We develop a machine-learning-based pipeline for forecasting 1-MeV electron flux variations, focusing first on a 6-hour forecast horizon. Using precipitating electrons measured by POES NOAA-15, near 1-MeV electron flux measured by GOES, solar wind measurements near L1, and geomagnetic activity indices as inputs in 2013-2023, we train algorithms including linear regression, 1-D convolutional and long short-term memory neural networks, and Transformer-Encoder to forecast 1-MeV electron flux in McIlwain's L-shells between 2.8 and 6.0 with 0.1 bin resolution. Particularly, we exploit the timeseries foundation model TimesFM for (1) a zero-shot prediction and (2) a hybrid application involving the ridge regression on the past dynamic covariates combined with the TimesFM inference on the residuals. Using data from January-June 2024 as an out-of-sample test, we find that the hybrid application of TimesFM, named TimesFM+Cov, yields the best results with an average R2 of 0.9 across L-shells, compared to an average R2 under 0.78 for all other models. The R2 of TimesFM+Cov remains above 0.9 for L-shells between 2.8 and 4.7 and drops to 0.77 at L=6.0, indicating improvements of 12% at the lowest L-shell and 48% at the highest L-shell compared to our second-best models. Our work offers an alternative perspective on how a pretrained foundation model could be adapted for space weather forecasting.
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All authors Rungployphan Kieokaew, Ryad Guezzi, François Ginisty, Hadrien Mariaccia

Cosmology and Nongalactic Astrophysics

Constraints on primordial black holes from the first part of LIGO-Virgo-KAGRA fourth observing run

M. Andrés-Carcasona, A.J. Iovino, E. Vallejo-Pagès et al. (+4 more)

We analyse primordial black hole (PBH) populations using state-of-the-art modelling of PBH binaries, deriving the strongest bounds on PBH abundance in the $0.6$-$100\,M_\odot$ range from LIGO-Virgo-KAGRA O4a data and demonstrating sensitivity in the $10^{-4}$-$10^4\,M_\odot$ range, for both monochromatic and log-normal mass functions. The constraints are dominated by resolvable PBH mergers, while the associated gravitational wave background provides complementary but weaker limits. To obtain limits that are agnostic about the astrophysical black hole (ABH) population, we devise two new methods, data-driven methods for statistical inference on scenarios in which PBHs account for a subset of the catalogued events. Allowing for this possibility relaxes slightly the bounds in the solar mass range $2$-$20\, M_\odot$. Our bounds are independent of the assumptions about the astrophysical black holes population and represent the most stringent constraints on the PBH abundance in the solar mass range to date.
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All authors M. Andrés-Carcasona, A.J. Iovino, E. Vallejo-Pagès, V. Vaskonen, H. Veermäe, M. Martínez, Ll. M. Mir

High Energy Astrophysical Phenomena

A Pilot Study of Mildly Recycled Pulsars: A Case Study of PSR J2338+4818

Yujie Chen, Yujie Lian, Yujie Wang et al. (+18 more)

Mildly recycled pulsars are neutron stars partially spun up through relatively short mass-transfer phases, typically with massive carbon-oxygen (CO) or oxygen-neon-magnesium (ONeMg) white dwarf companions. PSR J2338+4818, a mildly recycled pulsar, was discovered with the Five-hundred-meter Aperture Spherical Telescope (FAST). As a pilot study on the formation and evolutionary pathways of mildly recycled pulsars, we present the updated timing solution for PSR J2338+4818 and examine its single pulses and scintillation properties. Aided by the sensitivity of FAST, the single pulses of PSR J2338+4818 were systematically studied. 27,228 single pulses with S/N > 7 have been detected in our observations. For the FAST ultra-wideband observation on MJD 61045, the receiver was still in the technical commissioning phase, and then only a preliminary single-pulse search was performed. Pulse nulling was examined using a Markov Chain Monte Carlo (MCMC) method, but no evidence for nulling was found. The possible long-term nulling reported by previous studies did not occur in any of our observations in either the 1.0 to 1.5 GHz band or the 300 to 600 MHz band. Interstellar scintillation is evident in our observations. The measured scintillation timescales and bandwidths range from 2.93 to 25.26 minutes and 1.68 to 27.41 MHz, respectively. In all observations, no clear scintillation arc was found in the secondary spectra of PSR J2338+4818.
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All authors Yujie Chen, Yujie Lian, Yujie Wang, Liyun Zhang, Lei Qian, Zhichen Pan, Shuo Cao, Dejiang Yin, Baoda Li, Ruili He, Tong Liu, Wenze Li, Yichi Zhang, Yifeng Li, Qiaoli Hao, Jinyou Song, Shuangyuan Chen, Xingyi Wang, Xianghua Niu, Minglei Guo, Menglin Huang

Astrophysics of Galaxies

Early Emergence of Environmental Effects: Accelerated Galaxy Assembly in a z=2.96 Protocluster in the COSMOS Field

Shuaiyi Li, Zheng Cai, Yunjing Wu et al. (+4 more)

