Fundamental properties of core-collapse supernova and GRB progenitors: predicting the look of massive stars before death

Abstract

We investigate the fundamental properties of core-collapse supernova (SN) progenitors from single stars at solar metallicity. For this purpose, we combine Geneva stellar evolutionary models with initial masses of M ini = 20−120 M with atmospheric and wind models using the radiative transfer code CMFGEN. We provide synthetic photometry and high-resolution spectra of hot stars at the pre-SN stage. For models with M ini = 9−20 M , we supplement our analysis using publicly available MARCS model atmospheres of RSGs to estimate their synthetic photometry. We employ well-established observational criteria of spectroscopic classification and find that, depending on their initial mass and rotation, massive stars end their lives as red supergiants (RSG), yellow hypergiants (YHG), luminous blue variables (LBV), and Wolf-Rayet (WR) stars of the WN and WO spectral types. For rotating models, we obtained the following types of SN progenitors:, and RSGs (9 ≤ M ini ≤ 18 M ). For non-rotating models, we found spectral types WO1-, and RSGs (9 ≤ M ini ≤ 20 M ). Our rotating models indicate that SN IIP progenitors are all RSG, SN IIL/b progenitors are 56% LBVs and 44% YHGs, SN Ib progenitors are 96% WN10-11 and 4% WOs, and SN Ic progenitors are all WO stars. We find that the most massive and luminous SN progenitors are not necessarily the brightest ones in a given filter, since this depends on their luminosity, temperature, wind density, and the way the spectral energy distribution compares to a filter bandpass. We find that SN IIP progenitors (RSGs) are bright in the RIJHK S filters and faint in the UB filters. SN IIL/b progenitors (LBVs and YHGs), and SN Ib progenitors (WNs) are relatively bright in optical/infrared filters, while SN Ic progenitors (WOs) are faint in all optical filters. We argue that SN Ib and Ic progenitors from single stars should be undetectable in the available pre-explosion images with the current magnitude limits, in agreement with observational results.

Helium stars: towards an understanding of Wolf–Rayet evolution

“…Gräfener, Owocki & Vink (2012) created models suggesting the envelopes of these stars can be inflated; the radii of stellar evolution models are too small by a significant factor. This is in agreement with the detailed atmospheric models calculated by Groh et al (2013) for the Geneva stellar evolution models; hydrogen-free WN stars should be much hotter than we observe them to be. Inflation may solve this problem; however, such inflation is likely dependent on the mass-loss history of the star.…”

“…However, they differ in terms of mass: WO stars are from the most massive of stars (an initial helium star mass of 13 M ), while WC stars come from less massive stars (an initial helium star mass of 13 M ). Similar findings were made by Groh et al (2013) and Sander, Hamann & Todt (2012). We note that adding clumping improves the agreement but we find that WO stars must be unclumped.…”

“…It is, therefore, expected that helium giant Type Ib/c progenitors will be observable, while progenitors from WR stars will remain difficult to detect. However, we propose that these WR-star progenitors are not as faint as those suggested by Yoon et al (2012) and Groh et al (2013). We find brighter progenitors as our stars cool towards the end of their evolution, and so more radiation is emitted in the optical bands than these hotter models.…”

“…10) for the stars, compare well qualitatively with other similar models. For example, those by Habets (1986); Vanbeveren et al (1998);Wellstein & Langer (1999); Dewi et al (2002);Eldridge, Izzard & Tout (2008) ;Sander, Hamann & Todt (2012); Groh et al (2013);Sanyal et al (2015). The only significant difference between models is with the high-mass helium stars, which move on to the WR hook (or loop) during the WO phase following core-helium burning.…”

Multi-epoch VLTI-PIONIER imaging of the supergiant V766 Cen

“…Their characterization and location in the Hertzsprung-Russell (HR) diagram are important to calibrate stellar evolutionary models of massive stars and to understand their further evolution toward SNe (e.g., Dessart et al 2013;Groh et al 2013Groh et al , 2014. The majority of massive stars are members of binary systems with a preference for close pairs (Podsiadlowski 2010;Sana et al 2012).…”