Low and intermediate-mass close binary evolution and the initial - final mass relation

Using Eggleton's stellar evolution code, we carry out 150 runs of Pop I binary evolution calculations, with the initial primary mass between 1 and 8 solar masses the initial mass ratio between 1.1 and 4, and the onset of Roche lobe overflow (RLOF) at an early, middle, or late Hertzsprung-gap stage. We assume that RLOF is conservative in the calculations, and find that the remnant mass of the primary may change by more than 40 per cent over the range of initial mass ratio or orbital period, for a given primary mass. This is contrary to the often-held belief that the remnant mass depends only on the progenitor mass if mass transfer begins in the Hertzsprung gap. We fit a formula, with an error less than 3.6 per cent, for the remnant (white dwarf) mass as a function of the initial mass of the primary, the initial mass ratio, and the radius of the primary at the onset of RLOF. We also find that a carbon-oxygen white dwarf with mass as low as 0.33 solar masses may be formed if the primary's initial mass is around 2.5 solar masses.Comment: 7 pages for main text, 11 pages for appendix (table A1), 12 figure

La herencia del coro griego en el teatro de A. Buero Vallejo. El caso de "El sueño de la razón"

Varios especialistas aluden a la presencia de figuras y funciones corales en la obra de Buero Vallejo, sin profundizar, no obstante, en la materia. Al mismo tiempo, el propio Buero escribe algunos tratados sobre la tragedia y lo trágico en los que sostiene la supervivencia del coro en el drama moderno. Estas dos observaciones nos han impulsado a estudiar la herencia del coro clásico en la obra del dramaturgo, en particular, la función de las voces de las pinturas en “El sueño de la razón”. El texto aborda la crítica de la pieza desde el punto de vista del coro, y destaca los elementos indirectamente vinculados a lo coral: los efectos de inmersión y distanciamiento, la tensión entre la voz individual y la voz colectiva, y el impacto que las pinturas tienen sobre el desarrollo de la obra y sobre su recepción por el público. Mediante este nuevo enfoque es posible concebir las voces de las pinturas como un grupo coral íntimo, que exterioriza sobre la escena el mundo interior del protagonista (Goya), pero sin exponerlo públicamente delante de los demás personajes como solían hacer los coros griegos clásicos.Several critics have briefly referred to the presence of choral characters or functions in Buero Vallejo’s plays, but they have failed to discuss the topic more thoroughly. Interestingly, the playwright himself has pointed out the continuing importance of tragedy and choral elements in modern drama. It is these two observations which have inspired us to study the heritage of the classical chorus in the playwright’s work, and more specifically the function of painting in “El sueño de la razón”. This paper approaches the play from the point of view of the chorus, emphasizing those aspects indirectly related to it: the immersion and alienation effects, the tension between the individual and the collective voice, and the impact of painting on the play’s development and its reception. We will interpret the paintings’ voices as an intimate kind of choral group that exteriorizes on stage the interior world of the protagonist (Goya), without exhibiting him publicly to the other characters, as Greek classical choruses used to do.peerReviewe

Mass and angular momentum loss during RLOF in Algols

We present a set of evolutionary computations for binaries with a B-type primary at birth. Some liberal computations including loss of mass and angular momentum during binary evolution are added to an extensive grid of conservative calculations. Our computations are compared statistically to the observed distributions of orbital periods and mass ratios of Algols. Conservative Roche Lobe Over Flow (RLOF) reproduces the observed distribution of orbital periods decently but fails to explain the observed mass ratios in the range 0.4-1. In order to obtain a better fit the binaries have to lose a significant amount of matter, without transferring too much angular momentum.Comment: 6 pages, 5 figures. to appear in the proceedings of the meeting Massive Stars in Interacting Binaries, eds. N. St.-Louis and T. Moffa

