Pilar Esquej
Max-Planck-Institut für extraterrestrische Physik (MPE)
PhD Student

Research area: Tidal disruption of stars by quiescent supermassive
black holes at the centre of the galaxies using the XMM-Newton slew
survey Source Catalogue.

The XMM-Newton satellite traces slewing paths over the sky while
maneuvering between observation targets yielding a maximum of 15
seconds of on-source time. Sources detected during slew
observations in three different energy bands have been merged to
generate the XMM-Newton slew survey Source Catalogue (XMMSL1). A
systematic comparison of the soft 0.2-2 keV energy band slew count
rates with those in the ROSAT PSPC all-sky survey (RASS) has been
performed. A number of high amplitude variability events have been
identified and associated with intrinsic variability of the
sources. 

There is now strong evidence that the centres of non-active
galaxies are occupied by concentrated dark objects. Proof of this
is the discovery of giant-amplitude, non-recurrent X-ray flares
observed from several non-active galaxies. Such phenomena are
favorably explained in terms of tidal disruption of stars by a
central supermassive black hole. Six tidal disruption candidates
have been discovered from the XMMSL1 catalogue and the confirmation
of such events would begin to allow conclusions to be drawn about
their frequency and the feasibility of the phenomenon.
Multi-wavelenght follow-up observations will allow the
post-outburst evolution to be investigated in detail. Moreover,
they will provide information to connect galaxies and AGN in the
context of formation and evolution, and also to test the domain of
strong gravity studying precession effects around the Kerr metric.

In my PhD project, jointly supervised by MPE, ESAC and Liecester
scientists, I have been working in the production of the XMMSL1
catalogue and, currently, in its scientific exploitation, specially
in the topic mentioned above.