Abstract for Proposal 094078
XMM-Newton target of opportunity observation of a new transient ULX
Ultraluminous X-ray sources (ULXs) are our best laboratories for studying
extreme super-Eddington accretion. Most studies of these objects are
of relatively persistent sources, however there is growing evidence to
suggest a large fraction of these sources are transient. We propose
a 85-ks XMM-Newton target of opportunity (ToO) observation of a new
transient ultraluminous X-ray source (ULX) that will be identified
by searching through new Swift/XRT observations for serendipitous
detections. The XMM-Newton data will provide high throughput spectral
and timing data necessary to identify the nature of this new source.
Details on Observing Strategy and Trigger Criteria
Our trigger criteria will be the detection of a new X-ray source with
Swift/XRT where the measured count rate is 0.01 counts/s or above and the
corresponding luminosity is >10^39 erg/s, i.e. the threshold for a ULX. To
trigger, we will also require that a historical upper limit at least
a magnitude below this, or equivalent with another X-ray observatory,
exists, in order to ensure its transient nature.