Proposal Details - 0720011
Physics of the high energy tail of luminous accreting neutron stars - ultra deep observations of Sco X-1 (Revnivtsev)

Proposal Abstract

Over last years it was firmly established that luminous accreting neutron stars demonstrate high energy tails in their spectra, which while is very minor in terms of energy budget of a source, can tell us a lot about physical processes occuring in the innermost regions of the accretion flow. In particular, one can anticipate appearance of the high energy tail due to presence of hot optically thin corona above optically thick main emitting regions of the flow, which might upscatter soft photons on its thermal or non thermal population of electrons. The main observational apperance which might help us to determine the origin of the tail is its behavior at high energies. The presence of high energy cutoff in this component will allow to distinguish between thermal and non thermal population of electrons and also will allow to put constrains on possible influence of so called bulk motion comptonization on formation of the high energy component. INTEGRAL observatory is the only facility which can provide constrains on the physics of the high energy component of luminous accreting neutron stars. It has abilities to study photon spectra at energies more than 100-200 keV with unprecedented accuracy. The limits obtained in the proposed study will not be overcome by any existing and planning instruments for a long time. We suggest to perform 4 Msec-long observation of Sco X-1 split over two AOs, more than tripling the existing exposure. Among all possible galactic NS systems in the appropriate spectral state, Sco X-1 is by far the brightest one (including high energy tail). This makes this object a must do target for the proposed study.

Observation Strategy (Recommended by TAC)

1.5 Ms in the standard 5x5 mode centred on RA, Dec = 244.979, -15.64 (l, b = 359.094, 23.785).

Proposal grade: C

Data Rights (Recommended by TAC)

The TAC has allocated the following specific data rights to this proposal: Sco X-1.

Consult the Data Rights policy for more information on Russian Federation proposals.

Exposure Map

The exposure maps are in galactic coordinates and units of ksec, and the colour scale is indicated at the bottom. The green lines provide the 100 ksec contour.

Exposure Map