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An Ultraviolet Spectrum of the Tidal Disruption Flare ASASSN-14liWe 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 T(sub UV) = 3.5 x 10(exp. 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).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 {approx. 2000-8000 km s(exp. -1)} emission lines at or near the systemic host velocity. The absorption lines are blueshifted with respect to the emission lines by Delta(sub v) = -(250-400) km s(exp. -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.
Document ID
20170003446
Document Type
Reprint (Version printed in journal)
Authors
Cenko, S. Bradley (NASA Goddard Space Flight Center Greenbelt, MD United States)
Cucchiara, Antonio (Space Telescope Science Inst. Baltimore, MD, United States)
Roth, Nathaniel (California Univ. Berkeley, CA, United States)
Veilleux, Sylvain (Maryland Univ. College Park, MD, United States)
Prochaska, J. Xavier (California Univ. Santa Cruz, CA, United States)
Yan, Lin (California Inst. of Tech. Pasadena, CA, United States)
Guillochon, James (Harvard-Smithsonian Center for Astrophysics Cambridge, MA, United States)
Maksym, W. Peter (Harvard-Smithsonian Center for Astrophysics Cambridge, MA, United States)
Arcavi, Iair (Las Cumbres Observatory Global Telescope Network, Inc. Goleta, CA, United States)
Butler, Nathaniel R. (Arizona State Univ. Tempe, AZ, United States)
Date Acquired
April 14, 2017
Publication Date
February 18, 2016
Publication Information
Publication: The Astrophysical Journal Letters
Volume: 818
Issue: 2
ISSN: 2041-8205
Subject Category
Astrophysics
Report/Patent Number
GSFC-E-DAA-TN41611
Funding Number(s)
CONTRACT_GRANT: NAS5-26555
Distribution Limits
Public
Copyright
Other
Keywords
accretion disks – stars: flare – ultraviolet: general
accretion