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

journal contribution
posted on 2016-02-17, 09:28 authored by S. B. Cenko, A Cucchiara, N. Roth, S. Veilleux, J. X. Prochaska, L. Yan, J. Guillochon, W. P. Maksym, I. Arcavi, N. R. Butler, A. V. Filippenko, A. S. Fruchter, S. Gezari, D. Kasen, A. J. Levan, J. M. Miller, D. R. Pasham, E. Ramirez-Ruiz, L. E. Strubbe, Nial Tanvir, F. Tombesi
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 $\Delta v = -(250$-400) km s$^{-1}$. Together with 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.

History

Citation

Astrophysical Journal Letters, 2016, 818 L32

Author affiliation

/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Physics and Astronomy

Version

  • VoR (Version of Record)

Published in

Astrophysical Journal Letters

Publisher

IOP Publishing, American Astronomical Society

issn

2041-8205

eissn

2041-8213

Acceptance date

2016-02-02

Copyright date

2016

Available date

2016-04-20

Publisher version

http://iopscience.iop.org/article/10.3847/2041-8205/818/2/L32/meta

Language

en

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