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Title: Optical and ultraviolet spectroscopic analysis of SN 2011fe at late times

Abstract

This paper presents optical spectra of the nearby Type Ia supernova SN 2011fe at 100, 205, 311, 349 and 578 d post-maximum light, as well as an ultraviolet (UV) spectrum obtained with the Hubble Space Telescope at 360 d post-maximum light. We compare these observations with synthetic spectra produced with the radiative transfer code PHOENIX. The day +100 spectrum can be well fitted with models that neglect collisional and radiative data for forbidden lines. Curiously, including these data and recomputing the fit yields a quite similar spectrum, but with different combinations of lines forming some of the stronger features. At day +205 and later epochs, forbidden lines dominate much of the optical spectrum formation; however, our results indicate that recombination, not collisional excitation, is the most influential physical process driving spectrum formation at these late times. Consequently, our synthetic optical and UV spectra at all epochs presented here are formed almost exclusively through recombinationdriven fluorescence. Furthermore, our models suggest that the UV spectrum even as late as day +360 is optically thick and consists of permitted lines from several iron-peak species. These results indicate that the transition to the 'nebular' phase in Type Ia supernovae is complex and highly wavelengthmore » dependent.« less

Authors:
 [1];  [2];  [3];  [4];  [5];  [4];  [6];  [7];  [8];  [9];  [10];  [10];  [11];  [12];  [10];  [10];  [10];  [13];  [14]
  1. Homer L. Dodge Department of Physics and Astronomy, Norman, OK (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  2. Homer L. Dodge Department of Physics and Astronomy, Norman, OK (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Hamburger Stenwarte, Hamburg (Germany)
  3. Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States)
  4. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  5. Homer L. Dodge Department of Physics and Astronomy, Norman, OK (United States)
  6. Hamburger Stenwarte, Hamburg (Germany)
  7. Univ. of Illinois, Urbana-Champaign, IL (United States); Univ. of California, Santa Cruz, CA (United States)
  8. Queen's Univ., Belfast, Northern Ireland (United Kingdom)
  9. Univ. of Illinois, Urbana-Champaign, IL (United States)
  10. Univ. of California, Berkeley, CA (United States)
  11. Univ. of Texas, Austin, TX (United States)
  12. Kyoto Univ. (Japan); Univ. of Tokyo (Japan). Kavli Inst. for the Physics and Mathematics of the Universe
  13. Harvard Univ., Cambridge, MA (United States); Space Telescope Science Inst., Baltimore, MD (United States)
  14. Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1393113
Grant/Contract Number:
AC02-05CH11231
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Monthly Notices of the Royal Astronomical Society
Additional Journal Information:
Journal Volume: 467; Journal Issue: 2; Journal ID: ISSN 0035-8711
Publisher:
Royal Astronomical Society
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS

Citation Formats

Friesen, Brian, Baron, E., Parrent, Jerod T., Thomas, R. C., Branch, David, Nugent, Peter E., Hauschildt, Peter H., Foley, Ryan J., Wright, Darryl E., Pan, Yen-Chen, Filippenko, Alexei V., Clubb, Kelsey I., Silverman, Jeffrey M., Maeda, Keiichi, Shivvers, Isaac, Kelly, Patrick L., Cohen, Daniel P., Rest, Armin, and Kasen, Daniel. Optical and ultraviolet spectroscopic analysis of SN 2011fe at late times. United States: N. p., 2017. Web. doi:10.1093/mnras/stx241.
Friesen, Brian, Baron, E., Parrent, Jerod T., Thomas, R. C., Branch, David, Nugent, Peter E., Hauschildt, Peter H., Foley, Ryan J., Wright, Darryl E., Pan, Yen-Chen, Filippenko, Alexei V., Clubb, Kelsey I., Silverman, Jeffrey M., Maeda, Keiichi, Shivvers, Isaac, Kelly, Patrick L., Cohen, Daniel P., Rest, Armin, & Kasen, Daniel. Optical and ultraviolet spectroscopic analysis of SN 2011fe at late times. United States. doi:10.1093/mnras/stx241.
Friesen, Brian, Baron, E., Parrent, Jerod T., Thomas, R. C., Branch, David, Nugent, Peter E., Hauschildt, Peter H., Foley, Ryan J., Wright, Darryl E., Pan, Yen-Chen, Filippenko, Alexei V., Clubb, Kelsey I., Silverman, Jeffrey M., Maeda, Keiichi, Shivvers, Isaac, Kelly, Patrick L., Cohen, Daniel P., Rest, Armin, and Kasen, Daniel. Mon . "Optical and ultraviolet spectroscopic analysis of SN 2011fe at late times". United States. doi:10.1093/mnras/stx241. https://www.osti.gov/servlets/purl/1393113.
@article{osti_1393113,
title = {Optical and ultraviolet spectroscopic analysis of SN 2011fe at late times},
author = {Friesen, Brian and Baron, E. and Parrent, Jerod T. and Thomas, R. C. and Branch, David and Nugent, Peter E. and Hauschildt, Peter H. and Foley, Ryan J. and Wright, Darryl E. and Pan, Yen-Chen and Filippenko, Alexei V. and Clubb, Kelsey I. and Silverman, Jeffrey M. and Maeda, Keiichi and Shivvers, Isaac and Kelly, Patrick L. and Cohen, Daniel P. and Rest, Armin and Kasen, Daniel},
abstractNote = {This paper presents optical spectra of the nearby Type Ia supernova SN 2011fe at 100, 205, 311, 349 and 578 d post-maximum light, as well as an ultraviolet (UV) spectrum obtained with the Hubble Space Telescope at 360 d post-maximum light. We compare these observations with synthetic spectra produced with the radiative transfer code PHOENIX. The day +100 spectrum can be well fitted with models that neglect collisional and radiative data for forbidden lines. Curiously, including these data and recomputing the fit yields a quite similar spectrum, but with different combinations of lines forming some of the stronger features. At day +205 and later epochs, forbidden lines dominate much of the optical spectrum formation; however, our results indicate that recombination, not collisional excitation, is the most influential physical process driving spectrum formation at these late times. Consequently, our synthetic optical and UV spectra at all epochs presented here are formed almost exclusively through recombinationdriven fluorescence. Furthermore, our models suggest that the UV spectrum even as late as day +360 is optically thick and consists of permitted lines from several iron-peak species. These results indicate that the transition to the 'nebular' phase in Type Ia supernovae is complex and highly wavelength dependent.},
doi = {10.1093/mnras/stx241},
journal = {Monthly Notices of the Royal Astronomical Society},
number = 2,
volume = 467,
place = {United States},
year = {Mon Feb 27 00:00:00 EST 2017},
month = {Mon Feb 27 00:00:00 EST 2017}
}

