SN 2007od: A TYPE IIP SUPERNOVA WITH CIRCUMSTELLAR INTERACTION

Abstract

SN 2007od exhibits characteristics that have rarely been seen in a Type IIP supernova (SN). Optical V-band photometry reveals a very steep brightness decline between the plateau and nebular phases of ∼4.5 mag, likely due to SN 2007od containing a low mass of 56 Ni. The optical spectra show an evolution from normal Type IIP with broad Hα emission, to a complex, four-component Hα emission profile exhibiting asymmetries caused by dust extinction after day 232. This is similar to the spectral evolution of the Type IIn SN 1998S, although no early-time narrow (∼200 km s −1 ) Hα component was present in SN 2007od. In both SNe, the intermediate-width Hα emission components are thought to arise in the interaction between the ejecta and its circumstellar medium (CSM). SN 2007od also shows a mid-infrared excess due to new dust. The evolution of the Hα profile and the presence of the mid-IR excess provide strong evidence that SN 2007od formed new dust before day 232. Late-time observations reveal a flattening of the visible light curve. This flattening is a strong indication of the presence of a light echo, which likely accounts for much of the broad, underlying Hα component seen at late times. We believe that the multi-peaked Hα emission is consistent with the interaction of the ejecta with a circumstellar ring or torus (for the inner components at ±1500 km s −1 ) and a single blob or cloud of circumstellar material out of the plane of the CSM ring (for the outer component at −5000 km s −1 ). The most probable location for the formation of new dust is in the cool dense shell created by the interaction between the expanding ejecta and its CSM. Monte Carlo radiative transfer modeling of the dust emission from SN 2007od implies that up to ∼4 × 10 −4 M of new dust has formed. This is similar to the amounts of dust formed in other core-collapse supernovae such as SNe 1999em, 2004et, and 2006jc.

Asphericity, Interaction, and Dust in the Type Ii-P/Ii-L Supernova 2013ej in Messier 74

“…It most closely resembles the mid-IR light curves of SN 2004et, which was optically classified as an SNII-P (Li et al 2005), and SN 2007od, which was also classified as a SNII-P (Andrews et al 2010) but is potentially classifiable as a SNII-L, based on the criterion of Anderson et al (2014). Interestingly, both SNe exhibited evidence for late-time CSM interaction, similar to that of SN 2013ej (see showed that the mid-IR flux increased dramatically after day 1000, interpreted as the result of dust formation within a dense postshock shell that developed in response to the CSM interaction (Kotak et al 2009).…”

“…The broadband optical photometry from day 888 Andrews et al 2010), andSN 1993J (red;Tinyanont et al 2016). Data for SN 2011dh (yellow;Helou et al 2013;Ergon et al 2015) andSN 1998S (magenta;Gerardy et al 2002;Pozzo et al 2004) are also included for comparison.…”

“…Assuming a speed of 12,000 km s −1 for the fastest ejecta, this material would encounter the same light-scattering CSM dust at ∼800 days, which is near the time when we see the mid-IR emission possibly beginning to rise (see Figure 14). In the relatable cases of SN 2004et and SN 2007od, both which exhibited late-time interaction-powered spectra similar to that of SN 2013ej (see Section 3), their thermal excesses were interpreted as a result of dust formation within a dense postshock shell that developed in response to the CSM interaction (Kotak et al 2009;Andrews et al 2010;Inserra et al 2011). This interpretation is therefore appealing for SN 2013ej as well, not only because of its spectroscopic and SED similarities with SN 2004et and SN 2007od, but also because of the possible signs of scattering by preexisting circumstellar dust indicated by the spectropolarimetry in Section 2.5.1.…”

Dust formation in the ejecta of the type II-P supernova 2004dj

“…Evidence for newly condensed dust were obtained for SN 2003gd (Sugerman et al 2006;Meikle et al 2007), 2004et (Kotak et al 2009), 2007od (Andrews et al 2010), and type Ib/c SN 2006jc (Nozawa et al 2008;Mattila et al 2008;Tominaga et al 2008;and Sakon et al 2009). In every case, the estimated mass of recently formed dust was between 10 −5 −10 −3 M .…”

Cold dust in three massive evolved stars in the LMC

“…It has been suggested that supernovae (SNe) might be the dominant dust factory at high-z, since intermediate-mass stars have not yet had time to evolve into AGB stars (Morgan & Edmunds 2003;Dwek et al 2009). However, the amount of dust formed in SNe in the local universe is much less than required to explain the dust seen at high-z (e.g., Sugerman et al 2006;Andrews et al 2010). It is also unclear if the dust forms before or after the SN explosion.…”