The redshift range z=2-4 marks a critical transition in large scale structure formation, where the dynamically unrelaxed progenitors of local massive clusters undergo rapid stellar mass assembly. We report the discovery and physical characterization of a highly significant protocluster, PC J1001+0214, at z=2.96 within the COSMOS field. Leveraging the multi-wavelength COSMOS2025 catalog with exceptional photometric precision in conjunction with JWST/NIRCam wide-field slitless spectroscopy (WFSS) from the COSMOS-3D program, we robustly identify a cosmic overdensity with $\delta=2.66$. The structure comprises 131 member galaxies, including 21 spectroscopically confirmed members (identified primarily via He I $\lambda10830$ emission) and 110 high-fidelity photometric members. A comparative analysis against a mass-complete coeval field sample reveals a statistically significant +0.2 dex shift in the stellar mass distribution of protocluster members, signaling accelerated mass assembly in the dense environment by $z\sim3$. While the protocluster population broadly follows the star-forming main sequence, low-to-intermediate mass galaxies ($\log_{10}(M_{*}/M_{\odot})\le9.7$) exhibit a measurable star formation rate (SFR) enhancement of +0.11 to +0.15 dex. Crucially, the quiescent fraction remains extremely low and indistinguishable from the field sample, implying that environmental quenching mechanisms have not yet become dominant. Furthermore, a preliminary size-mass analysis hints at elevated morphological compactness among protocluster members at fixed stellar mass. These results suggest that PC J1001+0214 represents a growth-dominated protocluster phase in which environmental effects are already detectable, primarily through accelerated stellar mass assembly and ongoing growth rather than through strong quenching.
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All authors Shuaiyi Li, Zheng Cai, Yunjing Wu, Fujiang Yu, Xiaojing Lin, Jingyang Men, Xiaoyang Wei

High Energy Astrophysical Phenomena

Measuring contributions from single and multiple atmospheric secondary cosmic rays in the Princess Sirindhorn Neutron Monitor using cross-counter neutron time delay distributions

Warit Mitthumsiri, Alejandro Sáiz, David Ruffolo et al. (+4 more)

Neutron monitors (NMs) are ground-based devices designed to measure cosmic-ray count rates by monitoring atmospheric neutrons from cosmic-ray showers. We present results from new electronics that have recorded cross-counter time delay histograms for the Princess Sirindhorn Neutron Monitor (PSNM) at the summit of Doi Inthanon, Thailand. From these histograms, we have extracted the cross-counter leader fraction ($L$) and corrected it for atmospheric effects. For large counter separation, we measure nearly constant $L\approx0.997$, implying that 0.3% of counts in one counter are temporally associated with later counts on a given distant counter. Monte Carlo simulations confirm that individual secondary particles cannot account for the associated counts at large counter separation, which instead requires a contribution from multiple secondary particles in the same cosmic ray shower that is apparently independent of distance over 3 to 7.5 m. We infer that $\approx$4.5% of PSNM counts are associated with a later count in at least one of its 18 counters from a different secondary particle in the same shower. Monte Carlo simulations of atmospheric showers and NM yield functions can be validated using our measurements of neutron multiplicity across counters and the contributions of single and multiple secondary particles. These measurements also improve understanding of the single-counter $L$, which has been used for precise tracking of cosmic-ray spectral variations and extending the range of NM observations to higher energies.
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All authors Warit Mitthumsiri, Alejandro Sáiz, David Ruffolo, Paul Evenson, Pierre-Simon Mangeard, Waraporn Nuntiyakul, Chanoknan Banglieng

Earth and Planetary Astrophysics

Performance of the 4-m International Liquid Mirror Telescope tested in two fields at high and low ecliptic and galactic latitudes

Sara Filali, Kumar Pranshu, Jean Surdej et al. (+10 more)

The 4-m International Liquid Mirror Telescope (ILMT) offers a unique opportunity to detect transients in a narrow strip of sky. We explore ILMT's potential to detect astrometric and photometric transients at various ecliptic and galactic latitudes. We inspected CCD frames observed at both low and high ecliptic and galactic latitudes during the commissioning phase and the November 2023 - May 2024 observation cycle, respectively. We analysed these images using both visual inspection and the ILMT's transient detection and candidate classification pipeline. In the low ecliptic and galactic latitude field, we detected more than 500 transient candidates. We cross-matched these with the Minor Planet Checker (MPC) database, identifying 504 catalogued asteroids, all with predicted V-magnitudes brighter than 24 mag, representing a total of 152 distinct asteroids. We performed the same steps on the high ecliptic and galactic latitude field, detecting 30 MPC-catalogued asteroids, and one newly discovered photometric transient, named AT 2024fxn. We present the positions, trajectories, and magnitudes of the detected asteroids observed in the SDSS g', r', and i' spectral bands and compare results from both fields. We explore the lightcurve of AT 2024fxn, which shows partial compatibility with a supernova (SN) hypothesis, while the data invites further insights.
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All authors Sara Filali, Kumar Pranshu, Jean Surdej, Paul Hickson, Kuntal Misra, Bhavya Ailawadhi, Talat Akhunov, Monalisa Dubey, Naveen Dukiya, Brajesh Kumar, Priyanshi Kumari, Vibhore Negi, Anna Pospieszalska-Surdej

High Energy Astrophysical Phenomena

Disformal Kerr Imprints on BHL Accretion: Shock Morphology, PSD Signatures, and Observational QPO Counterparts

Orhan Donmez, M. Yousaf, Imtiaz Khan et al. (+1 more)

We reveal the effect of the spacetime parameters on the accretion morphology formed through the BHL mechanism around a slowly rotating disformal Kerr black hole. Thus, we investigate the measurable signatures of these parameters on the hydrodynamical morphology and the timing behavior of the accreting flow. It is shown that even weak disformal deviations from the Kerr solution modify the shock-cone structure, enhance the density in the post-shock region, and produce coherent oscillations in the accretion rate. The Kerr model produces coherent peaks at 42.99 Hz and 68.13 Hz, and these frequencies are consistent with the high-frequency QPOs observed from the source GRS 1915+105. In the models where the deviations from the Kerr solution are weak, low-frequency QPOs are produced and found to be coherent. These frequencies also fall within the frequency range observed in Galactic black-hole binaries. On the other hand, the models with large deviations from Kerr can be used to explain observational results that are more irregular, broad-band, and contain multiple peaks. In addition, by using inverse-mass scaling in this work, the numerically calculated frequencies are also compared with observations of intermediate-mass and supermassive black holes. In particular, the disformal black-hole models are found to be consistent with the observational results obtained from the sources M82 X-1, NGC 5408 X-1, and RE J1034+396. This comparison also allows the possible black-hole mass range of observed sources to be inferred from the relation between simulated and observed frequencies. This makes BHL accretion in disformal Kerr geometry a powerful framework for connecting modified-gravity black-hole spacetimes with observable QPO phenomenology.
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All authors Orhan Donmez, M. Yousaf, Imtiaz Khan, G. Mustafa

