SN 2013fs and SN 2013fr: exploring the circumstellar-material diversity in Type II supernovae

Abstract

We present photometry and spectroscopy of SN 2013fs and SN 2013fr in the first ∼ 100 days post-explosion. Both objects showed transient, relatively narrow Hα emission lines characteristic of SNe IIn, but later resembled normal SNe II-P or SNe II-L, indicative of fleeting interaction with circumstellar material (CSM). SN 2013fs was discovered within 8 hr of explosion; one of the earliest SNe discovered thus far. Its light curve exhibits a plateau, with spectra revealing strong CSM interaction at early times. It is a less luminous version of the transitional SN IIn PTF11iqb, further demonstrating a continuum of CSM interaction intensity between SNe II-P and SNe IIn. It requires dense CSM within 6.5 × 10 14 cm of the progenitor, from a phase of advanced pre-SN mass loss beginning shortly before explosion. Spectropolarimetry of SN 2013fs shows little continuum polarization (∼ 0.5%, consistent with zero), but noticeable line polarization during the plateau phase. SN 2013fr morphed from a SN IIn at early times to a SN II-L. After the first epoch its narrow lines probably arose from host-galaxy emission, but the bright, narrow Hα emission at early times may be intrinsic to the SN. As for SN 2013fs, this would point to a short-lived phase of strong CSM interaction if proven to be intrinsic, suggesting a continuum between SNe IIn and SNe II-L. It is a low-velocity SN II-L like SN 2009kr, but more luminous. SN 2013fr also developed an infrared excess at later times, due to warm CSM dust that require a more sustained phase of strong pre-SN mass loss.

The dusty progenitor star of the Type II supernova 2017eaw

“…RSGs form dust in their winds (Verhoelst et al 2009), and analysis of resolved circumstellar environments around RSGs in the Milky Way indicates that these winds can form compact shells obscuring the underlying star. SNe II exhibit evidence for coronal line emission in early-time spectra (Khazov et al 2016), narrow, transient lines of hydrogen consistent with a compact shell of circumstellar material that is irradiated by the SN (Bullivant et al 2018), and excess mid-infrared emission consistent with heated dust in their circumstellar environments (Tinyanont et al 2016). If high-mass RSGs are significantly dustobscured in pre-SN imaging, it is possible that their luminosities and initial masses are underpredicted, or even that some of these stars go completely undetected.…”

SN 2017gmr: An Energetic Type II-P Supernova with Asymmetries

“…All of these features disappear within a week of explosion, eliminating them from the traditional class of Type IIn SNe. To date, only a handful of objects have shown these early high-ionization narrow emission lines, including SN2013cu (Gal-Yam et al 2014), SN1998S (Shivvers et al 2015), PTF11iqb (Smith et al 2015), SN2013fs (Yaron et al 2017;Bullivant et al 2018), and SN2016bkv (Hosseinzadeh et al 2018;Nakaoka et al 2018). Others have shown a featureless, blue continuum with no lines (Khazov et al 2016).…”

The explosion energy of the type IIP supernova SN 2013fs with a confined dense circumstellar shell

“…The observational bolometric light curve reported by Yaron et al (2017) is truncated at 56 days. The sensible reconstruction of the later behavior can be performed with the R-band photometry (Bullivant et al 2018) that we match with the bolometric light curve in the range of 38-56 days (Fig. 4).…”

“…The study is based on the Keck-1 spectrum at the age of 2.42 days (Oct. 8.45) and the spectrum on day 51 (Nov. 26) taken at the Palomar 200-inch telescope; both spectra are retrieved from the WISeREP database (Yaron & Gal-Yam 2012) (https://wiserep.weizmann.ac.il). Below I use the explosion date Oct. 6.03 (UTC), the average between 2013 Oct. 6.12 (Yaron et al 2017) and Oct. 5.946 (Bullivant et al 2018).…”

“…The light curve models overploted on the bolometric light curve (squares) according(Yaron et al 2017). Asterisk symbols is the R band photometry(Bullivant et al 2018) matched to the bolometric light curve. The panel a shows the model A without CS interaction (blue) and with the CS interaction (red).…”