Abstract for Proposal 088335
On the quest of BeX-ray transients: how do highly magnetized neutron stars cool?
We aim to study the cooling emission of highly magnetized neutron stars
in Be/X- ray binaries. For this, we need to increase our sample with
high-quality post-outburst spectra. We require the flexibility of Swift
to monitor the behavior of the next potential target, and the exceptional
sensitivity and large effective area of XMM-Newton to study the low X-ray
luminosity regime of the source. These new observations will provide key
additional data to i) better constrain the temporal evolution of the crust
temperature in highly magnetized accreting NSs, and ii) use the observed
cooling curves as input into our 2D crust cooling model which incorporates
magnetic fields. This is required to understand the role of such magnetic
fields on the crust heating/cooling scenario of accreting NSs
Details on Observing Strategy and Trigger Criteria
We will trigger our joint XMM-Newton-Swift ToO proposal on the next
Be/X-ray transient that meets the following criteria: a) the source
needs to exhibit a giant type-II outburst (the more accreted matter,
the more heat released in the NS crust), b) the Pspin of the NS should
be <10 s (to guarantee that the source enters the propeller regime at
the end of the outburst), c) the system is at a distance of <8 kpc (so
that we obtain sufficient photons to perform spectral modeling), d) the
extinction is moderately low (nH <1e22 cm^-2; to accurately constrain
the spectra at soft energies), e) during our Swift monitoring, we have
determined that the source has entered the cooling phase. Once we confirm
that the potential target settles into this phase, we propose to continue
the Swift follow- up, and to observe the source within two observational
windows (1st within 45-75 days, and 2nd 140-200 days) after the peak of
the outburst using two XMM-Newton observations obtained at apastron. We
request 1 ks XRT (Auto mode) observations with a cadence of 4 days for
a total of 65 ks, and 2 XMM-Newton observations (EPIC-pn, Full Frame)
of 35 ks each (one observation per observing window)