Astrophysics of Galaxies

Sub-kpc scale gas density histograms of the nearby barred spiral galaxy M83: Multi-component molecular gas structure reflecting the galactic environment

Ren Matsusaka, Toshihiro Handa, Fumi Egusa et al. (+8 more)

We investigate the sub-kiloparsec (sub-kpc) molecular ISM structure and its relation to the galactic environment and star formation in the barred spiral galaxy M83 (NGC 5236). We employ the gas density histogram (GDH), which quantifies molecular gas surface density within $550~\mathrm{pc}\times550~\mathrm{pc}\times100~\mathrm{km~s^{-1}}$ cells. The GDHs are well described by one or two log-normal components, corresponding to the lower and higher-surface-density molecular components, referred to as L-LN and H-LN, respectively. The L-LN mass ($M_{\rm L}$) is relatively uniform across the disk, whereas the H-LN mass ($M_{\rm H}$) is highly structured and traces spiral arms. The fractional contribution of the H-LN component ($f^{\prime}_{\rm H}$) shows coherent structures across the disk and is enhanced along spiral arms, consistent with our previous Milky Way results. Moreover, while the L-LN correlates only weakly with star formation rate surface density ($\Sigma_{\rm SFR}$) and shows a steep Kennicutt-Schmidt (KS) relation with surface-density saturation reminiscent of atomic gas, the H-LN exhibits a tighter, nearly linear correlation similar to the conventional molecular KS relation. These results provide direct evidence that the molecular gas in M83 consists of multiple components. Star formation is more closely linked to the H-LN component, whereas the L-LN component appears to represent a more spatially extended molecular gas. Overall, our results suggest that galactic environments control the relative contribution of the two LN components, and that enhanced H-LN contribution is associated with elevated star formation activity.
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All authors Ren Matsusaka, Toshihiro Handa, Fumi Egusa, Yusuke Fujimoto, Fumiya Maeda, Takeru Murase, Yosuke Shibata, Rina Kasai, Ryo Amano, Tomoki Ikeda, Tomoki Yamaguchi

High Energy Astrophysical Phenomena

Searching for Spider-Like Pulsars from TESS Ellipsoidal Lightcurves with X-ray counterparts

Xiaoqing Liang, Partha Sarathi Pal, P. H. Thomas Tam et al. (+2 more)

We present a search for new spider pulsar candidates through multi-wavelength cross-matching, including $\gamma$-ray, X-ray, and optical data. A search for sinusoidal-like optical modulations in TESS data of 183 eROSITA X-ray sources coincident with unassociated Fermi-LAT gamma-ray sources led to the identification of four promising spider pulsar candidates. We found optical variability periods ranging from 5 to 13 hours. All candidates display smooth sinusoidal-like phase light curves, similar to what can be expected from ellipsoidal variation; one shows double-peaked profiles indicative of harmonics. The absence of sharp minima, which are often found in black widow systems due to irradiation, together with their optical magnitudes of about G~14, suggests these sources are more likely redback-type binaries. One of the Fermi-LAT counterparts is included in a machine-learning catalog of unassociated gamma-ray sources, with relatively high pulsar probabilities. We also identify potential Gaia counterparts for several sources and estimate their distances and luminosities where parallax measurements are available. Future observations, including further spectroscopic and multi-wavelength studies, are needed to fully characterize these systems.
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All authors Xiaoqing Liang, Partha Sarathi Pal, P. H. Thomas Tam, Rishank Diwan, Wen-Jun Huang

Earth and Planetary Astrophysics

Could life have been transferred from Mars to Earth? Laboratory and computational simulations of Martian ejecta

Gregory M. Davis, Jonathan Horner, Bradley D. Carter et al. (+1 more)

The study of the origin of life on Earth has been broadened due to panspermia models that suggest that early life may have been transferred between planets. Mars likely once had conditions that could support life, and it is interesting therefore to consider the question of early interplanetary transfer of life from Mars to the Earth. Endospore forming bacteria are ideal candidates for these studies as they can withstand harsh environmental conditions. For this reason, the idea that early life could have been delivered to Earth on Martian ejecta in the late Hadean period has gained considerable interest. To assess this, we have performed a series of both biological and astrophysical experiments. We exposed endospores shielded by a lysed colony of bacteria to extended UVC irradiation under a variety of rotation regimes, to simulate interplanetary exposure on ejecta with a variety of rotation periods. We also performed detailed n-body simulations of particles ejected from Mars at both perihelion and aphelion, finding that Martian ejecta can reach the Earth on timescales of just a few years - suggesting that, with ejection at the ideal time, transfer could occur within one year. Taken together, this study suggests this interplanetary transfer of biologically viable material from Mars to Earth is plausible under favourable conditions.
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All authors Gregory M. Davis, Jonathan Horner, Bradley D. Carter, Stephen C Marsden

Solar and Stellar Astrophysics

Rotationally modulated highly circularly polarised radio pulses from the rapidly rotating M dwarf ASKAP J181335-604720

Shouzhi Wang, Biwei Jiang, Qichen Huang et al. (+2 more)

