Catching a star before explosion: the luminous blue variable progenitor of SN 2015bh

Abstract

In this paper we analyse the pre-explosion spectrum of SN2015bh by performing radiative transfer simulations using the CMFGEN code. This object has attracted significant attention due to its remarkable similarity to SN2009ip in both its pre- and post-explosion behaviour. They seem to belong to a class of events for which the fate as a genuine core-collapse supernova or a non-terminal explosion is still under debate. Our CMFGEN models suggest that the progenitor of SN2015bh had an effective temperature between 8700 and 10000 K, luminosity in the range ~ 1.8-4.74e6 Lsun, contained at least 25% H in mass at the surface, and half-solar Fe abundances. The results also show that the progenitor of SN 2015bh generated an extended wind with a mass-loss rate of ~ 6e-4 to 1.5e-3 Msun/yr and a velocity of 1000 km/s. We determined that the wind extended to at least 2.57e14 cm and lasted for at least 30 days prior to the observations, releasing 5e-5 Msun into the circumstellar medium. In analogy to 2009ip, we propose that this is the material that the explosive ejecta could interact at late epochs, perhaps producing observable signatures that can be probed with future observations. We conclude that the progenitor of SN 2015bh was most likely a warm luminous blue variable of at least 35 Msun before the explosion. Considering the high wind velocity, we cannot exclude the possibility that the progenitor was a Wolf-Rayet star that inflated just before the 2013 eruption, similar to HD5980 during its 1994 episode. If the star survived, late-time spectroscopy may reveal either a similar LBV or a Wolf-Rayet star, depending on the mass of the H envelope before the explosion. If the star exploded as a genuine SN, 2015bh would be a remarkable case of a successful explosion after black-hole formation in a star with a possible minimum mass 35 Msun at the pre-SN stage.

13 pages, 10 figures, accepted for publication in A&A

References in corpus (26)

• Binary interaction dominates the evolution of massive stars
• Physical Properties of Wolf-Rayet Stars
• Pre-Supernova Evolution of Massive Single and Binary Stars
• Confined Dense Circumstellar Material Surrounding a Regular Type II Supernova: The Unique Flash-Spectroscopy Event of SN 2013fs
• A Wolf-Rayet-like progenitor of supernova SN 2013cu from spectral observations of a wind
• The Galactic WC stars: Stellar parameters from spectral analyses indicate a new evolutionary sequence
• PTF11iqb: Cool supergiant mass loss that bridges the gap between Type IIn and normal supernovae
• A Massive Progenitor of the Luminous Type IIn Supernova 2010jl
• SN 1994W: An Interacting Supernova or Two Interacting Shells?
• Numerical simulations of super-luminous supernovae of type IIn
• SN 2005 gj: Evidence for LBV supernovae progenitors?
• Early-time spectra of supernovae and their precursor winds: the luminous blue variable/yellow hypergiant progenitor of SN 2013cu
• Early Emission from the Type IIn Supernova 1998S at High Resolution
• Dead or Alive? Long-term evolution of SN 2015bh (SNhunt275)
• Supernovae 2016bdu and 2005gl, and their link with SN 2009ip-like transients: another piece of the puzzle
• Connecting the progenitors, pre-explosion variability, and giant outbursts of luminous blue variables with Gaia16cfr
• SN 2015bh: NGC 2770's 4th supernova or a luminous blue variable on its way to a Wolf-Rayet star?
• PTF 13efv - An outburst 500 days prior to the SNHunt 275 explosion and its radiative efficiency
• Explaining Two Recent Intermediate Luminosity Optical Transients (ILOTs) by a Binary Interaction and Jets
• The multiplicity of massive stars: a 2016 view
• On the behaviour of stellar winds that exceed the photon-tiring limit
• Clues to the Nature of SN 2009ip II: The Continuing Photometric and Spectroscopic Evolution to 1000 Days
• SN 2009ip: Constraining the latest explosion properties by its late-phase light curve
• FUSE observations of HD 5980: The wind structure of the eruptor
• A changing wind collision
• Photometry and spectroscopy of SN 2015bh in the galaxy NGC 2770

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