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An ultraluminous X-ray source powered by an accreting neutron star

Bachetti, M. and Harrison, F. A. and Walton, D. J. and Grefenstette, B. W. and Chakrabarty, D. and Fürst, F. and Barret, D. and Beloborodov, A. and Boggs, S. E. and Christensen, F. E. and Craig, W. W. and Fabian, A. C. and Hailey, C. J. and Hornschemeier, A. and Kaspi, V. and Kulkarni, S. R. and Maccarone, T. and Miller, J. M. and Rana, V. and Stern, D. and Tendulkar, S. P. and Tomsick, J. and Webb, N. A. and Zhang, W. W. (2014) An ultraluminous X-ray source powered by an accreting neutron star. Nature, 514 (7521). pp. 202-204. ISSN 0028-0836.

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[img] Image (JPEG) (Extended Data Figure 1: X-ray sources identified by Chandra in the central region of M82.) - Supplemental Material
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[img] Image (JPEG) (Extended Data Figure 2: Swift imaging of the region containing M82 X-1 and M82 X-2.) - Supplemental Material
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[img] Image (JPEG) (Extended Data Table 1: List of NuSTAR observations used in this analysis) - Supplemental Material
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[img] Image (JPEG) (Extended Data Table 2: Best-fit orbital parameters) - Supplemental Material
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[img] Image (JPEG) (Extended Data Table 3: Best fit period and period derivatives for individual NuSTAR observations) - Supplemental Material
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[img] Image (JPEG) (Extended Data Table 4: 3–10 keV flux contributions for bright sources near the nucleus of M82) - Supplemental Material
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The majority of ultraluminous X-ray sources are point sources that are spatially offset from the nuclei of nearby galaxies and whose X-ray luminosities exceed the theoretical maximum for spherical infall (the Eddington limit) onto stellar-mass black holes. Their X-ray luminosities in the 0.5–10 kiloelectronvolt energy band range from 10^(39) to 10^(41) ergs per second. Because higher masses imply less extreme ratios of the luminosity to the isotropic Eddington limit, theoretical models have focused on black hole rather than neutron star systems. The most challenging sources to explain are those at the luminous end of the range (more than 1040 ergs per second), which require black hole masses of 50–100 times the solar value or significant departures from the standard thin disk accretion that powers bright Galactic X-ray binaries, or both. Here we report broadband X-ray observations of the nuclear region of the galaxy M82 that reveal pulsations with an average period of 1.37 seconds and a 2.5-day sinusoidal modulation. The pulsations result from the rotation of a magnetized neutron star, and the modulation arises from its binary orbit. The pulsed flux alone corresponds to an X-ray luminosity in the 3–30 kiloelectronvolt range of 4.9 × 10^(39) ergs per second. The pulsating source is spatially coincident with a variable source that can reach an X-ray luminosity in the 0.3–10 kiloelectronvolt range of 1.8 × 10^(40) ergs per second. This association implies a luminosity of about 100 times the Eddington limit for a 1.4-solar-mass object, or more than ten times brighter than any known accreting pulsar. This implies that neutron stars may not be rare in the ultraluminous X-ray population, and it challenges physical models for the accretion of matter onto magnetized compact objects.

Item Type:Article
Related URLs:
URLURL TypeDescription ReadCube access Paper
Bachetti, M.0000-0002-4576-9337
Harrison, F. A.0000-0003-2992-8024
Walton, D. J.0000-0001-5819-3552
Grefenstette, B. W.0000-0002-1984-2932
Chakrabarty, D.0000-0001-8804-8946
Fürst, F.0000-0003-0388-0560
Barret, D.0000-0002-0393-9190
Boggs, S. E.0000-0001-9567-4224
Christensen, F. E.0000-0001-5679-1946
Fabian, A. C.0000-0002-9378-4072
Hornschemeier, A.0000-0001-8667-2681
Kaspi, V.0000-0001-9345-0307
Kulkarni, S. R.0000-0001-5390-8563
Maccarone, T.0000-0003-0976-4755
Rana, V.0000-0003-1703-8796
Stern, D.0000-0003-2686-9241
Tendulkar, S. P.0000-0003-2548-2926
Tomsick, J.0000-0001-5506-9855
Zhang, W. W.0000-0002-1426-9698
Additional Information:© 2014 Macmillan Publishers Limited. Received 24 June; accepted 6 August 2014. Published online 08 October 2014. This work was supported by NASA (grant no. NNG08FD60C), and made use of data from the Nuclear Spectroscopic Telescope Array (NuSTAR) mission, a project led by Caltech, managed by the Jet Propulsion Laboratory and funded by NASA. We thank the NuSTAR operations, software and calibration teams for support with execution and analysis of these observations. This work made use of data supplied by the UK Swift Science Data Centre at the University of Leicester. M.B. thanks the Centre National d’Etudes Spatiales (CNES) and the Centre National de la Recherche Scientifique (CNRS) for support. Line plots were done using Veusz software by J. Sanders.
Group:Space Radiation Laboratory, NuSTAR
Funding AgencyGrant Number
Centre National d’Études Spatiales (CNES)UNSPECIFIED
Centre National de la Recherche Scientifique (CNRS)UNSPECIFIED
Non-Subject Keywords:high energy astrophysics
Other Numbering System:
Other Numbering System NameOther Numbering System ID
Space Radiation Laboratory2014-25
Issue or Number:7521
Record Number:CaltechAUTHORS:20140804-165311189
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:47952
Deposited By: George Porter
Deposited On:08 Oct 2014 17:32
Last Modified:02 Dec 2019 21:57

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