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Review
. 2017 Oct 28;375(2105):20160268.
doi: 10.1098/rsta.2016.0268.

Luminous blue variables and the fates of very massive stars

Nathan Smith  1
Affiliations
Review

Luminous blue variables and the fates of very massive stars

Nathan Smith. Philos Trans A Math Phys Eng Sci. .

Abstract

Luminous blue variables (LBVs) had long been considered massive stars in transition to the Wolf-Rayet (WR) phase, so their identification as progenitors of some peculiar supernovae (SNe) was surprising. More recently, environment statistics of LBVs show that most of them cannot be in transition to the WR phase after all, because LBVs are more isolated than allowed in this scenario. Additionally, the high-mass H shells around luminous SNe IIn require that some very massive stars above 40 M⊙ die without shedding their H envelopes, and the precursor outbursts are a challenge for understanding the final burning sequences leading to core collapse. Recent evidence suggests a clear continuum in pre-SN mass loss from super-luminous SNe IIn, to regular SNe IIn, to SNe II-L and II-P, whereas most stripped-envelope SNe seem to arise from a separate channel of lower-mass binary stars rather than massive WR stars.This article is part of the themed issue 'Bridging the gap: from massive stars to supernovae'.

Keywords: mass loss; stellar evolution; stellar winds; supernovae.

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Conflict of interest statement

The authors declare that there are no competing interests.

