Main-sequence Mass Loss Research Articles

Systematic survey of the effects of wind mass loss algorithms on the evolution of single massive stars

Mass loss is a key uncertainty in the evolution of massive stars. Stellar evolution calculations must employ parametric algorithms for mass loss, and usually only include stellar winds. We carry out a parameter study of the effects of wind mass loss on massive star evolution using the open-source stellar evolution code MESA. We provide a systematic comparison of wind mass loss algorithms for solar-metallicity, nonrotating, single stars in the initial mass range of $15-35\,M_\odot$. We consider combinations drawn from two hot phase algorithms, three cool phase algorithms, and two Wolf-Rayet algorithms. We consider linear wind efficiency scale factors of $1$, $0.33$, and $0.1$ to account for reductions in mass loss rates due to wind inhomogeneities. We find that the initial to final mass mapping for each zero-age main-sequence (ZAMS) mass has a $\sim 50\%$ uncertainty if all algorithm combinations and wind efficiencies are considered. The ad-hoc efficiency scale factor dominates this uncertainty. While the final total mass and internal structure of our models vary tremendously with mass loss treatment, final observable parameters are much less sensitive for ZAMS mass $\lesssim 30\,M_\odot$. This indicates that uncertainty in wind mass loss does not negatively affect estimates of the ZAMS mass of most single-star supernova progenitors from pre-explosion observations. Furthermore, we show that the internal structure of presupernova stars is sensitive to variations in both main sequence and post main-sequence mass loss. We find that the compactness parameter $\xi\propto M/R(M)$ varies by as much as $30\%$ for a given ZAMS mass evolved with different wind efficiencies and mass loss algorithm combinations. [abridged]

WIYN/Hydra Detection of Lithium Depletion in F Stars of the Young Open Cluster M35 and Implications for the Development of the Lithium Gap

We report the discovery of significant depletion of on the surfaces of F dwarf stars in the 150 Myr old open cluster M35, analagous to a feature in the 700 Myr old Hyades that has been referred to as the Li gap. We have caught the gap in the act of forming: using high-resolution, high signal-to-noise ratio WIYN/Hydra observations, we detect in all but a few M35 F stars; the maximum depletion lies at least 0.6-0.8 dex below minimally depleted (or undepleted) stars. The M35 depletion region (1) is quite wide, with clear depletion seen from 6000 to 6700 K or hotter, (2) shows a significant dispersion in abundance at all Teff, even with stars of the same Teff, and (3) contains undepleted stars (as well as depleted ones) in the (narrow) classical Hyades gap region, which itself shows no undepleted stars. All of these M35 depletion properties support rotationally induced slow mixing as the primary physical mechanism that forms the gap and argue against other proposed mechanisms, particularly diffusion and steady main-sequence mass loss. When viewed in the context of the M35 depletion properties, the Hyades gap may well be wider than is usually recognized.

WIYN Open Cluster Study. VI. Interpretive Models of Light‐Element Depletion from M67 Subgiants

We present evolutionary models of subgiant stars in M67 that follow the surface abundances of lithium and beryllium. These models include a number of physical processes that have been proposed as explanations for the main-sequence depletion of lithium in the Hyades. We use the observed lithium abundance as a function of temperature in M67 subgiants and the correlation between lithium and beryllium depletion to distinguish between these models. We find that constant main-sequence mass loss and diffusion are strongly ruled out as viable mechanisms for light-element depletion in main-sequence stars. Rotationally induced mixing is strongly supported by the lithium- and beryllium-depletion correlation observed in Population I field F stars; such mixing is also consistent with the lithium abundances observed in M67 subgiants, although we discuss some possible complications.