We report the detection of strong, highly circularly polarised, and rotationally modulated radio pulses from the early-mid M dwarf ASKAP J181335-604720, based on strictly simultaneous radio and optical observations with the Australian Square Kilometre Array Pathfinder (ASKAP) and the Transiting Exoplanet Survey Satellite (TESS). The ASKAP data reveal recurrent broadband radio pulses across 800-1088 MHz, with peak circular polarisation fractions approaching 100%. A dominant period of P = 5.607 +- 0.003 h is derived from the TESS light curve using a Lomb-Scargle analysis, which we interpret as the stellar rotation period. When phase-folded on this period, the radio emission is confined to narrow phase intervals and recurs at fixed rotational phases, consisting of a dominant pulse and a weaker secondary component. No contemporaneous optical flares are detected at the epochs of the radio pulses in the simultaneous TESS data. Even under conservative assumptions, the inferred brightness temperature exceeds Tb > 1.8 * 10^12 K, ruling out incoherent emission mechanisms. Combining the observed characteristics, we interpret the emission as coherent electron cyclotron maser (ECM) radiation arising from the stellar magnetosphere, with the observed frequencies implying local magnetic field strengths of at least several hundred Gauss in the radio-emitting region. This work provides a clean, well-constrained, and strictly simultaneous radio-optical case, demonstrating that coordinated radio and optical observations offer a powerful means of distinguishing magnetospheric coherent radio emission from flare-associated coronal activity in M dwarfs.
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All authors Shouzhi Wang, Biwei Jiang, Qichen Huang, Shaoteng Huang, Jundan Nie

Astrophysics of Galaxies

A VLBA-resolved Jet Associated with Super-Eddington Accretion in a Radio-loud Quasar at $z=3.4$

Sakiko Obuchi, Ingyin Zaw, Kazuhiro Hada et al. (+2 more)

We report the detailed jet properties of eROSITA Final Equatorial Depth Survey (eFEDS) J084222.9+001000 (hereafter ID830), a radio-loud super-Eddington quasar at $z=3.4351$, revealed by Very Long Baseline Array (VLBA) observations at 1.6 GHz, 4.9 GHz, and 8.2 GHz. Thanks to the high spatial resolution of the VLBA, we successfully resolve a parsec-scale core-jet structure of ID830, and find a well-collimated jet extending over $\approx 745$ pc, making it the most distant and one of the very few currently known radio-loud quasars with a resolved jet associated with super-Eddington accretion. The physical scale and evolutionary track of ID830 differs markedly from the low-$z$ analogues, such as nearby radio-luminous high-Eddington narrow-line Seyfert 1 galaxies, suggesting that this source represents a distinct high-$z$ population compared to previously known samples, with important implications for AGN feedback in early galaxy evolution. We also find that the jet has a relativistic speed of $v \gtrsim 0.19c$ and a modest viewing angle of $\phi \lesssim 79^\circ$ to the line of sight, although its emission is not significantly Doppler-boosted ($\delta \sim 1$). This provides the first evidence that such a relativistic and collimated jet can be produced over several hundred parsecs in the super-Eddington phase, lasting for at least $10^{3\text{-}4}$ yr. Our results call for further theoretical and numerical studies to understand the physical processes required to sustain such large-scale collimation in super-Eddington accretion, which remains a missing piece.
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All authors Sakiko Obuchi, Ingyin Zaw, Kazuhiro Hada, Kohei Ichikawa, Joseph D. Gelfand

High Energy Astrophysical Phenomena

Impacts of radiative cooling on the images of a black hole shadow and extended jets in two-temperature GRMHD simulations

Mingyuan Zhang, Yosuke Mizuno, Indu K. Dihingia et al. (+4 more)

The recent 230 GHz observations from the Event Horizon Telescope collaboration have successfully imaged the supermassive black hole shadow of the M87 galaxy. However, the relatively high radiative efficiency observed in the hot accretion flow suggests that radiative cooling is non-negligible and should be considered when calculating the electron temperature. In this study, we compare accretion models without and with radiative cooling across a range of mass accretion rates, $\dot{M}_{\mathrm{BH}} = (1.0 - 10) \times 10^{-6}\,\dot{M}_{\mathrm{Edd}}$, aiming to assess the impact of cooling on the disk structure, electron temperature distribution (eDF), black hole shadow morphology, broadband spectral energy distributions (SEDs), and flux variability. We performed general relativistic radiative transfer (GRRT) calculations on two-temperature, radiative, general relativistic magnetohydrodynamic (GRMHD) simulations, employing different electron heating prescriptions and nonthermal eDFs, analyzing the radiation transfer due to synchrotron emission at 230 GHz with inclination angle of $163^\circ$. These simulations are targeted toward M87$^{*}$. By comparing density profiles, eDFs, GRRT images, SEDs, and time variability between models, we find that the radiative cooling sharply decreases the electron temperature in the dense inner disk around the equatorial plane ($r\lesssim 10\,r_\mathrm{g}$), while slightly reducing jet sheath temperature. Cooling leads to a dimmer disk, more extended and brighter jets, and reduced total flux. For a given accretion rate, cooling reduces the high-frequency flux. Time variability originates primarily from the midplane in both non-cooling and cooling cases and decreases as accretion rates rise. Although currently below the dynamic range of EHT observations, the features identified in this study could be resolved by next-generation arrays such as the ngEHT.
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All authors Mingyuan Zhang, Yosuke Mizuno, Indu K. Dihingia, Christian M. Fromm, Ziri Younsi, Hai Yang, Alejandro Cruz-Osorio

High Energy Astrophysical Phenomena

GeV {\gamma}-ray emission in the low-mass star-forming region AFGL 490

Li-Nuo Yang, Sheng Tang and Pak-Hin Thomas Tam

We report the discovery of an extended GeV {\gamma}-ray source, 4FGL J0330.7+5845e, associated with the star-forming region AFGL 490 using 17 years of Fermi-LAT data. The emission is spatially coincident with a dense molecular cloud and centered near the massive protostar AFGL 490. Its spectral energy distribution shows a distinct high-energy cutoff. Both leptonic and hadronic models can fit the {\gamma}-ray spectrum, but energetic arguments rule out stellar winds as the primary accelerator. Instead, the protostellar jet driven by AFGL 490 is identified as a plausible site for particle acceleration, and the derived timescales and maximum particle energies are consistent with theoretical predictions for such jets.
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Thursday 14 May

