Broad-band Spectroscopy of the Ongoing Large Eruption of the Luminous Blue Variable R71

Abstract

The Luminous Blue Variable (LBV) R71 is currently undergoing an eruption, which differs photometrically and spectroscopically from its last outburst in the 1970s. Valuable information on the physics of LBV eruptions can be gained by analyzing the spectral evolution during this eruption and by comparing R71's present appearance to its previous outburst and its quiescent state. Here we present the first spectra of an ongoing monitoring program with VLT/X-shooter and compare them to archival VLT/UVES and MPG/ESO-2.2m/FEROS spectra from 2002-2011. The discussed data include pre-eruption spectra in 2002 and 2005, a spectrum of the transitionary phase between quiescent and eruptive state in 2007, and spectra of the eruption in 2011-2012. The 2011-2012 spectra are dominated by strong neutral and singly ionized metal absorption lines likely formed in a large "pseudo-photosphere." We find an unusually low apparent temperature of R71 of only ~6650 K; the star resembles a late F supergiant. R71's visual lightcurve had a maximum in 2012 with mV ~ 8.7 mag. Given the uncertainty in the extinction towards R71, this corresponds to a bolometric luminosity of -9.8 mag to -10.3 mag. R71's 2011-2012 spectra do not show H I and Fe II P Cyg profiles, which were present during its last outburst in the 1970s and which are normally observed during LBV outbursts. The rise in R71's visual magnitude and the low apparent temperature of its pseudo-photosphere during the current eruption are unprecedented for this star. R71 most likely increased its bolometric luminosity by 0.4-1.3 mag compared to its quiescent state. The very low temperature of its pseudo-photosphere implies a very high-mass loss rate, a factor of 1000 higher than during the quiescence state. No fast-moving material indicative of an explosion is observed (abridged).

9 pages, 5 figures, submitted to A&A

References in corpus (5)

• An eclipsing binary distance to the Large Magellanic Cloud accurate to 2 per cent
• SN 2006tf: Precursor Eruptions and the Optically Thick Regime of Extremely Luminous Type IIn Supernovae
• SN 2008S: A Cool Super-Eddington Wind in a Supernova Impostor
• A Spitzer/IRS Spectrum of the 2008 Luminous Transient in NGC 300: Connection to Proto-Planetary Nebulae
• Spectral atlas of massive stars around He I 10830 A

Cited by in corpus (18)

• The luminosities of cool supergiants in the Magellanic Clouds, and the Humphreys-Davidson limit revisited
• On the Social Traits of Luminous Blue Variables
• Luminous and Variable Stars in M31 and M33. I. The Warm Hypergiants and Post-Red Supergiant Evolution
• Understanding Compact Object Formation and Natal Kicks. IV. The case of IC 10 X-1
• Operation of the jet feedback mechanism (JFM) in intermediate luminosity optical transients (ILOTs)
• 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
• IRAS 18357-0604 - an analogue of the galactic yellow hypergiant IRC +10420?
• The study of unclassified B[e] stars and candidates in the Galaxy and Magellanic Clouds
• Intermediate Luminosity Optical Transients (ILOTs) from merging giants
• A Tale of Two Impostors: SN2002kg and SN1954J in NGC 2403
• Gaia TGAS search for Large Magellanic Cloud runaway supergiant stars:Candidate hypervelocity star discovery, and the nature of R71
• Dust composition and mass-loss return from the luminous blue variable R71 in the LMC
• Detection of new eruptions in the Magellanic Clouds LBVs R 40 and R 110
• Luminous Blue Variables
• Search for LBVs in the Local Volume galaxies: study of two stars in NGC 1156
• The contribution by luminous blue variable stars to the dust content of the Magellanic Clouds
• Radiation-Driven Stellar Eruptions