Early Solar Mass Loss, Element Diffusion, and Solar Oscillation Frequencies

view Abstract Citations (42) References (51) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Early Solar Mass Loss, Element Diffusion, and Solar Oscillation Frequencies Guzik, Joyce A. ; Cox, Arthur N. Abstract Swenson & Faulkner and Boothroyd, Sackmann, & Fowler investigated the possibility that early mainsequence mass loss via a stronger early solar wind could be responsible for the observed solar lithium and beryllium depletion. This depletion requires a total mass loss of ∼0.1 Msun, nearly independent of the mass loss timescale. We calculate the evolution and oscillation frequencies of solar models including diffusion of helium and other elements, with such early solar mass loss. We show that extreme mass loss of 1 Msun is easily ruled out by the low-degree p-modes that probe the solar center and sense the steeper molecular weight gradient produced by the early phase of more rapid hydrogen burning. The effects on central structure are much smaller for models with an initial mass of 1.1 Msun, and exponentially decreasing mass-loss rate with e-folding timescale 0.45 Gyr. While such mass loss slightly worsens the agreement between observed and calculated low-degree modes, the observational uncertainties of several tenths of a microhertz weaken this conclusion. Surprisingly, the intermediate-degree modes with much smaller observational uncertainties that probe the convection zone bottom prove to be the key to discriminating between models: The early mass-loss phase decreases the total amount of helium and heavier elements diffused from the convection zone, and the extent of the diffusion-produced composition gradient just below the convection zone. These changes in the solar composition result in a marked deterioration in the agreement with observed frequencies for the intermediate degree modes. Mass loss on a timescale substantially longer than 0.2 Gyr appears to be incompatible with observed solar oscillation frequencies. It is significant that this discrimination between models with and without mass loss is possible only when element diffusion is incorporated in the modeling. Publication: The Astrophysical Journal Pub Date: August 1995 DOI: 10.1086/176019 Bibcode: 1995ApJ...448..905G Keywords: SUN: ABUNDANCES; SUN: EVOLUTION; SUN: INTERIOR; SUN: OSCILLATIONS; SUN: SOLAR WIND full text sources ADS |

A re-examination of the beta versus (R-I) diagram for normal and metallic-lined A stars

view Abstract Citations (1) References (43) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Re-Examination of the Beta Versus (R-I) Diagram for Normal and Metallic-Lined A Stars Hakkila, Jon ; Mayer, John G. Abstract In a photometric plot of the Stromgren beta index versus the (R-I) broadband color, Weiss (1979) has identified a 'gap' corresponding to an absence of late-type normal A main-sequence stars that is occupied by the metallic-lined A (Am) stars. This gap apparently corresponds to the (B - V) depletion observed by Bohm-Vitense and Canterna (1974), which has been explained by the onset of convection at around 7700 K. Since the beta vs (R-I) gap is limited to bright A stars with nonvariable nonpeculiar spectra, the most important observational selection effects are thought to have been removed. Reexamination of this plot is necessitated by (1) updated spectral classifications and modern photometric observations, and (2) an alternative theory involving main-sequence mass loss. The revised beta vs (R-I) plot indicates that (1) a depletion (as opposed to a 'gap') exists at about the position of the red edge of the instability strip for normal main-sequence stars, (2) normal stars in the depleted region are rapid rotators, (3) pulsating variable stars might be depleted here and elsewhere in the instability strip, and (4) Am stars are found in the depleted region and 'strong' Am stars appear to be slightly redder and more luminous than 'marginal' or 'weak' ones. The results are discussed in terms of both the onset of eonvection and the main-sequence mass-loss hypothesis. Publication: The Astronomical Journal Pub Date: July 1993 DOI: 10.1086/116647 Bibcode: 1993AJ....106..383H Keywords: A Stars; Astronomical Photometry; Late Stars; Main Sequence Stars; Metallic Stars; Stellar Color; Stellar Mass Ejection; Stellar Rotation; Stellar Temperature; Astrophysics; STARS: LATE-TYPE full text sources ADS |

Lithium dilution through main-sequence mass loss

view Abstract Citations (88) References (57) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Lithium Dilution through Main-Sequence Mass Loss Swenson, Fritz J. ; Faulkner, John Abstract We investigate the consequences of main-sequence mass loss for surface lithium abundances in stars through the use of evolving, mass-losing stellar models. In particular, we attempt to model lithium depletion observed in three areas: the sun, the Hyades G dwarfs, and the Hyades F dwarfs. Mass loss as an explanation for lithium depletion has mixed success. We conclude that mass loss can be marginal explanation for the solar lithium problem. In the case of the Hyades G dwarfs (the classical Hyades lithium problem) we find, contrary to preliminary investigations by ourselves and others, that mass loss cannot be a significant contributor to the depletion seen in these stars. Furthermore, we show that quasi-analytical means alone are sufficiently accurate to model the quantitative consequences of mass loss in these stars. For the Hyades F dwarfs, mass loss is a viable, although not particularly aesthetic, explanation. We highlight features that a theory of mass loss must posses to explain the remarkable pattern of lithium depletion seen among F dwarfs in the Hyades, in other clusters, and in the field. With the results of our calculations we limit the amount of mass that may have been lost on the main sequence by Hyades F and G dwarfs. Publication: The Astrophysical Journal Pub Date: August 1992 DOI: 10.1086/171686 Bibcode: 1992ApJ...395..654S Keywords: Lithium; Main Sequence Stars; Stellar Evolution; Stellar Mass Ejection; Stellar Models; Beryllium Isotopes; Dwarf Stars; Lithium Isotopes; Star Clusters; Astrophysics; ATOMIC DATA; STARS: ABUNDANCES; STARS: EVOLUTION; STARS: MASS LOSS; GALAXY: OPEN CLUSTERS AND ASSOCIATIONS: GENERAL full text sources ADS | data products SIMBAD (8)

