European Southern Observatory

Abstract We report a multi-epoch V-band campaign (2021–2023) with uniform processing and a common 550 km normalisation across Starlink generations. Median magnitudes (68% confidence intervals; N in brackets) are: v1.0: 5.365,[5.084,5.553] (34), Gen-2: 6.012,[5.801,6.173] (6), v1.5: 6.106,[6.065,6.154] (164), VisorSat: 6.618,[6.403,6.804] (54), DarkSat: 8.431,[5.916,10.947] (2). This yields the ordering v1.0 < Gen-2 ≲ v1.5 < VisorSat ≪ DarkSat, i.e. mitigation-era designs are typically fainter than the original v1.0. The Gen-2–v1.5 difference is small (0.094,mag) and Gen-2 has limited coverage (N = 6), so the trend is not strictly monotonic. We use an open, Python-based processing pipeline built on astropy for standard image calibration (bias, dark and flat-field correction), astrometric and photometric calibration against Gaia DR3, and derivation of the viewing geometry (solar phase angle, range, elongation and airmass). Satellite tracks are identified from TLE-based ephemerides, matched to the detections, and then used to measure a brightness value for each track in a reproducible way. At a common height, the medians are 5.37 (v1.0), 6.01 (Gen-2), 6.11 (v1.5), 6.62 (VisorSat) and 8.43 (DarkSat; N = 2), which are ∼0.4–1.6 mag brighter (numerically smaller) than the target of V ≈ 7. Thus, mitigation shows clear progress but does not yet meet the IAU CPS/SATCON goal of V ≥ 7 at ∼550 km. These benchmarks can guide future satellite designs, survey planning and avoidance strategies, with the main uncertainties arising from the very small samples for DarkSat and Gen-2.

Abstract The XRISM Resolve X-ray spectrometer makes it possible to gain detailed insights into the gas motions of the intracluster medium (ICM) of galaxy clusters. Current simulation studies focus mainly on statistical comparisons, making the comparison to the currently still small number of clusters difficult due to unknown selection effects. This study aims to bridge this gap, using simulated counterparts of Coma, Virgo, and Perseus from the SLOW constrained simulations. These clusters show excellent agreement in their properties and dynamical state with observations, thus providing an ideal testbed to understand the processes shaping the properties of the ICM. We find that the simulations match the order of the amount of turbulence for the three considered clusters, Coma being the most active, followed by Perseus, while Virgo is very relaxed. Typical turbulent velocities are a few hundred km s −1 , very close to observed values. The resulting turbulent pressure support is ≈1% for Virgo, ≈6% for Perseus, and ≈8% for Coma within the central 1%–2% of R 200 . Compared to previous simulations and observations, measured velocities and turbulent pressure support are on average lower, in line with XRISM findings, thus indicating the importance of selection effects.

The Chilean Atacama desert hosts the largest astronomical observatories world-wide due to its unique dry meteorological conditions and high altitude of the Andes. One of the largest facilities is Cerro Paranal, among others hosting the Very Large Telescope, which is equipped with several spectrographs ranging from the ultraviolet to the mid-infrared. As ground-based telescopes have to observe through the Earth's atmosphere, the spectra taken from astronomical objects are affected by molecular absorption arising from the present various species. This imprint -called telluric contamination- varies in the same way as the composition of the Earth's atmosphere varies. Therefore it is of crucial importance for astronomers to know about the chemical components of the atmosphere at the time of observation to be able to correct for these contaminations.In the past, mostly static atmospheric standard models were used to fit and correct the telluric contaminations. In the meanwhile, several sources of world-wide, time-dependent information of the chemical composition are available. We are currently investigating data from the Copernicus Atmospheric Monitoring Service (CAMS) Global Reanalysis (EAC4) and CAMS Global Greenhouse reanalysis (EGG4), which provide height profiles of various molecular species (e.g. NO, NO2, O3, CO, HNO3,...) on a 3-hourly resolution ranging from 2003 through 2020 (EGG4) and 2024 (EAC4). This allows us a detailed analysis on the hourly, daily, seasonal, and yearly variability of the chemical composition of the Earth’s atmosphere above Cerro Paranal.We found significant variations of nearly all species on various time scales, highly affecting the astronomical observations. In this presentation we show first results of our investigations. As astronomical observations are conducted during night, we focus on day/night-time differences and long-term trends to estimate the impact on telluric contamination.

