Aims. Gamma-ray line emission from the radioactive decay of 26 Al reflects nucleosynthesis in massive stars and supernovae. We use INTEGRAL 26 Al measurements to characterize the distribution and characteristics of 26 Al source regions throughout the Galaxy. Methods. The spectrometer SPI aboard INTEGRAL has accumulated over five years of data on 26 Al gamma-ray emission from the Galactic plane. We analyzed these data using suitable instrumental-background models and adopted sky distribution models to produce high-resolution 26 Al spectra of Galactic emission, spatially resolved along the Galaxy plane. Results. We detect the 26 Al line from the inner Galaxy at ∼28σ significance. The line appears narrow, and we constrain broadening in the source regions to <1.3 keV (2σ). Different sky distribution models do not significantly affect those large-scale results. The 26 Al intensity for the inner Galaxy is derived as (2.9 ± 0.2) × 10 −4 ph cm −2 s −1 rad −1 , consistent with earlier results from COMPTEL and SPI data. This can be translated to an 26 Al mass of 2.7 ± 0.7 M in the Galaxy as a whole. The 26 Al intensity is also confirmed to be somewhat brighter in the 4th than in the 1st quadrant (ratio ∼1.3 ± 0.2).

Context. The Scorpius-Centaurus association is the most-nearby group of massive and young stars. As nuclear-fusion products are ejected by massive stars and supernovae into the surrounding interstellar medium, the search for characteristic γ-rays from radioactivity is one way to probe the history of activity of such nearby massive stars on a My time scale through their nucleosynthesis. 26 Al decays with a radioactivity lifetime τ ∼1 My, 1809 keV γ-rays from its decay can be measured with current γ-ray telescopes. Aims. We aim to identify nucleosynthesis ejecta from the youngest subgroup of Sco-Cen stars, and interpret their location and bulk motion from 26 Al observations with INTEGRAL's γ-ray spectrometer SPI. Methods. Following earlier 26 Al γ-ray mapping with NASA's Compton observatory, we test spatial emission skymaps of 26 Al for a component which could be attributed to ejecta from massive stars in the Scorpius-Centaurus group of stars. Such a model fit of spatial distributions for large-scale and local components is able to discriminate 26 Al emission associated with Scorpius-Centaurus, in spite of the strong underlying nucleosynthesis signal from the Galaxy at large. Results. We find an 26 Al γ-ray signal above 5σ significance, which we associate with the locations of stars of the Sco-Cen group. The observed flux of 6 × 10 −5 ph cm −2 s −1 corresponds to ∼1.1 × 10 −4 M of 26 Al. This traces the nucleosynthesis ejecta of several massive stars within the past several million years. Conclusions. We confirm through direct detection of radioactive 26 Al the recent ejection of massive-star nucleosynthesis products from the Sco-Cen association. Its youngest subgroup in Upper Scorpius appears to dominate 26 Al contributions from this association. Our 26 Al signal can be interpreted as a measure of the age and richness of this youngest subgroup. We also estimate a kinematic imprint of these nearby massive-star ejecta from the bulk motion of 26 Al and compare this to other indications of Scorpius-Centaurus massive-star activity.

The isotopes 60 Fe and 26 Al originate from massive stars and their supernovae, reflecting ongoing nucleosynthesis in the Galaxy. We studied the gamma-ray emission from these isotopes at characteristic energies 1173, 1332, and 1809 keV with over 15 years of SPI data, finding a line flux in 60 Fe combined lines of (0.31 ± 0.06) × 10 −3 ph cm −2 s −1 and the 26 Al line flux of (16.8 ± 0.7) × 10 −4 ph cm −2 s −1 above the background and continuum emission for the whole sky. Based on the exponentialdisk grid maps, we characterise the emission extent of 26 Al to find scale parameters R 0 = 7.0 +1.5 −1.0 kpc and z 0 = 0.8 +0.3 −0.2 kpc, however the 60 Fe lines are too weak to spatially constrain the emission. Based on a point source model test across the Galactic plane, the 60 Fe emission would not be consistent with a single strong point source in the Galactic center or somewhere else, providing a hint for a diffuse nature. We carried out comparisons of emission morphology maps using different candidate-source tracers for both 26 Al and 60 Fe emissions, and suggests that the 60 Fe emission is more likely to be concentrated towards the Galactic plane. We determine the 60 Fe / 26 Al γ-ray flux ratio at (18.4 ± 4.2) % , when using a parameterized spatial morphology model. Across the range of plausible morphologies, it appears possible that 26 Al and 60 Fe are distributed differently in the Galaxy. Using the best fitting maps for each of the elements, we constrain flux ratios in the range 0.2-0.4. We discuss its implications for massive star models and their nucleosynthesis.

