News from Cosmic Gamma-ray Line Observations

Abstract

The measurement of gamma rays at MeV energies from cosmic radioactivities is one of the key tools for nuclear astrophysics, in its study of nuclear reactions and how they shape objects such as massive stars and supernova explosions. Additionally, the unique gamma-ray signature from the annihilation of positrons falls into this same astronomical window, and positrons are often produced from radioactive beta decays. Nuclear gamma-ray telescopes face instrumental challenges from penetrating gamma rays and cosmic-ray induced backgrounds. But the astrophysical benefits of such efforts are underlined by the discoveries of nuclear gamma~rays from the brightest of the expected sources. In recent years, both thermonuclear and core-collapse supernova radioactivity gamma~rays have been measured in spectral detail, and complement conventional supernova observations with measurements of origins in deep supernova interiors, from the decay of ${}^{56}$Ni, ${}^{56}$Co, and ${}^{44}$Ti. The diffuse afterglow in gamma rays of radioactivity from massive-star nucleosynthesis is analysed on the large (galactic) scale, with findings important for recycling of matter between successive stellar generations: From ${}^{26}$Al gamma-ray line spectroscopy, interstellar cavities and superbubbles have been recognised in their importance for ejecta transport and recycling. Diffuse galactic emissions from radioactivity and positron-annihilation $\gamma$~rays should be connected to nucleosynthesis sources: Recently new light has been shed on this connection, among others though different measurements of radioactive ${}^{60}$Fe, and through spectroscopy of positron annihilation gamma~rays from a flaring microquasar and from different parts of our Galaxy.

arXiv commentInvited talk at the international symposium "Nuclei in the Cosmos XIV", June 2016, at Niigata, Japan. Six pages, two figures. Accepted for publication in JPS (Japan Physical Society) Conference Proceedings (http://jpscp.jps.jp/)

References in corpus (22)

• X-ray Properties of Black-Hole Binaries
• The Nuclear Spectroscopic Telescope Array (NuSTAR) Mission
• Radioactive 26Al and massive stars in the Galaxy
• The all-sky distribution of 511 keV electron-positron annihilation emission
• Early SPI/INTEGRAL measurements of galactic 511 keV line emission from positron annihilation
• The 511 keV emission from positron annihilation in the Galaxy
• Asymmetries in core-collapse supernovae from maps of radioactive ${}^{44}$Ti in CassiopeiaA
• Cobalt-56 gamma-ray emission lines from the type Ia supernova 2014J
• Gamma-ray spectroscopy of Positron Annihilation in the Milky Way
• Early 56Ni decay γ-rays from SN2014J suggest an unusual explosion
• Positron annihilation signatures associated with the outburst of the microquasar V404 Cygni
• Are Ti44-Producing Supernovae Exceptional?
• SN2014J gamma-rays from the 56Ni decay chain
• Kinematics of massive star ejecta in the Milky Way as traced by 26Al
• On the morphology of the electron-positron annihilation emission as seen by SPI/INTEGRAL
• Nuclear-Astrophysics Lessons from INTEGRAL
• The 3-D Structure of SN 1987A's inner Ejecta
• Gamma-rays from Type Ia supernova SN2014J
• Revisiting INTEGRAL/SPI observations of 44Ti from Cassiopeia A
• GRIPS - Gamma-Ray Imaging, Polarimetry and Spectroscopy
• 26Al kinematics: superbubbles following the spiral arms? Constraints from the statistics of star clusters and HI supershells
• Gamma-Ray emission from SN2014J near maximum optical light

Cited by in corpus (1)

• Synthetic ${}^{26}$Al emission from galactic-scale superbubble simulations