IGR J18179 - 1621 is an obscured accreting X-ray pulsar discovered by INTEGRAL on 2012 February 29 .
We report on our 20 ksec Chandra -High Energy Transmission Gratings Spectrometer observation of the source performed on 2012 March 17 , on two short contemporaneous Swift observations , and on our two near-infrared ( \mathrm { K } _ { s } , \mathrm { H } _ { n } , and \mathrm { J } _ { n } ) observations performed on 2012 March 13 and March 26 .
We determine the most accurate X-ray position of IGR J18179 - 1621 , \alpha _ { \mathrm { J 2000 } } = 18 ^ { \mathrm { h } } 17 ^ { \mathrm { m } } 52 ^ { \mathrm { s } } .18 , \delta _ { \mathrm { J 2000 } } = -16 ^ { \circ } 21 \arcmin \hskip { -3.0 pt } 31 \arcsec \hskip { -3 % .0 pt } .68 ( 90 % uncertainty of 0″.6 ) .
A strong periodic variability at 11.82 s is clearly detected in the Chandra data , confirming the pulsating nature of the source , with the lightcurve softening at the pulse peak .
The quasi-simultaneous Chandra - Swift spectra of IGR J18179 - 1621 can be well fit by a heavily absorbed hard power-law ( N _ { \mathrm { H } } = 2.2 \pm 0.3 \times 10 ^ { 23 } \mathrm { cm } ^ { -2 } , and photon index \Gamma = 0.4 \pm 0.1 ) with an average absorbed 2–8 keV flux of 1.4 \times 10 ^ { -11 } \mathrm { erg } \mathrm { cm } ^ { -2 } \mathrm { s } ^ { -1 } .
At the Chandra -based position , a source is detected in our near infrared ( NIR ) maps with \mathrm { K } _ { s } = 13.14 \pm 0.04 mag , \mathrm { H } _ { n } = 16 \pm 0.1 mag , and no \mathrm { J } _ { n } band counterpart down to \sim 18 mag .
The NIR source , compatible with 2MASS J18175218 - 1621316 , shows no variability between 2012 March 13 and March 26 .
Searches of the UKIDSS database show similar NIR flux levels at epochs six months prior to and after a 2007 February 11 archival Chandra observation where the source ’ s X-ray flux was at least 87 times fainter .
In many ways IGR J18179 - 1621 is unusual : its combination of a several week long outburst ( without evidence of repeated outbursts in the historical record ) , high absorption column ( a large fraction of which is likely local to the system ) , and 11.82 s period does not fit neatly into existing X-ray binary categories .