ESPRESSO Observations of Gaia BH1: High-precision Orbital Constraints and no Evidence for an Inner Binary

IF 3.3 3区 物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS
Pranav Nagarajan, Kareem El-Badry, Amaury H. M. J. Triaud, Thomas A. Baycroft, David Latham, Allyson Bieryla, Lars A. Buchhave, Hans-Walter Rix, Eliot Quataert, Andrew Howard, Howard Isaacson, Melissa J. Hobson
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Abstract

We present high-precision radial velocity observations of Gaia BH1, the nearest known black hole (BH). The system contains a solar-type G star orbiting a massive dark companion, which could be either a single BH or an inner BH + BH binary. A BH + BH binary is expected in some models where Gaia BH1 formed as a hierarchical triple, which is attractive because they avoid many of the difficulties associated with forming the system through isolated binary evolution. Our observations test the inner binary scenario. We have measured 115 precise RVs of the G star, including 40 from ESPRESSO with a precision of 3–5 m s−1, and 75 from other instruments with a typical precision of 30–100 m s−1. Our observations span 2.33 orbits of the G star and are concentrated near a periastron passage, when perturbations due to an inner binary would be largest. The RVs are well-fit by a Keplerian two-body orbit and show no convincing evidence of an inner binary. Using REBOUND simulations of hierarchical triples with a range of inner periods, mass ratios, eccentricities, and orientations, we show that plausible inner binaries with periods P inner ≳ 1.5 days would have produced larger deviations from a Keplerian orbit than observed. Binaries with P inner ≲ 1.5 days are consistent with the data, but these would merge within a Hubble time and would thus imply fine-tuning. We present updated parameters of Gaia BH1's orbit. The RVs yield a spectroscopic mass function fMBH=3.9358±0.0002M —about 7000σ above the ∼2.5 M maximum neutron star mass. Including the inclination constraint from Gaia astrometry, this implies a BH mass of M BH = 9.27 ± 0.10 M .
对盖亚 BH1 的 ESPRESSO 观测:高精度轨道约束和没有内双星的证据
我们展示了对已知最近的黑洞 Gaia BH1 的高精度径向速度观测结果。该系统包含一颗太阳型G星,围绕着一颗大质量暗伴星运行,这颗伴星可能是单个黑洞,也可能是内部的黑洞+黑洞双星。在一些模型中,盖亚BH1会形成一个分层三重BH+BH双星,这很有吸引力,因为它们避免了通过孤立双星演化形成系统所带来的许多困难。我们的观测检验了内部双星的情况。我们测量了 G 星的 115 个精确 RV 值,其中 40 个来自 ESPRESSO,精度为 3-5 m s-1,75 个来自其他仪器,精度通常为 30-100 m s-1。我们的观测数据跨越了 G 星的 2.33 个轨道,并集中在近地轨道附近,此时内部双星造成的扰动最大。RV值与开普勒双体轨道拟合良好,没有显示出内部双星的令人信服的证据。我们利用REBOUND模拟了具有一系列内部周期、质量比、偏心率和方向的分级三体,结果表明周期Pinner ≳ 1.5天的可信内部双星会产生比观测到的更大的开普勒轨道偏差。Pinner≲1.5天的双星与数据一致,但这些双星会在哈勃时间内合并,因此意味着微调。我们给出了 Gaia BH1 轨道的最新参数。RVs得出的光谱质量函数fMBH=3.9358±0.0002M⊙-比∼2.5M⊙最大中子星质量高出约7000σ。包括来自盖亚天体测量的倾角约束,这意味着BH质量为MBH=9.27±0.10 M⊙。
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来源期刊
Publications of the Astronomical Society of the Pacific
Publications of the Astronomical Society of the Pacific 地学天文-天文与天体物理
CiteScore
6.70
自引率
5.70%
发文量
103
审稿时长
4-8 weeks
期刊介绍: The Publications of the Astronomical Society of the Pacific (PASP), the technical journal of the Astronomical Society of the Pacific (ASP), has been published regularly since 1889, and is an integral part of the ASP''s mission to advance the science of astronomy and disseminate astronomical information. The journal provides an outlet for astronomical results of a scientific nature and serves to keep readers in touch with current astronomical research. It contains refereed research and instrumentation articles, invited and contributed reviews, tutorials, and dissertation summaries.
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