The compact neutron star in 4U 1746-37 revisited: Reassessing the mass and radius
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| Main Authors: | , , , , |
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| Format: | Preprint |
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2026
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| _version_ | 1866910218855645184 |
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| author | Sung, Kwang Hyun Kim, Myungkuk Kim, Young-Min Kwak, Kyujin Lee, Chang-Hwan |
| author_facet | Sung, Kwang Hyun Kim, Myungkuk Kim, Young-Min Kwak, Kyujin Lee, Chang-Hwan |
| contents | A recent analysis of photospheric radius expansion X-ray bursts from the low-mass X-ray binary 4U 1746-37 reported unusually small mass and radius estimates for the neutron star, suggesting it could be a quark star or quark-cluster star. Here, we propose an alternative interpretation: the star's mass and radius could be underestimated from significant blocking of the X-ray flux. Significant blocking factors ($\mathcal{B} \gtrsim 0.8$, reducing the observed flux to $\sim17\%$ of the intrinsic emission) permit neutron star parameters consistent with the canonical values: $M = 1.59 \pm 0.69 M_{\odot}$, $R = 13.0 \pm 5.45\,\mathrm{km}$, or $M = 2.12 \pm 1.08 M_{\odot}$, $R = 9.80 \pm 4.13\,\mathrm{km}$. The blocking factor, which varies with the photospheric radius, provides a natural explanation for the anomalously large peak-to-touchdown flux ratio ($\sim2.0$) and highlights the importance of accounting for geometric system configuration in neutron star mass--radius estimates. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2605_14264 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | The compact neutron star in 4U 1746-37 revisited: Reassessing the mass and radius Sung, Kwang Hyun Kim, Myungkuk Kim, Young-Min Kwak, Kyujin Lee, Chang-Hwan High Energy Astrophysical Phenomena Solar and Stellar Astrophysics A recent analysis of photospheric radius expansion X-ray bursts from the low-mass X-ray binary 4U 1746-37 reported unusually small mass and radius estimates for the neutron star, suggesting it could be a quark star or quark-cluster star. Here, we propose an alternative interpretation: the star's mass and radius could be underestimated from significant blocking of the X-ray flux. Significant blocking factors ($\mathcal{B} \gtrsim 0.8$, reducing the observed flux to $\sim17\%$ of the intrinsic emission) permit neutron star parameters consistent with the canonical values: $M = 1.59 \pm 0.69 M_{\odot}$, $R = 13.0 \pm 5.45\,\mathrm{km}$, or $M = 2.12 \pm 1.08 M_{\odot}$, $R = 9.80 \pm 4.13\,\mathrm{km}$. The blocking factor, which varies with the photospheric radius, provides a natural explanation for the anomalously large peak-to-touchdown flux ratio ($\sim2.0$) and highlights the importance of accounting for geometric system configuration in neutron star mass--radius estimates. |
| title | The compact neutron star in 4U 1746-37 revisited: Reassessing the mass and radius |
| topic | High Energy Astrophysical Phenomena Solar and Stellar Astrophysics |
| url | https://arxiv.org/abs/2605.14264 |