Mass loss and a possible Population II lithium dip

view Abstract Citations (13) References (20) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Mass Loss and a Possible Population II Lithium Dip Dearborn, David S. P. ; Schramm, David N. ; Hobbs, L. M. Abstract It is shown that the recent observation of a subplateau lithium abundance for a high-surface-temperature Population II star relative to the Population II lithium plateau can be explained by main-sequence mass loss. This explanation is identical to a previously proposed explanation for the Population I lithium dip and predicts a similar dip for Population II. It is assumed that the main-sequence mass loss in both cases is associated with the instability strip intersecting the main sequence. This mass-loss process can also decrease globular cluster ages by about 1 Gyr. Publication: The Astrophysical Journal Pub Date: August 1992 DOI: 10.1086/186472 Bibcode: 1992ApJ...394L..61D Keywords: Lithium; Main Sequence Stars; Stellar Mass Ejection; Abundance; Globular Clusters; Stellar Evolution; Stellar Temperature; Astrophysics; STARS: ABUNDANCES; STARS: EVOLUTION; STARS: MASS LOSS; STARS: POPULATION II full text sources ADS | data products SIMBAD (2)

Our sun. II - Early mass loss of 0.1 solar mass and the case of the missing lithium

It is demonstrated that early main-sequence mass loss by the sun can solve the case of the missing solar Li. The mass loss is 0.10-0.11 solar if the ZAMS Li-7/H ratio is taken to be 1.0 x 10 to the -9th, the maximum value observed in Population I main-sequence stars. The mass loss is 0.12-0.13 solar if ZAMS Li-7/H is taken to be 2.6 x 10 to the -9th, the meteoritic value. The required amount of mass loss is nearly independent of the mass-loss time scale. A simple formula exists to estimate the amount of mass loss required by an observed Li depletion. Constant-mass models burn Li and Be at temperatures of 2.5 and 3.3 million K, respectively. Higher initial temperatures are required in mass-losing models. A prescription has been developed to estimate these temperatures as a function of initial stellar mass and initial mass-loss rate.

The lithium dip and Scuti variables: observational evidence, main-sequence mass loss and blue stragglers

The implications of observational evidence on the recent suggestion that the lithium dip seen in older galactic clusters is due to substantial main-sequence mass loss from δ Sct stars are analyzed. Examination of evidence for such mass loss in δ Sct stars, the relative locations of the instability strip and the lithium dip, and the implied mass-loss rates for a δ Sct star to evolve down the main sequence to the lithium dip are all inconsistent with these pulsational variables being the progenitors of lithium dips. The lithium abundance determinations in blue stragglers and δ Sct stars are still too few to make definitive statements as to the validity of the mass-loss hypothesis, but at present do not appear to favour this specific scenario

Main-sequence mass loss and the lithium dip

The significant dip in observed lithium abundances for Population I stars near M about 1.3 solar mass is discussed. It is noted that this dip occurs near where the instability strip crosses the main sequence on the lower edge of the Delta Scuti stars and that stellar pulsations are expected to give rise to mass loss. A total mass loss of 0.05 solar mass over the main-sequence lifetime of these stars would be sufficient to explain the observations of lithium depletion. The absence of a dip in the Pleiades and of significant depletion of beryllium in the Hyades places tight constraints on the rate of mass loss. These constraints make unlikely the high main-sequence mass-loss rates which would significantly affect globular cluster ages.

Main Sequence Mass Loss and the Ages of Starsa

The potentially observable consequences of the pulsation/rotation-induced mass loss from main-sequence A and F stars proposed by Willson et al. (1987) are discussed, reviewing the results of recent investigations. Particular attention is given to (1) evidence for a deficiency in A stars and an excess of F and G stars, as predicted by the theory, (2) cluster HR diagrams and age estimates, and (3) modifications to standard models of solar-system evolution. It is pointed out that the time scales and mass-loss rates required to explain the observed properties of clusters and field stars in this theory are the same as those needed to account for the early development of the solar system.

