SN 2015bh: NGC 2770's 4th supernova or a luminous blue variable on its way to a Wolf-Rayet star?

Abstract

Very massive stars in the final phases of their lives often show unpredictable outbursts that can mimic supernovae, so-called, "SN impostors", but the distinction is not always straigthforward. Here we present observations of a luminous blue variable (LBV) in NGC 2770 in outburst over more than 20 years that experienced a possible terminal explosion as type IIn SN in 2015, named SN 2015bh. This possible SN or "main event" was preceded by a precursor peaking $\sim$ 40 days before maximum. The total energy release of the main event is $\sim$1.8$\times$10${}^{49}$ erg, which can be modeled by a $<$ 0.5 M${}_{\odot }$ shell plunging into a dense CSM. All emission lines show a single narrow P-Cygni profile during the LBV phase and a double P-Cygni profile post maximum suggesting an association of this second component with the possible SN. Since 1994 the star has been redder than during a typical S-Dor like outburst. SN 2015bh lies within a spiral arm of NGC 2770 next to a number of small star-forming regions with a metallicity of $\sim$ 0.5 solar and a stellar population age of 7-10 Myr. SN 2015bh shares many similarities with SN 2009ip, which, together with other examples may form a new class of objects that exhibit outbursts a few decades prior to "hyper-eruption" or final core-collapse. If the star survives this event it is undoubtedly altered, and we suggest that these "zombie stars" may evolve from an LBV to a Wolf Rayet star over a very short timescale of only a few years. The final fate of these types of massive stars can only be determined with observations years after the possible SN.

29 pages, 20 figures

References in corpus (25)

• Pre-Supernova Evolution of Massive Single and Binary Stars
• Pulsational pair instability as an explanation for the most luminous supernovae
• A giant outburst two years before the core-collapse of a massive star
• A Wolf-Rayet-like progenitor of supernova SN 2013cu from spectral observations of a wind
• SN 2006jc: A Wolf-Rayet Star Exploding in a Dense He-Rich Circumstellar Medium
• SN 2006tf: Precursor Eruptions and the Optically Thick Regime of Extremely Luminous Type IIn Supernovae
• Shell-shocked diffusion model for the light curve of SN2006gy
• Rapid formation of large dust grains in the luminous supernova SN 2010jl
• Optical Spectra of 73 Stripped-Envelope Core-Collapse Supernovae
• Massive stars exploding in a He-rich circumstellar medium. I. Type Ibn (SN 2006jc-like) events
• Luminous Blue Variables are Antisocial: Their Isolation Implies that they are Kicked Mass Gainers in Binary Evolution
• Luminous Blue Variables as the progenitors of supernovae with quasi-periodic radio modulations
• A Massive Progenitor of the Luminous Type IIn Supernova 2010jl
• 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
• A Blast Wave from the 1843 Eruption of Eta Carinae
• Early Emission from the Type IIn Supernova 1998S at High Resolution
• Multi-epoch spectropolarimetry of SN 2009ip: direct evidence for aspherical circumstellar material
• SN 2009kn - the twin of the Type IIn supernova 1994W
• Environments of interacting transients: Impostors and type IIn supernovae
• SN Hunt 248: a super-Eddington outburst from a massive cool hypergiant
• Ancient eruptions of Eta Carinae: A tale written in proper motions
• Mass loss of massive stars near the Eddington luminosity by core neutrino emission shortly before their explosion
• Interacting supernovae and supernova impostors. SN 2007sv: the major eruption of a massive star in UGC 5979
• SN 2009ip: Constraining the latest explosion properties by its late-phase light curve

Cited by in corpus (29)

• A Cool and Inflated Progenitor Candidate for the Type Ib Supernova 2019yvr at 2.6 Years Before Explosion
• 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
• The role of jets in exploding supernovae and in shaping their remnants
• Constraining massive star activities in the final years through properties of supernovae and their progenitors
• Supernova Precursor Emission and the Origin of Pre-Explosion Stellar Mass-Loss
• A systematic reclassification of type IIn supernovae
• The Candidate Progenitor of the Type IIn SN 2010jl is Not an Optically Luminous Star
• An H-alpha survey of the host environments of 77 type IIn supernovae within z<0.02
• Gap Transients Interacting with Circumstellar Medium
• Spectroscopic observations of progenitor activity 100 days before a Type Ibn supernova
• SN 2021foa, a transitional event between a Type IIn (SN 2009ip-like) and a Type Ibn supernova
• Detection of supernova remnants in NGC 4030
• Searching for precursor activity of Type IIn Supernovae
• Unveiling the Nature of SN 2011fh: a Young and Massive Star Gives Rise to a Luminous SN 2009ip-like Event
• Asymmetries and Circumstellar Interaction in the Type II SN 2024bch
• SNhunt151: an explosive event inside a dense cocoon
• Early light curves of Type II supernovae interacting with a circumstellar disk
• SN 2020pvb: a Type IIn-P supernova with a precursor outburst
• ASASSN-14ms:the Most Energetic Known Explosion of a Type Ibn Supernova and its Physical Origin
• Ask The Machine: Systematic detection of wind-type outflows in low-mass X-ray binaries
• A long-lasting eruption heralds SN 2023ldh, a clone of SN 2009ip
• Pre-explosion, explosion, and post-explosion jets in supernova SN 2019zrk
• High Cadence TESS and ground-based data of SN 2019esa, the less energetic sibling of SN 2006gy
• Multi-epoch variability of AT 2000ch (SN 2000ch) in NGC 3432 -- A radio continuum and optical study
• Modeling the light curve of Type IIn-P SN 2005cl with red supergiant progenitors featuring pre-SN ourbursts
• Spectropolarimetry of the 2012 outburst of SN 2009ip: a bi-polar explosion in a dense, disk-like CSM
• SN 2024hpj: A perspective on SN 2009ip-like events
• Hubble Space Telescope Imaging Reveals That SN 2015bh Is Much Fainter than Its Progenitor