附近星系M33中的雙星X-射線源X-7,，已被證明對試圖解釋其演化歷史的理論工作者是一個挑戰(zhàn)。
此前,，一直沒有可能解釋該系統(tǒng)相對于繞快速旋轉(zhuǎn)的黑洞運(yùn)轉(zhuǎn)的富含氫的大伴星的尺寸來說的大質(zhì)量組成成分和較小的軌道?，F(xiàn)在,，Valsecchi等人報告了對演化軌跡所做的模擬,，其結(jié)果顯示,，如果M33 X-7在一個2.8-3.1天的軌道中以一個質(zhì)量為85–99個太陽質(zhì)量的主星和一個質(zhì)量為28–32個太陽質(zhì)量的伴星開始，那么其性質(zhì)將可以得到一致的解釋,。
作為對這一新模型的支持,，M33 X-7演化歷史的不同階段已在其他雙星體系中被觀測到。（生物谷Bioon.com）
生物谷推薦英文摘要：
Nature doi:10.1038/nature09463
Formation of the black-hole binary M33 X-7 through mass exchange in a tight massive system
Francesca Valsecchi,[email protected] Glebbeek,Will M. Farr,Tassos Fragos,Bart Willems,Jerome A. Orosz,Jifeng Liu& Vassiliki Kalogera
The X-ray source M33 X-7 in the nearby galaxy Messier 33 is among the most massive X-ray binary stellar systems known, hosting a rapidly spinning, 15.65M⊙ black hole orbiting an underluminous, 70M⊙ main-sequence companion in a slightly eccentric 3.45-day orbit1, 2 (M⊙, solar mass). Although post-main-sequence mass transfer explains the masses and tight orbit3, it leaves unexplained the observed X-ray luminosity, the star’s underluminosity, the black hole’s spin and the orbital eccentricity. A common envelope phase1, or rotational mixing4, could explain the orbit, but the former would lead to a merger and the latter to an overluminous companion. A merger would also ensue if mass transfer to the black hole were invoked for its spin-up5. Here we report simulations of evolutionary tracks which reveal that if M33 X-7 started as a primary body of 85M⊙–99M⊙ and a secondary body of 28M⊙–32M⊙, in a 2.8–3.1-d orbit, its observed properties can be consistently explained. In this model, the main-sequence primary transfers part of its envelope to the secondary and loses the rest in a wind; it ends its life as a ~16M⊙ helium star with an iron–nickel core that collapses to a black hole (with or without an accompanying supernova). The release of binding energy, and possibly collapse asymmetries, ‘kick’ the nascent black hole into an eccentric orbit. Wind accretion explains the X-ray luminosity, and the black-hole spin can be natal.