The Effects of Main-Sequence Mass Loss on Surface C/N Abundance Ratios During the Ascent of the First Giant Branch

The surface C/N abundance ratios of many cluster and field G and K giants following the 1st dredge-up phase are much lower than predicted from standard stellar evolution modeling. The occurrence of substantial mass loss, either during or immediately after the main-sequence phase would both reduce the mass fraction of the unprocessed envelope necessary to contaminate with CN-cycle products, as well as allow CN-processing of a greater amount of core material during the earlier high-mass phase. Willson, Bowen and Struck-Marcell (1987) have proposed that a combination of pulsation and rapid rotation could drive substantial mass loss in main-sequence stars of initial mass 1-3 MΘ. We evolved a grid of 16 mass-losing models from the zero-age main sequence through 1st dredge-up. The models have initial masses of 1.25, 1.5, 1.75 and 2.0 MΘ, and exponentially decreasing mass-loss rates with e-folding times 0.2, 0.4, 1.0 and 2.0 Gyr; all models evolve toward a final mass of 1.0 M". Since the mass-loss epoch is short-lived, most of the models reach 1.0 M0 rapidly, and follow the evolutionary track of a standard 1 MΘ model redward away from the main sequence and up the 1st giant branch. The convecuve envelope deepens during 1st dredge-up to homogenize the outer 3/4 of the star's final mass.

Galactic chemical evolution with main-sequence mass loss and the distribution of F and G dwarfs

Simple closed galactic chemical-evolution models incorporating early main-sequence stellar mass loss have been developed for disk ages of 5, 10, and 15 Gyr. Relative to models without stellar mass loss, the models are shown to produce a 30-60 percent increase in the present mass ratio of dwarfs to dwarfs plus remnants, and a 200-250 percent increase in the total mass of late F dwarfs remaining on the main sequence at the current disk age. For present disk ages 5 and 10 Gyr, the total mass of mid-F dwarfs remaining on the main sequence is also shown to increase by 90-120 percent. It is concluded that models with main-sequence mass loss have a slightly reduced gas metallicity and slightly increased gas fraction midway through the evolution. 30 references.

A comparison between mass-losing and standard solar models

view Abstract Citations (52) References (28) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Comparison between Mass-losing and Standard Solar Models Guzik, Joyce A. ; Willson, L. A. ; Brunish, Wendee M. Abstract The effects of main-sequence mass loss on the evolution, interior structure, and surface composition of the sun are studied. Modeling results are presented for three mass-losing solar models of initial mass two solar, plus a standard one solar mass comparison model. It is shown that the solar models can be evolved to produce present-day solar models that do not differ radically in structure and composition from standard solar models. The mass-losing models require low initial He-4 abundances and predict high surface He-3 abundances that are near the limits, yet still within the bounds, of observational estimates. The mass-losing models have somewhat higher B-8 neutrino fluxes, but standard solar models also fail to reproduce observations by a wide margin. For mass-losing models, protosolar Li and Be are completely destroyed, requiring a mechanism for partial replenishment to observed surface abundances. Publication: The Astrophysical Journal Pub Date: August 1987 DOI: 10.1086/165512 Bibcode: 1987ApJ...319..957G Keywords: Solar Physics; Stellar Evolution; Stellar Mass Ejection; Stellar Models; Abundance; Main Sequence Stars; Mass To Light Ratios; Stellar Interiors; Astrophysics; STARS: EVOLUTION; STARS: MASS LOSS; SUN: INTERIOR full text sources ADS |

Beryllium in the Hyades

Spectrograms of 6.7 A mm/sup -1/ have been obtained of six dwarfs and four giants in the Hyades Cluster to determine the Be/H content from one of the Be II resonance lines, lambda3131.064. A model-atmosphere abundance program was used which yielded a mean Be/H of 1.0 x 10/sup -11/ for the dwarfs and < or =3.1 x 10/sup -13/ for the giants. The Be content of the cluster dwarfs agrees well with that of field stars found by Boesgaard. The Be in both field stars and the Hyades can be explained through galactic--cosmic-ray (GCR) spallation reactions. The Li/Be ratio in the Hyades dwarfs is 80, in agreement with the cosmic Li/Be. Both Be and Li are deficient in the giants compared with their abundances in the dwarfs. A combination of post--main-sequence mass loss and dilution from any expanding convective envelope is required to explain the observed deficiencies. A mass-loss rate of 8 x 10/sup -11/ M/sub sun/ yr/sup -1/ appears to be sufficient.