X-Ray Observation of the Roche-lobe-filling White Dwarf plus Hot Subdwarf System ZTF J213056.71+442046.5
X-Ray Observation of the Roche-lobe-filling White Dwarf plus Hot Subdwarf System ZTF J213056.71+442046.5
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DOI：
10.3847/1538-4357/ac686e
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发表时间：
2022-04
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通讯作者：
S. Mereghetti;N. La Palombara;T. Kupfer;T. Marsh;C. Copperwheat;K. Deshmukh;P. Esposito;T. Maccarone;F. Pintore;M. Rigoselli;L. Rivera Sandoval;A. Tiengo
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作者：
S. Mereghetti;N. La Palombara;T. Kupfer;T. Marsh;C. Copperwheat;K. Deshmukh;P. Esposito;T. Maccarone;F. Pintore;M. Rigoselli;L. Rivera Sandoval;A. Tiengo
ZTFJ213056.71+442046.5是最近发现的一小类致密双星的原型，它由一颗白矮星和一颗充满其罗氏叶的热次矮星组成。它的轨道周期只有39分钟，是已知的此类天体中最短的。通过对其光学、光度和光谱数据的详细模拟，已经推断出高轨道倾角(i=86°)和吸积盘存在的证据。我们报告了2021年1月7日进行的XMM-牛顿观测的结果。光学监视器清楚地探测到ZTFJ213056.71+442046.5，它在UV波段(200-400 nm)显示出周期性的变化，其光曲线与在更长波长上看到的相似。尽管这颗白矮星的吸积率估计在10−9M⊙yr−1数量级，但EPIC仪器没有探测到X射线，在0.2keV-12keV光度上的极限是∼1030erg S−1。我们讨论了该系统没有强X射线发射的可能解释。
ZTF J213056.71+442046.5 is the prototype of a small class of recently discovered compact binaries composed of a white dwarf and a hot subdwarf that fills its Roche lobe. Its orbital period of only 39 minutes is the shortest known for the objects in this class. Evidence for a high orbital inclination (i = 86°) and for the presence of an accretion disk has been inferred from a detailed modeling of its optical photometric and spectroscopic data. We report the results of an XMM-Newton observation carried out on 2021 January 7. ZTF J213056.71+442046.5 was clearly detected by the Optical Monitor, which showed a periodic variability in the UV band (200–400 nm), with a light curve similar to that seen at longer wavelengths. Despite accretion on the white dwarf at an estimated rate of the order of 10−9 M ⊙ yr−1, no X-rays were detected with the EPIC instrument, with a limit of ∼1030 erg s−1 on the 0.2–12 keV luminosity. We discuss possible explanations for the lack of a strong X-ray emission from this system.