CORONAL LINES AND DUST FORMATION IN SN 2005ip: NOT THE BRIGHTEST, BUT THE HOTTEST TYPE IIn SUPERNOVA

Abstract

We present optical photometry and spectroscopy of SN 2005ip for the first 3 yr after discovery, showing an underlying Type II-L supernova (SN) interacting with a steady wind to yield an unusual Type IIn spectrum. For the first ∼160 d, it had a fast linear decline from a modest peak absolute magnitude of about −17.4 (unfiltered), followed by a plateau at roughly −14.8 for more than 2 yr. Initially having a normal broad-lined spectrum superposed with sparse narrow lines from the photoionized circumstellar medium (CSM), it quickly developed signs of strong CSM interaction with a spectrum similar to that of SN 1988Z. As the underlying SN II-L faded, SN 2005ip exhibited a rich high-ionization spectrum with a dense forest of narrow coronal lines, unprecedented among SNe but reminiscent of some active galactic nuclei. The line-profile evolution of SN 2005ip confirms that dust formation caused its recently reported infrared excess, but these lines reveal that it is the first SN to show clear evidence for dust in both the fast SN ejecta and the slower post-shock gas. SN 2005ip's complex spectrum confirms the origin of the strange blue continuum in SN 2006jc, which also had post-shock dust formation. We suggest that SN 2005ip's late-time plateau and coronal spectrum result from rejuvenated CSM interaction between a sustained fast shock and a clumpy stellar wind, where X-rays escape through the optically thin interclump regions to heat the pre-shock CSM to coronal temperatures.

Possible evidence of asymmetry in SN 2007rt, a type IIn supernova

“…Secondly, in an early epoch (<40 days) type IIn, a strong blue continuum would be expected which evolves rapidly along with the broad features (viz. SN 2005ip, SN 2005gj;Smith et al 2009a;Aldering et al 2006). However the blue continuum and broad features in SN 2007rt, do not evolve rapidly over a 60 day period between our first and fifth spectrum (see further discussion on continuum Sect.…”

“…The assumption of a short rise time of SN2005ip is also supported by the rapid change in the spectra after discovery. The first spectrum shows an almost featureless and very blue spectrum (Smith et al 2009a) and over the following days the broad features and continuum evolve rapidly (from unpublished spectra, Trundle et al in prep). At 95 days after its discovery, the spectrum of SN 2005ip best fits the broad features and slope of our first SN 2007rt spectrum (see Sect.…”

“…The light-curve of SN 2005ip declined rapidly after discovery, suggesting SN 2005ip was discovered close to maximum (Smith et al 2009a Fig. 2).…”

“…Smith et al (2009a) suggested that at late times the blue continuum present in the type IIn SN 2005ip was a result of the presence of a forest of high Article published by EDP Sciences ionisation forbidden emission lines and they refer to this as a pseudo-continuum. This verified earlier speculation by Stathakis & Sadler and Turatto et al that the source of the blue spectral region in SN 1988Z was a strong interaction with the surrounding circumstellar material.…”

Genesis and evolution of dust in galaxies in the early Universe

“…On the other hand, these models also show that the effectiveness of dust destruction depends on various properties such as the geometry of the shocks, the density of the ejecta and the ISM, the size and shape of the grains, clumping in the SNe ejecta, and different SN types. In addition there is some observational evidence that type IIn SNe and sources such as luminous blue variables are possibly efficient dust producers (Fox et al 2009;Smith et al 2009;Gomez et al 2010). While dust production and destruction in SNe is yet unresolved, a "maximum" SN efficiency cannot be ruled out (e.g., Gall et al in prep).…”