Evolution of Massive Stars along the Cosmic History

Meynet, Georges; Ekström, Sylvia; Georgy, Cyril; Chiappini, Cristina; Maeder, A.

doi:10.1002/9783527629190.ch5

Cited by 7 publications

(7 citation statements)

References 77 publications

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“…Judging by their dense CSM resulting from episodic mass ejection, LBVs are likely to appear as SNe IIn if they explode within 10 3 yr after a major outburst Gal-Yam et al 2007). This defies current stellar evolution models, however, which predict that at solar metallicity, stars massive enough to make LBVs should end their lives as WR stars after shedding their H envelopes (e.g., Heger et al 2003;Meynet et al 1994;Maeder & Meynet 1994;Woosley et al 1993). Possible exceptions are the lower-luminosity LBVs that are post-RSGs .…”

Section: Introductionmentioning

confidence: 79%

RED SUPERGIANTS AS POTENTIAL TYPE IIn SUPERNOVA PROGENITORS: SPATIALLY RESOLVED 4.6 μm CO EMISSION AROUND VY CMa AND BETELGEUSE

Smith¹,

Hinkle

Ryde

2009

The Astronomical Journal

181

179

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We present high-resolution 4.6 µm CO spectra of the circumstellar environments of two red supergiants (RSGs) that are potential supernova (SN) progenitors: Betelgeuse and VY Canis Majoris. Around Betelgeuse, 12 CO emission within ±3 ′′ (±12 km s −1 ) follows a mildly clumpy but otherwise spherical shell, smaller than its ∼55 ′′ shell in K i λ7699. In stark contrast, 4.6 µm CO emission around VY CMa is coincident with bright K i in its clumpy asymmetric reflection nebula, within ±5 ′′ (±40 km s −1 ) of the star. Our CO data reveal redshifted features not seen in K i spectra of VY CMa, indicating a more isotropic distribution of gas punctuated by randomly distributed asymmetric clumps. The relative CO and K i distribution in Betelgeuse arises from ionization effects within a steady wind, whereas in VY CMa, K i is emitted from skins of CO cloudlets resulting from episodic mass ejections 500-1000 yr ago. In both cases, CO and K i trace potential pre-SN circumstellar matter: we conclude that an extreme RSG like VY CMa might produce a Type IIn event like SN 1988Z if it were to explode in its current state, but Betelgeuse will not. VY CMa demonstrates that luminous blue variables (LBVs) are not necessarily the only progenitors of SNe IIn, but it underscores the requirement that SNe IIn suffer enhanced episodic mass loss shortly before exploding.

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Section: Introductionmentioning

confidence: 79%

RED SUPERGIANTS AS POTENTIAL TYPE IIn SUPERNOVA PROGENITORS: SPATIALLY RESOLVED 4.6 μm CO EMISSION AROUND VY CMa AND BETELGEUSE

Smith¹,

Hinkle

Ryde

2009

The Astronomical Journal

181

179

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“…Similar Revised distance to the 1806−20 cluster L27 Table 3. Ages and progenitor masses (M OB init ) of #4 (O9.5 I) and #11 (B0 I) from Lejeune & Schaerer (2001) isochrones using Meynet et al (1994) evolutionary tracks for a variety of DM plus inferred minimum magnetar progenitor masses (M SGR init Figure 4. Comparison of present results for the distance to the 1806−20 cluster with previous cluster and magnetar distance estimates, adapted to a Galactic Centre distance of 8 kpc (Reid 1993). conclusions were reached by Figer et al (2005).…”

Section: Discussion a N D C O N C L U S I O N Smentioning

confidence: 99%

“…OB supergiants #4 (O9.5 I) and 11 (B0 I) have the best determined spectral types, from which stellar temperatures (29 and 27.5 kK) and luminosities can be derived (Crowther et al 2006b), the latter obtained from K s -band bolometric corrections (BC Ks , see Table 1). For a variety of different adopted distances, these two stars provide cluster ages using isochrones from Lejeune & Schaerer (2001), which are based upon high mass-loss rate, solar metallicity evolutionary models from Meynet et al (1994). Table 3 presents ages, OB supergiant and (minimum) magnetar initial masses for distance moduli in the range 14.0 mag (6.3 kpc) to 15.9 mag (15 kpc).…”

Section: Distance From Isochrone Fittingmentioning

confidence: 99%

A downward revision to the distance of the 1806−20 cluster and associated magnetar from Gemini Near-Infrared Spectroscopy

