Measuring Cosmic Elements with Gamma-Ray Telescopes

AbstractGamma-ray telescopes are capable of measuring radioactive trace isotopes from cosmic nucleosynthesis events. Such measurements address new isotope production rather directly for a few key isotopes such as 44Ti, 26Al, 60Fe, and 56Ni, as well as positrons from the β+-decay variety. Experiments of the past decades have now established an astronomy with γ-ray lines, which is an important part of the study of nucleosynthesis environments in cosmic sources. For massive stars and supernovae, important constraints have been set: Co isotope decays in SN1987A directly demonstrated the synthesis of new isotopes in core-collapse supernovae, 44Ti from the 340-year-old Cas A supernova supports the concept of α-rich freeze-out, but results in interesting puzzles pursued by theoretical studies and future experiments. 26Al and 60Fe has been measured from superimposed nucleosynthesis within our Galaxy, and sets constraints on massive-star interior structure through its intensity ratio of ∼15%. The 26Al γ-ray line is now seen to trace current star formation and even the kinematics of interstellar medium throughout the Galaxy. Positron annihilation emission from nucleosynthesis throughout the plane of our Galaxy appears to be mainly from 26Al and other supernova radioactivity, but the striking brightness of the Galaxy's bulge region in positron annihilation γ-rays presents a puzzle involving several astrophysics issues beyond nuclear astrophysics. This paper focuses mainly on a discussion of 26Al and 60Fe from massive-star nucleosynthesis.

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Gamma-ray observations and massive stars

Symposium - International Astronomical Union ◽

10.1017/s0074180900205317 ◽

1999 ◽

Vol 193 ◽

pp. 205-217

Author(s):

Roland Diehl

Keyword(s):

Gamma Rays ◽

Massive Star ◽

Gamma Ray ◽

Massive Stars ◽

Cosmic Ray ◽

Interstellar Space ◽

Interstellar Matter ◽

Spatial Profile ◽

The Galaxy ◽

Γ Ray

Gamma-rays from astrophysical sources testify energetic processes such as nucleosynthesis and cosmic ray collisions. Gamma-rays are observable from throughout the Galaxy, unattenuated by interstellar matter, provided their intensity exceeds the current instrumental sensitivity level (∼ 10−5ph cm−2s−1 at 1 MeV). Massive stars are at the origin of relevant sources: The all-sky image in the 1.809 MeV γ-ray line from radioactive 26Al traces nucleosynthesis throughout the Galaxy. The structure of this emission along the plane of the Galaxy suggests massive stars as dominating sources of this radioactivity. Discrimination of the contribution from core collapse supernova against that from WR-wind ejected hydrostatic nucleosynthesis products may be obtained from 60Fe γ-ray line observations, or from spatial-profile consequences of the metallicity dependence of 26Al production in theories for both source sites. As a single source, the nearest WR star in the γ2 Vel system is found to eject less 26Al into interstellar space than current theories predict. However, a more adequate comparison must be based on a time-dependent 26Al light-curve of the system. Furthermore, continuum γ-ray production in WR binaries through wind-wind interaction, and constraints on the low-energy cosmic ray origin in WR winds through characteristic nuclear deexcitation line studies are targets of research. Studies stimulated by COMPTEL'S 3–7 MeV excess report from the Orion region indicate that the γ-ray line measurements could separate the origins from supernova ejecta and wind material. The COMPTEL Orion result is now attributed chiefly to an instrumental artifact, and has been withdrawn. Nevertheless, the search for MeV emission from massive star clusters, as well as from interacting binaries such as WR 140, promises a unique test of particle acceleration scenarios related to the source mechanism for cosmic ray production.

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Understanding the origin of the positron annihilation line and the physics of supernova explosions

Experimental Astronomy ◽

10.1007/s10686-021-09727-7 ◽

2021 ◽

Author(s):

F. Frontera ◽

E. Virgilli ◽

C. Guidorzi ◽

P. Rosati ◽

R. Diehl ◽

...

