一颗表现出快速过渡模转换的吸积白矮星
An accreting white dwarf displaying fast transitional mode switching
摘要:
吸积型白矮星通常存在于轨道周期从几十分钟到几小时的近距离双星系统中。在大多数情况下,吸积过程是相对稳定的,只有在~天或更长的时间尺度上才会发生显著的调制。在这里,我们报告的发现突然下降的光学光度的吸积白矮星双星系统TW风景如画的因素高达3.5的时间尺度短至30分钟。由凌日系外行星勘测卫星(TESS)获得的这一双星系统的光学光变曲线清楚地显示了两种不同强度模式之间的快速切换,这可能会跟踪白矮星上不断变化的质量吸积率。在低模中,系统还显示出磁门吸积爆发,这意味着白矮星的弱磁场在该模式中在共旋半径处截断了内盘。在TW Picture中观察到的模式切换的性质似乎类似于在过渡毫秒望远镜中观察到的那些,其中发生类似的转变,尽管时间尺度为数十秒。我们的发现建立了一个以前未被承认的白矮星吸积现象,并提出了一个紧密的联系,以物理管理磁吸积到中子星。
英文摘要:
Accreting white dwarfs are often found in close binary systems with orbital periods ranging from tens of minutes to several hours. In most cases, the accretion process is relatively steady, with significant modulations only occurring on time-scales of ~days or longer. Here, we report the discovery of abrupt drops in the optical luminosity of the accreting white dwarf binary system TW Pictoris by factors up to 3.5 on time-scales as short as 30 minutes. The optical light curve of this binary system obtained by the Transiting Exoplanet Survey Satellite (TESS) clearly displays fast switches between two distinct intensity modes that likely track the changing mass accretion rate onto the white dwarf. In the low mode, the system also displays magnetically-gated accretion bursts, which implies that a weak magnetic field of the white dwarf truncates the inner disk at the co-rotation radius in this mode. The properties of the mode switching observed in TW Pictoris appear analogous to those observed in transitional millisecond pulsars, where similar transitions occur, although on timescales of ~tens of seconds. Our discovery establishes a previously unrecognised phenomenon in accreting white dwarfs and suggests a tight link to the physics governing magnetic accretion onto neutron stars.
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