Abstract
Be X-ray binaries (Be-XRBs) are one of the largest subclasses of high-mass X-ray binaries, comprised of a rapidly rotating Be star and neutron star companion in an eccentric orbit, intermittently accreting material from a decretion disk around the donor. Originating from binary stellar evolution, Be-XRBs are of significant interest to binary population synthesis (BPS) studies, encapsulating the physics of supernovae, common envelope, and mass transfer (MT). Using the state-of-the-art BPS code, POSYDON, which relies on precomputed grids of detailed binary stellar evolution models, we investigate the Galactic Be-XRB population. POSYDON incorporates stellar rotation self-consistently during MT phases, enabling detailed examination of the rotational distribution of Be stars in multiple phases of evolution. Our fiducial BPS and Be-XRB model aligns well with the orbital properties of Galactic Be-XRBs, emphasizing the role of rotational constraints. Our modeling reveals a rapidly rotating population (ω/ω crit ≳ 0.3) of Be-XRB-like systems with a strong peak at intermediate rotation rates (ω/ω crit ≃ 0.6) in close alignment with observations. All Be-XRBs undergo an MT phase before the first compact object forms, with over half experiencing a second MT phase from a stripped helium companion (Case BB). Computing rotationally limited MT efficiencies and applying them to our population, we derive a physically motivated MT efficiency distribution, finding that most Be-XRBs have undergone highly nonconservative MT ( β ¯ rot ≃ 0.15 ). Our study underscores the importance of detailed angular momentum modeling during MT in interpreting Be-XRB populations, emphasizing this population as a key probe for the stability and efficiency of MT in interacting binaries.
| Original language | English (US) |
|---|---|
| Article number | 133 |
| Journal | Astrophysical Journal |
| Volume | 971 |
| Issue number | 2 |
| DOIs | |
| State | Published - Aug 1 2024 |
Funding
The POSYDON project is supported primarily by two sources: the Swiss National Scienfce Foundation (PI Fragos, project Nos. PP00P2_211006, and CRSII5_213497) and the Gordon and Betty Moore Foundation (PI Kalogera, grant award GBMF8477). K.A.R. is supported by the Gordon and Betty Moore Foundation (PI Kalogera, grant award GBMF8477) and the Riedel Family Fellowship. K.A.R. also thanks the LSSTC Data Science Fellowship Program, which is funded by LSSTC, NSF Cybertraining grant No. 1829740, the Brinson Foundation, and the Moore Foundation; their participation in the program has benefited this work. J.J.A. acknowledges support for Program No. JWST-AR-04369.001-A provided through a grant from the STScI under NASA contract NAS5-03127. Z.D. acknowledges support from the CIERA Board of Visitors Research Professorship. S.S.B., T.F., and Z.X. were supported by the project No. PP00P2_211006. S.S.B. was also supported by project No. CRSII5_213497. Z.X. acknowledges support from the Chinese Scholarship Council (CSC). K.K. acknowledges support from the Spanish State Research Agency, through the Mar\u00EDa de Maeztu Program for Centers and Units of Excellence in R&D, No. CEX2020-001058-M. E.Z. acknowledges funding support from the Hellenic Foundation for Research and Innovation (H.F.R.I.) under the \u201C3rd Call for H.F.R.I. Research Projects to Support Post-Doctoral Researchers\u201D (Project No: 7933). This research was supported in part by the computational resources and staff contributions provided for the Quest high-performance computing facility at Northwestern University, which is jointly supported by the Office of the Provost, the Office for Research, and Northwestern University Information Technology. K.A.R. sincerely thanks Prof. Tomer Shanar, Prof. Yoram Lithwick, and Prof. Giles Novak for insightful discussions on interpreting observations and accretion disk physics. We thank the referee for providing valuable feedback and improving the quality of this work.
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science