Keyword(s):

Positron Annihilation ◽

Large Scale ◽

Gamma Ray ◽

Nuclear Astrophysics ◽

High Energy ◽

Radioactive Isotopes ◽

Fusion Reactions ◽

Dark Matter Annihilation ◽

Annihilation Line ◽

Supernova Explosions

AbstractNuclear astrophysics, and particularly nuclear emission line diagnostics from a variety of cosmic sites, has remained one of the least developed fields in experimental astronomy, despite its central role in addressing a number of outstanding questions in modern astrophysics. Radioactive isotopes are co-produced with stable isotopes in the fusion reactions of nucleosynthesis in supernova explosions and other violent events, such as neutron star mergers. The origin of the 511 keV positron annihilation line observed in the direction of the Galactic Center is a 50-year-long mystery. In fact, we still do not understand whether its diffuse large-scale emission is entirely due to a population of discrete sources, which are unresolved with current poor angular resolution instruments at these energies, or whether dark matter annihilation could contribute to it. From the results obtained in the pioneering decades of this experimentally-challenging window, it has become clear that some of the most pressing issues in high-energy astrophysics and astro-particle physics would greatly benefit from significant progress in the observational capabilities in the keV-to-MeV energy band. Current instrumentation is in fact not sensitive enough to detect radioactive and annihilation lines from a wide variety of phenomena in our and nearby galaxies, let alone study the spatial distribution of their emission. In this White Paper (WP), we discuss how unprecedented studies in this field will become possible with a new low-energy gamma-ray space experiment, called ASTENA (Advanced Surveyor of Transient Events and Nuclear Astrophysics), which combines new imaging, spectroscopic and polarization capabilities. In a separate WP (Guidorzi et al. 39), we discuss how the same mission concept will enable new groundbreaking studies of the physics of Gamma–Ray Bursts and other high-energy transient phenomena over the next decades.

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Gamma-Ray Imaging of the Galactic Center Region

Symposium - International Astronomical Union ◽

10.1017/s007418090018708x ◽

1989 ◽

Vol 136 ◽

pp. 581-585

Author(s):

W. R. Cook ◽

D. M. Palmer ◽

T. A. Prince ◽

S. M. Schindler ◽

C. H. Starr ◽

...

Keyword(s):

Gamma Ray ◽

Galactic Center ◽

Coded Aperture ◽

Center Region ◽

Gamma Ray Imaging ◽

The Galaxy ◽

Γ Ray ◽

Luminous Objects

The Caltech imaging γ-ray telescope was launched by balloon from Alice Springs, NT, Australia and performed observations of the galactic center during the period 12.62 to 13.00 April 1988 UT. The first coded-aperture images of the galactic center region at energies above 30 keV show a single strong γ-ray source which is located 0.7±0.1° from the galactic nucleus and is tentatively identified as 1E1740.7-2942. If the source is at the distance of the galactic center, it is one of the most luminous objects in the galaxy at energies from 35 to 200 keV.

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What do Gamma Rays tell us about the ISM?: New Insight from the Compton Observatory

Symposium - International Astronomical Union ◽

10.1017/s007418090023009x ◽

1996 ◽

Vol 169 ◽

pp. 437-446 ◽

Cited By ~ 1

Author(s):

Hans Bloemen

Keyword(s):

Interstellar Medium ◽

Gamma Rays ◽

Gamma Ray ◽

Line Emission ◽

Cosmic Ray ◽

Gamma Ray Astronomy ◽

Early Results ◽

The Galaxy ◽

Γ Ray ◽

Insight Into

Gamma-ray astronomy has become a rich field of research and matured significantly since the launch of NASA's Compton Gamma Ray Observatory in April 1991. Studies of the diffuse γ-ray emission of the Galaxy can now be performed in far more detail and extended into the MeV regime, including both continuum and line emission. These studies provide unique insight into various aspects of the interstellar medium, in particular of the cosmic-ray component. This paper gives a brief review on the diffuse Galactic γ-ray emission and summarizes early results and prospects from the Compton Observatory.