Bibby

Crowther

Furness

et al. 2008

Monthly Notices of the Royal Astronomical Society: Letters

117

120

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We present H‐ and K‐band spectroscopy of OB and Wolf–Rayet (WR) members of the Milky Way cluster 1806−20 (G10.0–0.3) to obtain a revised cluster distance, of relevance to the 2004 giant flare from the (soft gamma repeater) SGR 1806−20 magnetar. From GNIRS (Gemini Near‐Infrared Spectrograph) spectroscopy obtained with Gemini South, four candidate OB stars are confirmed as late O/early B supergiants, while we support previous mid‐WN and late WC classifications for two WR stars. Based upon an absolute Ks‐band magnitude calibration for B supergiants and WR stars, and near‐infrared (IR) photometry from NIRI (Near‐Infrared Imager) at Gemini North plus archival VLT/ISAAC (Very Large Telescope/Infrared Spectrometer And Array Camera) data sets, we obtain a cluster distance modulus of 14.7 ± 0.35 mag. The known stellar content of the 1806−20 cluster suggests an age of 3–5 Myr, from which theoretical isochrone fits infer a distance modulus of 14.7 ± 0.7 mag. Together, our results favour a distance modulus of 14.7 ± 0.4 mag (8.7+1.8−1.5 kpc) to the 1806−20 cluster, which is significantly lower than the nominal 15 kpc distance to the magnetar. For our preferred distance, the peak luminosity of the 2004 December giant flare is reduced by a factor of 3 to 7 × 1046 erg s−1, such that the contamination of BATSE (Burst And Transient Source Experiment) short gamma‐ray bursts (GRBs) from giant flares of extragalactic magnetars is reduced to a few per cent. We infer a magnetar progenitor mass of ∼48+20−8 M⊙, in close agreement with that obtained recently for the magnetar in Westerlund 1.

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“…Because of their high mass-loss rates and consequent emission-line spectra, they are often discussed alongside or confused with core-He burning Wolf-Rayet (WR) stars (for reviews of WR stars, see Abbott & Conti [1987] and Crowther [2007]), and it is sometimes suggested that their H content indicates that they represent the early phases of core-He burning. In this interpretation, the WNH phase occurs immediately after -or sometimes instead of -the luminous blue varibale (LBV) phase, marking the beginning of the core-He burning WR stages (see for example, Schaller et al 1993;Meynet et al 1994;Maeder & Meynet 1994).…”

Section: Introductionmentioning

confidence: 99%

On the Role of the WNH Phase in the Evolution of Very Massive Stars: Enabling the LBV Instability with Feedback

Smith¹,

Conti

2008

ApJ

108

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We propose the new designation "WNH" for luminous Wolf-Rayet (WR) stars of the nitrogen sequence with hydrogen in their spectra. These have been commonly referred to as WNL stars (WN7h, for example), but this new shorthand avoids confusion because there are late-type WN stars without hydrogen and early-type WN stars with hydrogen. Clearly differentiating WNH stars from H-poor/Hfree WN stars is critical when discussing them as potential progenitors of Type Ib/c supernovae and gamma ray bursts -the massive WNH stars are not likely Type Ib/c supernova progenitors, and are distinct from core-He burning WR stars in several respects. We show that the stellar masses of WNH stars are systematically higher than for bona fide H-poor WR stars (both WN and WC), with little overlap. Also, the hydrogen mass fractions of the most luminous WNH stars are higher than those of luminous blue variables (LBVs). These two trends favor the interpretation that the most luminous WNH stars are still core-H burning, preceding the LBV phase (at lower luminosities the WNH stars are less clearly distinguished from LBVs). While on the main sequence, a star's mass is reduced due to winds and its luminosity slowly rises, so the star increases its Eddington factor, which in turn strongly increases the mass-loss rate, pushing it even closer to the Eddington limit. Accounting for this feedback from mass loss, we show that observed masses and mass-loss rates of WNH stars are a natural and expected outcome for very luminous stars approaching the end of core-H burning (ages ∼2 Myr). Feedback from the strong WNH wind itself plays a similar role, enabling the eruptive instability seen subsequently as an LBV. Altogether, for initial masses above 40-60 M ⊙ , we find a strong and self-consistent case that luminous WNH stars are pre-LBVs rather than post-LBVs. The steady march toward increased mass-loss rates from feedback also provides a natural explanation for the continuity in observed spectral traits from O3 V to O3 If* to WNH noted previously.

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Evolution of Massive Stars along the Cosmic History

Cited by 7 publications

References 77 publications

RED SUPERGIANTS AS POTENTIAL TYPE IIn SUPERNOVA PROGENITORS: SPATIALLY RESOLVED 4.6 μm CO EMISSION AROUND VY CMa AND BETELGEUSE

RED SUPERGIANTS AS POTENTIAL TYPE IIn SUPERNOVA PROGENITORS: SPATIALLY RESOLVED 4.6 μm CO EMISSION AROUND VY CMa AND BETELGEUSE

A downward revision to the distance of the 1806−20 cluster and associated magnetar from Gemini Near-Infrared Spectroscopy

On the Role of the WNH Phase in the Evolution of Very Massive Stars: Enabling the LBV Instability with Feedback

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