X-RAY AND NEAR-INFRARED OBSERVATIONS OF THE OBSCURED ACCRETING PULSAR IGR J18179-1621

Journal Article · Mon Oct 01 00:00:00 EDT 2012 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/757/2/143· OSTI ID:22092180

Nowak, M. A. ^[1]; Paizis, A. ^[2]; Rodriguez, J.; Chaty, S. ^[3]; Santo, M. Del; Ubertini, P. ^[4]; Grinberg, V.; Wilms, J. ^[5]

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1. Massachusetts Institute of Technology, Kavli Institute for Astrophysics, Cambridge, MA 02139 (United States)
2. Istituto Nazionale di Astrofisica, INAF-IASF, Via Bassini 15, I-20133 Milano (Italy)
3. AIM-Astrophysique, Instrumentation et Modelisation (UMR-E 9005 CEA/DSM-CNRS-Universite Paris Diderot) Irfu/Service d'Astrophysique, Centre de Saclay FR-91191 Gif-sur-Yvette Cedex (France)
4. Istituto Nazionale di Astrofisica, INAF-IAPS, Via Fosso del Cavaliere 100, I-00133 Rome (Italy)
5. Dr. Karl Remeis-Sternwarte and Erlangen Centre for Astroparticle Physics, Universitaet Erlangen-Nuernberg, Sternwartstr. 7, D-96049 Bamberg (Germany)

IGR J18179-1621 is an obscured accreting X-ray pulsar discovered by INTEGRAL on 2012 February 29. We report on our 20 ks 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 (K{sub s} , H{sub n} , and J{sub n} ) observations performed on 2012 March 13 and 26. We determine the most accurate X-ray position of IGR J18179-1621, {alpha}{sub J2000} = 18{sup h}17{sup m}52.{sup s}18, {delta}{sub J2000} = -16 Degree-Sign 21'31.''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 light-curve 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{sub H} = 2.2 {+-} 0.3 Multiplication-Sign 10{sup 23} cm{sup -2} and photon index {Gamma} = 0.4 {+-} 0.1) with an average absorbed 2-8 keV flux of 1.4 Multiplication-Sign 10{sup -11} erg cm{sup -2} s{sup -1}. At the Chandra-based position, a source is detected in our near-infrared (NIR) maps with K{sub s} 13.14 {+-} 0.04 mag, H{sub n} = 16 {+-} 0.1 mag, and no J{sub n} -band counterpart down to {approx}18 mag. The NIR source, compatible with 2MASS J18175218-1621316, shows no variability between 2012 March 13 and 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.

• OSTI ID: 22092180
• Journal Information: Astrophysical Journal, Vol. 757, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ACCRETION DISKS
ASTRONOMY
ASTROPHYSICS
BINARY STARS
COSMIC X-RAY SOURCES
DIAGRAMS
EMISSION SPECTRA
INDEXES
KEV RANGE
PERIODICITY
PULSARS
PULSES
VISIBLE RADIATION
X RADIATION