Gamma-ray flux limits from brown dwarfs: Implications for dark matter annihilating into long-lived mediators
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| Format: | Preprint |
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2022
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| _version_ | 1866929428039204864 |
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| author | Bhattacharjee, Pooja Calore, Francesca Serpico, Pasquale Dario |
| author_facet | Bhattacharjee, Pooja Calore, Francesca Serpico, Pasquale Dario |
| contents | Brown dwarfs (BDs) are celestial objects representing the link between the least massive main-sequence stars and giant gas planets. In the first part of this article, we perform a model-independent search of a gamma-ray signal from the direction of nine nearby BDs in 13 years of \Fermi-LAT data. We find no significant excess of gamma rays, and we, therefore, set 95\% confidence level upper limits on the gamma-ray flux with a binned-likelihood approach. In the second part of the paper, we interpret these bounds within an exotic mechanism proposed for gamma-ray production in BDs: If the dark matter (DM) of the universe is constituted of particles with non-negligible couplings to the standard model, BDs may efficiently accumulate them through scatterings. DM particles eventually thermalise, and can annihilate into light, long-lived, mediators which later decay into photons outside the BD. Within this framework, the current Fermi-LAT stacked upper limits on the gamma-ray flux of the selected BDs do not enable setting a bound on the DM-nucleon cross-section. An improvement of approximately a factor of 9 in the gamma-ray limits is required to obtain bounds on the scattering cross-section $σ_{χn}$ $\sim 10^{-36}$ cm$^{2}$ for DM masses below 10 GeV. This improvement would cover a larger portion of the parameter space in mediator decay length and DM mass. The code and data to reproduce the results of this study are available on GitLab at \github{https://gitlab.in2p3.fr/francesca.calore/brown-dwarfs-gamma}. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2211_08067 |
| institution | arXiv |
| publishDate | 2022 |
| record_format | arxiv |
| spellingShingle | Gamma-ray flux limits from brown dwarfs: Implications for dark matter annihilating into long-lived mediators Bhattacharjee, Pooja Calore, Francesca Serpico, Pasquale Dario High Energy Astrophysical Phenomena Cosmology and Nongalactic Astrophysics Earth and Planetary Astrophysics Solar and Stellar Astrophysics High Energy Physics - Phenomenology Brown dwarfs (BDs) are celestial objects representing the link between the least massive main-sequence stars and giant gas planets. In the first part of this article, we perform a model-independent search of a gamma-ray signal from the direction of nine nearby BDs in 13 years of \Fermi-LAT data. We find no significant excess of gamma rays, and we, therefore, set 95\% confidence level upper limits on the gamma-ray flux with a binned-likelihood approach. In the second part of the paper, we interpret these bounds within an exotic mechanism proposed for gamma-ray production in BDs: If the dark matter (DM) of the universe is constituted of particles with non-negligible couplings to the standard model, BDs may efficiently accumulate them through scatterings. DM particles eventually thermalise, and can annihilate into light, long-lived, mediators which later decay into photons outside the BD. Within this framework, the current Fermi-LAT stacked upper limits on the gamma-ray flux of the selected BDs do not enable setting a bound on the DM-nucleon cross-section. An improvement of approximately a factor of 9 in the gamma-ray limits is required to obtain bounds on the scattering cross-section $σ_{χn}$ $\sim 10^{-36}$ cm$^{2}$ for DM masses below 10 GeV. This improvement would cover a larger portion of the parameter space in mediator decay length and DM mass. The code and data to reproduce the results of this study are available on GitLab at \github{https://gitlab.in2p3.fr/francesca.calore/brown-dwarfs-gamma}. |
| title | Gamma-ray flux limits from brown dwarfs: Implications for dark matter annihilating into long-lived mediators |
| topic | High Energy Astrophysical Phenomena Cosmology and Nongalactic Astrophysics Earth and Planetary Astrophysics Solar and Stellar Astrophysics High Energy Physics - Phenomenology |
| url | https://arxiv.org/abs/2211.08067 |