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Abstract
The recent discoveries of pulsed X-ray emission from three ultraluminous X-ray (ULX) sources have finally enabled us to recognize a subclass within the ULX class: the great pretenders, neutron stars (NSs) that appear to emit X-ray radiation at isotropic luminosities L X = 7 × 1039 erg s-1 - 1 × 1041 erg s-1 only because their emissions are strongly beamed toward our direction and our sight lines are offset by only a few degrees from their magnetic-dipole axes. The three known pretenders appear to be stronger emitters than the presumed black holes of the ULX class, such as Holmberg II & IX X-1, IC10 X-1, and NGC300 X-1. For these three NSs, we have adopted a single reasonable assumption, that their brightest observed outbursts unfold at the Eddington rate, and we have calculated both their propeller states and their surface magnetic-field magnitudes. We find that the results are not at all different from those recently obtained for the Magellanic Be/X-ray pulsars: the three NSs reveal modest magnetic fields of about 0.3-0.4 TG and beamed propeller-line X-ray luminosities of ~ 1036-37 erg s-1, substantially below the Eddington limit.
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Affiliation(s)
- Dimitris M Christodoulou
- Lowell Center for Space Science and Technology, University of Massachusetts Lowell, Lowell, MA, 01854, USA
- Department of Mathematical Sciences, University of Massachusetts Lowell, Lowell, MA, 01854, USA
| | - Silas G T Laycock
- Lowell Center for Space Science and Technology, University of Massachusetts Lowell, Lowell, MA, 01854, USA
- Department of Physics & Applied Physics, University of Massachusetts Lowell, Lowell, MA, 01854, USA
| | - Demosthenes Kazanas
- NASA Goddard Space Flight Center, Laboratory for High-Energy Astrophysics, Code 663, Greenbelt, MD 20771, USA
| | - Rigel Cappallo
- Lowell Center for Space Science and Technology, University of Massachusetts Lowell, Lowell, MA, 01854, USA
- Department of Physics & Applied Physics, University of Massachusetts Lowell, Lowell, MA, 01854, USA
| | - Ioannis Contopoulos
- Research Center for Astronomy and Applied Mathematics, Academy of Athens, Athens 11527, Greece
- National Research Nuclear University, Moscow 115409, Russia
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Israel GL, Belfiore A, Stella L, Esposito P, Casella P, De Luca A, Marelli M, Papitto A, Perri M, Puccetti S, Castillo GAR, Salvetti D, Tiengo A, Zampieri L, D'Agostino D, Greiner J, Haberl F, Novara G, Salvaterra R, Turolla R, Watson M, Wilms J, Wolter A. An accreting pulsar with extreme properties drives an ultraluminous x-ray source in NGC 5907. Science 2017; 355:817-819. [PMID: 28219970 DOI: 10.1126/science.aai8635] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Accepted: 01/27/2017] [Indexed: 11/02/2022]
Abstract
Ultraluminous x-ray sources (ULXs) in nearby galaxies shine brighter than any x-ray source in our Galaxy. ULXs are usually modeled as stellar-mass black holes (BHs) accreting at very high rates or intermediate-mass BHs. We present observations showing that NGC 5907 ULX is instead an x-ray accreting neutron star (NS) with a spin period evolving from 1.43 seconds in 2003 to 1.13 seconds in 2014. It has an isotropic peak luminosity of [Formula: see text]1000 times the Eddington limit for a NS at 17.1 megaparsec. Standard accretion models fail to explain its luminosity, even assuming beamed emission, but a strong multipolar magnetic field can describe its properties. These findings suggest that other extreme ULXs (x-ray luminosity [Formula: see text] 1041 erg second[Formula: see text]) might harbor NSs.