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Gamma-ray observations and the large scale structure of the galaxy

Symposium - International Astronomical Union ◽

10.1017/s0074180900014327 ◽

1979 ◽

Vol 84 ◽

pp. 125-130

Author(s):

J. A. Paul

Keyword(s):

Present Status ◽

Large Scale ◽

Gamma Ray ◽

Galactic Plane ◽

Large Scale Structure ◽

Galactic Disc ◽

Γ Radiation ◽

Latitude Dependence ◽

The Galaxy ◽

Γ Ray

Within the last few years, γ-ray astronomy has shifted from the discovery phase to the exploratory phase, thanks to the SAS-2 and COS-B satellites. The strongest feature of the γ-ray sky is the overwhelming emission of the galactic disc; even the radiation observed away from the galactic plane appears to be predominantly galactic, on the basis of its latitude dependence (Fichtel et al., 1978). Nevertheless, extragalactic γ-ray astronomy is not hopeless: the γ-radiation of the nearby quasar 3C273 has been very recently detected (Swanenburg et al., 1978). A brief summary of the present status of the galactic γ-ray astronomy follows.

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Gamma-ray line measurements from supernova explosions

Proceedings of the International Astronomical Union ◽

10.1017/s1743921317004343 ◽

2017 ◽

Vol 12 (S331) ◽

pp. 157-163 ◽

Cited By ~ 1

Author(s):

Roland Diehl

Keyword(s):

Supernova Remnant ◽

Gamma Ray ◽

Radioactive Decay ◽

Line Emission ◽

Gamma Ray Spectrometry ◽

Young Supernova Remnant ◽

Supernova Explosions ◽

Cas A ◽

Integral Data ◽

Gamma Ray Telescopes

AbstractGamma ray lines are expected to be emitted as part of the afterglow of supernova explosions, because radioactive decay of freshly synthesised nuclei occurs. Significant radioactive gamma ray line emission is expected from56Ni and44Ti decay on time scales of the initial explosion (56Ni, τ ~days) and the young supernova remnant (44Ti,τ ~90 years). Less specific, and rather informative for the supernova population as a whole, are lessons from longer lived isotopes such as26Al and60Fe. From isotopes of elements heavier than iron group elements, any interesting gamma-ray line emission is too faint to be observable. Measurements with space-based gamma-ray telescopes have obtained interesting gamma ray line emissions from two core collapse events, Cas A and SN1987A, and one thermonuclear event, SN2014J. We discuss INTEGRAL data from all above isotopes, including all line and continuum signatures from these two objects, and the surveys for more supernovae, that have been performed by gamma ray spectrometry. Our objective here is to illustrate what can be learned from gamma-ray line emission properties about the explosions and their astrophysics.

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High-energy Galactic phenomena and the interstellar medium

Symposium - International Astronomical Union ◽

10.1017/s0074180900242502 ◽

1985 ◽

Vol 106 ◽

pp. 225-233

Author(s):

Catherine J. Cesarsky

Keyword(s):

Magnetic Fields ◽

Interstellar Medium ◽

Molecular Hydrogen ◽

Gamma Ray ◽

Cosmic Ray ◽

High Energy ◽

Small Scale ◽

The Galaxy ◽

Γ Rays ◽

Γ Ray

Gamma rays of energy in the range 30 MeV-several GeV, observed by the satellites SAS-2 and COS-B, are emitted in the interstellar medium as a result of interactions with gas of cosmic-ray nuclei in the GeV range (π° decay γ rays) and cosmic-ray electrons of energy > 30 MeV (bremsstrahlung γ rays). W. Hermsen has presented at this conference the γ ray maps of the Galaxy in three “colours” constructed by the COS-B collaboration; the information in such maps is supplemented by radio-continuum studies (see lecture by R. Beck), and is a useful tool for studying the distribution of gas, cosmic rays (c.r.) and magnetic fields in the Galaxy. The variables in this problem are many:large-scale (~ 1 kpc) and small-scale (~10 pc) distributions of c.r. nuclei, of c.r. electrons, of atomic and molecular hydrogen, of magnetic fields, fraction of the observed radiation due to localized sources, etc. Of these, only the distribution - or at least the column densities - of atomic hydrogen are determined in a reliable way. Estimates of the amount of molecular hydrogen can be derived from CO observations or from galaxy counts. The radio and gamma-ray data are not sufficient to disentangle all the other variables in a unique fashion, unless a number of assumptions are made (e.g. Paul et al. 1976). Still, the COS-B team has been able to show that :a) there is a correlation between the gamma-ray emission from local regions, as observed at intermediate latitudes, and the total column density of dust, as measured by galaxy counts. The simplest interpretation is that the density of c.r. nuclei and electrons is uniform within 500 pc of the sun, and that dust and gas are well mixed. Then, γ rays can be used as excellent tracers of local gas complexes (Lebrun et al. 1982, Strong et al. 1982).b) In the same way, the simplest interpretation of the γ-ray emission at energy > 300 MeV from the inner Galaxy, is that c.r. nuclei and electrons are distributed uniformly as well : there is no need for an enhanced density of c.r. in the 3–6 kpc ring; on the contrary, even assuming a uniform density of c.r., the γ-ray data are in conflict with the highest estimates of molecular hydrogen in the radio-astronomy literature (Mayer-Hasselwander et al. 1982).c) In the outer Galaxy, the gradient of c.r. which had become apparent in the early SAS-2 data can now, with COS-B data, be studied in three energy ranges. A gradient in the c.r. distribution is only required to explain the low-energy radiation, which is dominated by bremsstrahlung from relativistic electrons (Bloemen et al., in preparation).

