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Enoto T, Kisaka S, Shibata S. Observational diversity of magnetized neutron stars. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2019; 82:106901. [PMID: 31549688 DOI: 10.1088/1361-6633/ab3def] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Young and rotation-powered neutron stars (NSs) are commonly observed as rapidly-spinning pulsars. They dissipate their rotational energy by emitting pulsar wind with electromagnetic radiation and spin down at a steady rate, according to the simple steadily-rotating magnetic dipole model. In reality, however, multiwavelength observations of radiation from the NS surface and magnetosphere have revealed that the evolution and properties of NSs are highly diverse, often dubbed as 'NS zoo'. In particular, many of young and highly magnetized NSs show a high degree of activities, such as sporadic electromagnetic outbursts and irregular changes in pulse arrival times. Importantly, their magnetic field, which are the strongest in the universe, makes them ideal laboratories for fundamental physics. A class of highly-magnetized isolated NSs is empirically divided into several subclasses. In a broad classification, they are, in the order of the magnetic field strength (B) from the highest, 'magnetars' (historically recognized as soft gamma-ray repeaters and/or anomalous x-ray pulsars), 'high-B pulsars', and (nearby) x-ray isolated NSs. This article presents an introductory review for non-astrophysicists about the observational properties of highly-magnetized NSs, and their implications. The observed dynamic nature of NSs must be interpreted in conjunction with transient magnetic activities triggered during magnetic-energy dissipation process. In particular, we focus on how the five fundamental quantities of NSs, i.e. mass, radius, spin period, surface temperature, and magnetic fields, as observed with modern instruments, change with evolution of, and vary depending on the class of, the NSs. They are the foundation for a future unified theory of NSs.
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Affiliation(s)
- Teruaki Enoto
- Department of Astronomy and The Hakubi Center for Advanced Research, Kyoto University, Kyoto 606-8302, Japan
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Lazzarini M, Hornschemeier AE, Williams BF, Wik D, Vulic N, Yukita M, Zezas A, Lewis AR, Durbin M, Ptak A, Bodaghee A, Lehmer BD, Antoniou V, Maccarone T. Young Accreting Compact Objects in M31: The Combined Power of NuSTAR, Chandra, and Hubble. THE ASTROPHYSICAL JOURNAL 2018; 862:28. [PMID: 31631897 PMCID: PMC6800711 DOI: 10.3847/1538-4357/aacb2a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We present 15 high-mass X-ray binary (HMXB) candidates in the disk of M31 for which we are able to infer compact object type, spectral type of the donor star, and age using multiwavelength observations from NuSTAR, Chandra, and the Hubble Space Telescope. The hard X-ray colors and luminosities from NuSTAR permit the tentative classification of accreting X-ray binary systems by compact object type, distinguishing black hole from neutron star systems. We find hard-state black holes, pulsars, and non-magnetized neutron stars associated with optical point-source counterparts with similar frequency. We also find nine non-magnetized neutron stars coincident with globular clusters and an equal number of pulsars with and without point-source optical counterparts. We perform spectral energy distribution (SED) fitting for the most likely optical counterparts to the HMXB candidates, finding seven likely high-mass stars and one possible red helium-burning star. The remaining seven HMXB optical counterparts have poor SED fits, so their companion stars remain unclassified. Using published star formation histories, we find that the majority of HMXB candidates-X-ray sources with UV-bright point-source optical counterpart candidates-are found in regions with star formation bursts less than 50 Myr ago, and three are associated with young stellar ages (<10Myr). This is consistent with similar studies of HMXB populations in the Magellanic Clouds, M33, NGC 300, and NGC 2403.
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Affiliation(s)
- M Lazzarini
- Department of Astronomy, Box 351580, University of Washington, Seattle, WA 98195, USA
- Laboratory for X-ray Astrophysics, NASA Goddard Space Flight Center, Code 662, Greenbelt, MD 20771, USA
| | - A E Hornschemeier
- Laboratory for X-ray Astrophysics, NASA Goddard Space Flight Center, Code 662, Greenbelt, MD 20771, USA
- Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218, USA
| | - B F Williams
- Department of Astronomy, Box 351580, University of Washington, Seattle, WA 98195, USA
| | - D Wik
- Laboratory for X-ray Astrophysics, NASA Goddard Space Flight Center, Code 662, Greenbelt, MD 20771, USA
- Department of Physics and Astronomy, University of Utah, 201 James Fletcher Building, Salt Lake City, UT 84112, USA
| | - N Vulic
- Laboratory for X-ray Astrophysics, NASA Goddard Space Flight Center, Code 662, Greenbelt, MD 20771, USA
- Department of Astronomy and Center for Space Science and Technology (CRESST), University of Maryland, College Park, MD 20742, USA
| | - M Yukita
- Laboratory for X-ray Astrophysics, NASA Goddard Space Flight Center, Code 662, Greenbelt, MD 20771, USA
- Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218, USA
| | - A Zezas
- Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA
| | - A R Lewis
- Department of Astronomy, Box 351580, University of Washington, Seattle, WA 98195, USA
- Department of Astronomy, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210, USA
- Center for Cosmology and AstroParticle Physics, The Ohio State University, Columbus, OH 43210, USA
| | - M Durbin
- Department of Astronomy, Box 351580, University of Washington, Seattle, WA 98195, USA
| | - A Ptak
- Laboratory for X-ray Astrophysics, NASA Goddard Space Flight Center, Code 662, Greenbelt, MD 20771, USA
- Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218, USA
| | - A Bodaghee
- Department of Chemistry, Physics and Astronomy, Georgia College and State University, Milledgeville, GA 31061, USA
| | - B D Lehmer
- Department of Physics, University of Arkansas, 226 Physics Building, 825 West Dickson Street, Fayetteville, AR 72701, USA
| | - V Antoniou
- Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA
| | - T Maccarone
- Department of Physics and Astronomy, Box 41051, Science Building, Texas Tech University, Lubbock, TX 79409, USA
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