SPECTRAL EVOLUTION OF THE EXTRAORDINARY TYPE IIn SUPERNOVA 2006gy

By N. Smith, Ryan Chornock, J. Silverman, A. Filippenko, R. Foley. 2009

137 citations recorded by the source corpus.

We present a detailed analysis of the extremely luminous and long-lasting Type IIn supernova (SN) 2006gy using spectra obtained between days 36 and 237 after explosion. We derive the temporal evolution of the effective temperature, radius, blast-wave and SN-ejecta expansion speeds, and bolometric luminosity, as well as the progenitor wind density and total swept-up mass overtaken by the shock. SN 2006gy can be interpreted in the context of shock interaction with a dense circumstellar medium (CSM), but with quite extreme values for the CSM mass of ∼20 M☉ and SN explosion kinetic energy of at least 5 × 1051 erg. A key difference between SN 2006gy and other SNe IIn is that, owing to its large amount of swept-up mass, the interaction region remained opaque much longer. At early times, Hα emission-line widths suggest that the photosphere is ahead of the shock, and photons diffuse out through the opaque CSM shell. The pivotal transition to optically thin emission occurs around day 110, when we start to see a decrease in the blackbody radius RBB and strengthening tracers of the post-shock shell. From the evolution of pre-shock velocities, we deduce that the CSM was ejected by the progenitor star in a ≳1049 erg precursor event ∼8 yr before the explosion. The large CSM mass definitively rules out models involving stars with initial masses of ≲10 M☉. If the pre-SN mass budget also includes the likely SN ejecta mass of 10–20 M☉ and the distant >10 M☉ shell inferred from a light echo, then even massive MZAMS = 30–40 M☉ progenitor stars are inadequate. At roughly solar metallicity, substantial mass loss probably occurred during the star's life, so SN 2006gy's progenitor is more consistent with sequential giant luminous blue variable eruptions or pulsational pair-instability ejections in extremely massive stars with initial masses above 100 M☉. This requires significant revision to current paradigms of massive-star evolution.

Subfields: Astronomy and Astrophysics, Instrumentation, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/369dacb1e6aff8105afdafa3b82aac9980312e89

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In Astronomy and Astrophysics

