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arXiv 2404.14722astro-ph.HEastro-ph.SR
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关于白矮星脉冲星候选体 ZTF J190132.9+145808.7 的 X 射线效率

On the X-ray efficiency of the white dwarf pulsar candidate ZTF J190132.9+145808.7

Aya Bamba, Yukikatsu Terada, Kazumi Kashiyama, Shota Kisaka, Takahiro Minami, Tadayuki Takahashi

AI总结:

本文利用钱德拉 X 射线天文台研究大质量孤立白矮星 ZTF J1901+14 的 X 射线辐射,发现边缘性信号并测得 X 射线效率与中子星脉冲星相当,支持其作为白矮星脉冲星候选体。

摘要:

强磁化、快速旋转的大质量白矮星(WDs)是双简并并合的潜在产物。这些白矮星可以作为非热辐射和宇宙线的来源,作为白矮星脉冲星而受到关注。在此背景下,我们利用钱德拉 X 射线天文台研究了 ZTF J190132.9+145808.7(以下简称 ZTF J1901+14)的 X 射线辐射,它是银河系中一颗值得注意的大质量孤立白矮星。我们的结果显示存在 3.5σ 水平的 X 射线信号证据,尽管该证据较为边缘。在光子指数为 2 的假设下,我们推导出其在 0.5–7 keV 能段的内禀流量为 2.3(0.9–4.7)×10⁻¹⁵ erg cm⁻² s⁻¹,光度为 4.6(2.0–9.5)×10²⁶ erg s⁻¹,置信区间为 90%,距离为 41 pc。我们推导出相对于自转减慢光度的 X 射线效率(η)为 0.012(0.0022–0.074),该值与普通中子星脉冲星相当。所推断的 X 射线光度可能与在 ZTF J1901+14 磁层开放磁力线内加速的亚 TeV 电子产生的曲率辐射相符。开展更广泛的 X 射线观测对于确认类似 ZTF J1901+14 的孤立白矮星是否也像吸积系统中的其他白矮星脉冲星一样,是 X 射线和亚 TeV 电子宇宙线的重要来源至关重要。

英文摘要:

Strongly magnetized, rapidly rotating massive white dwarfs (WDs) emerge as potential outcomes of double degenerate mergers. These WDs can act as sources of non-thermal emission and cosmic rays, gethering attention as WD pulsars. In this context, we studied the X-ray emissions from ZTF J190132.9+145808.7 (hereafter ZTF J1901+14), a notable massive isolated WD in the Galaxy, using the Chandra X-ray observatory. Our results showed 3.5sigma level evidence of X-ray signals, although it is marginal. Under the assumption of a photon index of 2, we derived its intrinsic flux to be 2.3 (0.9--4.7) $\times 10^{-15}$~erg~cm$^{-2}$s$^{-1}$ and luminosity 4.6 (2.0--9.5) $\times 10^{26}$~erg~s$^{-1}$ for a 0.5--7 keV band in the 90% confidence range, given its distance of 41 pc. We derived an X-ray efficiency (eta) concerning the spin-down luminosity to be 0.012 (0.0022--0.074), a value comparable to that of ordnary neutron star pulsars. The inferred X-ray luminosity may be compatible with curvature radiation from sub-TeV electrons accelerated within open magnetic fields in the magnetosphere of ZTF J1901+14. Conducting more extensive X-ray observations is crucial to confirm whether ZTF J1901+14-like isolated WDs are also significant sources of X-rays and sub-TeV electron cosmic rays, similar to other WD pulsars in accreting systems.

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