The diversity of massive star outbursts. I. Observations of SN2009ip, UGC2773 OT2009-1, and their progenitors

Ryan J. Foley, Edo Berger, Ori Fox, Emily M. Levesque, Peter J. Challis, Inese I. Ivans, James E. Rhoads, Alicia M. Soderberg

Research output: Contribution to journalArticlepeer-review

95 Scopus citations

Abstract

Despite both being outbursts of luminous blue variables (LBVs), SN2009ip and UGC2773 OT2009-1 have very different progenitors, spectra, circumstellar environments, and possibly physical mechanisms that generated the outbursts. From pre-eruption Hubble Space Telescope images, we determine that SN2009ip and UGC2773 OT2009-1 have initial masses of ≳ 60 and ≳ 25 M , respectively. Optical spectroscopy shows that at peak, SN2009ip had a 10,000K photosphere and its spectrum was dominated by narrow H Balmer emission, similar to classical LBV giant outbursts, also known as "supernova impostors." The spectra of UGC2773 OT2009-1, which also have narrow Hα emission, are dominated by a forest of absorption lines, similar to an F-type supergiant. Blueshifted absorption lines corresponding to ejecta at a velocity of 2000-7000kms-1 are present in later spectra of SN2009ip - an unprecedented observation for LBV outbursts, indicating that the event was the result of a supersonic explosion rather than a subsonic outburst. The velocity of the absorption lines increases between two epochs, suggesting that there were two explosions in rapid succession. A rapid fading and rebrightening event concurrent with the onset of the high-velocity absorption lines is consistent with the double-explosion model. A near-infrared excess is present in the spectra and photometry of UGC2773 OT2009-1 that is consistent with 2100K dust emission. We compare the properties of these two events and place them in the context of other known massive star outbursts such as η Car, NGC300 OT2008-1, and SN2008S. This qualitative analysis suggests that massive star outbursts have many physical differences that can manifest as the different observables seen in these two interesting objects.

Original languageEnglish (US)
Article number32
JournalAstrophysical Journal
Volume732
Issue number1
DOIs
StatePublished - May 1 2011

Keywords

  • circumstellar matter
  • dust, extinction
  • stars: evolution
  • stars: individual (SN 2009ip, UGC 2773 OT2009-1)
  • stars: mass-loss
  • stars: massive
  • stars: variables: S Doradus
  • stars: variables: general
  • stars: winds, outflows

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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