Search for primordial black hole dark matter with X-ray satellites and prospects for future missions

Ultralight primordial black holes (PBHs) in the mass range of 10¹⁶ – 10²² g are allowed by current observations to constitute a significant fraction, if not all, of the dark matter in the Universe. In this work, we present limits on ultralight, nonrotating PBHs which arise from the nondetection of the Hawking radiation signals from such objects in the keV – MeV energy band. Namely, we consider observations from the current-generation missions XMM-Newton and INTEGRAL/SPI and discuss the observational perspectives of the future missions Athena, eXTP, and THESEUS for PBH searches. Based on 3.4 Msec total exposure time of XMM-Newton observations of Draco dwarf spheroidal galaxy, we conclude that PBH with masses ≲ 10¹⁶ g cannot make all dark matter at 95% confidence level. Our ON-OFF-type analysis of >100 Msec of INTEGRAL/SPI data on the Milky Way halo puts significantly stronger constraints. Only ≲ 10 % of dark matter can be presented by PBHs with masses ≲ 3 × 10¹⁶ g while the majority of dark matter cannot be represented by PBHs lighter than 7 × 10¹⁶ g at 95% confidence level. We discuss the strong impact of systematic uncertainty related to the variations of instrumental and astrophysical INTEGRAL/SPI background on the derived results and estimate its level. We also show that future large field-of-view missions such as THESEUS /X-GIS will be able to improve the constraints by a factor of 10 – 100 depending on the level of control of the systematics of these instruments.

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