Abstract We report the discovery of the first transient relativistic iron K α line in an active galactic nucleus (AGN), J1047+5907. The line was detected 21.5 days (rest frame) after an X-ray coronal flare was observed in 2008, and it exhibits significant broadening consistent with relativistic reflection from the accretion disk in the vicinity of the central supermassive black hole (SMBH). The line has a width of ∼300 eV, corresponding to a Keplerian velocity of 14,000 km s −1 , at a distance of 5–41 light-days from the SMBH, strongly implying that the observed coronal flare triggered the emergence of the line. This event provides rare direct evidence of the response of the accretion disk to impulsive coronal illumination and offers a new method to probe the SMBH and disk physics. The relativistic modeling favors a broadened line produced by distant reflection from an accretion disk around a rapidly spinning black hole viewed at an intermediate inclination, consistent with other observations. Systematic monitoring of type 1 AGN following strong X-ray flares may open a new observational window into the innermost regions of AGN, enabling constraints on the physics of SMBH and its accretion disk at different radii that are otherwise challenging to access.

Using JWST/MIRI observations, we report the detection of CO$_2$ ice in the dusty torus of the planetary nebula NGC 6302, an environment generally considered hostile to fragile molecular species and ices due to intense UV irradiation. This detection accompanies cold (20-50 K) gas-phase CO$_2$ along the same sightlines. The ice absorption profile exhibits a double-peak profile, a characteristic of pure, crystalline CO$_2$ ice. The CO$_2$ gas-to-ice ratio is more than an order of magnitude higher than in young stellar objects, pointing to distinct ice formation or processing mechanisms in evolved stellar environments. This discovery demonstrates that the dusty torus provides sufficient shielding to harbour ice chemistry, and that ice-mediated surface reactions must be incorporated into chemical models of planetary nebulae.

ABSTRACT We present JWST/NIRSpec IFU observations of the $z=7.152$ galaxy system B14-65666, as part of the GA-NIFS survey. Line and continuum emission in this massive system ($\log _{10}(M_*/{\rm M}_{\odot })=9.8\pm 0.2$) is resolved into two strong cores surrounded by diffuse emission, as seen in recent JWST/NIRCam imaging. Our data set contains detections of [O ii]$\lambda \lambda 3726{,}3729$, [Ne iii]$\lambda \lambda 3869{,}3968$, Balmer lines, [O iii]$\lambda \lambda 4959{,}5007$, He i$\lambda 5875$, and weak [O iii]$\lambda 4363$. Each spectrum is fit with a model that consistently incorporates interstellar medium conditions (i.e. electron temperature, $T_{\rm e}$, electron density, $n_{\rm e}$, and colour excess, $E(B-V)$). The resulting line fluxes are used to constrain the gas-phase metallicity ($Z_{\rm g}\sim 0.2\mathrm{ -}0.3$ solar) and H$\beta$-based star formation rate for each region. Common line ratio diagrams (O32–R23, R3–R2, Ne3O2–R23) reveal that each line-emitting region lies at the intersection of low- and high-redshift galaxies, suggesting low ionization and higher metallicity compared to the predominantly lower-mass galaxies studied with the JWST/NIRSpec IFU so far at $z\gt 5.5$. Spaxel-by-spaxel fits reveal evidence for both narrow (FWHM $\lt 400$ km s$^{-1}$) and broad (FWHM $\gt 500$ km s$^{-1}$) line emission, the latter of which likely represents tidal interaction or outflows. Comparison to ALMA [C ii]158$\mu$m and [O iii]88$\mu$ m data shows a similar velocity structure, and we explore optical-far infrared diagnostics. The two core galaxies both lie on the mass-metallicity relation at $z\gt 4$, but show contrasting properties (e.g. $M_*$, $Z_{\rm g}$), suggesting distinct evolutionary pathways. Combining the NIRSpec IFU and ALMA data sets, our analysis opens new windows into the merging system B14-65666.

ABSTRACT Modern surveys such as Euclid report a decline in the fraction of barred galaxies from the local Universe to $z \sim 1$, whereas the TNG50 simulation predicts higher bar fractions, in tension with observations. This discrepancy may be due to observational biases in bar detectability when comparing simulations with observations. We present a proof-of-concept study quantifying how Euclid-like observational conditions affect bar detectability in TNG50. We analysed the entire galaxy sample at $z=0.5$ and highlight one borderline case with a bar length of 2.1 kpc and strength $A_2=0.4$. Synthetic images were produced with Monte Carlo radiative transfer and realistic post-processing, and analysed with ellipse fitting and Fourier decomposition, as well as the recently constructed Zoobot analysis. Results were compared to idealized noise-free stellar mass maps. In the illustrative case the bar is clearly detected in the mass map and remains visible in the Euclid VIS $I_{\rm E}$ filter, where Zoobot also classifies it as barred, but becomes undetectable in $Y_{\rm E}$ and in the VIS–NISP RGB composite, with all methods failing outside VIS. Extending to the full $z=0.5$ sample, Zoobot recovers only 31/141 galaxies, while $A_2$ and ellipse fitting perform better (80/141 and 67/141) but still miss many short or weak bars. When non-detections are counted as unbarred, the bar fraction of 44 per cent falls to 12–33 per cent depending on method. These results demonstrate the strong impact of observational effects on bar detectability and motivate bar-fraction estimates that incorporate realistic instrumental conditions across redshift in cosmological simulations.

