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Title: An Ultraviolet Excess in the Superluminous Supernova Gaia16apd Reveals a Powerful Central Engine

Abstract

Since the discovery of superluminous supernovae (SLSNe) in the last decade, it has been known that these events exhibit bluer spectral energy distributions than other supernova subtypes, with significant output in the ultraviolet. However, the event Gaia16apd seems to outshine even the other SLSNe at rest-frame wavelengths below ∼3000 Å. Yan et al. have recently presented HST UV spectra and attributed the UV flux to low iron-group abundance in the outer ejecta, and hence reduced line blanketing. Here, we present UV and optical light curves over a longer baseline in time, revealing a rapid decline at UV wavelengths despite a typical optical evolution. Combining the published UV spectra with our own optical data, we demonstrate that Gaia16apd has a much hotter continuum than virtually any SLSN at maximum light, but it cools rapidly thereafter and is indistinguishable from the others by ∼10–15 days after peak. Comparing the equivalent widths of UV absorption lines with those of other events, we show that the excess UV continuum is a result of a more powerful central power source, rather than a lack of UV absorption relative to other SLSNe or an additional component from interaction with the surrounding medium. These findings strongly supportmore » the central-engine hypothesis for hydrogen-poor SLSNe. An explosion ejecting M {sub ej} = 4.8(0.2/ κ ) M {sub ⊙}, where κ is the opacity in cm{sup 2} g{sup −1}, and forming a magnetar with spin period P = 2 ms, and B = 2 × 10{sup 14} G (lower than other SLSNe with comparable rise times) can consistently explain the light curve evolution and high temperature at peak. The host metallicity, Z = 0.18 Z {sub ⊙}, is comparable to other SLSNe.« less

Authors:
; ; ; ;  [1];  [2];  [3];  [4]
  1. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138 (United States)
  2. Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208 (United States)
  3. Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States)
  4. Astrophysical Institute, Department of Physics and Astronomy, 251B Clippinger Lab, Ohio University, Athens, OH 45701 (United States)
Publication Date:
OSTI Identifier:
22654566
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 835; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABSORPTION; ABUNDANCE; COMPARATIVE EVALUATIONS; ENERGY SPECTRA; EVOLUTION; EXPLOSIONS; HYDROGEN; HYPOTHESIS; INTERACTIONS; IRON; METALLICITY; NEUTRON STARS; OPACITY; SPIN; SUPERNOVAE; ULTRAVIOLET RADIATION; ULTRAVIOLET SPECTRA; VISIBLE RADIATION; WAVELENGTHS

Citation Formats

Nicholl, M., Berger, E., Blanchard, P. K., Milisavljevic, D., Challis, P., Margutti, R., Metzger, B. D., and Chornock, R., E-mail: matt.nicholl@cfa.harvard.edu. An Ultraviolet Excess in the Superluminous Supernova Gaia16apd Reveals a Powerful Central Engine. United States: N. p., 2017. Web. doi:10.3847/2041-8213/AA56C5.
Nicholl, M., Berger, E., Blanchard, P. K., Milisavljevic, D., Challis, P., Margutti, R., Metzger, B. D., & Chornock, R., E-mail: matt.nicholl@cfa.harvard.edu. An Ultraviolet Excess in the Superluminous Supernova Gaia16apd Reveals a Powerful Central Engine. United States. doi:10.3847/2041-8213/AA56C5.
Nicholl, M., Berger, E., Blanchard, P. K., Milisavljevic, D., Challis, P., Margutti, R., Metzger, B. D., and Chornock, R., E-mail: matt.nicholl@cfa.harvard.edu. Fri . "An Ultraviolet Excess in the Superluminous Supernova Gaia16apd Reveals a Powerful Central Engine". United States. doi:10.3847/2041-8213/AA56C5.
@article{osti_22654566,
title = {An Ultraviolet Excess in the Superluminous Supernova Gaia16apd Reveals a Powerful Central Engine},
author = {Nicholl, M. and Berger, E. and Blanchard, P. K. and Milisavljevic, D. and Challis, P. and Margutti, R. and Metzger, B. D. and Chornock, R., E-mail: matt.nicholl@cfa.harvard.edu},
abstractNote = {Since the discovery of superluminous supernovae (SLSNe) in the last decade, it has been known that these events exhibit bluer spectral energy distributions than other supernova subtypes, with significant output in the ultraviolet. However, the event Gaia16apd seems to outshine even the other SLSNe at rest-frame wavelengths below ∼3000 Å. Yan et al. have recently presented HST UV spectra and attributed the UV flux to low iron-group abundance in the outer ejecta, and hence reduced line blanketing. Here, we present UV and optical light curves over a longer baseline in time, revealing a rapid decline at UV wavelengths despite a typical optical evolution. Combining the published UV spectra with our own optical data, we demonstrate that Gaia16apd has a much hotter continuum than virtually any SLSN at maximum light, but it cools rapidly thereafter and is indistinguishable from the others by ∼10–15 days after peak. Comparing the equivalent widths of UV absorption lines with those of other events, we show that the excess UV continuum is a result of a more powerful central power source, rather than a lack of UV absorption relative to other SLSNe or an additional component from interaction with the surrounding medium. These findings strongly support the central-engine hypothesis for hydrogen-poor SLSNe. An explosion ejecting M {sub ej} = 4.8(0.2/ κ ) M {sub ⊙}, where κ is the opacity in cm{sup 2} g{sup −1}, and forming a magnetar with spin period P = 2 ms, and B = 2 × 10{sup 14} G (lower than other SLSNe with comparable rise times) can consistently explain the light curve evolution and high temperature at peak. The host metallicity, Z = 0.18 Z {sub ⊙}, is comparable to other SLSNe.},
doi = {10.3847/2041-8213/AA56C5},
journal = {Astrophysical Journal Letters},
number = 1,
volume = 835,
place = {United States},
year = {Fri Jan 20 00:00:00 EST 2017},
month = {Fri Jan 20 00:00:00 EST 2017}
}