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Quasi-simultaneous XMM-Newton and VLA observation of the non-thermal radio emitter HD\168112 (O5.5III(f^+))

M. De Becker·G. Rauw·R. Blomme·W. L. Waldron·H. Sana·J. M. Pittard·P. Eenens·I. R. Stevens·M. C. Runacres·S. Van Loo·A. M. T. Pollock
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Abstract

We report the results of a multiwavelength study of the non-thermal radio emitter HD168112 (O5.5III(f^+)). The detailed analysis of two quasi-simultaneous XMM-Newton and VLA observations reveals strong variability of this star both in the X-ray and radio ranges. The X-ray observations separated by five months reveal a decrease of the X-ray flux of ~30%. The radio emission on the other hand increases by a factor 5-7 between the two observations obtained roughly simultaneously with the XMM-Newton pointings. The X-ray data reveal a hard emission that is most likely produced by a thermal plasma at kT ~2-3 keV while the VLA data confirm the non-thermal status of this star in the radio waveband. Comparison with archive X-ray and radio data confirms the variability of this source in both wavelength ranges over a yet ill defined time scale. The properties of HD168112 in the X-ray and radio domain point towards a binary system with a significant eccentricity and an orbital period of a few years. However, our optical spectra reveal no significant changes of the star's radial velocity suggesting that if HD168112 is indeed a binary, it must be seen under a fairly low inclination.

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M. De Becker, G. Rauw, R. Blomme, W. L. Waldron, H. Sana, J. M. Pittard, P. Eenens, I. R. Stevens, M. C. Runacres, S. Van Loo, A. M. T. Pollock. 2004-06-09. Quasi-simultaneous XMM-Newton and VLA observation of the non-thermal radio emitter HD\168112 (O5.5III(f^+)). https://doi.org/10.1051/0004-6361%3A20041030-1

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