A dataset provided by the European Space Agency

Proposal ID 1520024
Obs ID 15200240001
Title Positron Annihilation in the Dwarf Satellite Galaxy Reticulum II
Download Data Associated to the proposal https://isla.esac.esa.int/tap/download/bundle?format=ascii_curl&product_id=prop_id:1520024
DOI https://doi.org/10.57780/esa-z7vx9km
Author Siegert
Abstract Koposov et al. (2015) used data from the Dark Energy Survey to search for new dwarf satellite galaxies (DSGs) of the Milky Way (MW). They found nine candidates in the southern sky, which may be related to the magellanic systems. Among their sample, Reticulum II (Ret II) is the closest and was detected with a significance of more than 48 sigma. Looking for a possible low energy gamma-ray emission from these new DSGs, Siegert et al. (2016) found a 3.1 sigma signal at photon energies around 511 keV from the direction of Ret II, with a flux of 1.7E-4 ph/cm2/s. The origins of such a 511 keV signal from electron-positron annihilations are versatile and probably not attributable to one particular source. The connection between this excess and the galactic centre signal remains unexplored. Massive stars and supernovae have been considered as a possible source of 511 keV photons in the MW since they can produce beta+-unstable isotopes. However they are unlikely to be responsible for the signal in Ret II since we do not expect any in DSGs. Dark matter (DM) has also been proposed as a possible source of low-energy positron emitters in the MW and could be a source of positrons in Ret II as it is dominated by DM. However, the cross section needed to explain the 511 keV signal in Ret II would make the MW brighter at these energies. Another source of low-energy positrons could be microquasars. These may produce electron-positron pair-plasma, predominantly in outbursts. In fact, one single microquasar in Ret II might be enough to explain the whole emission. In this proposal, we ask for 1.5 Ms of observation time towards the direction of Ret II, (l/b) = (266.3/-49.7), which would add to the currently available 250 ks. This observation would consolidate or falsify the discovery of a 511 keV line signal in Ret II and understand its origin if it is indeed present. In addition, observing these DSGs with SPI may help to solve the 40 years old galactic positron puzzle.
Publications
  • An INTEGRAL/SPI view of reticulum II: particle dark matter and primordial black holes limits in the MeV range - Siegert, Thomas, Boehm, Celine,Calore, Francesca,Diehl, Roland,Krause, Martin G. H.,Serpico, Pasquale D.,Vincent, Aaron C. (2022-03-01) http://ui.adsabs.harvard.edu/#abs/2022MNRAS.511..914S
  • Diffuse Galactic emission spectrum between 0.5 and 8.0 MeV - Siegert, Thomas, Berteaud, Joanna,Calore, Francesca,Serpico, Pasquale D.,Weinberger, Christoph (2022-04-01) http://ui.adsabs.harvard.edu/#abs/2022A&A...660A.130S
  • 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
  • Sub-GeV dark matter annihilation: limits from Milky Way observations with INTEGRAL - Siegert, Thomas, Calore, Francesca,Serpico, Pasquale Dario (2024-02-01) http://ui.adsabs.harvard.edu/#abs/2024MNRAS.528.3433S
  • 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
  • The First Insight-HXMT Localization Catalog of Short-duration Gamma-Ray Bursts: The First Six Years - Xiao, Shuo, Zhang, Yan-Ting,Wang, Yue,Zhang, Yan-Qiu,Xiong, Shao-Lin,Zhang, Shuang-Nan,Zheng, Shi-Jie,Zhang, Jin-Peng,Zhang, Peng,Li, Cheng-Kui,Li, Xiao-Bo,Yi, Shu-Xu,Zhang, Zhen,Li, Bing,Feng, Hua,Liu, Cong-Zhan,Ge, Ming-Yu,Li, Xu-Fang,Li, Zheng-Wei,Xu, Yu-Peng,Wen, Xiang-Yang,Sun, Jian-Chao,Tao, Lian,Yi, Qi-Bin,Cai, Ce,Zhao, Yi,Xue, Wang-Chen,Liu, Jia-Cong,Zheng, Chao,Wang, Chen-Wei,Tan, Wen-Jun,Tuo, You-Li,Song, Li-Ming,Lu, Fang-Jun,Li, Ti-Pei (2025-06-01) http://ui.adsabs.harvard.edu/#abs/2025ApJS..278...60X
Temporal Coverage 2017-12-27T17:24:30Z / 2018-12-25T11:13:27Z
Version 1.0
Mission Description 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.
Creator Contact https://www.cosmos.esa.int/web/integral/helpdesk
Date Published 2026-03-05T13:05:59Z
Keywords INTEGRAL gamma-ray data, ESA INTEGRAL mission dataset, gamma-ray astronomy observations, high-energy astrophysics data, IBIS imaging data, SPI spectrometer data, JEM-X X-ray monitoring data, OMC optical monitoring data, coded mask telescope observations, gamma-ray spectroscopy dataset, MeV astrophysics data, keV–MeV photon observations, gamma-ray burst observations dataset, black hole gamma-ray data, neutron star high-energy observations, positron annihilation 511 keV line data, Galactic Center gamma-ray emission dataset, supernova nucleosynthesis gamma-ray lines, active galactic nuclei high-energy data, transient astrophysical source monitoring, calibrated photon event lists, gamma-ray light curves, high-energy spectra data, sky maps gamma-ray, time-series astrophysical observations, long-term gamma-ray monitoring dataset
Publisher And Registrant European Space Agency
Credit Guidelines European Space Agency, Siegert, 2026, 'Positron Annihilation in the Dwarf Satellite Galaxy Reticulum II', 1.0, European Space Agency, https://doi.org/10.57780/esa-z7vx9km