Earth and Planetary Astrophysics · Cross-listed from eess.SY

Inflatable devices for planetary aerocapture and aerobraking manoeuvres

Philippe Reynier

Future missions to Mars and Venus will make use of aerobraking and aerocapture in order to gain mass through the saving of fuel at planetary arrival. So far only aerobraking has been demonstrated, if the Mars Premier project has paved the way for aerocapture, no demonstration was performed due to the project interruption. The use of these techniques induces additional constraints for planetary probes, since additional heating and mechanical loads have to be carefully managed. Moreover, aerocapture requires a high level of accuracy for the Guidance Navigation and Control aspects, since a pass at an altitude of the atmosphere with a different density could lead to the vehicle destruction. This document surveys the existing state-of-the-art on inflatable devices (including ballutes, sails, or inflatable heat-shield capsule) for orbital manoeuvres at planetary arrival.
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Cosmology and Nongalactic Astrophysics

Expected redshift drift for tilted observers

Franco R. de Pedro and Gabriel R. Bengochea

Redshift drift is usually discussed for observers comoving with the cosmological background, but realistic observations are made by observers with nonzero peculiar motion. In this work, we calculate the expected redshift drift for tilted observers within the covariant 1+3 formalism. Starting from the exact redshift measured in the tilted frame, we derive the corresponding drift as an FLRW background term plus a directional correction driven by the observer's peculiar kinematics, encoded through peculiar expansion, projected shear, and projected acceleration along the line of sight. We analyse first an Einstein–de Sitter (EdS) background, which isolates the purely kinematic effect of tilt in the absence of background acceleration, and then extend the calculation to $\Lambda$CDM in order to quantify how the same anisotropic corrections deform the standard drift signal in the concordance model.
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High Energy Astrophysical Phenomena

Polarization Birefringence and Waveform Systematics in GW231123

Tonghua Liu, Chenggang Shao and Kai Liao

GW231123 is a short, massive binary-black-hole event whose source properties show strong waveform dependence. We use this event to test gravitational-wave polarization birefringence, modeled as a frequency-dependent rotation of the tensor-polarization basis. Instead of sampling a distance-normalized coefficient directly, we sample the band-differential rotation $\delta_{\rm br}=\Delta(448\,\mathrm{Hz})-\Delta(20\,\mathrm{Hz})$ with prior $[-\pi,\pi]$, and report the derived coefficient $\beta_{\rm br}^{\rm derived}$ for comparison with standard propagation parametrizations. We analyze three waveform families: IMRPhenomXPHM (XPHM), IMRPhenomXO4a (XO4a), and NRSur7dq4. The derived posteriors are consistent with the general relativity value, giving $90\%$ upper limits $|\beta_{\rm br}^{\rm derived}|_{90}=0.378,\,0.097,\,0.273$ for XPHM, XO4a, and NRSur7dq4, respectively. The directly sampled $\delta_{\rm br}$ posterior remains broad, with $|\delta_{\rm br}|_{90}\simeq2.8\,\mathrm{rad}$, so the accumulated rotation across the analysis band is weakly constrained. The Bayes factors are waveform dependent: $\ln\mathcal{B}_{\rm br/GR}=-1.26\pm0.30$, $+3.64\pm0.28$, and $-0.86\pm0.29$, respectively. We therefore find no waveform-robust evidence for parity-violating propagation. The positive XO4a result is better interpreted as a waveform-dependent birefringence-like response associated with the mass-ratio–distance–spin degeneracy of this short high-mass event.
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Instrumentation and Methods for Astrophysics

Mosaic: Area-Closed Spherical Surface Mosaics Induced by Cartesian Grids

H.F. Counts, Mihaela Dobrescu, D. Heddle et al. (+2 more)

We describe Mosaic, a computational geometry method for constructing the surface mosaic induced when a Cartesian volume grid intersects a spherical shell. The motivating application is conservative coupling between data produced on rectangular grids and diagnostics or boundary conditions defined on spherical surfaces, as occurs in space-weather, magnetohydrodynamic, atmospheric, and geophysical models. The method identifies Cartesian cells that intersect the shell, constructs cell-sphere prepatches, splices those regions by the spherical colatitude grid, and then splices by azimuth to produce final patches indexed by the five-tuple (nx, ny, nz, ntheta, nphi). The implementation explicitly treats the polar singularity by separating polar-derived theta patches from ordinary phi splicing. A near-pole numerical failure mode, caused by linear interpolation in azimuth, is removed by computing exact intersections between great-circle boundary segments and meridian planes. The prepatch construction also handles several degeneracy cases that occur beyond the ordinary corner-straddling geometry, including doubly-crossing edges, lens-shaped prepatches, secondary closed loops, and re-entrant face arcs. For a representative nonuniform Cartesian test grid, the current implementation builds 3618 intersecting Cartesian cells, 3602 ordinary prepatches, 6476 theta patches, and 9714 final phi patches, with all 3602 ordinary cells built successfully and zero theta or phi splicing failures. The final phi-spliced patches close in normalized area to roundoff relative to their theta-spliced parents. The method is implemented in the Java/Maven application mdi-mosaic, which provides visualization, diagnostics, mouse-over patch inspection, and JSON export of final patch boundaries and normalized areas.
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All authors H.F. Counts, Mihaela Dobrescu, D. Heddle, Aubrie Kooiker, Walter Pierce

High Energy Astrophysical Phenomena

Constraints on the Metallicity-dependent Explodability of Massive Stars from Galactic Chemical Evolution: Toward Alleviating the Red Supergiant Problem

