IGR J18179-1621

• Discovery and detection both by JEM-X and ISGRI onboard INTEGRAL
• Combined JEM-X and IBIS/ISGRI spectrum => cut-off power-law (Γ~-0.5, Ecut~4.9 keV) + broad Gaussian absorption line at ~20.8 keV
• If absorption line = cyclotron scattering => source is a high mass X-ray binary pulsar with B~1.7e12 G

• Swift XRT observation=>strong signal in the periodogram at 11.82s
• Pulse fraction of 27%.
• Interpreted as the signature of a HMXB with pulsar

• Swift XRT observation=>refined X-ray position (after correction for pile up)
• Spectra (2 Swift observations) => absorbed power law with N_H,1=11.0 x 10²² cm-2 and N_H,2=15.1 x 10²²cm-2 Γ1=0.4 and Γ2=0.7
• 3-10 keV fluxes compatible with JEMX detection
• 2MASS J18175218-1621316 (RA =274.467438 dec=-16.358791) is a Ks=11.4 IR counterpart

• Detection of 11.82s pulsations with Fermi/GBM
• Pulsations detected at 84.5896 mHz (84.5908 mHz) with rms amplitude 5.9 mCrab (8.5 mCrab) in data of Feb. 20-23 (Feb. 24-27) 2012.

• Chandra refined position
• 2MASS has Ks=13.136 and is confirmed as the IR counterpart

• Swift and INTEGRAL observations
• Confirm the detection of a 11.82s pulsation, with a pulse fraction of 22%
• Presence of an absorption feature at 21.5 keV in addition to an absorbed (N_H=12.3 x10²² cm-2) cutoff power law (Γ=0.59, Ecut =9.97 keV)
• Absorption line, ifattributed to a cyclotron resonant scattering feature, => B~2.4e12 G
• Source is an accreting pulsar.

• Chandra and NIR observations
• NIR observations => source compatible with 2MASS source, with Ks=13.14, Hn=16.0 and Jn> 18
• No variability in NIR source when comparing to previous (eg UKIDSS) measurements at time of no X-ray emission
• Strong periodic signal at 11.82s confirming pulsating nature of the source
• Quasi simultaneous Chandra+Swift spectra => absorbed power law (N_H2.2 x 10²³ cm-2, Γ=0.4)
• LMXB nature unlikely, and an HMXB is preferred although the source is unusual in many ways