# XMM-Newton and NuSTAR simultaneous X-ray observations of IGR J11215-5952

## TL;DR

This study presents simultaneous X-ray observations of the SFXT IGR J11215-5952, revealing its timing and spectral properties, including a consistent spin period, large variability, and spectral features, supporting a quasi-spherical settling accretion model.

## Contribution

First simultaneous broad-band X-ray timing and spectral analysis of IGR J11215-5952 during outburst, providing insights into its accretion regime and spectral characteristics.

## Key findings

- Measured spin period of 187.0 +/- 0.4 s.
- Observed large variability and luminous flares on ks timescales.
- Spectral analysis supports a quasi-spherical settling accretion regime.

## Abstract

We report the results of an XMM-Newton and NuSTAR coordinated observation of the Supergiant Fast X-ray Transient (SFXT) IGRJ11215-5952, performed on February 14, 2016, during the expected peak of its brief outburst, which repeats every about 165 days. Timing and spectral analysis were performed simultaneously in the energy band 0.4-78 keV. A spin period of 187.0 +/- 0.4 s was measured, consistent with previous observations performed in 2007. The X-ray intensity shows a large variability (more than one order of magnitude) on timescales longer than the spin period, with several luminous X-ray flares which repeat every 2-2.5 ks, some of which simultaneously observed by both satellites. The broad-band (0.4-78 keV) time-averaged spectrum was well deconvolved with a double-component model (a blackbody plus a power-law with a high energy cutoff) together with a weak iron line in emission at 6.4 keV (equivalent width, EW, of 40+/-10 eV). Alternatively, a partial covering model also resulted in an adequate description of the data. The source time-averaged X-ray luminosity was 1E36 erg/s (0.1-100 keV; assuming 7 kpc). We discuss the results of these observations in the framework of the different models proposed to explain SFXTs, supporting a quasi-spherical settling accretion regime, although alternative possibilities (e.g. centrifugal barrier) cannot be ruled out.