Sojun Ono, Keiichi Maeda and Akihiro Suzuki

The explodability of massive stars, namely whether they undergo core-collapse supernovae (CCSNe) or form black holes (BHs), strongly influences galactic chemical evolution (GCE). Details of the explodability are still controversial, but realistic predictions including metallicity-dependence are becoming available through stellar-evolution and explosion calculations. In the present work, we implement recently-proposed metallicity-dependent explodability prescriptions into a GCE framework. We show that the physics-motivated explodability prescriptions reproduce the key observed abundance trends. Further, within uncertainties of the explodability models, the GCE model provides important constraints on the region of the BH formation in the mass-metallicity space. Guided by these findings, we further construct a simplified form of the metallicity-dependent explodability designed to alleviate the red supergiant (RSG) problem and explore its compatibility with GCE constraints. We find that such a solution exists, if (1) the net outflows from the system are negligible/absent, and (2) the transition of the explodability takes place at sub-solar metallicity. These results demonstrate that GCE can provide meaningful constraints on massive-star explodability and that explodability prescriptions capable of addressing the RSG problem can be constructed without violating chemical-evolution observables. We also show that a metallicity-dependent initial mass function can improve agreement with observations; this effect becomes important once coupled with the metallicity-dependent explodability.
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Cosmology and Nongalactic Astrophysics

Clusters Hiding Under Millimeter Sources (CHUMS) I: Extreme CHUMS

Harshda Saxena, Adam B. Mantz, Jack Sayers et al. (+2 more)

Galaxy cluster abundance provides a powerful probe of the $\Lambda$CDM model and enables precise constraints on cosmological parameters. Millimeter-wavelength surveys detect clusters through the Sunyaev-Zeldovich (SZ) effect, and are particularly effective at high redshifts. However, the SZ signal can be significantly contaminated by emission from Active Galactic Nuclei (AGN), particularly AGN within the Central Galaxies (CGs). This contamination reduces the SZ signal strength at the frequencies most accessible from the ground, which reduces detection significances or converts cluster detections to non-detections, thereby diminishing survey completeness and introducing biases in cosmological analyses. In this work, we analyze three clusters that host bright AGN in their CGs using 30 and 90 GHz observations from the Combined Array for Research in Millimeter-wave Astronomy (CARMA). In each case the AGN emission overwhelms the cluster SZ signal, resulting in non-detections in the Atacama Cosmology Telescope (ACT) survey. We present signal to noise ratio (SNR) estimates for the clusters after subtracting the AGN signal from 90 GHz ACT maps using the CARMA measurements, demonstrating high SNR cluster detections once this contaminating emission is removed. Using cluster pressure profiles derived from Chandra X-ray data, we subtract the expected SZ signal from the 150 GHz ACT maps to estimate the flux density of the AGN in that band. Leveraging the time-asynchronous CARMA observations, we also assess temporal variability in the AGN emission, and find low fractional variability for our sample. Finally, we discuss the importance of modeling and mitigating AGN contamination in SZ cluster surveys.
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All authors Harshda Saxena, Adam B. Mantz, Jack Sayers, Denise G. Yudovich, Steve W. Allen

Solar and Stellar Astrophysics

The Nova Synthetic Data Base: A Principal Component/AI Analysis of Novae Synoptic Spectra

Bruno C. Santos, Marcos P. Diaz and Larissa Takeda

The Nova Synthetic Data Base (NSDB) is presented as the first publicly available database of synthetic spectra for classical nova shells, spanning an unprecedented range of physical parameters (e.g., ejecta mass, chemical composition, temperature, and luminosity of the white dwarf) at several post-eruption ages. Generated using detailed 3D photoionization models, this homogeneous database enables a systematic exploration of spectral features in novae. In this work, we introduce a principal component analysis/AI-based framework to derive time-dependent proxies for retrieving the physical properties of novae from limited spectral data. By analyzing the correlations between the eigenspectra and the grid's variables, a reduced set of diagnostic spectral lines is derived, paving the way for robust multiregressor machine-learning algorithms with a minimal effort observational set. The prediction capability of the method is high and robust to data noise. The results establish a proof of concept for the use of model grids combined with physically controlled AI as a tool to interpret novae observations in the context of the large number of events expected from future wide-area surveys.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc

Ringdown and echoes from compact objects: Debye series and Debye quasinormal modes

Mohamed Ould El Hadj and Sam R. Dolan

We introduce a new series decomposition of the waveform constructed in the spirit of Debye expansions in scattering theory, and we use this to analyse the time-domain response of compact, horizonless bodies to scalar-field perturbations on curved spacetimes. The Debye decomposition separates out direct exterior propagation, surface reflection, and successive transmissions through the interior of a compact body, and it provides an intuitive interpretation of the waveform in terms of geodesic trajectories. By analysing the quasinormal-mode (QNM) content of individual Debye terms, we set out a Debye-QNM description that is complementary to the standard QNM description. With this framework, we examine a scalar field propagating on two illustrative `Schwarzschild star' compact-body spacetimes: a neutron-star-like model $R>3M$ and an ultracompact object $R<3M$. We show that the closed-form Debye reconstruction matches well with the exact waveform, and that it converges even at early times, giving an accurate description of all waveform features including the prompt response. In the neutron-star case, the low-order Debye terms mainly describe the ringdown and a non-modal component associated with the sub-threshold branch cut. In the ultracompact case, the Debye series organizes the waveform into a prompt/ringdown contribution followed by a succession of echo-like wavepackets. The new Debye-QNM expansion and the standard QNM expansion have complementary spectral interpretations: the former identifies modes in individual propagation channels, whereas the latter describes collective resonances that are resummations of the former. This distinction clarifies how echo-like structures emerge from repeated interior propagation, and how pole and branch-cut contributions enter the time-domain signal.
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Instrumentation and Methods for Astrophysics · Cross-listed from cs.DC

Using the Open Science Data Federation for data distribution: Big Bear Solar Observatory use case