On the formation of oxygen-neon white dwarfs in close binary systems

The evolution of a star of initial mass 10 $M_{\odot}$, and metallicity $Z = 0.02$ in a Close Binary System (CBS) is followed from its main sequence until an ONe degenerate remnant forms. Restrictions have been made on the characteristics of the companion as well as on the initial orbital parameters in order to avoid the occurrence of reversal mass transfer before carbon is ignited in the core. The system undergoes three mass loss episodes. The first and second ones are a consequence of a case B Roche lobe overflow. During the third mass loss episode stellar winds may play a role comparable to, or even more important than Roche lobe overflow. In this paper, we extend the previously existing calculations of stars of intermediate mass belonging to close binary systems by following carefully the carbon burning phase of the primary component. We also propose different possible outcomes for our scenario and discuss the relevance of our findings. In particular, our main result is that the resulting white dwarf component of mass $1.1 M_\odot$ more likely has a core composed of oxygen and neon, surrounded by a mantle of carbon-oxygen rich material. The average abundances of the oxygen-neon rich core are $X({\rm O}^{16})=0.55$, $X({\rm Ne}^{20})=0.28$, $X({\rm Na}^{23})=0.06$ and $X({\rm Mg}^{24})=0.05$. This result has important consequences for the Accretion Induced Collapse scenario. The average abundances of the carbon-oxygen rich mantle are $X({\rm O}^{16})=0.55$, and $X({\rm C}^{12})=0.43$. The existence of this mantle could also play a significant role in our understanding of cataclysmic variables.Comment: 13 pages, 12 figures, accepted for publication in A&

Spin-up and hot spots can drive mass out of a binary

The observed distribution of periods and mass ratios of Algols with a B type primary at birth was updated. Conservative evolution fails to produce the large fraction with a high mass ratio: i.e. q in [0.4-0.6]. Interacting binaries thus have to lose mass before or during Algolism. During RLOF mass is transferred continuously from donor to gainer. The gainer spins up; sometimes up to critical velocity. Equatorial material on the gainer is therefore less bound to the system. The material coming from the donor through the first Langrangian point impinges violently on the surface of the gainer or the edge of the accretion disc, creating a hot spot in the area of impact. The sum of rotational energy (fast rotation) and radiative energy (hot spot) depends on the mass-loss rate. The sum of both energies on a test mass located in the impact area equals exactly its binding energy at some critical value. As long as the mass transfer rate is smaller than this value the gainer accepts all the mass coming from the donor: RLOF happens conservatively. But as soon as the critical rate is exceeded the gainer will acquire no more than the critical value and RLOF runs into its liberal era. Low mass binaries never achieve mass-loss rates larger than the critical value. Intermediate mass binaries evolve mainly conservatively but mass will be blown away from the system during the short era of rapid mass transfer soon after RLOF-ignition. Binaries with 9+5.4 solar masses (P in [2-4] d) evolve almost always conservatively. Only during some 20,000 years the gainer is not capable of grasping all the material that comes from the donor. During this short lapse of time a significant fraction of the mass of the system is blown into interstellar space. The mass ratio bin [0.4-0.6] is now much better represented.Comment: 12 pages, 7 figures, accepted for publication in A&A; accepted versio

Blue supergiant progenitor models of Type II supernovae

In the present paper we show that within all the uncertainties that govern the process of Roche lobe overflow in Case Br type massive binaries, it can not be excluded that a significant fraction of them merge and become single stars. We demonstrate that at least some of them will spend most of their core helium burning phase as hydrogen rich blue stars, populating the massive blue supergiant region and/or the massive Be type star population. The evolutionary simulations let us suspect that these mergers will explode as luminous hydrogen rich stars and it is tempting to link them to at least some super luminous supernovae.Comment: Accepted for publication in A&A; accepted versio

Mass loss out of close binaries. II

Liberal evolution of interacting binaries has been proposed previously by several authors in order to meet various observed binary characteristics better than conservative evolution does. Since Algols are eclipsing binaries the distribution of their orbital periods is precisely known. The distribution of their mass ratios contains however more uncertainties. We try to reproduce these two distributions theoretically using a liberal scenario in which the gainer star can lose mass into interstellar space as a consequence of its rapid rotation and the energy of a hot spot. In a recent paper (Van Rensbergen et al. 2010, A&A) we calculated the liberal evolution of binaries with a B-type primary at birth where mass transfer starts during core hydrogen burning of the donor. In this paper we include the cases where mass transfer starts during hydrogen shell burning and it is our aim to reproduce the observed distributions of the system parameters of Algol-type semi-detached systems. Our calculations reveal the amount of time that an Algol binary lives with a well defined value of mass ratio and orbital period. We use these data to simulate the distribution of mass ratios and orbital periods of Algols. Binaries with a late B-type initial primary hardly lose any mass whereas those with an early B primary evolve in a non-conservative way. Conservative binary evolution predicts only ~ 12 % of Algols with a mass ratio q above 0.4. This value is raised up to ~ 17 % using our scenario of liberal evolution, which is still far below the ~ 45 % that is observed. Observed orbital periods of Algol binaries larger than one day are faithfully reproduced by our liberal scenario. Mass ratios are reproduced better than with conservative evolution, but the resemblance is still poor.Comment: 11 pages, 6 figures, accepted for publication in A&A; accepted versio

