Progenitors of Type IIb Supernovae. II. Observable Properties

Abstract

Type IIb supernovae (SNe IIb) present a unique opportunity for investigating the evolutionary channels and mechanisms governing the evolution of stripped-envelope SN progenitors due to a variety of observational constraints available. Comparison of these constraints with the full distribution of theoretical properties not only help ascertain the prevalence of observed properties in nature, but can also reveal currently unobserved populations. In this follow-up paper, we use the large grid of models presented in Sravan et al. (2019) to derive distributions of single and binary SNe IIb progenitor properties and compare them to constraints from three independent observational probes: multi-band SN light-curves, direct progenitor detections, and X-ray/radio observations. Consistent with previous work, we find that while current observations exclude single stars as SN IIb progenitors, SN IIb progenitors in binaries can account for them. We also find that the distributions indicate the existence of an unobserved dominant population of binary SNe IIb at low metallicity that arise due to mass transfer initiated on the Hertzsprung Gap. In particular, our models indicate the existence of a group of highly stripped (envelope mass ∼ 0.1 − 0.2M ) progenitors that are compact (< 50R ) and blue (T eff 10 5 K) with ∼ 10 4.5 − 10 5.5 L and low density circumstellar mediums. As discussed in Sravan et al. (2019), this group is necessary to account for SN IIb fractions and likely exist regardless of metallicity. The detection of the unobserved populations indicated by our models would support weak stellar winds and inefficient mass transfer in SN IIb progenitors.

Revisiting the explodability of single massive star progenitors of stripped-envelope supernovae

“…Our results alone are not necessarily a motivation to revise single-star mass-loss rates or their explodability properties, since the binary progenitors of SESNe are a suggested alternative path for SNe Ib/c and SNe IIb (e.g., Podsiadlowski et al 1992;De Donder & Vanbeveren 1998;Yoon et al 2010;Eldridge et al 2013;Zapartas et al 2017;Sravan et al 2019Sravan et al , 2020. This scenario helps explain their low ejecta masses and short timescales (e.g., Drout et al 2011;Lyman et al 2016;Modjaz et al 2016), their relatively high occurrence rate (e.g., Eldridge et al 2013;Graur et al 2017;Shivvers et al 2019), the difficulty to directly image their progenitors (e.g., Eldridge et al 2013, although see Yoon et al 2012Van Dyk et al 2019), and the detection of binary companions at SN IIb sites (Maund et al 2004;Fox et al 2014;Ryder et al 2018).…”

“…Evolution in a binary system offers two advantages over single-star progenitors. First, binary interactions do not have a minimum mass threshold for removing the H-rich envelope (Podsiadlowski et al 1992;Eldridge et al 2013;Yoon et al 2017;Götberg et al 2018;Sravan et al 2018Sravan et al , 2020, allowing progenitors of initial masses of ∼10−25 M (which have lower final cores and thus will explode in most cases) to produce SESNe. Secondly, binary stripping seems to affect the final core structure and chemical composition, on average increasing the explodability of binary stripped stars compared to single stars of the same initial mass or even the same carbon core mass (Schneider et al 2021;Laplace et al 2021;Vartanyan et al 2021).…”

Searching for Surviving Companion in the Young SMC Supernova Remnant 1E 0102.2-7219

“…They have also provided the expected broad-band photometry for these three types of companions, e.g., M V ∼ −4.65 mag, −6.22 mag, and −6.14 mag, respectively. Similarly, Sravan et al (2020) used single and binary models to probe a wider parameter space for Type IIb SNe. and found a dominant fraction of blue MS companions with 500-160,000 L and a smaller fraction of red and yellow evolved companions with 25,000-250,000 L .…”

“…This upper limit of V corresponds to a ∼2 M star in the SMC. It is a fairly safe limit for our search for surviving companions of Type IIb SNe, which are expected to be brighter than 500L in most cases (Maund et al 2004;Claeys et al 2011;Sravan et al 2020). We thus examine the spectra of photometrically selected candidates of surviving companions (i.e., those with V < 21.5 mag and near the SN explosion site) and use large radial velocities to further evaluate their nature and advance their candidacy as surviving companion of the SN progenitor.…”

SN2017jgh: a high-cadence complete shock cooling light curve of a SN IIb with the Kepler telescope

“…Stripped supernovae can show two prominent peaks in their optical light curve. The first peak is a burst of emission after the explosion known as the shock cooling light curve (SCL; Arcavi 2017; Gal-Yam 2017; Sravan et al 2020), and the second peak is nuclear powered emission fuelled by the decay of 56 Ni.…”