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Affiliation(s)
- Gian Luca Israel
- Osservatorio Astronomico di Roma, Istituto Nazionale di Astrofisica (INAF), via Frascati 33, I-00078 Monteporzio Catone, Italy.
| | - Andrea Belfiore
- Istituto di Astrofisica Spaziale e Fisica Cosmica, INAF, via E. Bassini 15, I-20133 Milano, Italy
| | - Luigi Stella
- Osservatorio Astronomico di Roma, Istituto Nazionale di Astrofisica (INAF), via Frascati 33, I-00078 Monteporzio Catone, Italy
| | - Paolo Esposito
- Anton Pannekoek Institute for Astronomy, University of Amsterdam, Postbus 94249, NL-1090GE Amsterdam, Netherlands.,Istituto di Astrofisica Spaziale e Fisica Cosmica, INAF, via E. Bassini 15, I-20133 Milano, Italy
| | - Piergiorgio Casella
- Osservatorio Astronomico di Roma, Istituto Nazionale di Astrofisica (INAF), via Frascati 33, I-00078 Monteporzio Catone, Italy
| | - Andrea De Luca
- Istituto di Astrofisica Spaziale e Fisica Cosmica, INAF, via E. Bassini 15, I-20133 Milano, Italy.,Istituto Nazionale di Fisica Nucleare, Sezione di Pavia, Via Bassi 6, 27100 Pavia, Italy
| | - Martino Marelli
- Istituto di Astrofisica Spaziale e Fisica Cosmica, INAF, via E. Bassini 15, I-20133 Milano, Italy
| | - Alessandro Papitto
- Osservatorio Astronomico di Roma, Istituto Nazionale di Astrofisica (INAF), via Frascati 33, I-00078 Monteporzio Catone, Italy
| | - Matteo Perri
- Agenzia Spaziale Italiana Science Data Center, via del Politecnico snc, I-00133 Roma, Italy.,Osservatorio Astronomico di Roma, Istituto Nazionale di Astrofisica (INAF), via Frascati 33, I-00078 Monteporzio Catone, Italy
| | - Simonetta Puccetti
- Agenzia Spaziale Italiana Science Data Center, via del Politecnico snc, I-00133 Roma, Italy.,Osservatorio Astronomico di Roma, Istituto Nazionale di Astrofisica (INAF), via Frascati 33, I-00078 Monteporzio Catone, Italy
| | - Guillermo A Rodríguez Castillo
- Osservatorio Astronomico di Roma, Istituto Nazionale di Astrofisica (INAF), via Frascati 33, I-00078 Monteporzio Catone, Italy
| | - David Salvetti
- Istituto di Astrofisica Spaziale e Fisica Cosmica, INAF, via E. Bassini 15, I-20133 Milano, Italy
| | - Andrea Tiengo
- Scuola Universitaria Superiore IUSS Pavia, piazza della Vittoria 15, I-27100 Pavia, Italy.,Istituto di Astrofisica Spaziale e Fisica Cosmica, INAF, via E. Bassini 15, I-20133 Milano, Italy.,Istituto Nazionale di Fisica Nucleare, Sezione di Pavia, Via Bassi 6, 27100 Pavia, Italy
| | - Luca Zampieri
- Osservatorio Astronomico di Padova, INAF, vicolo dell'Osservatorio 5, I-35122 Padova, Italy
| | - Daniele D'Agostino
- Istituto di Matematica Applicata e Tecnologie Informatiche "E. Magenes," CNR, via de Marini 6, I-16149 Genova, Italy
| | - Jochen Greiner
- Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse, D-85748 Garching, Germany
| | - Frank Haberl
- Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse, D-85748 Garching, Germany
| | - Giovanni Novara
- Scuola Universitaria Superiore IUSS Pavia, piazza della Vittoria 15, I-27100 Pavia, Italy.,Istituto di Astrofisica Spaziale e Fisica Cosmica, INAF, via E. Bassini 15, I-20133 Milano, Italy
| | - Ruben Salvaterra
- Istituto di Astrofisica Spaziale e Fisica Cosmica, INAF, via E. Bassini 15, I-20133 Milano, Italy
| | - Roberto Turolla
- Dipartimento di Fisica e Astronomia, Università di Padova, via F. Marzolo 8, I-35131 Padova, Italy
| | - Mike Watson
- Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH , UK
| | - Joern Wilms
- Dr. Karl-Remeis-Sternwarte and Erlangen Centre for Astroparticle Physics, Sternwartstrasse 7, D-96049 Bamberg, Germany
| | - Anna Wolter
- Osservatorio Astronomico di Brera, INAF, via Brera 28, I-20121 Milano, Italy
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