Discovery of 105 Hz coherent pulsations in the ultracompact binary IGR J16597-3704

Journal
Date Issued
2018
Author(s)
•
Bahramian, A.
•
Bozzo, E.
•
Heinke, C.
•
Altamirano, D.
•
Wijnands, R.
•
Degenaar, N.
•
Maccarone, T.
•
Riggio, A.
•
Di Salvo, T.
•
Iaria, R.
•
•
•
Ferrigno, C.
•
•
Sivakoff, G. R.
•
•
Burderi, L.
DOI
Abstract
We report the discovery of X-ray pulsations at 105.2 Hz (9.5 ms) from the transient X-ray binary IGR J16597-3704 using NuSTAR and Swift. The source was discovered by INTEGRAL in the globular cluster NGC 6256 at a distance of 9.1 kpc. The X-ray pulsations show a clear Doppler modulation that implies an orbital period of 46 min and a projected semi-major axis of 5 lt-ms, which makes IGR J16597-3704 an ultracompact X-ray binary system. We estimated a minimum companion mass of 6.5 × 10-10 M☉, assuming a neutron star mass of 1.4 M☉, and an inclination angle of <75° (suggested by the absence of eclipses or dips in its light curve). The broad-band energy spectrum of the source is well described by a disk blackbody component (kT 1.4 keV) plus a comptonised power-law with photon index 2.3 and an electron temperature of 30 keV. Radio pulsations from the source were unsuccessfully searched for with the Parkes Observatory.
Volume
610
Start page
L2
Uri
Url
Issn Identifier
0004-6361
Ads BibCode
2018A&A...610L...2S
Rights
open.access
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