Context. The space based γ-ray observatory INTEGRAL of the European Space Agency (ESA) includes the spectrometer instrument "SPI". This is a coded mask telescope featuring a 19-element Germanium detector array for high-resolution γ-ray spectroscopy, encapsulated in a scintillation detector assembly that provides a veto for background from charged particles. In space, cosmic rays irradiate spacecraft and instruments, which, in spite of the vetoing detectors, results in a large instrumental background from activation of those materials, and leads to deterioration of the charge collection properties of the Ge detectors. Aims. We aim to determine the measurement characteristics of our detectors and their evolution with time, that is, their spectral response and instrumental background. These incur systematic variations in the SPI signal from celestial photons, hence their determination from a broad empirical database enables a reduction of underlying systematics in data analysis. For this, we explore compromises balancing temporal and spectral resolution within statistical limitations. Our goal is to enable modelling of background applicable to spectroscopic studies of the sky, accounting separately for changes of the spectral response and of instrumental background. Methods. We use 13.5 years of INTEGRAL/SPI data, which consist of spectra for each detector and for each pointing of the satellite. Spectral fits to each such spectrum, with independent but coherent treatment of continuum and line backgrounds, provides us with details about separated background components. From the strongest background lines, we first determine how the spectral response changes with time. Applying symmetry and long-term stability tests, we eliminate degeneracies and reduce statistical fluctuations of background parameters, with the aim of providing a self-consistent description of the spectral response for each individual detector. Accounting for this, we then determine how the instrumental background components change in intensities and other characteristics, most-importantly their relative distribution among detectors. Results. Spectral resolution of Ge detectors in space degrades with time, up to 15% within half a year, consistently for all detectors, and across the SPI energy range. Semi-annual annealing operations recover these losses, yet there is a small long-term degradation. The intensity of instrumental background varies anti-correlated to solar activity, in general. There are significant differences among different lines and with respect to continuum. Background lines are found to have a characteristic, well-defined and long-term consistent intensity ratio among detectors. We use this to categorise lines in groups of similar behaviour. The dataset of spectral-response and background parameters as fitted across the INTEGRAL mission allows studies of SPI spectral response and background behaviour in a broad perspective, and efficiently supports precision modelling of instrumental background.

While the importance of continuous monitoring of electrocardiographic (ECG) or photoplethysmographic (PPG) signals to detect cardiac anomalies is generally accepted in preventative medicine, there remain numerous challenges to its widespread adoption. Most notably, difficulties arise regarding crucial characteristics such as real-time capability, computational complexity, the amount of required training data, and the avoidance of too-restrictive modeling assumptions. We propose a lightweight and model-free approach for the online detection of cardiac anomalies such as ectopic beats in ECG or PPG signals on the basis of the change detection capabilities of singular spectrum analysis (SSA) and nonparametric rank-based cumulative sum (CUSUM) control charts. The procedure is able to quickly detect anomalies without requiring the identification of fiducial points such as R-peaks, and it is computationally significantly less demanding than previously proposed SSA-based approaches. Therefore, the proposed procedure is equally well suited for standalone use and as an add-on to complement existing (e.g., heart rate (HR) estimation) procedures.