Magnetar Bursts

Magnetars

Magnetars are young (age ≲ 10⁴ yrs), highly magnetized (Bsurf∼ 10¹³⁻¹⁶ G) neutron stars, that are notorious for their wide variety of high-energy transient phenomena (see Kaspi & Beloborodov 2017, for an observational and theoretical review). These include outbursts which last for months to giant flares that have been known to emit 10⁴⁶ erg in ≈100 ms (Hurley et al. 2005). With its lower fluence threshold, wide energy range, and sky coverage Daksha will be a valuable tool for probing magnetar bursts and flares from the Milky Way magnetars as well as giant flares from magnetars in nearby galaxies (d ≲ 10² Mpc). The increased volume probed by Daksha will allow for a better understanding of magnetar burst rates, luminosity distributions, and the birth-to-death cycle of magnetars.

For brighter bursts, Daksha’s polarization capabilities will allow for the measurement of linear polarization which is expected to occur due to the propagation of photons through extremely strong magnetic fields (B ∼ 10¹⁵ G, Taverna & Turolla 2017). While other planned X-ray polarization missions aim to study the polarization of persistent emission from magnetars, Daksha’s polarization measurement capabilities over a near-all-sky field of view are required for polarization measurements of magnetar bursts.