Multiwavelength characterisation of the accreting millisecond X-ray pulsar and ultra-compact binary IGR J17062-6143

HERNÁNDEZ SANTISTEBAN, J. V.; CUNEO, V. ; DEGENAAR, N.; DEN VAN EIJNDEN, J.; ALTAMIRANO, D.; GOMEZ, M.; RUSSELL, D. M.; WIJNANDS, R.; GOLOVAKOVA, R.; REYNOLDS, M. T.; MILLER, J. M.

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2019 vol. 488 p. 4596 - 4606

0035-8711

IGRJ17062-6143 is an ultra-compact X-ray binary (UCXB) with an orbitalperiod of 37.96 min. It harbours a millisecond X-ray pulsar that is spinning at 163 Hz and and has continuously been accreting from itscompanion star since 2006. Determining the composition of the accreted matter in UCXBs is of high interest for studies of binaryevolution and the monuclear burning on the surface of neutron stars. Here, we present a multi-wavelength study of IGR J17062-6143 aimed to determine the detailed properties of its accretion disc and companion star. The multi-epoch photometric UV to near-infrared spectral energy distribution (SED) is consistent with an accretion disc Fnu prop nu^1/3. The SED modelling of the accretion disc allowed us to estimate anouter disc radius of Rout=2.2(+0.9-0.4)x10^10 cm and a mass-transfer rate of m=1.8(+1.8−0.5)x10^−10 MSun/yr. Comparing this with the estimated mass-accretion rate inferred fromits X-ray emission suggests that more than or about 90% of the transferred mass is lost from the system. Moreover, our SED modelling shows that the thermal emission component seen in the X-ray spectrum is highly unlikely from the accretion disc and must therefore represent emission from the surface of the neutron star. Our low-resolution optical spectrum revealed a blue continuum and no emission lines, i.e. lacking H and He features. Based on the current data we cannot conclusively identify the nature of the companion star, but we make recommendations for future study that can distinguish between the different possible evolution histories of this X-ray binary. Finally, we demonstrate how multiwavelength observations can be effectively used to find more UCXBs among the LMXBs.