Proposal Details - 1020009
Probing the circumstellar environment during periastron passage in the SFXTs IGR J17354-3255 and IGR J18483-0311 (Drave)

Proposal Abstract

The mass transfer and accretion mechanisms in SFXTs are key questions to be answered in order to place the SFXTs in the wider context of HMXB systems. Current theories centre on mass transfer via isotropic but inhomogeneous ('clumpy') winds, but some systems also show evidence of disk-like structures around the supergiant, analogous to those seen in Be/X-ray binaries. We propose a campaign of periastron observations of 2 SFXTs with known ephemerides following on from the accepted AO-9 programme 'Probing the nature of the circumstellar environment around periastron in SFXTs' (P.I. Drave, PropID 0920016). Using both INTEGRAL and XMM-Newton we will measure the instantaneous accretion rate, emission spectrum and time variability generated on and around the neutron star. Now that the orbital parameters of these SFXTs are well-determined, targeted continuous broad-band observations around periastron provide us with the best opportunity to use the (assumed) neutron star as a direct probe of the circumstellar wind environment. To achieve the goals outlined in this proposal we request 467ks of fixed time INTEGRAL observations complemented with 80ks of simultaneous XMM-Newton observations.

Observation Strategy (Recommended by TAC)

Total of 146 ks in the standard 5x5 dither pattern is to be done to provide continuous coverage across the periastron ± 0.1 orbital phase regions (range 0.95-1.15) of the SFXT system IGR J17354-3255, centered at RA, Dec (J2000.0, in degrees) = 263.865, -32.932 (l, b = 355.457, - 0.273 degrees). The INTEGRAL observation is accompanied by two 20 ks XMM-Newton observations within the duration of each observation (i.e., a total of 40 ks of XMM-Newton observing time).

Proposal grade: B

Data Rights (Recommended by TAC)

Data rights were granted for IGR J17354-3255 only.

Exposure Map

The exposure maps are in galactic coordinates using the Aitoff projection and units of seconds, and the colour scale is indicated at the bottom. The green lines provide the 50, 200, 350, 500 and 650 ksec contour.