Steady-state nucleosynthesis throughout the Galaxy

Abstract

The measurement and astrophysical interpretation of characteristic γ-ray lines from nucleosynthesis was one of the prominent science goals of the INTEGRAL mission and in particular its spectrometer SPI. Emission from 26 Al and from 60 Fe decay lines, due to their My decay times, originates from accumulated ejecta of nucleosynthesis sources, and appears diffuse in nature. 26 Al and 60 Fe are believed to originate mostly from massive star clusters. The radioactive decay γ-ray observations open an interesting window to trace the fate and flow of nucleosynthesis ejecta, after they have left the immediate sources and their birth sites, and on their path to mix with ambient interstellar gas. The 26 Al emission image obtained with INTEGRAL confirms earlier findings of clumpiness and an extent along the entire plane of the Galaxy, supporting its origin from massive-star groups. INTEGRAL spectroscopy resolved the line and found Doppler broadenings and systematic shifts with longitude, originating from large-scale galactic rotation. But an excess velocity of ∼200 km s −1 suggests that 26 Al decays preferentially within large superbubbles that extend in forward directions between spiral arms. The detection of 26 Al line emission from the nearby Orion clusters

A New Versatile Code for Gamma-Ray Monte-Carlo Radiative Transfer

“…Even though novae eject a small mass during its outburst, their occurrence rate is still about 100-1000 times higher than supernovae in a galaxy; they are one of the robust sources for producing the diffusive γ-ray background in the galactic plane (Diehl et al 2021). Here we demonstrate the performance of the code using a representative C+O nova model.…”

Measurement of the low energy 25Mg(p,γ)26Al resonances

“…On the other hand, it is much shorter than the evolution time of the Galaxy so the observation of 26 Al decay is direct evidence of the ongoing nucleosynthesis in the Galaxy. Therefore, 26 Al is expected to be a tracer for stellar nucleosynthesis and a thermometer for its production site [4]. 26 Al can be synthesized by Mg-Al reaction cycle in the H burning environments, e.g., asymptotic giant branch (AGB) stars, Wolf-Rayet stars, O-Ne-Mg novae and core collapse supernovae.…”

“…26 Al can be synthesized by Mg-Al reaction cycle in the H burning environments, e.g., asymptotic giant branch (AGB) stars, Wolf-Rayet stars, O-Ne-Mg novae and core collapse supernovae. It is believed that 26 Al in the interstellar medium of the Galaxy is mainly from massive stars and partly from AGB stars and novae [4]. In the Mg-Al reaction cycle, 26 Al is produced via the 25 Mg(p, γ) 26 Al reaction and destroyed by β-decay or other reactions, e.g., 26 Al(p, γ) 27 Si, 26 Al(n, p) 26 Mg, 26 Al(n, α) 23 Na, depending on the astrophysical sites.…”

COSI: From Calibrations and Observations to All-sky Images

“…The gamma-ray sky from a few hundred keV to several MeV is host to a multitude of phenomena, including the life cycle of matter in our Universe, the most energetic explosions (supernovae, mergers), and the most extreme environments such as pulsars and accreting black holes. Up to now, this energy range has not been very deeply explored, and a plethora of open questions remain, ranging from the origin of the 511-keV emission near the center of our Galaxy (Prantzos et al 2011;Churazov et al 2020), to element creation during supernovae and mergers (Isern et al 2021;Korobkin et al 2020;Diehl et al 2021), and more.…”