SPI measurements of Galactic $\mathsf{^{26}}$Al

Diehl, R.; Knödlseder, J.; Lichti, G.; Kretschmer, Karsten; Schanne, S.; Schönfelder, V.; Strong, A. W.; Kienlin, A. von; Weidenspointner, G.; Winkler, Christoph; Wunderer, C.

doi:10.1051/0004-6361:20031347

Cited by 41 publications

(35 citation statements)

References 32 publications

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“…INTEGRAL's sky exposure has emphasis in the inner Galactic plane and some special extragalactic source regions. 26 Al emission from the sky was detected at the intensities expected from COMPTEL's earlier survey (Diehl et al 2003). Making use of the advance in spectral resolution, the line intensity and shape were determined for the inner Galaxy region, and could be used to determine the global properties of 26 Al in the Galaxy's interstellar medium (Diehl et al 2006b,a).…”

Section: Earlier Data and Hintsmentioning

confidence: 99%

Radioactive²⁶Al from the Scorpius-Centaurus association

Diehl

Lang

Martin

et al. 2010

A&A

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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.

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Section: Earlier Data and Hintsmentioning

confidence: 99%

Radioactive²⁶Al from the Scorpius-Centaurus association

Diehl

Lang

Martin

et al. 2010

A&A

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129

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“…Prior knowledge (or assumptions) about the spatial characteristics of the sky are then used to fit intensity parameters of such sky models to the data, as a function of (fine-binned) energy and the background behaviour. Software tools which implement such model fitting are "spidiffit" and "spi obs fit" (see Knödlseder 2003, for details and further references, and Diehl et al 2003 for an application).…”

Section: Spectramentioning

confidence: 99%

SPI-specific analysis method and software overview

Diehl

Baby

Beckmann

et al. 2003

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Abstract. The SPI spectrometer on INTEGRAL features a camera system with 19 Ge detector modules, imaging photons through a tungsten coded mask. Background is reduced by an anticoincidence detector system surrounding these. The specifics of this instrument lead to data correction and analysis methods which are described here. Raw data for science analysis are detector event messages and spectra for different categories of detector hits and pulse shapes. Preprocessing combines calibrated spectra from these, which are then interpreted using the imaging and spectral response function for measured spectra where parts of the detector plane are occulted by the mask. Background dominates the overall signal, tailored background estimates and models are based on instrument-specific signatures, their correlations, and trends.

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“…It was clear that only rather unusual circumstances such as large interstellar cavities, or high fraction of 26 Al being deposited onto grains near the 26 Al sources, could offer an explanation. With recent space-based gamma-ray spectroscopy experiments, in particular from the RHESSI (Lin et al 2002) and INTEGRAL (Winkler et al 2003) missions, it became apparent that the GRIS result may not be valid (Smith 2003(Smith , 2004Diehl et al 2003Diehl et al , 2004. The interstellar medium surrounding sources of 26 Al may be less extreme; 26 Al is considered an important probe of these astrophysical sites.…”

Section: Introductionmentioning

confidence: 99%

$\mathsf{^{26}}$Al in the inner Galaxy

Diehl¹,

Halloin²,

Kretschmer³

et al. 2006

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Aims. We performed a spectroscopic study of the 1809 keV gamma-ray line from 26 Al decay in the Galaxy using the SPI imaging spectrometer with its high-resolution Ge detector camera on the INTEGRAL observatory. Methods. We analyzed observations of the first two mission years, fitting spectra from all 7130 telescope pointings in narrow energy bins to models of instrumental background and the 26 Al sky. Instrumental background is estimated from independent tracers of cosmic-ray activation. The shape of the 26 Al signal is compared to the instrumental response to extract the width of the celestial line. Results. We detect the 26 Al line at 16σ significance. The line is broadened only slightly, if at all; we constrain the width to be below 2.8 keV (FWHM, 2σ). The average Doppler velocities of 26 Al at the time of its decay in the interstellar medium (τ ∼ 1.04 My) therefore are probably around 100 km s −1 , in agreement with expectations from Galactic rotation and interstellar turbulence. The flux (3.3 (±0.4) × 10 −4 ph cm −2 s −1 rad −1 ) and spatial distribution of the emission are found consistent with previous observations. The derived amount of 26 Al in the Galaxy is 2.8 (±0.8) M .

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SPI measurements of Galactic $\mathsf{^{26}}$Al

Cited by 41 publications

References 32 publications

Radioactive²⁶Al from the Scorpius-Centaurus association

Radioactive²⁶Al from the Scorpius-Centaurus association

SPI-specific analysis method and software overview

$\mathsf{^{26}}$Al in the inner Galaxy

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SPI measurements of Galactic $\mathsf{^{26}}$Al

Cited by 41 publications

References 32 publications

Radioactive26Al from the Scorpius-Centaurus association

Radioactive26Al from the Scorpius-Centaurus association

SPI-specific analysis method and software overview

$\mathsf{^{26}}$Al in the inner Galaxy

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Radioactive²⁶Al from the Scorpius-Centaurus association

Radioactive²⁶Al from the Scorpius-Centaurus association