The elements in the Universe are synthesized primarily in stars and supernovae, where nuclear fusion favours the production of even-Z elements. In contrast, odd-Z elements are less abundant and their yields are highly dependent on detailed stellar physics, making theoretical predictions of their cosmic abundance uncertain. In particular, the origin of odd-Z elements such as phosphorus (P), chlorine (Cl) and potassium (K), which are important for planet formation and life, is poorly understood. While the abundances of these elements in Milky Way stars are close to solar values, supernova explosion models systematically underestimate their production by up to an order of magnitude, indicating that key mechanisms for odd-Z nucleosynthesis are currently missing from theoretical models. Here we report the observation of P, Cl and K in the Cassiopeia A supernova remnant using high-resolution X-ray spectroscopy with X-Ray Imaging and Spectroscopy Mission data, with the detection of K at above the 6 sigma level being the most significant finding. Supernova explosion models of normal massive stars cannot explain the element abundance pattern, especially the high abundances of Cl and K, while models that include stellar rotation, binary interactions or shell mergers agree closely with the observations. Our observations suggest that such stellar activity plays an important role in supplying these elements to the Universe.
Cities around the world have united to form coalitions, like the C40 network, in pursuit of ambitious climate goals. These efforts often include reducing methane emissions. However, sources and magnitudes of urban methane emissions are not well known, and there is not currently a method to evaluate implementation of mitigation measures. Here, we fill this observational gap with a tracer-tracer approach using space-based observations of methane and carbon monoxide from the TROPOspheric Monitoring Instrument satellite instrument. We measure methane emissions of 92 global cities, including their broader metropolitan area, and find aggregate emissions of 31.2 Tg CH4/y (95%CI: 22.3, 40.4 Tg CH4/y) in 2023, equivalent to [Formula: see text]10% of the global anthropogenic methane budget. We track emissions for 72 of these cities (51 C40 cities and 21 non-C40 cities) from 2019-2023. Methane emissions from these cities weakly declined in 2020 followed by steady growth, with a 2.3 Tg aggregate increase over 4 y. This growth contributes minimally to the recent atmospheric methane surge. While C40 cities have largely pledged 34% reductions by 2030, we observe significant growth from 2020 to 2023 (10%, 95%CI: 2%, 17%), similar to growth observed in non-C40 cities (12%, 95%CI: [Formula: see text]1.5%, 25%). Inventories fail to capture observed growth, suggesting urban emissions are not well characterized, and mitigation approaches may not be optimally designed. For the C40 network to achieve its methane target (34% by 2030), steep, rapid reductions will be needed. Emission reductions of this magnitude would be detectable with the space-based approach used in this work.
The X-ray Integral Field Unit is the X-ray imaging spectrometer on-board one of ESA's next large missions, Athena. Athena is set to investigate the theme of the Hot and Energetic Universe, with a launch planned in the late-2030s. Based on a high sensitivity Transition Edge Sensor (TES) detector array operated at very low temperature (50 mK), X-IFU will provide spatially resolved high resolution spectroscopy of the X-ray sky in the 0.2-12 keV energy band, with an energy resolution goal of 4 eV up to 7 keV [3 eV design goal]. This paper presents the current calibration plan of the X-IFU. It provides the requirements applicable to the X-IFU calibration, describes the overall calibration strategy, and details the procedure and sources needed for the ground calibration of each parameter or characteristics of the X-IFU.
Aims. We update the status of the spectropolarimetric campaign dedicated to characterise the magnetic field properties of a sample of known exoplanet-hosting stars included in the current target list of the Ariel mission. The main aims are to inform observing strategies and subsequent analysis of the data of the Ariel mission, and to provide background information on the magnetic properties of the target and their variability on timescales of at least a few years. Methods. We analysed spectropolarimetric data collected for 15 G-M type stars with Neo-Narval, HARPSpol, and SPIRou to assess the detectability of the large-scale magnetic field. For three stars we reconstructed the magnetic field topology and its temporal evolution via Zeeman-Doppler imaging (ZDI). Such reconstructions were then used to perform three-dimensional magnetohydrodynamical simulations of the stellar wind and environment impinging on the hosted exoplanets. Results. We detected the magnetic field of six stars. Of these, we performed ZDI reconstructions for the first time of TOI-1860 and DS Tuc A, and for the second time of HD 63433, providing temporal information of its large-scale magnetic field. Consistently with previous results on young (similar to 50-100 Myr) solar-like stars, the large-scale magnetic field is moderately strong (30-60 G on average) and complex, with a significant fraction of magnetic energy in the toroidal component and high-order poloidal components. From the simulations of the stellar wind, we found the orbit of TOI-1860 b to be almost completely sub-Alfvenic, the orbits of DS Tuc A b and HD 63433 d to be trans-Alfvenic, and the orbits of HD 63433 b and c to be super-Alfvenic. We obtained marginal detections of the magnetic field for TOI-836 and TOI-2076, and detections for TOI-1136, but the number of observations is not sufficient for magnetic mapping. Conclusions. A magnetic star-planet connection can occur for most of TOI-1860 b's orbit. This can happen more sporadically for DS Tuc A b and HD 63433 c given the lower fraction of their orbit in the sub-Alfvenic regime. The orbit of HD 63433 c is nevertheless more sub-Alfvenic than previously simulated owing to the temporal evolution of the stellar magnetic field. For HD 63433 b and c, we expect the formation of a bow shock between the stellar wind and the planet despite the evolution of the stellar magnetic field.
Aims. We update the status of the spectropolarimetric campaign dedicated to characterise the magnetic field properties of a sample of known exoplanet-hosting stars included in the current target list of the Ariel mission. The main aims are to inform observing strategies and subsequent analysis of the data of the Ariel mission, and to provide background information on the magnetic properties of the target and their variability on timescales of at least a few years. Methods. We analysed spectropolarimetric data collected for 15 G-M type stars with Neo-Narval, HARPSpol, and SPIRou to assess the detectability of the large-scale magnetic field. For three stars we reconstructed the magnetic field topology and its temporal evolution via Zeeman-Doppler imaging (ZDI). Such reconstructions were then used to perform three-dimensional magnetohydrodynamical simulations of the stellar wind and environment impinging on the hosted exoplanets. Results. We detected the magnetic field of six stars. Of these, we performed ZDI reconstructions for the first time of TOI-1860 and DS Tuc A, and for the second time of HD 63433, providing temporal information of its large-scale magnetic field. Consistently with previous results on young (~50–100 Myr) solar-like stars, the large-scale magnetic field is moderately strong (30–60 G on average) and complex, with a significant fraction of magnetic energy in the toroidal component and high-order poloidal components. From the simulations of the stellar wind, we found the orbit of TOI-1860 b to be almost completely sub-Alfvénic, the orbits of DS Tuc A b and HD 63433 d to be trans-Alfvénic, and the orbits of HD 63433 b and c to be super-Alfvénic. We obtained marginal detections of the magnetic field for TOI-836 and TOI-2076, and detections for TOI-1136, but the number of observations is not sufficient for magnetic mapping. Conclusions. A magnetic star-planet connection can occur for most of TOI-1860 b’s orbit. This can happen more sporadically for DS Tuc A b and HD 63433 c given the lower fraction of their orbit in the sub-Alfvénic regime. The orbit of HD 63433 c is nevertheless more sub-Alfvénic than previously simulated owing to the temporal evolution of the stellar magnetic field. For HD 63433 b and c, we expect the formation of a bow shock between the stellar wind and the planet despite the evolution of the stellar magnetic field.