Sydney Montiel, Alexsandra Guadarrama and Fabio Andrijauskas

The growing demand for extensive data processing is now a standard in many scientific fields. Efficiently distributing data to processing sites and enabling seamless sharing has become crucial. The Open Science Data Federation (OSDF) builds on the success of the StashCache project to establish a global data distribution network. By expanding StashCache, OSDF integrates additional data origins and caches, enhancing accessibility and performance (20 origins and 30 caches), new access methods, and monitoring and accounting mechanisms. Additionally, the OSDF has become essential to the US national cyber-infrastructure landscape due to the sharing requirements of recent NSF solicitations. One use case for the OSDF is the data access to the Big Bear Solar Observatory (BBSO). Integrating the BBSO data into the OSDF provided standard and reliable data access. Moreover, the OSDF caches provide local data worldwide. Using the OSDF and the BBSO data, creating a pipeline to apply image processing techniques to all images from BBSO anywhere on the planet was possible.
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Cosmology and Nongalactic Astrophysics

Warm, not Fuzzy: Generalized Ultralight Dark Matter Limits from Milky Way Satellites

Ethan O. Nadler, Mustafa A. Amin, Risa H. Wechsler et al. (+3 more)

We generalize lower limits on the dark matter (DM) particle mass $m$ derived from Milky Way (MW) satellite galaxy abundances to scenarios in which DM is an ultralight scalar field produced with a field power spectrum peaked at a subhorizon wavenumber $k_*$. In these models, the DM field free-streams similarly to warm DM while also exhibiting significant small-scale wave interference effects. The resulting dimensionless density power spectrum shows two effects: (i) free-streaming suppression at $k_{\rm fs}\sim k_{\rm eq}/[(k_*/a_{\rm eq}m)\ln(a_{\rm eq}m/k_*)]$; (ii) Poisson-like enhancement related to wave interference at $k\gtrsim10^{-2}k_*$, which saturates near the Jeans scale $k_{\rm J}\sim k_{\rm eq}/(k_*/a_{\rm eq}m)$. Comparing these predictions with established constraints on a free-streaming cutoff in the linear matter power spectrum from the MW satellite population and assuming that warm ultralight DM does not change the form of the galaxy–halo connection relative to cold DM, we obtain $m>6\times10^{-18}\,{\rm eV}\,(k_*/10^4\,{\rm Mpc}^{-1})$ for $k_*>10^4\,{\rm Mpc}^{-1}$ at 95% confidence. For smaller $k_*$, Poisson-noise enhancement on MW satellite scales weakens the constraint, yielding $m>6\times10^{-18}\,{\rm eV}\,(k_*/10^4\,{\rm Mpc}^{-1})^2$ for $k_*<10^4\,{\rm Mpc}^{-1}$ at 95% confidence.
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All authors Ethan O. Nadler, Mustafa A. Amin, Risa H. Wechsler, M. Sten Delos, Andrew Benson, Vera Gluscevic

Earth and Planetary Astrophysics

Juno Microwave Radiometer Observations Reveal A Warmer Polar Atmosphere on Jupiter

Jiheng Hu, Cheng Li, Sushil K. Atreya et al. (+15 more)

The intriguing circumpolar cyclone pattern at Jupiter's poles raises fundamental questions about how these systems are organized vertically and, further, how the planet's internal heat shapes and sustains them in the absence of solar insolation. We report recent close-in observations of Jupiter's north pole acquired by NASA's Juno Microwave Radiometer (MWR), which achieved comprehensive microwave mapping of the region at an unprecedentedly high resolution. Using six-channel measurements from eleven perijove passes (PJ51-PJ61) poleward of 75N, we derive polar-mean nadir brightness temperatures and limb-darkening spectra that together point to two equally plausible atmospheric scenarios: (1) a dry-adiabatic profile with slightly depleted ammonia gas at a few bars, or (2) a moist-adiabatic profile with uniform ammonia. Markov chain Monte Carlo retrievals yield a deep ammonia abundance of 354.8+12.0/-11.0 ppmv (3+/-0.1 x solar) and a water abundance of 1.8+1.5/-1.1 x 1000 ppmv (2.1+1.8/-1.3 x solar), resembling previous estimates at lower latitudes. Remarkably, the north pole is found to be 6-7 K warmer than the equator at the 1-bar level, although the inferred difference is close to the 1-sigma uncertainty level. If confirmed, this result would suggest an enhanced internal heat flux toward the poles, which is consistent with the more intense lightning activity observed at high latitudes.
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All authors Jiheng Hu, Cheng Li, Sushil K. Atreya, Leigh N. Fletcher, Eli Galanti, Tristan Guillot, Yohai Kaspi, Liming Li, Yuan Lian, Alessandro Mura, Glenn S. Orton, Fabiano A. Oyafuso, Maria Smirnova, J. Hunter Waite, Michael H. Wong, Zhimeng Zhang, Steven M. Levin, Scott J. Bolton

Astrophysics of Galaxies

Clumps in spiral galaxies at $z \lesssim 3$: Disentangling two spatial modes of star formation

Ilia V. Chugunov and Alexander A. Marchuk

At high redshifts, star formation in galaxies is more often concentrated in clumps than in spiral arms. Although clumps are actively studied, it is rarely done considering spiral arms as objects for study as well, and the connection between clumps and spirals remains understudied. We used a sample of 159 spiral galaxies at $0.1 \leq z \leq 3.3$ observed by HST and JWST. Using the residual images from photometric models with spiral arms constructed before, which was not done previously, we have done identification of clumps and measured their properties with photometric decomposition, finding 3003 clumps in overall, and performing SED fitting for a fraction of them. We examined the overall properties of clumps, focusing on the properties of spiral structure. We found that clumps luminosities, masses and sizes are smaller than commonly accepted in literature, either for the reason spiral arms were modelled separately, or because clumps in spiral galaxies are different compared to clumpy ones. We demonstrate the connection between clumps and spirals, in particular clumps are spatially concentrated towards spirals and various parameters of clumps and spirals correlate. Also, clumps in spiral arms tend to be smaller but brighter compared to clumps in inter-arm area, but their colours are similar. There are also some differences between clumps and spirals such as colour, emphasizing the importance of their separate analysis. Our results probably indicate that spiral arms stimulate the formation of clumps, although star formation properties of clumps in spiral arms is not changed compared to inter-arm region.
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High Energy Astrophysical Phenomena

