Back in 1997, McConnell et al. searched for 2.2 MeV emission from neutron capture processes with COMPTEL and reported one 3.7 sigma signal in their full sky survey. As exceptional as this discovery was, as surprising it still is, that no targeted follow-up observation of this source with a gamma-ray telescope has been performed up to now. In addition, the only suggested counterpart to this 2.2 MeV signal is very peculiar, and INTEGRAL/SPI is the only instrument capable of clarifying this 20 year old puzzle.The most promising candidate is claimed to be RE J0317-853, a fast rotating, extremely hot, and highly magnetised binary white dwarf (WD). This claim was barely investigated further, only trying to connect radio emission as a possible proof of particle acceleration and flaring activity. In general, the properties of such exceptional objects and extreme environments are widely debated.A detailed spectral analysis of the 2.2 MeV line from RE J0317-853 can confirm its correspondence to the signal found by McConnell et al. (1997). Furthermore, this will provide basic insight in fundamental processes concerning X-ray binary feedback in WD systems. This includes neutron production and accretion in the presence of large magnetic fields, as well as recombination physics in extreme environments. RE J0317-853 is the closest high-B WD, only 27 pc awayat (l/b) = (299.85/-30.68), and the most massive WD known. This makes it also one of the best candidates to study a possible progenitor of a type Ia supernova in a double-degenerate, WD-merger, scenario. Its properties, especially the extreme values of temperature, magnetisation, rotation, and mass, make it to one of the most promising INTEGRAL/SPI high-energy targets.We propose a dedicated 1.5 Ms observation of this serendipitous 2.2 MeV source with INTEGRAL/SPI in addition to the currently available, not solar-flare contaminated or zenith-angle constrained, 500 ks.
Publications
Primordial black hole dark matter in the context of extra dimensions - Friedlander, Avi, Mack, Katherine J.,Schon, Sarah,Song, Ningqiang,Vincent, Aaron C. (2022-05-01) http://ui.adsabs.harvard.edu/#abs/2022PhRvD.105j3508F
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
Temporal Coverage
2020-01-15T20:14:12Z / 2020-12-12T13:32:18Z
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.
European Space Agency, Pleintinger, 2025, '2.2 MeV Emission from a Highly Magnetised White Dwarf', 1.0, European Space Agency, https://doi.org/10.57780/esa-spc6wgt
