A less explored procedure for a thermal relic to reach its current abundance is that it first elastically (thermally) decouples from the relativistic species before it freezes out from the number-changing processes. Here we present a novel dark matter (DM) candidate, an Elastically Decoupling Relic (ELDER), which is a thermal relic whose present-day abundance is determined by the cross-section of its elastic scattering with Standard Model particles, based on the aforementioned procedure.

Assuming that this scattering is mediated by a kinetically mixed dark photon, the ELDER scenario makes robust predictions for electron-recoil direct-detection experiments, as well as for dark photon searches. These predictions are independent of the details of interactions within the dark sector. The ELDER predictions provide a target region that will be almost entirely accessible to the next generation of searches for sub-GeV dark matter and dark photons.

If time permits, I will talk briefly about the gravitational-wave (mergers), optical (kilonovae), and radio signatures of DM-induced neutron star (NS) Implosions.
The astrophysical signatures are ways to go orders-of-magnitude beyond the DM direct-detection limits, demonstrated using superheavy asymmetric DM as an example.
The recently detected NS merger event, GW170817, provided us with the first robust data point for the statistical test.

The talk is based on Phys. Rev. Lett. 116, 221302 (arXiv:1512.04545), JHEP, 08:078, 2017 (arXiv:1706.05381), and arXiv:1706.00001.