The Perseus OB2 association is the second closest (300 pc) massive star region, and is about 6 Myr old. Among its stellar content of approximately 20000 stars, there are 17 high-mass stars of spectral type B. Since the birth of the stellar group, already the most-massive stars exploded and enriched the surrounding interstellar medium with freshly-produced elements. This is direct evidence for ongoing nucleosynthesis in the Milky Way. One of the most important tracers of this chemical enrichment is the beta+-unstable isotope 26Al. The decay of radioactive 26Al nuclei, as observed by gamma-ray line at 1808.63 keV, provides a unique tool to study the effects of massive stars onto their environment, the feedback scenario. This is only possible with SPI aboard INTEGRAL.Previous 26Al studies focussed on other prominent massive star regions, such as Cygnus, Orion, and Scorpius Centaurus. These associations are well studied in kinematics (Doppler-shift, and -broadening) and 26Al content (flux, mass). However, the morphology of the 26Al emission cannot accurately be modelled there, as either the signals are too weak or the galactic background emission is glaring into the desired region. Per OB2 is located in the galactic anti-centre and below the galactic plane, probably associated with the Gould Belt, and thus predestinated for 26Al observations.In this proposal, we ask for a 3 Ms two-year observation campaign towards the direction of Per OB2 in order to:1) validate and refine the previous measurements with COMPTEL and SPI (2.9 Ms);2) measure the kinematics of the 26Al ejecta from the congeries of Per OB2 stars and supernovae;3) determine the spatial distribution of 26Al with respect to the Perseus supershell;4) search for 60Fe gamma-rays at 1173 and 1332 keV from a spatially distinguished OB association;5) provide another measure of the 1.8 MeV foreground emission towards a galactic-wide picture.
Publications
Gamma-Ray Emission of 60Fe and 26Al Radioactivity in Our Galaxy - Wang, W., Siegert, T.,Dai, Z. G.,Diehl, R.,Greiner, J.,Heger, A.,Krause, M.,Lang, M.,Pleintinger, M. M. M.,Zhang, X. L. (2020-02-01) http://ui.adsabs.harvard.edu/#abs/2020ApJ...889..169W
Searching for redshifted 2.2 MeV neutron-capture lines from accreting neutron stars: Theoretical X-ray luminosity requirements and INTEGRAL/SPI observations - Ducci, L., Santangelo, A.,Tsygankov, S.,Mushtukov, A.,Ferrigno, C. (2024-10-01) http://ui.adsabs.harvard.edu/#abs/2024A&A...690A.309D
26Al gamma rays from the Galaxy with INTEGRAL/SPI - Pleintinger, Moritz M. M., Diehl, Roland,Siegert, Thomas,Greiner, Jochen,Krause, Martin G. H. (2023-04-01) http://ui.adsabs.harvard.edu/#abs/2023A&A...672A..53P
V348 And and V572 Per: Bright Triple Systems with Eccentric Eclipsing Binaries - Zasche, P., Uhlar, R.,Svoboda, P.,Jurysek, J.,Korcakova, D.,Wolf, M.,Slechta, M.,Kotkova, L. (2019-08-01) http://ui.adsabs.harvard.edu/#abs/2019AJ....158...95Z
The INTEGRAL (International Gamma-Ray Astrophysics Laboratory) mission, launched by the European Space Agency (ESA) on October 17, 2002, was designed to study high-energy phenomena in the universe. INTEGRAL was operating until february 2025 and it was equipped with three high-energy instruments: the Imager on Board the INTEGRAL Satellite (IBIS), the Spectrometer on INTEGRAL (SPI), and the JEM-X (Joint European Monitor for X-rays). Its Optical Monitoring Camera (OMC) provided optical V-band magnitude measurements, complementing the high-energy observations.
