We report on the results of the multiwavelength campaign carried out after the discovery of the INTEGRAL transient IGR J17329-2731 .
The optical data collected with the SOAR telescope allowed us to identify the donor star in this system as a late M giant at a distance of 2.7 ^ { +3.4 } _ { -1.2 } kpc .
The data collected quasi-simultaneously with XMM–Newton and NuSTAR showed the presence of a modulation with a period of 6680 \pm 3 s in the X-ray light curves of the source .
This unveils that the compact object hosted in this system is a slowly rotating neutron star .
The broadband X-ray spectrum showed the presence of a strong absorption ( \gg 10 ^ { 23 } cm ^ { -2 } ) and prominent emission lines at 6.4 keV , and 7.1 keV .
These features are usually found in wind-fed systems , in which the emission lines result from the fluorescence of the X-rays from the accreting compact object on the surrounding stellar wind .
The presence of a strong absorption line around \sim 21 keV in the NuSTAR spectrum suggests a cyclotron origin , thus allowing us to estimate the neutron star magnetic field as \sim 2.4 \times 10 ^ { 12 } G. All evidence thus suggests IGR J17329-2731 is a symbiotic X-ray binary .
As no X-ray emission was ever observed from the location of IGR J17329-2731 by INTEGRAL ( or other X-ray facilities ) during the past 15 yr in orbit and considering that symbiotic X-ray binaries are known to be variable but persistent X-ray sources , we concluded that INTEGRAL caught the first detectable X-ray emission from IGR J17329-2731 when the source shined as a symbiotic X-ray binary .
The Swift XRT monitoring performed up to \sim 3 months after the discovery of the source , showed that it maintained a relatively stable X-ray flux and spectral properties .