1,766 research outputs found
Gamma-ray line measurements from supernova explosions
Gamma 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 from 56Ni
and 44Ti decay on time scales of the initial explosion (56Ni, tau~days) and the
young supernova remnant (44Ti,tau~90 years). Less specific, and rather
informative for the supernova population as a whole, are lessons from longer
lived isotopes such as 26Al and 60Fe. 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.Comment: 7 pages, 4 figures. IAU Symposium 331 "SN1987A 30 years after", La
Reunion, Feb. 2017. Accepted for publication in IAU Conf Pro
GRIPS and the Perspective of Next-generation Gamma-ray Surveys
GRIPS is one example of next generation telescopes proposed for astronomy the
energy range between hard X-ray mirror instruments such as NuStar and the Fermi
telescope. The Compton telescope principle is an advantageous concept in view
of background suppression, imaging sensitivity within a large field of view and
energy range, and capability to measure polarization. The diversity of
astrophysical sources at high energies (diffuse emission from cosmic-ray
interactions, nuclear lines from point-like and diffuse sources, accreting
binaries, cosmic-ray acceleration sites, novae and supernovae, GRBs) presents a
challenge, and in particular emphasizes the need for large fields of view and
surveys. We discuss the astrophysical challenges which are expected to remain
after the extended INTEGRAL mission, and how such a next-generation survey at
low-energy gamma-rays would impact on these. We argue that qualitatively new
and more direct insights could be obtained on cosmic high-energy phenomena and
their underlying physical processes.Comment: 7 pages, 2 figures. INTEGRAL Science Worlshop "The Restless Gamma-Ray
Universe", Dublin (IRL) Oct 201
Nucleosynthesis and Gamma-Ray Line Spectroscopy with INTEGRAL
Cosmic nucleosynthesis co-produces unstable isotopes, which emit
characteristic gamma-ray emission lines upon their radioactive decay that can
be measured with SPI on INTEGRAL. High spectral resolution allows to derive
velocity constraints on nucleosynthesis ejecta down to ~100 km/s. Core-collapse
supernovae apparently do not always produce significant amounts of 44Ti, as in
the Galaxy fewer sources than expected from the supernova rate have been found.
INTEGRAL's 44Ti data on the well-observed Cas A and SN1987A events are evidence
that non-spherical explosions and 44Ti production may be correlated.
Characteristic gamma-ray lines from radioactive decays of long-lived 26Al and
60Fe isotopes have been exploited to obtain information on the structure and
dynamics of massive stars in their late evolution and supernovae, as their
yields are sensitive to those details. The extended INTEGRAL mission
establishes a database of sufficiently-deep observations of several specific
regions of massive star groups, such as Cygnus, Carina, and Sco-Cen. In the
inner Galaxy, 26Al nucleosynthesis gamma-rays help to unravel the Galaxy's
structure and the role of a central bar, as the kinematically-shifted 26Al
gamma-ray line energy records the longitude-velocity behavior of hot
interstellar gas. Thus, INTEGRAL has consolidated the feasibility of
constraining cosmic nucleosynthesis through gamma-ray line observations. Due to
its extended mission INTEGRAL maintains its chance to also see rare
sufficiently-nearby events, such as a nova to provide first nova
nucleosynthesis measurements of 7Be and 22Na production.Comment: Conference "The extreme and variable high-energy sky", Italy Sep
2011. 10 pages, 4 figure
Introduction to Astronomy with Radioactivity
In the late nineteenth century, Antoine Henri Becquerel discovered
radioactivity and thus the physics of weak interactions, well before atomic and
quantum physics was known. The different types of radioactive decay, alpha,
beta, and gamma decay, all are different types of interactions causing the
same, spontaneous, and time-independent decay of an unstable nucleus into
another and more stable nucleus. Nuclear reactions in cosmic sites re-arrange
the basic constituents of atomic nuclei (neutrons and protons) among the
different configurations which are allowed by Nature, thus producing
radioactive isotopes as a by-product. Throughout cosmic history, such reactions
occur in different sites, and lead to rearrangements of the relative abundances
of cosmic nuclei, a process called cosmic chemical evolution, which can be
studied through the observations of radioactivity. The special role of
radioactivity in such studies is contributed by the intrinsic decay of such
material after it has been produced in cosmic sites. This brings in a new
aspect, the clock of the radioactive decay. Observational studies of cosmic
radioactivities intrinsically obtain isotopic information which are at the
heart of cosmic nucleosynthesis. They are best performed by precision mass
spectroscopy in terrestrial laboratories, which has been combined with
sophisticated radiochemistry to extract meteoritic components originating from
outside the solar system, and by spectroscopy of characteristic gamma-ray lines
emitted upon radioactive decay in cosmic environments and measured with
space-based telescopes. This book describes where and how specific astronomical
messages from cosmic radioactivity help to complement the studies of cosmic
nucleosynthesis sites anad of cosmic chemical evolution.Comment: 20 pages, 9 figure
Gamma rays from a supernova of type Ia: SN2014J
SN2014J is the closest supernova of type Ia that occured in the last 40
years. This provides an opportunity for unprecedented observational detail and
coverage in many astronomical bands, which will help to better understand the