1. N. Smith
2. E. Berger
3. S. Smartt
4. A. Filippenko
5. Stan Woosley
6. B. Metzger
7. Ryan Chornock
8. Bing Zhang

In Instrumentation

1. N. Smith
2. Stan Woosley
3. A. Filippenko
4. Weidong Li
5. S. Smartt
6. E. Berger
7. J. Silverman
8. Ryan Chornock

In Nuclear and High Energy Physics

1. N. Smith
2. S. Smartt
3. E. Berger
4. Stan Woosley
5. J. C. Wheeler
6. A. Filippenko
7. R. Kirshner
8. A. Gal-yam

Citations in the corpus

• Mass Loss: Its Effect on the Evolution and Fate of High-Mass Stars (2014, methodology): “A number of extragalactic LBV-like eruptions show spectra that closely resemble shock-powered Type IIn SNe and also show evidence for extremely fast ejecta that may signify a shock-powered event, such as the precursor outbursts of SN2009ip (Foley et al. 2011, Smith et al. 2010a).”
• A PANCHROMATIC VIEW OF THE RESTLESS SN 2009ip REVEALS THE EXPLOSIVE EJECTION OF A MASSIVE STAR ENVELOPE (2013, methodology): “Among the most important findings is the presence of blue-shifted absorption lines corresponding to ejecta traveling at a velocity of 2000−7000kms−1 during the 2009 outbursts (Smith et al. 2010b, Foley et al. 2011), extending to v ∼ 13000kms−1 in Semptember 2011 (Pastorello et al. 2012).”
• Pulsational Pair-instability Supernovae (2016, background): “Later, Smith et al. (2010a) showed that this event required a kinetic energy of 5×1051 erg which may be just out of reach.”
• PREPARING FOR AN EXPLOSION: HYDRODYNAMIC INSTABILITIES AND TURBULENCE IN PRESUPERNOVAE (2013, background): “Progenitor star detections We now have four directly detected quiescent progenitors of SNe IIn with rough mass estimates.”
• Luminous blue variable eruptions and related transients: diversity of progenitors and outburst properties (2010, methodology): “Based on the [Ca ii] emission lines and associations with dusty environments (Smith et al. 2009a, 2010; Prieto et al. 2008), however, it is possible that the progenitor could potentially be intrinsically more luminous than this.”
• The Unprecedented Third Outburst of SN 2009ip: A Luminous Blue Variable Becomes a Supernova (2012, methodology): “The first 2009 outburst was very brief compared to other LBV-like eruptions, lasting only a few days (Smith et al. 2010b), instead of a few months or more like most LBV eruptions (Smith et al. 2011).”
• PS16dtm: A Tidal Disruption Event in a Narrow-line Seyfert 1 Galaxy (2017, methodology): “In Figure 13 we compare the optical spectrum of PS16dtm to the spectra of several well-studied Type IIn SNe: SN 2006gy (Smith et al. 2010), SN 2011ht (Humphreys et al. 2012), SN 2008iy (Miller et al. 2010), SN 1994Y (Filippenko 1997), SN 1998S (Leonard et al. 2000), SN 2010jl (Zhang et al. 2012),…”
• HIGH-DENSITY CIRCUMSTELLAR INTERACTION IN THE LUMINOUS TYPE IIn SN 2010jl: THE FIRST 1100 DAYS (2013, background): “Besides the discussed SNe, two recent Type IIn SNe SN 2009ip (Smith et al. 2010; Foley et al. 2011; Pastorello et al. 2013; Mauerhan et al. 2013) and SN 2010mc (Ofek et al. 2013) have received considerable attention.”
• DISCOVERY OF PRECURSOR LUMINOUS BLUE VARIABLE OUTBURSTS IN TWO RECENT OPTICAL TRANSIENTS: THE FITFULLY VARIABLE MISSING LINKS UGC 2773-OT AND SN 2009ip (2009, background): “…of 550 km s−1 along with an intermediate-width component of a few 103 km s−1 is also reminiscent of the broader class of SNe IIn (see the discussion of line profiles in Smith et al. 2010 and Chugai & Danziger 1994), although the intermediate-width components tend to be stronger in SNe IIn.”
• Observed Fractions of Core-Collapse Supernova Types and Initial Masses of their Single and Binary Progenitor Stars (2010, background): “…interaction in SNe IIn indicate that heavy mass-loss sometimes occurs shortly before core collapse (e.g. Chugai et al. 2004; Smith & McCray 2007; Smith et al. 2007, 2008b, 2010); if heavy mass-loss is concentrated in brief events during the last few thousand years before core collapse, then the…”
• CALTECH CORE-COLLAPSE PROJECT (CCCP) OBSERVATIONS OF TYPE IIn SUPERNOVAE: TYPICAL PROPERTIES AND IMPLICATIONS FOR THEIR PROGENITOR STARS (2010, methodology): “Later analysis by Agnoletto et al. (2009), Smith et al. (2010) and Miller et al. (2010a) do seem to converge on a model invoking an extremely massive star experiencing strong CSM interaction.”
• Wave‐driven mass loss in the last year of stellar evolution: setting the stage for the most luminous core‐collapse supernovae (2012, background): “In the well-studied case of SN 2006gy – whose lightcurve is consistent with ∼ 10M of ejecta in the 8 years prior to corecollapse (Smith et al. 2010) – there is also evidence for a comparable amount of ejecta ∼ 103 years earlier (via an IR light echo; Miller et al. 2010).”
• SHOCK BREAKOUT IN DENSE MASS LOSS: LUMINOUS SUPERNOVAE (2011, methodology): “Outside of the shell is an electron scattering region of moderate optical depth (between c/vsh and 1) where the peaked Hα profile with a broad base can be formed (Chugai 2001; Smith et al. 2010); the broadening is due to scattering in the thermal gas as opposed to the Doppler effect.”
• Light-curve modelling of superluminous supernova 2006gy: collision between supernova ejecta and a dense circumstellar medium (2012, methodology): “The bolometric correction of Smith et al. (2010) is based on TBB and the correction may add extra luminosities because it ignores the effect of line depletion.”
• ANALYTICAL LIGHT CURVE MODELS OF SUPERLUMINOUS SUPERNOVAE: χ2-MINIMIZATION OF PARAMETER FITS (2013, background): “It has been suggested (Smith et al. 2007; 2010) that the intermediate-width emission lines are formed within the shocked CSM and thus are related to the velocity of the forward shock, while the narrow-width components are formed in the mediated but yet un-shocked, extended CSM material.”
• GENERALIZED SEMI-ANALYTICAL MODELS OF SUPERNOVA LIGHT CURVES (2011, methodology): “A rich database of optical spectra were obtained for SLSN 2006gy (Smith et al. 2007, 2008, 2010) that provides an extensive record of its spectral evolution.”
• HYDROGEN-POOR SUPERLUMINOUS SUPERNOVAE AND LONG-DURATION GAMMA-RAY BURSTS HAVE SIMILAR HOST GALAXIES (2013, background): “…example, members of the subclass of the SLSNe that show hydrogen in their spectra can be classified as Type IIn SNe, with the origin of the extreme luminosity being interaction with a dense circumstellar medium (e.g., Ofek et al. 2007; Smith et al. 2007, 2010; Rest et al. 2011; Moriya et al. 2013).”
• DUST AND THE TYPE II-PLATEAU SUPERNOVA 2004dj (2009, background): “…the bulk motion of the ejecta however, some of the width of the Hα and Paβ lines may also have been produced by scattering from thermal electrons as in the cases of SN 1998S (Chugai 2001) and SN 2006gy (Smith et al. 2010), but this effect is unlikely to have a significant influence at later epochs.”