Ultraviolet spectroscopy of type iib supernovae: Diversity and the impact of circumstellar material

Sagi Ben-Ami, Stephan Hachinger, Avishay Gal-Yam, Paolo A. Mazzali, Alexei V. Filippenko, Assaf Horesh, Thomas Matheson, Maryam Modjaz, Daniel N. Sauer, Jeffrey M. Silverman, Nathan Smith, Ofer Yaron

Research output: Contribution to journalArticlepeer-review

14 Scopus citations


ABSTRACT We present new Hubble Space Telescope (HST) multi-epoch ultraviolet (UV) spectra of the bright Type IIb SN 2013df, and undertake a comprehensive analysis of the set of four SNe IIb for which HST UV spectra are available (SN 1993J, SN 2001ig, SN 2011dh, and SN 2013df). We find strong diversity in both continuum levels and line features among these objects. We use radiative-transfer models that fit the optical part of the spectrum well, and find that in three of these four events we see a UV continuum flux excess, apparently unaffected by line absorption. We hypothesize that this emission originates above the photosphere, and is related to interaction with circumstellar material (CSM) located in close proximity to the SN progenitor. In contrast, the spectra of SN 2001ig are well fit by single-temperature models, display weak continuum and strong reverse-fluorescence features, and are similar to spectra of radioactive 56Ni-dominated SNe Ia. A comparison of the early shock-cooling components in the observed light curves with the UV continuum levels which we assume trace the strength of CSM interaction suggests that events with slower cooling have stronger CSM emission. The radio emission from events having a prominent UV excess is perhaps consistent with slower blast-wave velocities, as expected if the explosion shock was slowed down by the CSM that is also responsible for the strong UV, but this connection is currently speculative as it is based on only a few events.

Original languageAmerican English
Article number40
Pages (from-to)1-11
Number of pages11
JournalAstrophysical Journal
Issue number1
StatePublished - 10 Apr 2015
Externally publishedYes

Bibliographical note

Publisher Copyright:
© 2015. The American Astronomical Society. All rights reserved.


Dive into the research topics of 'Ultraviolet spectroscopy of type iib supernovae: Diversity and the impact of circumstellar material'. Together they form a unique fingerprint.

Cite this