From Be X-Ray Binaries to Double Neutron Stars: Exploring the Spin and Orbital Evolution
We explore the evolutionary link between Galactic Be X-ray binaries (BeXBs) and Galactic field double neutron stars (DNSs) based on the properties of the NS spin period—<i>P</i> and binary orbital period—<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML"...
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| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-02-01
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| Series: | Universe |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2218-1997/11/2/51 |
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| Summary: | We explore the evolutionary link between Galactic Be X-ray binaries (BeXBs) and Galactic field double neutron stars (DNSs) based on the properties of the NS spin period—<i>P</i> and binary orbital period—<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>P</mi><mi>orb</mi></msub></semantics></math></inline-formula>. First, both BeXB and DNS sources show positive correlation trends in <i>P</i> versus <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>P</mi><mi>orb</mi></msub></semantics></math></inline-formula> relation (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>P</mi><mo>−</mo><msub><mi>P</mi><mi>orb</mi></msub></mrow></semantics></math></inline-formula> diagram), which may relate to the influence of the accretion evolution. Secondly, the two types of sources exhibit similar bi-modal <i>P</i>/<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>P</mi><mi>orb</mi></msub></semantics></math></inline-formula> distributions with the gaps of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>P</mi><mo>∼</mo><mn>40</mn></mrow></semantics></math></inline-formula> s/<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>P</mi><mi>orb</mi></msub><mo>∼</mo><mn>60</mn></mrow></semantics></math></inline-formula> days for BeXBs and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>P</mi><mo>∼</mo><mn>50</mn></mrow></semantics></math></inline-formula> ms/<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>P</mi><mi>orb</mi></msub><mo>∼</mo><mn>1</mn></mrow></semantics></math></inline-formula> day for DNSs, respectively. We propose a possibility that Galactic BeXBs may transfer the bi-modal <i>P</i>/<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>P</mi><mi>orb</mi></msub></semantics></math></inline-formula> classifications to Galactic field DNSs during the evolution process. Furthermore, based on the bi-modal gaps, we infer the contraction factors of <i>P</i> (by <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo>∼</mo><mstyle scriptlevel="0" displaystyle="true"><mfrac><mn>1</mn><mn>800</mn></mfrac></mstyle></mrow></semantics></math></inline-formula>) and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>P</mi><mi>orb</mi></msub></semantics></math></inline-formula> (by <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo>∼</mo><mstyle scriptlevel="0" displaystyle="true"><mfrac><mn>1</mn><mn>60</mn></mfrac></mstyle></mrow></semantics></math></inline-formula>) valuesin the evolution from Galactic BeXBs to Galactic field DNSs. We find that the scaled <i>P</i> or <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>P</mi><mi>orb</mi></msub></semantics></math></inline-formula> values of Galactic BeXBs share the similar bi-modal distributions to that of Galactic field DNSs, and these results can offer a reference to trace the classification and evolution between the two types of sources. |
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| ISSN: | 2218-1997 |