Year: 2024
Type: article
Abstract: Binary evolution theory predicts that the second common envelope (CE) ejection can produce low-mass (0.32-0.36 M⊙) subdwarf~B (sdB) stars inside ultrashort-orbital-period binary systems as their helium cores are ignited under nondegenerate conditions. With the orbital decay driven by radiation of gravitational waves, the minimum orbital period that an sdB binary formed in this channel can reach before the Roche-lobe overflow is ~20 minutes. However, only four sdB binaries with orbital periods below an hour have been reported so far, while none of them has an orbital period approaching the above theoretical limit. This leads to an unclear role of the second CE ejection in forming ultracompact sdB binaries and a blocked link between detached helium-burning-star binaries and gravitational-wave sources, AM CVn stars. Here we report the discovery of a 20.5-minute-orbital-period ellipsoidal binary, TMTS J052610.43+593445.1, in which the visible helium-burning sdB star is being tidally deformed by an invisible carbon-oxygen white dwarf (WD) companion. This sdB star is inferred to have a mass of ~0.33 M⊙, approaching that of the helium-ignition limit. Owing to the low-mass sdB star, WD companion, and extremely short orbital period, this system provides the first clear case to justify the formation of sdB binaries through the nondegenerate channel of second CE ejection. In particular, the radius of this low-mass sdB star is only 0.066 R⊙, about seven Earth radii, representing the most compact nondegenerate star ever known. As the shortest-orbital-period single-degenerate detached binary discovered up to date, TMTS J052610.43+593445.1 provides a crucial bridge to map the binary evolution scheme from the second CE ejection to the formation of AM CVn stars having a helium-star donor, and will serve as a crucial verification binary of space-borne gravitational-wave detectors in the future.
Source: Nature Astronomy
Authors: Jie Lin, Chengyuan Wu, Heran Xiong, Xiaofeng Wang, Péter Németh, Zhanwen Han, Jiangdan Li, Nancy Elias-Rosa, Irene Salmaso, Alexei V. Filippenko, Thomas G. Brink, Yi Yang, Xuefei Chen, Shengyu Yan, Jujia Zhang, Sufen Guo, Yongzhi Cai, Jun Mo, Gaobo Xi, Jialian Liu, Jincheng Guo, Qiqi Xia, Danfeng Xiang, Gaici Li, Zhenwei Li, WeiKang Zheng, Jicheng Zhang, Qichun Liu, Fangzhou Guo, Liyang Chen, Wenxiong Li
Institutions: University of Science and Technology of China, Chinese Academy of Sciences, Tsinghua University, Yunnan Observatories, Australian National University, Beijing Planetarium, Beijing Academy of Science and Technology, Czech Academy of Sciences, Astronomical Institute, Astroserver (Hungary), Institute of Space Sciences, Osservatorio Astronomico di Padova, National Institute for Astrophysics, University of Padua, University of California, Berkeley, Beijing Normal University, Xinjiang University, Tel Aviv University, National Astronomical Observatories
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Funders: National Science Foundation, Smithsonian Institution, National Aeronautics and Space Administration, W. M. Keck Foundation, Gordon and Betty Moore Foundation, California Institute of Technology, University of Washington, Johns Hopkins University, Space Telescope Science Institute, Tencent, European Space Agency, European Commission, Queen's University Belfast, Durham University, National Natural Science Foundation of China, Grantová Agentura České Republiky, Queen's University, Ministero dell’Istruzione, dell’Università e della Ricerca, Università degli Studi di Padova, Ministerio de Ciencia e Innovación, Istituto Nazionale di Astrofisica, National Central University, Stockholms Universitet, Eötvös Loránd Tudományegyetem, Max-Planck-Institut für Astronomie, Instituto de Astrofísica de Canarias, Jet Propulsion Laboratory, University of California, Los Angeles, Smithsonian Astrophysical Observatory, Science Mission Directorate, Deutsches Elektronen-Synchrotron, Agencia Estatal de Investigación, Planetary Science Division, Los Alamos National Laboratory
Awards: G1122307025, G1175115578, G121809054, The new frontier of Multi-Messenger Astrophysics: follow-up of electromagnetic transient counterparts of gravitational wave sources., G1576260938, G15967578, G1849103467, G1855990336, G1902886428, G210041235, G2262748287, G2309174360, G2586010942, G2599072453, G2601397997, G2660406951, G279363373, G2945112853, G3002654571, G300979063, G3042354070, G34346518, G3480869486, ZWICKY TRANSIENT FACILITY, G3553203022, G3578086565, G3681454997, G3690828678, G387506447, G4042783231, Exoplanet Athmosphere New Emission Transmission Spectra Analysis, G425668148, G430777504, G434337789, 基于极大视场多波段巡天的时域天文学前沿研究, G4474636675, G5080475149, G5195188938, G5421974903, G5560776957, G5633776668, G5662792045, Binary interaction on the red giant branch: Hot subdwarfs as a test case., G5805502524, G6085756319, G618131832, G6576599148, A NEO SEARCH PROGRAM USING THE PAN-STARRS PS1 TELESCOPETHE GOAL OF THE PROPOSED RESEARCH IS TO USE T, G6916909652, G7084143925, G7187964967, G7291478082, Pan-STARRS1: Operations; Public Data Release; Education and Outreach, G7870691232, G833430883, G837175144, G8518170077, G8684520763, G897484643, G899293041, G99296377
OpenAlex ID: W4391680741