Mirabal, Nestor2020-09-032020-09-032010-11-01N. Mirabal, Swift observation of Segue 1: constraints on sterile neutrino parameters in the darkest galaxy, Monthly Notices of the Royal Astronomical Society: Letters, Volume 409, Issue 1, November 2010, Pages L128–L131, https://doi.org/10.1111/j.1745-3933.2010.00963.xhttps://doi.org/10.1111/j.1745-3933.2010.00963.xhttp://hdl.handle.net/11603/19584Some extensions of standard particle physics postulate that dark matter may be partially composed of weakly interacting sterile neutrino particles that have so far eluded detection. We use a short (∼5 ks) archival X-ray observation of Segue 1 obtained with the X-ray Telescope (XRT) onboard the Swift satellite to exclude the presence of sterile neutrinos in the 1.6–14 keV mass range down to a flux limit of 6 × 10⁻¹² erg cm⁻² s⁻¹ within 67 pc of its centre. With an estimated mass-to-light ratio of ∼3400 M⊙/L⊙, Segue 1 is the darkest ultrafaint dwarf galaxy currently measured. Spectral analysis of the Swift XRT data fails to find any non-instrumental spectral feature possibly connected with the radiative decay of a dark matter particle. Accordingly, we establish upper bounds on the sterile neutrino parameter space based on the non-detection of emission lines in the spectrum. The present work provides the most sensitive X-ray search for sterile neutrinos in a region with the highest dark matter density yet measured.5 pagesen-USThis item is likely protected under Title 17 of the U.S. Copyright Law. Unless on a Creative Commons license, for uses protected by Copyright Law, contact the copyright holder or the author.This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society: Letters Published by Oxford University Press on behalf of the Royal Astronomical Society.Text