The Transition of a Type IIL Supernova into a Supernova Remnant: Late-time Observations of SN 2013by

Abstract

We present early-time Swift and Chandra X-ray data along with late-time optical and near-infrared observations of SN 2013by, a Type IIL supernova (SN) that occurred in the nearby spiral galaxy ESO 138−G10 (D ∼ 14.8 Mpc). Optical and NIR photometry and spectroscopy follow the late-time evolution of the supernova from days +89 to +457 post-maximum brightness. The optical spectra and X-ray light curves are consistent with the picture of a SN having prolonged interaction with circumstellar material (CSM) that accelerates the transition from supernova to supernova remnant (SNR). Specifically, we find SN 2013by's Hα profile exhibits significant broadening (∼ 10,000 km s −1 ) on day +457, the likely consequence of high-velocity, H-rich material being excited by a reverse shock. A relatively flat X-ray light curve is observed that cannot be modeled using inverse-Compton scattering processes alone but requires an additional energy source most likely originating from the SN-CSM interaction. In addition, we see the first overtone of CO emission near 2.3 µm on day +152, signaling the formation of molecules and dust in the SN ejecta and is the first time CO has been detected in a Type IIL supernova. We compare SN 2013by to Type IIP supernovae whose spectra show the rarely observed SN-to-SNR transition in varying degrees and conclude that Type IIL SNe may enter the remnant phase at earlier epochs than their Type IIP counterparts.

SN 2017ivv: two years of evolution of a transitional Type II supernova

“…This 'bridge' has been seen before in both SNe IIL (e.g. 2013by; Black et al 2017 and2014G;Terreran et al 2016) and SNe IIb (e.g. SN 1993J;Matheson et al 2000).…”

“…For this reason, we will compare SN 2017ivv to both fast-declining SNe II and SNe IIb with well-sampled light curves and some spectra during both the photospheric and nebular phase. The fast-declining SN II group consists of ASASSN-15oz (Bostroem et al 2019), SN 2014G (Terreran et al 2016), SN 2013ej (Valenti et al 2014;Huang et al 2015;Yuan et al 2016), and SN 2013by (Valenti et al 2015;Black et al 2017), while the SNe IIb sample consists of SN 2015as (Gangopadhyay et al 2018), SN 2013df (Morales-Garoffolo et al 2014;Szalai et al 2016), SN 2011hs (Bufano et al 2014), SN 2011dh (Arcavi et al 2011;Sahu et al 2013;Ergon et al 2014), SN 2008ax (Pastorello et al 2008Taubenberger et al 2011;Modjaz et al 2014), and SN 1993J (Barbon et al 1995;Matheson et al 2000). Because of the extremely low luminosity of the host of SN 2017ivv, we also include SN 2015bs (Anderson et al 2018), which is a slow-declining SN II that exploded in the faintest host galaxy found before SN 2017ivv.…”

SN 2017ivv: two years of evolution of a transitional Type II supernova

“…For this reason we will compare SN 2017ivv to both fast-declining SNe II and SNe IIb with well-sampled light curves and some spectra during both the photospheric and nebular phase. The fast-declining SN II group consists of ASASSN-15oz (Bostroem et al 2019), SN 2014G (Terreran et al 2016), SN 2013ej (Valenti et al 2014Huang et al 2015;Yuan et al 2016), and SN 2013by (Valenti et al 2015Black et al 2017), while the SNe IIb sample consists of SN 2015as (Gangopadhyay et al 2018), SN 2013df (Morales-Garoffolo et al 2014Szalai et al 2016), SN 2011hs (Bufano et al 2014), SN 2011dh (Arcavi et al 2011Sahu et al 2013;Ergon et al 2014Ergon et al , 2015, SN 2008ax (Pastorello et al 2008;Taubenberger et al 2011;Modjaz et al 2014), and SN 1993J (Barbon et al 1995Matheson et al 2000). Because of the extremely low luminosity of the host of SN 2017ivv, we also include SN 2015bs (Anderson et al 2018), which is a slow-declining SN II that exploded in the faintest host galaxy found before SN 2017ivv.…”

Detection of Late-Time Circumstellar Interaction of SN 2017eaw in NGC 6946

“…Signatures of ejecta-CSM interactions have been observed in a few SNe II-L/P before ∼ 500 days: SN 2007od (Andrews et al 2010), SN 2004dj (Andrews et al 2016), PTF11iqb (Smith et al 2015), SN 2011ja (Andrews et al 2016), SN 2013by (Black et al 2017), and SN 2017gmr (Andrews et al 2019). However, boxlike emission profiles indicating ejecta-CSM interaction with CSM shells have only been observed for three SNe II-P, and in these cases the ejecta-CSM interaction was observed after ∼ 800 days: SN 2004et (Kotak et al 2009;Maguire et al 2010), SN 2013ej (Mauerhan et al 2017, and iPTF14hls (Andrews & Smith 2018;Sollerman et al 2019).…”