Abstract for Proposal 090455

Detecting New Hyper-Luminous X-ray Sources Among Low-Luminosity AGN ignitions

We propose three ToOs (40 ks each) to follow up on luminous extragalactic X-ray ignitions, with the aim of detecting new Hyper-Luminous X-ray sources (HLXs). During the all-sky scans of eROSITA, ignition events with a luminosity range log(Lx/[erg cm^-2])=41.5--42 were detected in local galaxies. This luminosity range is of particular interest as it covers the overlap of HLXs and low-luminosity AGN. The nuclei of the host galaxies of these ignition events showed no change in their optical spectra, when comparing before and after the X-ray brightening. The proposed pilot study investigates whether HLXs are in fact responsible for these ignitions. This programme has the potential to triple the number of objects at the extreme end of the Lx range.

Details on Observing Strategy and Trigger Criteria
Our trigger criteria are: i) eROSITA flux (0.2-5 keV) > 8E-13 cgs, after a flux increase of at least a factor 10, ii) ignition not caused by an AGN or TDE, this is established by comparison of optical spectra before and after the event, iii) log (Lx/[erg/s])=41.5-42, and iv) optical extent of the galaxy >5 arcsec (diameter). We request a ToO reaction time within two weeks. Primary instrument PN in full window mode.