The First Empirical Mass-Loss Law for Population II Giants

Origlia, L.; Rood, Robert T.; Fabbri, S.; Ferraro, F. R.; Pecci, F. Fusi; Rich, R. Michael

doi:10.1086/521980

Cited by 102 publications

(174 citation statements)

References 24 publications

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“…While we underline that A41, page 8 of 15 ours is an empirical result based on evolutionary models, we notice that the mass loss rate measures are instantaneous values that may differ substantially from the values integrated over the whole RGB phase, since it is very likely that mass loss is episodic (see e.g. Origlia et al 2007). We also note that our result does not exclude that a small minority of stars in 47 Tuc have very different mass loss histories due e.g.…”

Section: Na-o Anticorrelationmentioning

confidence: 77%

The Na-O anticorrelation in horizontal branch stars

Gratton

Lucatello

Sollima

et al. 2012

A&A

108

127

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To check the impact of the multiple population scenario for globular clusters on their horizontal branch (HB), we present an analysis of the composition of 110 red HB (RHB) stars in 47 Tucanae and of 61 blue HB (BHB) and 30 RHB stars in M 5. In 47 Tuc we found tight relations between the colours of the stars and their abundances of p-capture elements. This strongly supports the idea that the He content -which is expected to be closely correlated with the abundances of p-capture elements -is the third parameter (after overall metallicity and age) that determines the colour of HB stars. However, the range in He abundance must be small (ΔY < 0.03) in 47 Tuc to reproduce our observations; this agrees with previous analyses. There is possibly a correlation between the abundances of p-and n-capture elements in 47 Tuc. If confirmed, this might suggest that asymptotic giant branch stars of moderate mass contributed to the gas from which second-generation stars formed. Considering the selection effects in our sample (which does not include stars warmer than 11 000 K and RR Lyrae variables, which were excluded because we could not obtain accurate abundances with the adopted observing procedure) is important to understand our results for M 5. In this case, we find that, as expected, RHB stars are Na-poor and O-rich, and likely belong to the primordial population. There is a clear correlation of the [Na/O] ratio and N abundance with colour along the BHB. A derivation of the He abundance for these stars yields a low value of Y = 0.22 ± 0.03. This is expected because HB stars of a putative He-rich population in this cluster should be warmer than 11 000 K, and would accordingly not have been sampled by our analysis. However, we need some additional source of scatter in the total mass loss of stars climbing up the red giant branch to reproduce our results for M 5. Finally, we found a C-star on the HB of 47 Tuc and a Ba-rich, fast-rotating, likely binary star on the HB of M 5. These stars are among the brightest and coolest HB stars.

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Section: Na-o Anticorrelationmentioning

confidence: 77%

The Na-O anticorrelation in horizontal branch stars

Gratton

Lucatello

Sollima

et al. 2012

A&A

108

127

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“…However, we note that this does not mean that these stars do not have circumstellar material. As shown by Origlia et al (2007), moderate (∼0.5 mag) excess in K − 8 μm is not detectable in the near IR.…”

Section: Circumstellar Materials and Infrared Excessmentioning

confidence: 90%

Li-rich red giant branch stars in the Galactic bulge

Gonzalez

Zoccali²,

Monaco

et al. 2009

A&A

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Aims. We present lithium abundance determination for a sample of K giant stars in the Galactic bulge. The stars presented here are the only 13 stars with a detectable lithium line (6767.18 Å) among ∼400 stars for which we have spectra in this wavelength range, half of them in Baade's Window (b = −4 • ) and half in a field at b = −6 • . Methods. The stars were observed with the GIRAFFE spectrograph of FLAMES mounted on VLT, with a spectral resolution of R ∼ 20 000. Abundances were derived from spectral synthesis and the results are compared with those of stars with similar parameters, but no detectable Li line. Results. We find 13 stars with a detectable Li line, among which 2 have abundances A(Li) > 2.7. No clear correlations were found between the Li abundance and those of other elements. With the exception of the two most Li rich stars, the others follow a fairly tight A(Li) − T eff correlation. Conclusions. There is strong indication of a Li production phase during the red giant branch (RGB), acting either on a very short timescale, or selectively only in some stars. That the proposed Li production phase is associated with the RGB bump cannot be excluded, although our targets are significantly brighter than the predicted RGB bump magnitude for a population at 8 kpc.

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“…Since not all giants display excess infrared emission, mass loss associated with dust appears to be episodic (Origlia et al 2007;Mészáros et al 2008). Caloi & D'Antona (2008) further suggest that the mass loss rate might be "sharply" peaked at one value along the RGB.…”

Section: Introductionmentioning

confidence: 98%

Fast Winds and Mass Loss From Metal-Poor Field Giants

Dupree

Smith

Strader

2009

The Astronomical Journal

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Echelle spectra of the infrared He i λ10830 line were obtained with NIRSPEC on the Keck 2 telescope for 41 metal-deficient field giant stars including those on the red giant branch (RGB), asymptotic giant branch (AGB), and red horizontal branch (RHB). The presence of this He i line is ubiquitous in stars with T eff 4500 K and M V fainter than −1.5, and reveals the dynamics of the atmosphere. The line strength increases with effective temperature for T eff 5300 K in RHB stars. In AGB and RGB stars, the line strength increases with luminosity. Fast outflows ( 60 km s −1 ) are detected from the majority of the stars and about 40% of the outflows have sufficient speed as to allow escape of material from the star as well as from a globular cluster. Outflow speeds and line strengths do not depend on metallicity for our sample ([Fe/H]= −0.7 to −3.0), suggesting the driving mechanism for these winds derives from magnetic and/or hydrodynamic processes. Gas outflows are present in every luminous giant, but are not detected in all stars of lower luminosity indicating possible variability. Mass loss rates ranging from ∼3 × 10 −10 to ∼6 × 10 −8 M yr −1 estimated from the Sobolev approximation for line formation represent values with evolutionary significance for red giants and RHB stars. We estimate that 0.2 M will be lost on the RGB, and the torque of this wind can account for observations of slowly rotating RHB stars in the field. About 0.1-0.2 M will be lost on the RHB itself. This first empirical determination of mass loss on the RHB may contribute to the appearance of extended horizontal branches in globular clusters. The spectra appear to resolve the problem of missing intracluster material in globular clusters. Opportunities exist for "wind smothering" of dwarf stars by winds from the evolved population, possibly leading to surface pollution in regions of high stellar density.

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The First Empirical Mass-Loss Law for Population II Giants

Cited by 102 publications

References 24 publications

The Na-O anticorrelation in horizontal branch stars

The Na-O anticorrelation in horizontal branch stars

Li-rich red giant branch stars in the Galactic bulge

Fast Winds and Mass Loss From Metal-Poor Field Giants

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