Abstract The Vera C. Rubin Observatory’s Legacy Survey of Space and Time (LSST) will monitor tens of millions of active galactic nuclei (AGNs) for a period of 10 yr with an average cadence of 3 days in six broad photometric bands. This unprecedented data set will enable robust characterizations of AGN UV/optical variability across a wide range of AGN physical properties. However, existing tools for modeling AGN light curves are not yet capable of fully leveraging the volume, cadence, and multiband nature of LSST data. We present EzTaoX , a scalable light-curve modeling tool designed to take advantage of LSST’s multiband observations to simultaneously characterize AGN UV/optical stochastic variability and measure interband time delays. EzTaoX achieves a speed increase of ∼10 2 –10 4 × on CPUs over current tools with similar capabilities, while maintaining equal or better accuracy in recovering simulated variability properties. This performance gain enables continuum time-delay measurements for all AGNs discovered by LSST—both in the Wide Fast Deep survey and the Deep Drilling Fields—thereby opening new opportunities to probe AGN accretion-flow geometries. In addition, EzTaoX ’s multiband capability allows for robust characterization of AGN stochastic variability down to hourly timescales, facilitating the identification of accreting low-mass AGNs—such as those residing in dwarf galaxies—through their distinctive variability signatures.

Abstract The metallicity of the star-forming environment is a fundamental parameter shaping the evolution of protoplanetary disks and the formation of planetary systems, yet its influence remains poorly constrained. We present a spectroscopic study of low-mass pre-main-sequence (PMS) stars ( M < 1 M ⊙ ) in the exceptionally metal-poor cluster Dolidze 25 ( Z ≈ 0.2 Z ⊙ ), using Very Large Telescope/MUSE observations to probe accretion processes and disk evolution in a subsolar environment. We identify 132 cluster members using a combination of Gaia astrometry and spectroscopic youth indicators, including lithium absorption and Balmer emission. The stellar parameters are derived using low-metallicity BT-Settl models yielding effective temperatures, extinctions, and luminosities enabling robust estimates of stellar masses and ages. Mass accretion rates ( M ̇ acc ) derived from H α emission span 10 −10 –10 −8 M ⊙ yr −1 with a median value of 8 × 10 −10 M ⊙ yr −1 . These rates are comparable to those in solar-metallicity regions of a similar age, such as Lupus and Orion, indicating minimal metallicity dependence in accretion processes. Our analysis shows that using solar-metallicity templates to fit low-metallicity stars leads to systematic overestimations of T eff (by approximately 300 K) and A V (by around 0.5 mag), underscoring the importance of employing metallicity-matched models for reliable characterization in low- Z environments. We present flux-calibrated, extinction-corrected spectra of these metal-poor PMS stars as a valuable resource for future investigations of disk evolution in subsolar regimes.

Abstract Recent discoveries of streamer-like structures around protostellar sources challenge the traditional picture of isolated, axisymmetric star formation. Here, we present new Atacama Large Millimeter/submillimeter Array observations of [BHB2007]-1, a flat-spectrum source connected to at least three such elongated structures. Two of these features are symmetrically located to the north and south of the disk, with velocities aligned with the disk on their respective sides. However, their unbound kinematics and curved morphology make it difficult to determine their origin. Possible explanations include outflows, interactions with the nearby [BHB2007]-2 system, and hyperbolic infall, but none fully account for all observed properties. In contrast, a newly identified collimated structure to the west shows clear evidence of gravitationally bound infall. Estimates of its mass, mass infall rate, and angular momentum suggest that this infalling streamer would roughly double the mass budget available to form planets and tilt the disk by a few tens of degrees. Furthermore, its misalignment with the midplane of the disk and the lack of diffuse envelope emission indicate that the streamer may have formed due to gravitational capture of cloud material unrelated to the source’s natal core. Together, these findings support a more dynamic picture of star formation, one where environmental interactions continue to shape the conditions for building planetary systems.