still unknown astrophysics of these supernovae. For the first time, such an
event occurs sufficiently nearby so that also gamma rays are able to contribute
to such investigations. This is important, as the primary source of the
supernova light is the radioactive energy from about 0.5 M of Ni
produced in the explosion, and the gamma rays associated with this decay make
the supernova shine for months. The INTEGRAL gamma-ray observatory of ESA has
followed the supernova emission for almost 5 months. The characteristic gamma
ray lines from the Ni decay chain through Co to Fe have
been measured. We discuss these observations, and the implications of the
measured gamma-ray line characteristics as they evolve.Comment: 7 pages, 8 figures; highlight talk at AG conference Bamberg, Germany,
Sep 201
Nuclear-Astrophysics Lessons from INTEGRAL
Measurements of high-energy photons from cosmic sources of nuclear radiation
through ESA's INTEGRAL mission have advanced our knowledge: New data with high
spectral resolution showed that characteristic gamma-ray lines from radioactive
decays occur throughout the Galaxy, in its interstellar medium and from
sources. Although the number of detected sources and often the significance of
the astrophysical results remain modest, conclusions derived from this unique
astronomical window of radiation originating from nuclear processes are
important, complementing the widely-employed atomic-line based spectroscopy. We
review the results and insights obtained in the past decade from gamma-ray line
measurements of cosmic sources, in the context of their astrophysical
questions.Comment: Invited review. 30 pages, 26 figures. This is an author-created,
un-copyedited version of an article accepted for publication in Reports on
Progress in Physics. IOP Publishing Ltd is not responsible for any errors or
omissions in this version of the manuscript or any version derived from it.
The Version of Record is available online at DOI
10.1088/0034-4885/76/2/02630
Gamma-Rays from Positron Annihilation
SPI on INTEGRAL has provided spectra and a map of the sky in the emission
from annihilations of positrons in the interstellar medium of our Galaxy. From
high-resolution spectra we learned that a warm, partially-ionized medium is the
site where the observed gamma-rays originate. The gamma-ray emission map shows
a major puzzle for broader astrophysics topics, as it is dominated by a bright
and extended apparently spherical emission region centered in the Galaxy's
center. Only recently has the disk of the Galaxy been detected with SPI. This
may be regarded as confirmation of earlier expectations that positrons should
arise predominantly from sources of nucleosynthesis distributed throughout the
plane of the Galaxy, which produce proton-rich unstable isotopes. But there are
other plausible sources of positrons, among them pulsars and accreting binaries
such as microquasars. SPI results may be interpreted also as hints that these
are more significant as positron sources on the Galactic scale than thought
before, in the plane and therefore also in the bulge of the Galaxy. This is
part of the attempt to understand the surprisingly-bright emission from the
central region in the Galaxy, which otherwise also could be interpreted as a
first rather direct detection of dark matter annihilations in the Galaxy's
gravitational well. INTEGRAL has a unique potential to shed light on the
various aspects of positron astrophysics, through its capability for imaging
spectroscopy.Comment: 17 pages; invited contribution to 7th INTEGRAL Science Workshop, Sep
2008; accepted for publication in Proceedings of Science; V2 for ref 47
updat
Gamma-ray lines from SN2014J
On 21 January 2014, SN2014J was discovered in M82 and found to be the closest
type Ia supernova (SN Ia) in the last four decades. INTEGRAL observed SN2014J
from the end of January until late June for a total exposure time of about 7
Ms. SNe Ia light curves are understood to be powered by the radioactive decay
of iron peak elements of which Ni is dominantly synthesized during the
thermonuclear disruption of a CO white dwarf (WD). The measurement of
-ray lines from the decay chain
NiCoFe provides unique
information about the explosion in supernovae. Canonical models assume
Ni buried deeply in the supernova cloud, absorbing most of the early
-rays, and only the consecutive decay of Co should become
directly observable through the overlaying material several weeks after the
explosion when the supernova envelope dilutes as it expands. Surprisingly, with
the spectrometer on INTEGRAL, SPI, we detected Ni -ray lines at
158 and 812 keV at early times with flux levels corresponding to roughly 10% of
the total expected amount of Ni, and at relatively small velocities.
This implies some mechanism to create a major amout of Ni at the
outskirts, and at the same time to break the spherical symmetry of the
supernova. One plausible explanation would be a belt accreted from a He
companion star, exploding, and triggering the explosion of the white dwarf. The
full set of observations of SN2014J show Co -ray lines at 847
and 1238 keV, and we determine for the first time a SN Ia -ray light
curve. The irregular appearance of these -ray lines allows deeper
insights about the explosion morphology from its temporal evolution and
provides additional evidence for an asymmetric explosion, from our
high-resolution spectroscopy and comparisons with recent models.Comment: 12 pages, 15 figures, 10th INTEGRAL Workshop: "A Synergistic View of
the High Energy Sky" - Integral2014, 15-19 September 2014, Annapolis, MD, US
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