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| Main Authors: | , , , , , , , , , , , , |
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| Format: | Preprint |
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2026
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2605.05708 |
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| _version_ | 1866911654980091904 |
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| author | Li, Linjia Qian, Shengbang Asfandiyarov, Ildar Matekov, Azizbek Zhu, Liying Soonthornthum, Boonrucksar Gaynullina, Evelina Khalikova, Alina He, Jiajia Meng, Fangbin Zhang, Huiting Wang, Jiangjiao Shi, Xiangdong |
| author_facet | Li, Linjia Qian, Shengbang Asfandiyarov, Ildar Matekov, Azizbek Zhu, Liying Soonthornthum, Boonrucksar Gaynullina, Evelina Khalikova, Alina He, Jiajia Meng, Fangbin Zhang, Huiting Wang, Jiangjiao Shi, Xiangdong |
| contents | IY Lyr, historically misclassified as an eclipsing binary, is now established as a first-overtone RR Lyrae star (RRc star). Using multi-band photometry (ASAS-SN, ZTF, TESS, and our BVRI data), LAMOST spectroscopy, and Gaia astrometry, we investigate its pulsation, binarity, and Galactic population. From O-C analysis, we detect a long-term period decrease and a light-travel time effect with an orbital period of 3.94 years, eccentricity of 0.46, and a mass function of 0.65 M$_{\odot}$. The companion is independently confirmed by radial velocity residuals and Gaia proper motions. Combined constraints yield an orbital inclination of 94.8$^{\circ}$ and a companion mass of 1.37 M$_{\odot}$. Chemical abundances ([Fe/H] $\simeq$ -1.0, [$α$/Fe] $\simeq$ +0.27, Xiang et al. 2019) and dynamics ($L_{\rm z}$ $\simeq$ 1250 kpc km s$^{-1}$, $Z_{\rm max}$ $\simeq$ 1.31 kpc) identify IY Lyr as an old, high-$α$, thick-disk star. The companion mass lies at the peak of the neutron star mass distribution, and the system's age excludes a main-sequence star; we conclude the companion is most likely a typical neutron star, although a massive white dwarf near the Chandrasekhar limit cannot be ruled out. IY Lyr is among the few RRc binaries with a compact companion verified by multiple methods, and it has important implications for thick-disk binary evolution and neutron star formation. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2605_05708 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | IY Lyr: A Thick-Disk first-overtone RR Lyrae Star with a Possible Neutron Star Companion Li, Linjia Qian, Shengbang Asfandiyarov, Ildar Matekov, Azizbek Zhu, Liying Soonthornthum, Boonrucksar Gaynullina, Evelina Khalikova, Alina He, Jiajia Meng, Fangbin Zhang, Huiting Wang, Jiangjiao Shi, Xiangdong Solar and Stellar Astrophysics IY Lyr, historically misclassified as an eclipsing binary, is now established as a first-overtone RR Lyrae star (RRc star). Using multi-band photometry (ASAS-SN, ZTF, TESS, and our BVRI data), LAMOST spectroscopy, and Gaia astrometry, we investigate its pulsation, binarity, and Galactic population. From O-C analysis, we detect a long-term period decrease and a light-travel time effect with an orbital period of 3.94 years, eccentricity of 0.46, and a mass function of 0.65 M$_{\odot}$. The companion is independently confirmed by radial velocity residuals and Gaia proper motions. Combined constraints yield an orbital inclination of 94.8$^{\circ}$ and a companion mass of 1.37 M$_{\odot}$. Chemical abundances ([Fe/H] $\simeq$ -1.0, [$α$/Fe] $\simeq$ +0.27, Xiang et al. 2019) and dynamics ($L_{\rm z}$ $\simeq$ 1250 kpc km s$^{-1}$, $Z_{\rm max}$ $\simeq$ 1.31 kpc) identify IY Lyr as an old, high-$α$, thick-disk star. The companion mass lies at the peak of the neutron star mass distribution, and the system's age excludes a main-sequence star; we conclude the companion is most likely a typical neutron star, although a massive white dwarf near the Chandrasekhar limit cannot be ruled out. IY Lyr is among the few RRc binaries with a compact companion verified by multiple methods, and it has important implications for thick-disk binary evolution and neutron star formation. |
| title | IY Lyr: A Thick-Disk first-overtone RR Lyrae Star with a Possible Neutron Star Companion |
| topic | Solar and Stellar Astrophysics |
| url | https://arxiv.org/abs/2605.05708 |