EVIDENCE FOR PRE-EXISTING DUST IN THE BRIGHT TYPE IIn SN 2010jl

Abstract

SN 2010jl was an extremely bright, Type IIn SNe which showed a significant IR excess no later than 90 days after explosion. We have obtained Spitzer 3.6 and 4.5 µm and JHK observations of SN 2010jl ∼90 days post explosion. Little to no reddening in the host galaxy indicated that the circumstellar material lost from the progenitor must lie in a torus inclined out of the plane of the sky. The likely cause of the high mid-IR flux is the reprocessing of the initial flash of the SN by pre-existing circumstellar dust. Using a 3D Monte Carlo Radiative Transfer code, we have estimated that between 0.03-0.35 M ⊙ of dust exists in a circumstellar torus around the SN located 6 × 10 17 cm away from the SN and inclined between 60-80 • to the plane of the sky. On day 90, we are only seeing the illumination of approximately 5% of this torus, and expect to see an elevated IR flux from this material up until day ∼ 450. It is likely this dust was created in an LBV-like mass loss event of more than 3 M ⊙ , which is large but consistent with other LBV progenitors such as η Carinae.

SYSTEMATIC BLUESHIFT OF LINE PROFILES IN THE TYPE IIn SUPERNOVA 2010jl: EVIDENCE FOR POST-SHOCK DUST FORMATION?

“…This, in turn, supported the hypothesis that the pre-SN CSM of SN 2006gy was formed in an LBV-like outburst rather than in a steady wind, and a similar scenario may apply to SN 2010jl. This appears to be consistent with the very massive progenitor star inferred for SN 2010jl (Smith et al 2011b) and its dense, dusty CSM (Andrews et al 2011). However, additional analysis of the CSM emission lines is needed.…”

“…Andrews et al (2011) favor the interpretation that the IR excess they observe in SN 2010jl is due to an IR echo caused by pre-existing CSM dust that is warmed by the luminosity of the SN, and not due to newly formed dust. They favor this interpretation based on the relatively cool dust temperatures of T = 750 K in their model, whereas they expect newly formed dust to emit at 1600 K. Andrews et al (2011) did mention, however, that without a detailed study of the optical emission-line profiles, it is difficult to rule out the possibility of new dust formation as an explanation for the IR emission. As noted above, the Hα profile does in fact show very clear evidence of a systematic blueshift with time, which would normally be taken as strong evidence for new dust formation.…”

“…SNe IIn constitute only about 6%-9% of core-collapse SNe (Smith et al 2011a;Li et al 2011), so even if they are very efficient dust producers, it is not clear that they can account for the dust present in high-redshift galaxies unless they are more common at high redshift. Andrews et al (2011) recently reported an IR excess in the very bright Type IIn SN 2010jl. They note that the IR excess may arise from either newly formed dust or an IR echo from pre-existing dust, although they favor the hypothesis of an IR echo because of the observed dust temperature.…”

“…In a previous paper (Smith et al 2011b), we analyzed preexplosion archival images of the field of SN 2010jl obtained with the Hubble Space Telescope (HST), showing that the progenitor of SN 2010jl was likely to be a very massive star with an initial mass above 30 M , and with dense CSM expanding at 40-120 km s −1 along our line of sight. Attributing the IR excess to pre-existing dust, Andrews et al (2011) infer a very large amount of mass in the CSM of SN 2010jl, possibly suggesting a massive progenitor similar to luminous blue variables (LBVs). Additional information on the basic observed properties of SN 2010jl can be found in recent reports (Patat et al 2011;Smith et al 2011b;Andrews et al 2011).…”

“…Attributing the IR excess to pre-existing dust, Andrews et al (2011) infer a very large amount of mass in the CSM of SN 2010jl, possibly suggesting a massive progenitor similar to luminous blue variables (LBVs). Additional information on the basic observed properties of SN 2010jl can be found in recent reports (Patat et al 2011;Smith et al 2011b;Andrews et al 2011). …”