TY - JOUR
T1 - SN 2022acko
T2 - The First Early Far-ultraviolet Spectra of a Type IIP Supernova
AU - Bostroem, K. Azalee
AU - Dessart, Luc
AU - Hillier, D. John
AU - Lundquist, Michael
AU - Andrews, Jennifer E.
AU - Sand, David J.
AU - Dong, Yize
AU - Valenti, Stefano
AU - Haislip, Joshua
AU - Hoang, Emily T.
AU - Hosseinzadeh, Griffin
AU - Janzen, Daryl
AU - Jencson, Jacob E.
AU - Jha, Saurabh W.
AU - Kouprianov, Vladimir
AU - Pearson, Jeniveve
AU - Meza Retamal, Nicolas E.
AU - Reichart, Daniel E.
AU - Shrestha, Manisha
AU - Ashall, Christopher
AU - Baron, E.
AU - Brown, Peter J.
AU - DerKacy, James M.
AU - Farah, Joseph
AU - Galbany, Lluís
AU - Hernández, J. I.González
AU - Green, Elizabeth
AU - Hoeflich, Peter
AU - Howell, D. Andrew
AU - Kwok, Lindsey A.
AU - McCully, Curtis
AU - Müller-Bravo, Tomás E.
AU - Newsome, Megan
AU - Gonzalez, Estefania Padilla
AU - Pellegrino, Craig
AU - Rho, Jeonghee
AU - Rowe, Micalyn
AU - Schwab, Michaela
AU - Shahbandeh, Melissa
AU - Smith, Nathan
AU - Strader, Jay
AU - Terreran, Giacomo
AU - Van Dyk, Schuyler D.
AU - Wyatt, Samuel
N1 - Publisher Copyright: © 2023. The Author(s). Published by the American Astronomical Society.
PY - 2023/8/1
Y1 - 2023/8/1
N2 - We present five far- and near-ultraviolet spectra of the Type II plateau supernova, SN 2022acko, obtained 5, 6, 7, 19, and 21 days after explosion, all observed with the Hubble Space Telescope/Space Telescope Imaging Spectrograph. The first three epochs are earlier than any Type II plateau supernova has been observed in the far-ultraviolet revealing unprecedented characteristics. These three spectra are dominated by strong lines, primarily from metals, which contrasts with the featureless early optical spectra. The flux decreases over the initial time series as the ejecta cool and line blanketing takes effect. We model this unique data set with the non-local thermodynamic equilibrium radiation transport code CMFGEN, finding a good match to the explosion of a low-mass red supergiant with energy E kin = 6 × 1050 erg. With these models we identify, for the first time, the ions that dominate the early ultraviolet spectra. We present optical photometry and spectroscopy, showing that SN 2022acko has a peak absolute magnitude of V = − 15.4 mag and plateau length of ∼115 days. The spectra closely resemble those of SN 2005cs and SN 2012A. Using the combined optical and ultraviolet spectra, we report the fraction of flux as a function of bluest wavelength on days 5, 7, and 19. We create a spectral time-series of Type II supernovae in the ultraviolet, demonstrating the rapid decline of flux over the first few weeks of evolution. Future observations of Type II supernovae are required to map out the landscape of exploding red supergiants, with and without circumstellar material, which is best revealed in high-quality ultraviolet spectra.
AB - We present five far- and near-ultraviolet spectra of the Type II plateau supernova, SN 2022acko, obtained 5, 6, 7, 19, and 21 days after explosion, all observed with the Hubble Space Telescope/Space Telescope Imaging Spectrograph. The first three epochs are earlier than any Type II plateau supernova has been observed in the far-ultraviolet revealing unprecedented characteristics. These three spectra are dominated by strong lines, primarily from metals, which contrasts with the featureless early optical spectra. The flux decreases over the initial time series as the ejecta cool and line blanketing takes effect. We model this unique data set with the non-local thermodynamic equilibrium radiation transport code CMFGEN, finding a good match to the explosion of a low-mass red supergiant with energy E kin = 6 × 1050 erg. With these models we identify, for the first time, the ions that dominate the early ultraviolet spectra. We present optical photometry and spectroscopy, showing that SN 2022acko has a peak absolute magnitude of V = − 15.4 mag and plateau length of ∼115 days. The spectra closely resemble those of SN 2005cs and SN 2012A. Using the combined optical and ultraviolet spectra, we report the fraction of flux as a function of bluest wavelength on days 5, 7, and 19. We create a spectral time-series of Type II supernovae in the ultraviolet, demonstrating the rapid decline of flux over the first few weeks of evolution. Future observations of Type II supernovae are required to map out the landscape of exploding red supergiants, with and without circumstellar material, which is best revealed in high-quality ultraviolet spectra.
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U2 - 10.3847/2041-8213/ace31c
DO - 10.3847/2041-8213/ace31c
M3 - Article
SN - 2041-8205
VL - 953
JO - Astrophysical Journal Letters
JF - Astrophysical Journal Letters
IS - 2
M1 - L18
ER -