Event Rate Density and Luminosity Function of Newborn-magnetar-driven X-Ray Transients from Neutron Star Binary Mergers
X-ray transients (XTs) driven by newborn magnetars from mergers of neutron star binaries (NSBs) have occasionally been detected in the narrow-field Chandra Deep Field-South (CDF-S) survey and the Swift/X-Ray Telescope observations of short gamma-ray bursts. Quantifying their event rate density (ERD)...
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2025-01-01
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| author | Le Zou Ji-Gui Cheng Rui-Chong Hu Wen-Jin Xie En-Wei Liang |
| author_facet | Le Zou Ji-Gui Cheng Rui-Chong Hu Wen-Jin Xie En-Wei Liang |
| author_sort | Le Zou |
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| description | X-ray transients (XTs) driven by newborn magnetars from mergers of neutron star binaries (NSBs) have occasionally been detected in the narrow-field Chandra Deep Field-South (CDF-S) survey and the Swift/X-Ray Telescope observations of short gamma-ray bursts. Quantifying their event rate density (ERD) and luminosity function (LF) is critical for understanding NSB coalescence and magnetar formation. Utilizing population synthesis calculations incorporating various equations of state (EoSs), we derive a local ERD of ∼300 Gpc ^−3 yr ^−1 and a redshift-dependent ERD profile peaking at z = 1.81 followed by a rapid decline beyond z ∼ 4. Constructing an XT sample based on CDF-S and Swift observations, we characterize the LF by a single power-law function at L ≤ 4.75 × 10 ^46 erg s ^−1 with a slope of −1.03, followed by a broken power-law function in which the break luminosity is L _b = 4.38 × 10 ^47 erg s ^−1 and the slopes are −0.28 and −1.66. Based on the ERD and the LF, we estimate that the Einstein Probe (EP) detection rate is ∼31 yr ^−1 , adopting a conservative threshold flux of 10 ^−9 erg s ^−1 , a luminosity range of L ∈ [2 × 10 ^44 , 2 × 10 ^49 ] erg s ^−1 , and a correction for the jet opening angle of ∼16 ^∘ . This detection rate is consistent with the EP observations during its first year of operation. It is important to note that our estimation is subject to uncertainties arising from the LF derivation. Future EP observations of these XT events will be crucial in reducing these uncertainties. |
| format | Article |
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| institution | Kabale University |
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| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
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| series | The Astrophysical Journal |
| spelling | doaj-art-c91b813a4e4b4efc87fec05710b024702025-08-20T03:26:34ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-0198612810.3847/1538-4357/add2f7Event Rate Density and Luminosity Function of Newborn-magnetar-driven X-Ray Transients from Neutron Star Binary MergersLe Zou0https://orcid.org/0000-0003-4639-5397Ji-Gui Cheng1https://orcid.org/0000-0002-2585-442XRui-Chong Hu2https://orcid.org/0000-0002-6442-7850Wen-Jin Xie3En-Wei Liang4https://orcid.org/0000-0002-7044-733XDepartment of Physics, Xiangtan University , Xiangtan 411105, People’s Republic of China; Key Laboratory of Stars and Interstellar Medium, Xiangtan University , Xiangtan 411105, People’s Republic of ChinaSchool of Physics and Electronics, Hunan University of Science and Technology , Xiangtan 411201, People’s Republic of ChinaGuangxi Key Laboratory for Relativistic Astrophysics, School of Physical Science and Technology, Guangxi University , Nanning 530004, People’s Republic of China ; lew@gxu.edu.cnUniversité Paris Cité , CEA Paris-Saclay, IRFU/DAp-AIM, 91191 Gif-sur-Yvette, FranceGuangxi Key Laboratory for Relativistic Astrophysics, School of Physical Science and Technology, Guangxi University , Nanning 530004, People’s Republic of China ; lew@gxu.edu.cnX-ray transients (XTs) driven by newborn magnetars from mergers of neutron star binaries (NSBs) have occasionally been detected in the narrow-field Chandra Deep Field-South (CDF-S) survey and the Swift/X-Ray Telescope observations of short gamma-ray bursts. Quantifying their event rate density (ERD) and luminosity function (LF) is critical for understanding NSB coalescence and magnetar formation. Utilizing population synthesis calculations incorporating various equations of state (EoSs), we derive a local ERD of ∼300 Gpc ^−3 yr ^−1 and a redshift-dependent ERD profile peaking at z = 1.81 followed by a rapid decline beyond z ∼ 4. Constructing an XT sample based on CDF-S and Swift observations, we characterize the LF by a single power-law function at L ≤ 4.75 × 10 ^46 erg s ^−1 with a slope of −1.03, followed by a broken power-law function in which the break luminosity is L _b = 4.38 × 10 ^47 erg s ^−1 and the slopes are −0.28 and −1.66. Based on the ERD and the LF, we estimate that the Einstein Probe (EP) detection rate is ∼31 yr ^−1 , adopting a conservative threshold flux of 10 ^−9 erg s ^−1 , a luminosity range of L ∈ [2 × 10 ^44 , 2 × 10 ^49 ] erg s ^−1 , and a correction for the jet opening angle of ∼16 ^∘ . This detection rate is consistent with the EP observations during its first year of operation. It is important to note that our estimation is subject to uncertainties arising from the LF derivation. Future EP observations of these XT events will be crucial in reducing these uncertainties.https://doi.org/10.3847/1538-4357/add2f7Stellar mergersMagnetarsGamma-ray bursts |
| spellingShingle | Le Zou Ji-Gui Cheng Rui-Chong Hu Wen-Jin Xie En-Wei Liang Event Rate Density and Luminosity Function of Newborn-magnetar-driven X-Ray Transients from Neutron Star Binary Mergers The Astrophysical Journal Stellar mergers Magnetars Gamma-ray bursts |
| title | Event Rate Density and Luminosity Function of Newborn-magnetar-driven X-Ray Transients from Neutron Star Binary Mergers |
| title_full | Event Rate Density and Luminosity Function of Newborn-magnetar-driven X-Ray Transients from Neutron Star Binary Mergers |
| title_fullStr | Event Rate Density and Luminosity Function of Newborn-magnetar-driven X-Ray Transients from Neutron Star Binary Mergers |
| title_full_unstemmed | Event Rate Density and Luminosity Function of Newborn-magnetar-driven X-Ray Transients from Neutron Star Binary Mergers |
| title_short | Event Rate Density and Luminosity Function of Newborn-magnetar-driven X-Ray Transients from Neutron Star Binary Mergers |
| title_sort | event rate density and luminosity function of newborn magnetar driven x ray transients from neutron star binary mergers |
| topic | Stellar mergers Magnetars Gamma-ray bursts |
| url | https://doi.org/10.3847/1538-4357/add2f7 |
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