Sn 2008d: A Wolf-Rayet Explosion Through a Thick Wind

Abstract

Supernova (SN) 2008D/XRT 080109 is considered to be the only direct detection of a shock breakout from a regular SN to date. While a breakout interpretation was favored by several papers, inconsistencies remain between the observations and current SN shock breakout theory. Most notably, the duration of the luminous X-ray pulse is considerably longer than expected for a spherical breakout through the surface of a type Ibc SN progenitor, and the X-ray radiation features, mainly its flat spectrum and its luminosity evolution, are enigmatic. We apply a recently developed theoretical model for the observed radiation from a Wolf-Rayet SN exploding through a thick wind and show that it naturally explains all the observed features of SN 2008D X-ray emission, including the energetics, the spectrum and the detailed luminosity evolution. We find that the inferred progenitor and SN parameters are typical for an exploding Wolf-Rayet. A comparison of the wind density found at the breakout radius to the density at much larger radii, as inferred by late radio observations, suggests an enhanced mass loss rate taking effect about ten days or less prior to the SN explosion. This finding joins accumulating evidence for a possible late phase in the stellar evolution of massive stars, involving vigorous mass loss a short time before the SN explosion.

The two promising scenarios to explode core collapse supernovae

“…It seems that the pre-explosion outbursts of CCSNe are common (e.g., Moriya et al 2014;Ofek et al 2014;Svirski & Nakar 2014;Tartaglia et al 2016;Yaron et al 2017), with about one in ten CCSNe suffering a pre-explosion outburst (e.g., Margutti et al 2017). The outburst might result from a single-star process, e.g., strong convection in the pre-collapsing core (Quataert & Shiode 2012;Shiode & Quataert 2014).…”

Ejection of the Massive Hydrogen-rich Envelope Timed with the Collapse of the Stripped SN 2014C

“…A precursor to the SN explosion has been identified in the H-stripped type-Ibn SN 2006jc, which showed signs of interaction with a He-rich medium (e.g., Foley et al 2007;Pastorello et al 2007;Immler et al 2008). Evidence for significantly enhanced mass loss timed with the explosion has been found for the H-poor progenitors of both type-IIb SNe (GalYam et al 2014;Kamble et al 2015;Maeda et al 2015) and type-Ib SNe (Svirski & Nakar 2014), as well as for the H-and He-poor progenitors of type-Ic SNe associated with some nearby gamma-ray bursts (Margutti et al 2015;Nakar 2015). Along the same line, it is relevant to mention the possible detection of an outburst from the progenitor of the broad-line type-Ic SN PTF11qcj ∼2.5 years before stellar death (Corsi et al 2014), a possible precursor in the type-IIb SN 2012cs (Strotjohann et al 2015), and the recent detection of interaction of the H-poor superluminous SN iPTF13ehe with H-rich material at late times (Yan et al 2015), as well the evidence for significant temporal variability in the radio lightcurves of Ib/c SNe (Soderberg 2007;Wellons et al 2012), which suggests significant structure in their circumstellar media (CSM).…”

Collisionless shocks and X-ray emission around supernova shock breakout

“…A CS may have formed before SB for SN 2008D/XRF 080109, assuming a progenitor with the parameters proposed in Reference [34]. This gives another important reason to search for SN 2008D-like events in the future.…”

“…We suggest here that the CS may have formed before SB for SN 2008D/XRF 080109. Svirski & Nakar [34] proposed that the progenitor was a Wolf-Rayet star surrounded with a moderately thick wind (r br 10 r * ). They suggested that the progenitor underwent enhanced mass-loss prior to the explosion, for 10 d, with mass-loss rate…”