Figures

Figure 1.
Figure 1.
LBVs on the HR diagram, from Smith et al. [13], showing the standard locations of the quiescent S Doradus instability strip and the constant temperature strip of LBVs at their maximum light phase in S Dor variations.
Figure 2.
Figure 2.
Cumulative distribution plot illustrating the differing degrees of isolation among various classes of massive stars in the LMC, from Smith & Tombleson [28]. Classes of objects that are more clustered with young O-type stars appear farther to the left. The relative isolation is represented here by the distribution of distances to the nearest O-type star of any spectral type or luminosity class. The sample includes all O-type stars, WR stars, LBVs, sgB[e] stars and RSGs within a 10° projected radius of 30 Dor (except for the SMC stars). The O-type stars are further subdivided into early (O5 and earlier; green), mid (O6+O7, orange) and late (O8+O9, cyan) subtypes. For WR stars, we show WC stars (magenta), a collection of all WN stars including WNH stars (solid blue), as well as WN stars without WNH (dashed blue). The mustard dot-dashed line is for all H-poor WR stars (WN+WC). For LBVs, we include both LMC and SMC targets (the separation of the three SMC targets has been multiplied by 1.2 to adjust for the difference in distance), and we include both confirmed and candidate LBVs. RSGs (red) are stars with spectral types later than K3 and luminosity classes of I, Ia or Iab, and the supergiant B[e] sample (cyan dashed) is from the literature [32,33]. See Smith & Tombleson [28] for further details. (Online version in colour.)
Figure 3.
Figure 3.
HR diagram (similar to figure 1 but with an expanded L scale) comparing LBVs and some model evolutionary tracks. The LBVs plotted here are the same as in Smith et al. [13], with some updates as noted by Smith & Tombleson [28]. The evolutionary tracks are from fig. 4a in Langer & Kudritzki [39], although as they note, the single-star tracks up to 60 M⊙ are originally from Brott et al. [40]. The blue dotted tracks are single-star evolution tracks for Z⊙ and an initial rotation speed of 100 km s−1. The solid blue and red tracks are for a binary system that undergoes Roche lobe overflow (RLOF)on the main sequence, with an initially 16 M⊙ mass donor and an initially 14 M⊙ mass gainer. This illustrates just one example of how a star that initially had a relatively low mass can end up as a much more luminous star that could resemble the low-luminosity LBVs; binary systems with higher initial masses might obviously populate the more extreme LBVs in a similar manner [37]. For reference, the approximate locations of supergiant B[e] stars and BSGs are shown, as are the progenitor of SN 1987A and the putative companion of SN 1993J's progenitor. (Online version in colour.)
Figure 4.
Figure 4.
Evidence for shock powering of LBV giant eruptions, from Smith et al. [44]. (a) A comparison of the early (day 34) and late-time (day 1836) spectra for UGC 2773-OT, highlighting the excess blue emission. Both spectra are normalized to the red continuum level, and in fact the red spectra appear very similar except for Hα and Ca+. In the blue,there is a clear excess of line emission at late times. (b) Isolates this excess blue emission by subtracting the normalized day 34 spectrum from the normalized day 1836 spectrum. The grey plot is the residual, and the black plot is a smoothed version of the residual emission. This residual is compared to the ‘blue pseudo-continuum’ seen in SN 2005ip (red) on day 905 [45], which is characteristic of the forest of blue emission lines seen in interacting SNe IIn. This indicates that the excess blue line emission in UGC 2773-OT is most likely powered by a shock interacting with CSM. (Online version in colour.)
Figure 5.
Figure 5.
Comparison between the asymmetric Hα line profile observed in UGC 2773-OT and the H2 emission from the Homunculus nebula around η Carinae. (a) The two-dimensional long-slit spectrum of H2 S(1-0) 2.122 μm emission from the Homunculus [25]. Panel (b) compares the lineprofile of this H2 emission integrated along the slit (meant to mimic the integrated H2 line profile observed for the whole Homunculus nebula). This is the thick orange curve, which is compared to the Hα profile observed in UGC 2773-OT (black). From Smith et al. [44]. (Online version in colour.)
Figure 6.
Figure 6.
Plot of mass-loss rate as a function of wind velocity, comparing values for interacting SNe to those of known types of stars. The solid coloured regions correspond to values for various types of evolved massive stars taken from Smith [1], corresponding to asymptotic giant branch (AGB) and super-AGB stars, red supergiants (RSGs) and extreme RSGS (eRSG), yellow supergiants (YSG), yellow hypergiants (YHG), LBV winds and LBV giant eruptions, binary Roche-lobe overflow (RLOF), luminous WN stars with hydrogen (WNH) and H-free WN and WC Wolf–Rayet (WR) stars. A few individual stars with well-determinedvery high mass-loss rates are shown with circles (VY CMa, IRC+10420, η Car's eruptions and P Cyg's eruption). Also shown with ‘X's are some representative examples of SNe IIn (and one SN Ibn) that have observational estimates of the pre-shock CSM speed from the narrow emission component as measured in moderately high-resolution spectra as well as estimates of the progenitor mass loss required, taken from the literature. The diagonal lines are wind density parameters (formula image) of 5×1016 and 5×1015 g cm−1, which are typically the lowest wind densities required to make a SN IIn. Note that in some cases, an observationally derived value for the mass of the CSM has been converted to a mass-loss rate with a rough estimate of the time elapsed since ejection (figure from [51]). (Online version in colour.)
See this image and copyright information in PMC

References

    1. Smith N. 2014. Mass loss: its effect on the evolution and fate of high-mass stars. Annu. Rev. Astron. Astrophys. 52, 487–528. ( 10.1146/annurev-astro-081913-040025) - DOI
    1. Smith N, Owocki SP. 2006. On the role of continuum-driven eruptions in the evolution of very massive stars and population III stars. Astrophys. J. 645, L45 ( 10.1086/506523) - DOI
    1. Smith N, Li W, Silverman JM, Ganeshalingam M, Filippenko AV. 2011. Luminous blue variable eruptions and related transients: diversity of progenitors and outburst properties. Mon. Not. R. Astron. Soc. 415, 773–810. ( 10.1111/j.1365-2966.2011.18763.x) - DOI
    1. Van Dyk SD, Matheson T. 2012. The supernova impostors. In Eta Carinae and the supernova impostors (eds K Davidson, RM Humphreys). Astrophysics and Space Science Library, vol. 384, pp. 249–274. Boston, MA: Springer ( 10.1007/978-1-4614-2275-4.11) - DOI
    1. Conti PS. 1984. In Observational tests of the stellar evolution theory (eds A Maeder, A Renzini). IAU Symp. no. 105, pp. 233–254 (Dordrecht, The Netherlands: Reidel).

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