@article{1437792277b142deb2cf0cc48749cce4,
title = "Discovery of 105 Hz coherent pulsations in the ultracompact binary IGR J16597-3704",
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.",
keywords = "Accretion, accretion disks, Binaries: general, Stars: neutron, X-rays: binaries",
author = "A. Sanna and A. Bahramian and E. Bozzo and C. Heinke and D. Altamirano and R. Wijnands and N. Degenaar and T. Maccarone and A. Riggio and {Di Salvo}, T. and R. Iaria and M. Burgay and A. Possenti and C. Ferrigno and A. Papitto and Sivakoff, {G. R.} and N. D'Amico and L. Burderi",
note = "Funding Information: rapid scheduling of the ToO observation of IGR J16597−3704. D. A. acknowledges support from the Royal Society. N. D. is supported by a Vidi grant awarded by The Netherlands organization for scientific research (NWO). We acknowledge financial contribution from the agreement ASI-INAF I/037/12/0, and the International Space Science Institute (ISSI) Bern, which funded and hosted the international team “The disk-magnetosphere interaction around transitional millisecond pulsars”. The Parkes radio telescope is part of the Australia Telescope National Facility which is funded by the Australian Government for operation as a National Facility managed by CSIRO. C. O. H. and G. R. S. are supported by NSERC Discovery Grants. A. P. acknowledges funding from the EUs Horizon 2020 Framework Programme for Research and Innovation under the Marie Sk{\l}odowska-Curie Individual Fellowship grant agreement 660657-TMSP-H2020-MSCA-IF-2014. Funding Information: We thank the NuSTAR, Swift, and Parkes teams for the rapid scheduling of the ToO observation of IGR J16597-3704. D. A. acknowledges support from the Royal Society. N. D. is supported by a Vidi grant awarded by The Netherlands organization for scientific research (NWO). We acknowledge financial contribution from the agreement ASI-INAF I/037/12/0, and the International Space Science Institute (ISSI) Bern, which funded and hosted the international team {"}The disk-magnetosphere interaction around transitional millisecond pulsars{"}. The Parkes radio telescope is part of the Australia Telescope National Facility which is funded by the Australian Government for operation as a National Facility managed by CSIRO. C. O. H. and G. R. S. are supported by NSERC Discovery Grants. A. P. acknowledges funding from the EUs Horizon 2020 Framework Programme for Research and Innovation under the Marie Sklodowska-Curie Individual Fellowship grant agreement 660657-TMSP-H2020-MSCA-IF-2014. Publisher Copyright: {\textcopyright} ESO, 2018.",
year = "2018",
month = feb,
day = "1",
doi = "10.1051/0004-6361/201732262",
language = "English",
volume = "610",
journal = "Astronomy and Astrophysics",
issn = "0004-6361",
}