A new and unusual LBV-like outburst from a Wolf-Rayet star in the outskirts of M33

Abstract

MCA-1B (also called UIT003) is a luminous hot star in the western outskirts of M33, classified over 20yr ago with a spectral type of Ofpe/WN9 and identified then as a candidate luminous blue variable (LBV). Palomar Transient Factory data reveal that this star brightened in 2010, with a light curve resembling that of the classic LBV star AFAnd in M31. Other Ofpe/WN9 stars have erupted as LBVs, but MCA-1B was unusual because it remained hot. It showed a WN-type spectrum throughout its eruption, whereas LBVs usually get much cooler. MCA-1B showed an almost four-fold increase in bolometric luminosity and a doubling of its radius, but its temperature stayed around 29kK. As it faded, it shifted to even hotter temperatures, exhibiting a WN7/WN8-type spectrum, and doubling its wind speed. MCA-1B is reminiscent of some supernova impostors, and its location resembles the isolated environment of SN 2009ip. It is most similar to HD5980 (in the SMC) and GR 290 (also in M33). Whereas these two LBVs exhibited B-type spectra in eruption, MCA-1B is the first clear case where a Wolf-Rayet (WR) spectrum persisted at all times. Together, MCA-1B, HD 5980, and GR 290 constitute a class of WN-type LBVs, distinct from S Doradus LBVs. They are most interesting in the context of LBVs at low metallicity, a possible post-LBV/WR transition in binaries, and as likely Type~Ibn supernova progenitors.

accepted in MNRAS. 20 pages, 15 figures

References in corpus (22)

• A giant outburst two years before the core-collapse of a massive star
• A Survey of Local Group Galaxies Currently Forming Stars. I. UBVRI Photometry of Stars in M31 and M33
• The Galactic WN stars: Spectral analyses with line-blanketed model atmospheres versus stellar evolution models with and without rotation
• SN 2006jc: A Wolf-Rayet Star Exploding in a Dense He-Rich Circumstellar Medium
• 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
• A Survey of Local Group Galaxies Currently Forming Stars: III. A Search for Luminous Blue Variables and Other H-alpha Emission-Lined Stars
• Luminous Blue Variables and superluminous supernovae from binary mergers
• The spectroscopic Hertzsprung-Russell diagram
• The metallicity gradient of M 33: chemical abundances of HII regions
• Orbits of Massive Satellite Galaxies: I. A Close Look at the Large Magellanic Cloud and a New Orbital History for M33
• On the role of the WNH phase in the evolution of very massive stars: Enabling the LBV instability with feedback
• Multi-epoch spectropolarimetry of SN 2009ip: direct evidence for aspherical circumstellar material
• Massive stars exploding in a He-rich circumstellar medium. IV. Transitional Type Ibn Supernovae
• The HD5980 multiple system: Masses and evolutionary status
• Type Ibn Supernovae May not all Come from Massive Stars
• On Rejuvenation in Massive Binary Systems
• Massive stars dying alone: The extremely remote environment of SN 2009ip
• The isolation of Luminous Blue Variables: On subdividing the sample
• Light Echoes from Eta Carinae's Great Eruption: Spectrophotometric Evolution and the Rapid Formation of Nitrogen-rich Molecules
• Spectroscopic and photometric oscillatory envelope variability during the S Doradus outburst of the Luminous Blue Variable R71
• The 2006 hot phase of Romano's star (GR 290) in M33

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• The Panchromatic Hubble Andromeda Treasury: Triangulum Extended Region (PHATTER) I. Ultraviolet to Infrared Photometry of 22 Million Stars in M33
• Evidence for past interaction with an asymmetric circumstellar shell in the young SNR Cassiopeia A
• Wind-envelope interaction as the origin of the slow cyclic brightness variations of luminous blue variables
• SN 2018gjx reveals that some SNe Ibn are SNe IIb exploding in dense circumstellar material
• An H-alpha survey of the host environments of 77 type IIn supernovae within z<0.02
• Comparison between the first and second mass eruptions from progenitors of Type IIn supernovae
• Investigating 39 Galactic Wolf-Rayet stars with VLTI/GRAVITY: Uncovering A Long Period Binary Desert
• Luminous Blue Variables
• ASASSN-14ms:the Most Energetic Known Explosion of a Type Ibn Supernova and its Physical Origin
• Kinematics of Luminous Blue Variables in the Large Magellanic Cloud
• How long can LBVs sleep? A long-term photometric vaiability and spectral study of the Galactic candidate luminous blue variable MN112
• On variability of DDO68-V1, a unique extremely metal-poor LBV
• A machine-learning photometric classifier for massive stars in nearby galaxies II. The catalog
• Discovery of a 310-day Period from the Enshrouded Massive System NaSt1 (WR 122)
• Spectroscopy of AT 2016blu's recurring supernova impostor outbursts