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arXiv 1601.03331astro-ph.HEastro-ph.GA
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ASASSN-14 li潮汐破裂耀斑的紫外光谱

An Ultraviolet Spectrum of the Tidal Disruption Flare ASASSN-14li

S. Bradley Cenko, Antonino Cucchiara, Nathaniel Roth, Sylvain Veilleux, J. Xavier Prochaska, Lin Yan, James Guillochon, W. Peter Maksym, Iair Arcavi, Nathaniel … 展开作者

S. Bradley Cenko, Antonino Cucchiara, Nathaniel Roth, Sylvain Veilleux, J. Xavier Prochaska, Lin Yan, James Guillochon, W. Peter Maksym, Iair Arcavi, Nathaniel R. Butler, Alexei V. Filippenko, Andrew S. Fruchter, Suvi Gezari, Daniel Kasen, Andrew J. Levan, Jon M. Miller, Dheeraj R. Pasham, Enrico Ramirez-Ruiz, Linda E. Strubbe, Nial R. Tanvir, Francesco Tombesi

摘要:

我们提出了一个哈勃空间望远镜的STIS光谱ASASSN-14 li,第一个休息帧的潮汐破裂耀斑(TDF)的紫外光谱。下面的连续体与具有$T_{\mathrm{UV}} = 3.5 \times 10^{4}$ K的黑体很好地拟合,该黑体比从X射线光谱推断的温度小一个数量级(并且比以前基于光学和近紫外测光的努力更精确)。叠加在这个蓝色的连续,我们检测到三类功能:窄吸收银河系(可能是一个高速云),窄吸收和广泛的(半高宽$\approx 2000$-8000公里秒$^{-1}$)发射线在/附近的系统主机速度。吸收线相对于发射线蓝移了$Δv = -(250$-400)km s $^{-1}$。由于这两个速度偏移和缺乏共同的低电离功能(镁II,铁II),我们认为,这些来自相同的吸收材料,负责低速外流发现在X射线波长。宽的核发射线显示出明显的丰度模式:N Ⅲ]、N Ⅳ]、He Ⅱ相当突出,而普通类星体C Ⅲ]和Mg Ⅱ的发射线则很弱或完全不存在。对这一光谱的详细建模将有助于阐明有关TDFs中发射过程性质的基本问题,而ASASSN-14 li未来的紫外光谱将有助于证实(或反驳)之前提出的TDFs和“富氮”类星体之间的联系。

英文摘要:

We present a Hubble Space Telescope STIS spectrum of ASASSN-14li, the first rest-frame UV spectrum of a tidal disruption flare (TDF). The underlying continuum is well fit by a blackbody with $T_{\mathrm{UV}} = 3.5 \times 10^{4}$ K, an order of magnitude smaller than the temperature inferred from X-ray spectra (and significantly more precise than previous efforts based on optical and near-UV photometry). Super-imposed on this blue continuum, we detect three classes of features: narrow absorption from the Milky Way (probably a high-velocity cloud), and narrow absorption and broad (FWHM $\approx 2000$-8000 km s$^{-1}$) emission lines at/near the systemic host velocity. The absorption lines are blueshifted with respect to the emission lines by $Δv = -(250$-400) km s$^{-1}$. Due both to this velocity offset and the lack of common low-ionization features (Mg II, Fe II), we argue these arise from the same absorbing material responsible for the low-velocity outflow discovered at X-ray wavelengths. The broad nuclear emission lines display a remarkable abundance pattern: N III], N IV], He II are quite prominent, while the common quasar emission lines of C III] and Mg II are weak or entirely absent. Detailed modeling of this spectrum will help elucidate fundamental questions regarding the nature of the emission process(es) at work in TDFs, while future UV spectroscopy of ASASSN-14li would help to confirm (or refute) the previously proposed connection between TDFs and "N-rich" quasars.

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