- 
								[1]
								P. Minkowski, Phys. Lett. B 67, 421 (1977) 
- 
								[2]
								T. Yanagida, Horizontal gauge symmetry and masses of neutrinos, Proceedings: Workshop on the Unified Theories and the Baryon Number in the Universe: KEK, Japan, February 13-14, 1979, Conf. Proc. C7902131 , 95 (1979); T. Yanagida, Horizontal Symmetry and Mass of the Top Quark, Phys. Rev. D 20 , 2986 (1979) 
- 
								[3]
								M. Gell-Mann, P. Ramond, and R. Slansky, Conf. Proc. C790927, 315 (1979), arXiv:1306.4669[hep-th] 
- 
								[4]
								F. Wilczeck, Proceedings: Lepton-Photon Conference (Fermilab, Aug 1979), Conf. Proc. C790885, (1979) 
- 
								[5]
								M. Fukugita and T. Yanagida, Phys. Lett. B 174, 45 (1986) 
- 
								[6]
								G. Choi, T. T. Yanagida, and N. Yokozaki, Phys. Lett. B 810, 135836 (2020), arXiv:2007.04278[hep-ph] 
- 
								[7]
								N. Okada, S. Okada, D. Raut et al., Phys. Lett. B 810, 135785 (2020), arXiv:2007.02898[hep-ph] 
- 
								[8]
								W. Lin, L. Visinelli, D. Xu et al., Neutrino astronomy as a probe of physics beyond the Standard Model: decay of sub-MeV B-L gauge boson dark matter, arXiv: 2202.04496[hep-ph] 
- 
								[9]
								W. Lin and T. T. Yanagida, Phys. Rev. D 106(7), 075012 (2022), arXiv:2205.08171[hep-ph] 
- 
								[10]
								W. N. III. Johnson, F. R Harnden, and R. C. Haymes, ApJ 172 , L1 (1972) 
- 
								[11]
								R. C. Haymes, G. D. Walraven, C. A. Meegan et al., Detection of nuclear gamma rays from the galactic center region, ApJ 201 , 593 (1975) 
- 
								[12]
								M. Leventhal, C. J. MacCallum, and P. D. Stang, Detection of 511 keV positron annihilation radiation from the galactic center direction, ApJ 225 , L11 (1978) 
- 
								[13]
								J. F. Beacom and H. Yuksel, Phys. Rev. Lett. 97, 071102 (2006), arXiv:astro-ph/0512411 
- 
								[14]
								Y. Ascasibar, P. Jean, C. Bœhm et al., Constraints on dark matter and the shape of the Milky Way dark halo from the 511-keV line, Monthly Notices of the Royal Astronomical Society 368 (4), 1695 (2006) 
- 
								[15]
								H. Fukuda, S. Matsumoto, and T. Yanagida, unpublished discussion (2024) 
- 
								[16]
								N. Prantzos et al., Rev. Mod. Phys. 83, 1001 (2011), arXiv:1009.4620[astro-ph.HE] 
- 
								[17]
								J. F. Navarro, C. S. Frenk, and S. D. M. White, Astrophys. J. 462, 563 (1996), arXiv:astro-ph/9508025 
- 
								[18]
								T. Siegert, R. Diehl, G. Khachatryan et al., Astron. Astrophys. 586, A84 (2016), arXiv:1512.00325[astro-ph.HE] 
- 
								[19]
								J. N. Bahcall and M. H. Pinsonneault, Phys. Rev. Lett. 92, 121301 (2004), arXiv:astro-ph/0402114 
- 
								[20]
								S. Kumaran, L. Ludhova, O. Penek et al., Universe 7(7), 231 (2021), arXiv:2105.13858[hep-ex] 
- 
								[21]
								G. 't Hooft, Phys. Lett. B 37, 195 (1971) 
- 
								[22]
								G. Bellini et al., Phys. Rev. Lett. 107, 141302 (2011), arXiv:1104.1816[hep-ex] 
- 
								[23]
								A. Pocar et al. (BOREXINO Collaboration), SciPost Phys. Proc. 1, 025 (2019), arXiv:1810.12967[nucl-ex] 
- 
								[24]
								G. Bellini, Nucl. Phys. B 908, 178 (2016) 
- 
								[25]
								E. Vitagliano, I. Tamborra, and G. Raffelt, Rev. Mod. Phys. 92, 45006 (2020), arXiv:1910.11878[astro-ph.HE] 
- 
								[26]
								M. Agostini et al. (BOREXINO Collaboration), Phys. Rev. D 105(5), 052002 (2022), arXiv:2109.04770[hep-ex] 
- 
								[27]
								W. Buchmuller and T. Yanagida, Phys. Lett. B 445, 399 (1999), arXiv:hep-ph/9810308 
- 
								[28]
								S. De Lope Amigo, W. M. Y. Cheung, Z. Huang et al., JCAP 06, 005 (2009), arXiv:0812.4016[hep-ph] 
- 
								[29]
								B. Audren, J. Lesgourgues, G. Mangano et al., JCAP 12, 028 (2014), arXiv:1407.2418[astro-ph.CO] 
- 
								[30]
								A. Chen et al. (DES Collaboration), Phys. Rev. D 103(12), 123528 (2021), arXiv:2011.04606[astro-ph.CO] 
- 
								[31]
								K. Enqvist, S. Nadathur, T. Sekiguchi et al., JCAP 04, 015 (2020), arXiv:1906.09112[astro-ph.CO] 
- 
								[32]
								J. A. Tomsick et al. (COSI Collaboration), PoS ICRC2021, 652 (2021), arXiv:2109.10403[astro-ph.IM] 
- 
								[33]
								P. W. Graham, J. Mardon, and S. Rajendran, Phys. Rev. D 93(10), 103520 (2016), arXiv:1504.02102[hep-ph] 
- 
								[34]
								Y. Akrami et al. (Planck Collaboration), Astron. Astrophys. 641, A10 (2020), arXiv:1807.06211[astro-ph.CO] 
- 
								[35]
								K. Abazajian et al. (CMB-S4 Collaboration), Snowmass 2021 CMB-S4 White Paper, arXiv: 2203.08024[astro-ph.CO] 
- 
								[36]
								M. Vignati and M. Lusignoli, 163ho as a target for cosmic antineutrinos, Journal of Physics: Conference Series 375 (4), 042006 (2012) 
- 
								[37]
								L. Gastaldo et al., Eur. Phys. J. ST 226(8), 1623 (2017) 
- 
								[38]
								T. Siegert, R. Diehl, A. C. Vincent et al., Astron. Astrophys. 595, A25 (2016), arXiv:1608.00393[astro-ph.HE]