恒星级双黑洞旋近及其探测

Stellar-mass binary black holes:Inspirals and their detection

在经历恒星演化后,大质量恒星最终会形成中子星或黑洞等致密星。此外,宇宙早期的局部密度涨落也可能形成恒星级原初黑洞。从宇宙诞生至今,这些恒星级黑洞可以通过不同的机制形成双星,包括协同演化模型和动力学相互作用模型。在地面引力波探测器实现探测之前,电磁波观测到的恒星级黑洞质量较小,即不超过15个太阳质量左右。LIGO/Virgo对GW150914等恒星级双黑洞并合产生的引力波信号的探测,将这一领域引入到相关学者的关注视野中,由此激发了大量空间引力波探测对恒星级双黑洞旋近等信号的研究。通过当前地面引力波探测结果的统计,可以预言:天琴在五年的观测时间内,可以探测到数起到几十起的恒星级双黑洞旋近事件。由于长时间的积分,这些空间引力波信号可以精确测量一些参数,如并合时间精度预期可达约1 s水平,空间定位能力可达约1 deg^(2)水平,等等。因此,恒星级双黑洞旋近为多波段引力波探测提供了极佳的天文实验室。

According to stellar evolution theory,a massive star will eventually become a compact object such as a neutron star or a black hole.On the other hand,local density fluctuations in the early Universe could also form primordial black holes of stellar mass.Since the dawn of the Universe,stellar-mass black holes(SBHs)can come together to form binaries through mechanisms such as coevolution and dynamical processes.Before ground-based gravitational wave(GW)detectors made their first successful detections,the masses of SBHs had been measured by electromagnetic waves only,and never exceeded around 15 solar masses.The LIGO/Virgo detection of GWs from binary SBH mergers has drawn the attention of many scientists,in particular,the GW signals resulting from the inspirals of binary SBHs should be detectable by space-borne GW detectors.Based on the number of GW events detected by groundbased detectors,it is expected that TianQin will be able to detect a few to dozens of GW events related to inspirals of binary SBHs.Given the long expected duration for each inspiral event,such signals can help measure parameters including the expected merger time(down to~1 second)and the exact location of the SBH(down to 1 square degree).The inspiral through merging of binary SBHs will provide excellent astrophysical probes for multi-frequency GW observations.