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Gravitational waves from mountains in newly born millisecond magnetars

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stab307 ◽

2021 ◽

Vol 502 (4) ◽

pp. 4680-4688

Author(s):

Ankan Sur ◽

Brynmor Haskell

Keyword(s):

Gravitational Wave ◽

Gravitational Waves ◽

Massive Star ◽

Gamma Ray ◽

Dipole Radiation ◽

X Ray ◽

Binary Neutron Star ◽

Spin Period ◽

Lower Maximum ◽

Wave Emission

ABSTRACT In this paper, we study the spin-evolution and gravitational-wave luminosity of a newly born millisecond magnetar, formed either after the collapse of a massive star or after the merger of two neutron stars. In both cases, we consider the effect of fallback accretion; and consider the evolution of the system due to the different torques acting on the star, namely the spin-up torque due to accretion and spin-down torques due to magnetic dipole radiation, neutrino emission, and gravitational-wave emission linked to the formation of a ‘mountain’ on the accretion poles. Initially, the spin period is mostly affected by the dipole radiation, but at later times, accretion spin the star up rapidly. We find that a magnetar formed after the collapse of a massive star can accrete up to 1 M⊙, and survive on the order of 50 s before collapsing to a black hole. The gravitational-wave strain, for an object located at 1 Mpc, is hc ∼ 10−23 at kHz frequencies, making this a potential target for next-generation ground-based detectors. A magnetar formed after a binary neutron star merger, on the other hand, accretes at the most 0.2 M⊙ and emits gravitational waves with a lower maximum strain of the order of hc ∼ 10−24, but also survives for much longer times, and may possibly be associated with the X-ray plateau observed in the light curve of a number of short gamma-ray burst.

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Searching for Mg ii absorbers in and around galaxy clusters

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stab637 ◽

2021 ◽

Vol 503 (3) ◽

pp. 4309-4319

Author(s):

Jong Chul Lee ◽

Ho Seong Hwang ◽

Hyunmi Song

Keyword(s):

Galaxy Clusters ◽

Detection Rate ◽

Massive Star ◽

Sloan Digital Sky Survey ◽

Number Density ◽

Cluster Galaxies ◽

Star Forming ◽

Quasar Spectra ◽

Sky Survey ◽

The Galaxy

ABSTRACT To study environmental effects on the circumgalactic medium (CGM), we use the samples of redMaPPer galaxy clusters, background quasars, and cluster galaxies from the Sloan Digital Sky Survey (SDSS). With ∼82 000 quasar spectra, we detect 197 Mg ii absorbers in and around the clusters. The detection rate per quasar is 2.7 ± 0.7 times higher inside the clusters than outside the clusters, indicating that Mg ii absorbers are relatively abundant in clusters. However, when considering the galaxy number density, the absorber-to-galaxy ratio is rather low inside the clusters. If we assume that Mg ii absorbers are mainly contributed by the CGM of massive star-forming galaxies, a typical halo size of cluster galaxies is smaller than that of field galaxies by 30 ± 10 per cent. This finding supports that galaxy haloes can be truncated by interaction with the host cluster.

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