Correlation Between Hard X-Ray and Cosmic Neutrino Sources: From Obscured AGN to Blazars

Emma Kun, Imre Bartos, Claudio Ricci et al. (+5 more)

The origin of high-energy astrophysical neutrinos remains a key open question in multimessenger astrophysics. A correlation between unabsorbed hard X-ray and high-energy neutrino luminosity has been reported in six active galactic nuclei with the highest individual IceCube significances, linking neutrino production to compact, photon-rich environments near supermassive black holes. We study whether the threshold-near IceCube excesses associated with seven NuSTAR-observed blazars are statistically consistent with that relation. Calibrating the $L_\mathrm{hX}$-$L_\nu$ relation on the six published sources via a Bayesian regression with errors on both axes, the slope is consistent with $\beta = 1$ and the intrinsic scatter is $\sim 0.6$\,dex. All seven new blazars are posterior-predictively consistent with this calibration ($\chi^2_7 = 1.58$, $p = 0.98$) under the working hypothesis that the published IceCube $\hat{n}_s$ values reflect the signal. A null-injection test confirms that, at the present calibration sample size, the consistency test does not by itself adjudicate between signal and selected-background origins. A distance-free $L_\mathrm{hX}/L_\nu$ ratio diagnostic places both populations within the photohadronic prediction band, statistically indistinguishable. Two diagnostics that control the common $d_L^{\,2}$ distance bias, a redshift-partial rank correlation ($\tau|z = 0.69$, $\sim\!2.7\,\sigma$) and a flux-space permutation test on the 13-source joint sample ($p = 6.3\times10^{-4}$, $3.23\,\sigma$), indicate a residual $L_\mathrm{hX}$-$L_\nu$ association beyond the distance-induced trend. We interpret these results as a conditional consistency check; a detection-level statement requires either an enlarged calibration set or an X-ray-weighted IceCube stacking likelihood with internal data.
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All authors Emma Kun, Imre Bartos, Claudio Ricci, Santiago del Palacio, Francis Halzen, Julia Becker Tjus, Peter L. Biermann, Anna Franckowiak

High Energy Astrophysical Phenomena

Population synthesis of Galactic middle-aged pulsar wind nebulae I. Detection prospects for current and future instruments

A. De Sarkar, D. F. Torres, B. Olmi et al. (+2 more)

Pulsar wind nebulae (PWNe) constitute the largest population of Galactic very-high-energy (VHE; $E > 100$ GeV) $\gamma$-ray sources and are key laboratories for studying particle acceleration and pulsar–supernova remnant (SNR) interactions. However, realistic population-level predictions have so far lacked any detailed treatment of the reverberation phase, when the nebula is compressed by the SNR reverse shock, significantly altering its dynamics and radiative spectrum. We employ the hybrid TIDE+L framework, which combines a thin-shell dynamical model with a Lagrangian treatment of the SNR structure during reverberation, allowing self-consistent evolution of thousands of PWNe across all stages up to $10^5$ yr. Each source is evolved under distributions of pulsar spin-down, SNR, and environmental properties, and the resulting $\gamma$-ray fluxes are used to estimate the detectability by current and next-generation $\gamma$-ray observatories while accounting for their sensitivity and sky coverage. The model predicts that the upcoming Cherenkov Telescope Array Observatory (CTAO) will detect an order of magnitude more PWNe than those firmly detected in the TeV range, confirming its dominant contribution to the forthcoming TeV population census. Our results demonstrate that realistic modeling of reverberation is important for predicting the Galactic TeV PWNe population.
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All authors A. De Sarkar, D. F. Torres, B. Olmi, N. Bucciantini, D. M.-A. Meyer

Earth and Planetary Astrophysics

A framework for evaluating biosignature potential against the abiotic baseline on ocean worlds

Peter M. Higgins, Weibin Chen, Oliver Warr et al. (+4 more)

Ocean worlds are considered as targets for life detection missions because they meet several key requirements for habitability. However, identifying potential life on other worlds requires observing clear and unambiguous biosignature signals above the existing abiotic baseline. Consequently, this necessitates evaluating uncertainty and variability in the abiotic baseline, including processes that can overlap, attenuate, or obfuscate biosignatures before they are observed. This article develops a quantitative framework for holistically evaluating abiotic baselines on ocean worlds to guide life detection strategies. Using Enceladus as an example, we assess the potential of using: i) CH$_{4}$ isotopes and their relationship with CO$_{2}$, and ii) amino acid chirality as biosignatures, demonstrating that uncertainties in abiotic processes currently prevent hypothetical future ${\delta}^{13}$C$_{\mathrm{CO2}}$ and ${\delta}^{13}$C$_{\mathrm{CH4}}$ measurements from definitively inferring a biosphere on Enceladus. Additionally, our results quantitatively show that neglecting the abiotic baseline risks false negative life detection claims for both isotopic and chiral biosignatures. Interpreting these and other alternative biosignatures on Enceladus, Europa, Titan, and similar planetary bodies therefore requires complimentary geophysical observations such as constraining internal temperatures to within $\sim$10-100$^{\circ}$C, and improving characterisation of the target's rheology, lithology, initial abiotic organic inventory and ocean transport timescales.
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All authors Peter M. Higgins, Weibin Chen, Oliver Warr, Lucas M. Fifer, Wanying Kang, Charles S. Cockell, Barbara Sherwood Lollar