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 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. TanvirFrancesco Tombesi

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32 Scopus citations

Abstract

We present a Hubble Space Telescope Space Telescope Imaging Spectrograph spectrum of ASASSN-14li, the first rest-frame ultraviolet (UV) spectrum of a tidal disruption flare (TDF). The underlying continuum is well fit by a blackbody with 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). Superimposed 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 (∼2000-8000 km s-1) emission lines at or 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], and 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 processes 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.

Original languageEnglish (US)
Article numberL32
JournalAstrophysical Journal Letters
Volume818
Issue number2
DOIs
StatePublished - Feb 20 2016

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Cenko, S. B., Cucchiara, A., Roth, N., Veilleux, S., Prochaska, J. X., Yan, L., Guillochon, J., Maksym, W. P., Arcavi, I., Butler, N., Filippenko, A. V., Fruchter, A. S., Gezari, S., Kasen, D., Levan, A. J., Miller, J. M., Pasham, D. R., Ramirez-Ruiz, E., Strubbe, L. E., ... Tombesi, F. (2016). AN ULTRAVIOLET SPECTRUM OF THE TIDAL DISRUPTION FLARE ASASSN-14li. Astrophysical Journal Letters, 818(2), [L32]. https://doi.org/10.3847/2041-8205/818/2/L32