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  • The nearby Type Ia supernova (SN Ia) SN 2011fe in M101 (cz = 241 km s{sup -1}) provides a unique opportunity to study the early evolution of a 'normal' SN Ia, its compositional structure, and its elusive progenitor system. We present 18 high signal-to-noise spectra of SN 2011fe during its first month beginning 1.2 days post-explosion and with an average cadence of 1.8 days. This gives a clear picture of how various line-forming species are distributed within the outer layers of the ejecta, including that of unburned material (C+O). We follow the evolution of C II absorption features until theymore » diminish near maximum light, showing overlapping regions of burned and unburned material between ejection velocities of 10,000 and 16,000 km s{sup -1}. This supports the notion that incomplete burning, in addition to progenitor scenarios, is a relevant source of spectroscopic diversity among SNe Ia. The observed evolution of the highly Doppler-shifted O I {lambda}7774 absorption features detected within 5 days post-explosion indicates the presence of O I with expansion velocities from 11,500 to 21,000 km s{sup -1}. The fact that some O I is present above C II suggests that SN 2011fe may have had an appreciable amount of unburned oxygen within the outer layers of the ejecta.« less
  • We present time series photometric and spectroscopic data for the transient SN 2009ip from the start of its outburst in 2012 September until 2013 November. These data were collected primarily with the new robotic capabilities of the Las Cumbres Observatory Global Telescope Network, a specialized facility for time domain astrophysics, and includes supporting high-resolution spectroscopy from the Southern Astrophysical Research Telescope, Kitt Peak National Observatory, and Gemini Observatory. Based on our nightly photometric monitoring, we interpret the strength and timing of fluctuations in the light curve as interactions between fast-moving ejecta and an inhomogeneous circumstellar material (CSM) produced by pastmore » eruptions of this massive luminous blue variable (LBV) star. Our time series of spectroscopy in 2012 reveals that, as the continuum and narrow Hα flux from CSM interactions declines, the broad component of Hα persists with supernova (SN)-like velocities that are not typically seen in LBVs or SN impostor events. At late times, we find that SN 2009ip continues to decline slowly, at ≲ 0.01 mag day{sup –1}, with small fluctuations in slope similar to Type IIn supernovae (SNe IIn) or SN impostors but no further LBV-like activity. The late-time spectrum features broad calcium lines similar to both late-time SNe and SN impostors. In general, we find that the photometric and spectroscopic evolution of SN 2009ip is more similar to SNe IIn than either continued eruptions of an LBV star or SN impostors but we cannot rule out a nonterminal explosion. In this context, we discuss the implications for episodic mass loss during the late stages of massive star evolution.« less
  • The Type Ia supernova SN 2011fe is one of the closest supernovae of the past decades. Due to its proximity and low dust extinction, this object provides a very rare opportunity to study the extremely late time evolution (>900 days) of thermonuclear supernovae. In this Letter, we present our photometric data of SN 2011fe taken at an unprecedented late epoch of ≈930 days with GMOS-N mounted on the Gemini North telescope (g = 23.43 ± 0.28, r = 24.14 ± 0.14, i = 23.91 ± 0.18, and z = 23.90 ± 0.17) to study the energy production and retention in the ejecta of SN 2011fe. Together with previousmore » measurements by other groups, our result suggests that the optical supernova light curve can still be explained by the full thermalization of the decay positrons of {sup 56}Co. This is in spite of theoretical predicted effects (e.g., infrared catastrophe, positron escape, and dust) that advocate a substantial energy redistribution and/or loss via various processes that result in a more rapid dimming at these very late epochs.« less
  • We present the earliest ultraviolet (UV) observations of the bright Type Ia supernova SN 2011fe/PTF11kly in the nearby galaxy M101 at a distance of only 6.4 Mpc. It was discovered shortly after explosion by the Palomar Transient Factory and first observed by Swift/UVOT about a day after explosion. The early UV light is well defined, with {approx}20 data points per filter in the five days after explosion. These early and well-sampled UV observations form new template light curves for comparison with observations of other SNe Ia at low and high redshift. We report fits from semiempirical models of the explosionmore » and find the time evolution of the early UV flux to be well fitted by the superposition of two parabolic curves. Finally, we use the early UV flux measurements to examine a possible shock interaction with a non-degenerate companion. From models predicting the measurable shock emission, we find that even a solar mass companion at a distance of a few solar radii is unlikely at more than 95% confidence.« less
  • We measure the decay rate of the mid-IR luminosity from Type Ia supernova 2011fe between six months and one year after explosion using Spitzer/IRAC observations. The fading in the 3.6 {mu}m channel is 1.48 {+-} 0.02 mag/100{sup d}, which is similar to that seen in blue optical bands. The supernova brightness fades at 0.78 {+-} 0.02 mag/100{sup d} in the 4.5 {mu}m channel which is close to that observed in the near-IR. We argue that the difference is a result of doubly ionized iron-peak elements dominating the bluer IRAC band while singly ionized species are controlling the longer wavelength channel.more » To test this, we use Large Binocular Telescope spectra taken during the same phases to show that doubly ionized emission lines do fade more slowly than their singly ionized cousins. We also find that [Co III] emission fades at more than twice the radioactive decay rate due to the combination of decreasing excitation in the nebula, recombination and cobalt decaying to iron. The nebular emission velocities of [Fe III] and [Co III] lines show a smaller blueshift than emission from singly ionized atoms. The Si II velocity gradient near maximum light combined with our nebular velocity measurements suggest SN 2011fe was a typical member of the ''low velocity gradient'' class of Type Ia. Analyzing IRAC photometry from other supernovae we find that mid-IR color of Type Ia events is correlated with the early light curve width and can be used as an indicator of the radioactive nickel yield.« less