Publications (2)0 Total impact
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ABSTRACT: 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
(K_s, H_n, and J_n) observations performed on 2012 March 13 and March 26. We
determine the most accurate X-ray position of IGR J18179-1621, alpha_{J2000}=18
h 17m 52.18 s, delta_{J2000}=-16^\circ 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 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_H =2.2+/-0.3 \times
10^{23} cm^{-2}, and photon index \Gamma = 0.4+/-0.1) with an average absorbed
2-8 keV flux of 1.4\times 10^{-11} erg cm^{-2} s^{-1}. At the Chandra-based
position, a source is detected in our near infrared (NIR) maps with K_s =
13.14+/-0.04 mag, H_n = 16+/-0.1 mag, and no J_n band counterpart down to ~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.
07/2012;
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ABSTRACT: We report on the first broad-band (1-200 keV) simultaneous Chandra-INTEGRAL
observations of the recently discovered hard X-ray transient IGR J17177-3656
that took place on 2011, March 22, about two weeks after the source discovery.
The source had an average absorbed 1-200 keV flux of about 8x10^(-10) erg
cm^(-2) s^(-1). We extracted a precise X-ray position of IGR J17177-3656, RA=17
17 42.62, DEC= -36 56 04.5 (90% uncertainty of 0.6"). We also report Swift,
near infrared and quasi simultaneous radio follow-up observations. With the
multi-wavelength information at hand, we propose IGR J17177-3656 is a low-mass
X-ray binary, seen at high inclination, probably hosting a black hole.
07/2011;
