Direct Detection of Core-Collapse SN Progenitors: The Explosive Deaths of the Most Massive Stars


Highlights:

The hypergiant progenitor of SN 2005gl (Nature paper)
A postmortem search for the progenitor of SN 2007fo (Recently approved HST program)

The program:

Direct observations of massive stars - before they explode - provide a model free identification of SN progenitors. A high-resolution image of the location of a SN, serendipitously obtained before it exploded, is combined with a precise localization of the SN (after it exploded) to enable us to select the correct progenitor from among the stars in the pre-explosion SN images. After decades of effort, less than a dozen SN progenitors have so far been detected. Once or twice a year a SN is discovered in an area previously observed by the Hubble Space telescope (HST). Efforts to localize nearby SNe with post-explosion HST data are difficult. Furthermore, HST is ill-suited to observe bright point sources such as nearby SNe, requiring either the use of highly saturated images, or a forced long wait while the SN declines. We have shown that laser-guide-star assisted adaptive optics systems (LGS-AO) are a superb alternative, providing deep, unsaturated, high resolution (HST-like or better) images of any bright SN within minutes, leading to precise localization of these SNe. We have already applied this approach in several cases (e.g., Gal-Yam et al. 2005; 2007; Leonard et al. 2008; see below) using the Keck and Palomar LGS systems with great success. More recently, we have been using the Gemini ALTAIR-LGS (in collaboration with the Smartt group at Queen's University, Belfast) with excellent results.


Our previous LGS work set the tightest luminosity constraints on the progenitor of type Ic SN 2004gt (Gal-Yam et al. 2005). Our suggestion that the progenitor of type IIn SN 2005gl was a Luminous Blue Variable (LBV; Gal-Yam et al. 2007) was instrumental in making the LBV-IIn connection among the hottest current topics. We continue to intensively pursue this avenue of research utilizing the ALTAIR LGS system on the Gemini North telescope (2010B program recently approved). Doubling the number of detected SN progenitors within a few years, we, along with other workers in this area, can construct a robust progenitor-SN map (see right) relating specific types of progenitor stars to the resulting classes of SNe. This represents a fundamental progress in the determination of the origins of each core-collapse SN subtype. Furthermore, I expect that constraining SN models to fit both the initial conditions (the properties of the pre-explosion star) and a set of end products (the observed SN explosions), as was so clearly demonstrated by the case of SN 1987A, should eventually lead to rapid advancement in our understanding of SN physics.



Publications:

Keck/Palomar:

  • A massive hypergiant star as the progenitor of the supernova SN 2005gl
  • An Upper Mass Limit on a Red Supergiant Progenitor for the Type II-Plateau Supernova SN 2006my
  • On the progenitor of SN 2005gl and the nature of Type IIn supernovae
  • A high angular-resolution search for the progenitor of the type Ic supernova SN 2004gt

    Gemini:

  • On the Progenitor and Early Evolution of the Type II Supernova 2009kr
  • The type IIb SN 2008ax: the nature of the progenitor
  • The Type IIb SN 2008ax: spectral and light curve evolution

    Collaborators:

    A. Gal-Yam (Weizmann Institute)
    Y. Green (Graduate student, Weizmann Institute)
    D. Leonard (SDSU)
    D. Fox (PSU)


    Constructed: December 2008, by: Avishay Gal-Yam , E-Mail: email