The High Energy X-ray Probe (HEX-P): Sensitive Broadband X-ray Observations of Transient Phenomena in the 2030s

HEX-P is a probe-class mission concept that will combine high spatial resolution X-ray imaging (<10 arcsec FWHM) and broad spectral coverage (0.1-150 keV) with an effective area far superior to current facilities (including XMM-Newton and NuSTAR), to enable revolutionary new insights into a variety of important astrophysical problems. HEX-P will launch at a time when the sky is being routinely scanned for transient gravitational wave, electromagnetic and neutrino phenomena that will require the capabilities of a sensitive, broadband X-ray telescope for follow up studies. These include the merger of compact objects such as neutron stars and black holes, and transient phenomena in galaxy nuclei, such as tidal disruption events, quasi-periodic eruptions, and extreme AGN variability. Observations with HEX-P will probe the accretion and ejecta from these transient phenomena through the study of relativistic outflows and reprocessed emission, provide unique capabilities for jet physics, and potentially reveal the nature of the central engine. More information on HEX-P, including the full team list, is available at https://hexp.org.