La herencia del coro griego en el teatro de A. Buero Vallejo. El caso de "El sueño de la razón"

Varios especialistas aluden a la presencia de figuras y funciones corales en la obra de Buero Vallejo, sin profundizar, no obstante, en la materia. Al mismo tiempo, el propio Buero escribe algunos tratados sobre la tragedia y lo trágico en los que sostiene la supervivencia del coro en el drama moderno. Estas dos observaciones nos han impulsado a estudiar la herencia del coro clásico en la obra del dramaturgo, en particular, la función de las voces de las pinturas en “El sueño de la razón”. El texto aborda la crítica de la pieza desde el punto de vista del coro, y destaca los elementos indirectamente vinculados a lo coral: los efectos de inmersión y distanciamiento, la tensión entre la voz individual y la voz colectiva, y el impacto que las pinturas tienen sobre el desarrollo de la obra y sobre su recepción por el público. Mediante este nuevo enfoque es posible concebir las voces de las pinturas como un grupo coral íntimo, que exterioriza sobre la escena el mundo interior del protagonista (Goya), pero sin exponerlo públicamente delante de los demás personajes como solían hacer los coros griegos clásicos.Several critics have briefly referred to the presence of choral characters or functions in Buero Vallejo’s plays, but they have failed to discuss the topic more thoroughly. Interestingly, the playwright himself has pointed out the continuing importance of tragedy and choral elements in modern drama. It is these two observations which have inspired us to study the heritage of the classical chorus in the playwright’s work, and more specifically the function of painting in “El sueño de la razón”. This paper approaches the play from the point of view of the chorus, emphasizing those aspects indirectly related to it: the immersion and alienation effects, the tension between the individual and the collective voice, and the impact of painting on the play’s development and its reception. We will interpret the paintings’ voices as an intimate kind of choral group that exteriorizes on stage the interior world of the protagonist (Goya), without exhibiting him publicly to the other characters, as Greek classical choruses used to do.peerReviewe

The Evolution of Massive Stars. I. Red Supergiants in the Magellanic Clouds

We investigate the red supergiant (RSG) content of the SMC and LMC using multi-object spectroscopy on a sample of red stars previously identified by {\it BVR} CCD photometry. We obtained high accuracy ($<1$ km s$^{-1}$) radial velocities for 118 red stars seen towards the SMC and 167 red stars seen towards the LMC, confirming most of these (89% and 95%, respectively) as red supergiants (RSGs). Spectral types were also determined for most of these RSGs. We find that the distribution of spectral types is skewed towards earlier type at lower metallicities: the average (median) spectral type is K5-7 I in the SMC, M1 I in the LMC, and M2 I in the Milky Way. We argue that RSGs in the Magellanic Clouds are 100deg (LMC) and 300deg (SMC) cooler than Galactic RSGs of the same spectral type. We compare the distribution of RSGs in the H-R diagram to that of various stellar evolutionary models; we find that none of the models produce RSGs as cool and luminous as what is actually observed. In all of our H-R diagrams, however, there is an elegant sequence of decreasing effective temperatures with increasing luminosities; explaining this will be an important test of future stellar evolutionary models.Comment: Version with eps figures embedded can be obtained from ftp://ftp.lowell.edu/pub/massey/rsgs.ps.gz Accepted by the Astronomical Journa

Numerical simulations of the full ink-jet printing processes: From jetting to evaporation

Ink-jet printing requires to perfectly control both the jetting of droplets and the subsequent droplet evaporation and absorption dynamics. Considerable complexity arises due to the fact that ink is constituted of a mixture of different liquids, surfactants and pigments. Using a sharp-interface ALE finite element method, we numerically investigate the main aspects of ink-jet printing, both on the jetting side and on the drying side. We show how a short pause in jetting can result in clogged nozzles due to solvent evaporation and discuss approaches how to prevent this undesired phenomenon. Once the droplets have been jetted on paper and is evaporating, the print quality can be deteriorated by the well-known coffee-stain effect, i.e. the preferential deposition of particles near the rim of the droplet. This can be prevented in several ways, e.g. employing controlled Marangoni flow via surfactants or co-solvents or printing on a primer layer jetted in beforehand, thus creating a homogeneous deposition pattern for a perfect final printout