Pulsating B and Be stars in the Small Magellanic Cloud

Context. Stellar pulsations in main-sequence B-type stars are driven by the κ-mechanism due to the Fe-group opacity bump. The current models do not predict the presence of instability strips in the B spectral domain at very low metallicities. As the metallicity of the SMC is lower than Z = 0.005, it constitutes a very suitable object to test these predictions. Aims. The main objective is to investigate the existence of B-type pulsators at low metallicities, searching for short-term periodic variability in absorption-line B and Be stars in the SMC. The analysis has been performed in a sample of 313 B and Be stars with fundamental astrophysical parameters accurately determined from high-resolution spectroscopy. Methods. Photometric light curves of the MACHO project have been analyzed using standard Fourier techniques and linear and non- linear least squares fitting methods. The position of the pulsating stars in the HR diagram has been used to ascertain their nature and to map the instability regions in the SMC. Results. We have detected 9 absorption-line B stars showing short-period variability, two among them being multiperiodic. One star is most likely a β Cephei variable and the remaining 8 are SPB stars. The SPB instability strip in the SMC is shifted towards higher temperatures than the Galaxy. In the Be star sample, 32 stars are short-period variables, 20 among them multiperiodic. 4.9% of B stars and 25.3% of Be stars are pulsating stars. Conclusions. β Cephei and SPB stars do exist at the SMC metallicity. The fractions of SPB stars and pulsating Be stars in the SMC are lower than in the Galaxy. The fraction of pulsating Be stars in the SMC is much higher than the fraction of pulsating absorption-line B stars, as in the [email protected]; [email protected]; [email protected]

Variability of B and Be stars in the LMC/SMC: binaries and pulsations

To study the variability of the 523 B and Be stars observed in the Magellanic clouds with the VLT-FLAMES, we cross-matched the stars of our sample with the photometric database MACHO, which provides for each star an 8 years lightcurve. We searched for long, medium, and short-term periodicity and found the eclipsing binaries in our sample. For these stars, combining, spectroscopy and photometry, we were able to provide information on several systems of stars (systemic velocities, ratios of masses, etc). We also present the ratios of B-binaries to B-non binaries in the LMC/SMC in comparison with the MW. Note that this ratio is also an important issue to understand the mechanism of star-formation at low metallicity. We also found the first multiperiodic B and Be stars in the SMC, in particular the first SMC Beta Cep and SPB, while, according to the models, pulsations were not foreseen in low metallicity environments, i.e. typically in the SMC. Our results show that the instability strips are shifted towards higher temperatures in comparison with the Milky Way' strips of pulsating B-type stars. By the fact that we found more pulsating Be stars than pulsating B stars in the SMC, it seems that the fast rotation favours the presence of pulsations. However, the ratio of pulsating B-type stars to "non"-pulsating B-type stars at low metallicity is lower than at high metallicity.Comment: poster IAUS25

Effect of ozone therapy upon clinical and bacteriological parameters of the oral cavity: an update

Objective: To review the literature on ozone therapy in oral health, as assessed by different clinical and bacteriological parameters. Material and methods: A PubMed literature search was made using the key words “ozone dental”, and establishing as limits “randomized controlled trial” and “dental journal”. Thirteen articles were identified, with access to only 6 of them. Results: Four studies used ozone for the treatment of caries. One study examined its effect upon dental hypersensitivity, while another evaluated the efficacy of ozone as a tooth whitening technique. Five studies explored the bacteriological actions of ozone therapy in reference to different types of bacteria. Conclusion: The reviewed literature yields a number of studies describing a high antimicrobial potential of ozone therapy in different dental areas, though very few in vivo studies have evidenced the success of such treatment. Further studies are therefore needed in this field

Una herramienta de análisis de los accesos al número propuestos en los libros de texto de infantil

Presentamos una descripción de los accesos al número natural en educación infantil y de cómo secuencia cada uno los distintos usos del número. Diseñamos una herramienta que permite analizar los accesos al número propuestos en libros de texto. Presentamos el análisis de dos textos de la etapa en la que los libros seguían las directrices curriculares correspondientes a diferentes épocas. El objetivo del trabajo es ofrecer a los maestros de infantil una propuesta de cómo evaluar la adecuación de los libros de texto a las disposiciones curriculares relativas a la enseñanza del número en el segundo Ciclo de educación infantil

Asteroseismology and mass loss in Be stars. Study with CoRoT

The interiors of the stars are among the most difficult parts of the Universe to observe. Essentially, asteroseismology tries to make use of the oscillations to prove the stellar interiors, which are not directly observable. The basic principles of asteroseismology are, to a certain extent, similar to those developed and employed by Earth seismologists. Asteroseismology relies on advanced mathematical descriptions of oscillations in a three-dimensional body and numerical modeling. It is therefore a prominent example of interdisciplinary science. The general aim of this work is the study of Be stars with the CoRoT space mission. Classical Be stars are B-type stars that exhibit line emission over the pho- tospheric spectrum. The excess is attributed to a circumstellar gaseous component that is commonly accepted to be in the form of an equatorial disk. The mechanisms responsible for the production and dynamics of the circumstellar gas are still not constrained. Observations of non-radial pulsation beating phenomena connected to outbursts point toward a relevance of pulsation, but this mechanism cannot be gene- ralized. In this regard, the observation of classical Be stars with the high-precision CoRoT satellite is providing important keys to understand the physics of these objects and the nature of the Be phenomenon. In order to study the light variations of the selected stars we use photometric and spectroscopic observations. These observations allow us to extract frequencies, amplitudes and phases of these variations. As we will show, these light variations can be connected with pulsations on the stellar surface. For carrying out the frequency analysis we have developed a new code based on standard Fourier analysis. The point is that this code, called pasper, allows the frequency analysis of large sets of light curves in an automatic mode. This Ph.D. thesis is arranged as follows: In the first three Chapters we describe the scientific framework of this project, giving a brief description on Asteroseismology, presenting the current status of Be stars, and describing the basics of the Fourier analysis and the rudiments of the time series analysis. At the early begin of this Ph.D. thesis, the CoRoT satellite was still on ground getting ready for the launch. In this context, we perform a search for shortperiod B and Be star variables in the low metallicity environment of the Magellanic Clouds. This study constitutes the Part I of this Ph.D. thesis. This Part has a double goal: i) to test the frequency analysis codes; and ii) to detect observationally β Cephei and SPB-like B-type pulsators in low metallicity environments, actually not predicted by the pulsational theory and models. This constitutes the Part I. Part II is devoted to the study of Be stars with the CoRoT space mission. Here we depict a complete review on the CoRoT mission. We also describe the results on the analysis of three Be stars from the CoRoT exoplanet field. Finally, we present the results on the frequency analysis of the late Be star HD 50 209, observed in the seismology field of the CoRoT satellite. The analysis of this Be star has revealed up to sixty frequencies, grouped in six different and separated sets, attributed to g-mode pulsations. Finally, we resume the main conclusions of the whole project, including prospects and future work to be done. An addendum with all the published results derived from this project has been added at the end of this Part II. Part III encloses the Appendixes, providing a brief summary of this work in Spanish, a complete description on basic equations of non-radial oscillation, the user guide of the PASPER code and the user guide of the KURTZ_BOS code.El objetivo de la asterosismología es describir el interior de las estrellas a partir de las oscilaciones. El interior de las estrellas es, posiblemente, el lugar más difícil de estudiar de todo el Universo, ya que las condiciones especiales que allí se dan no pueden reproducirse en ningún laboratorio terrestre. Así, la importancia de esta ciencia en el estudio global de la física estelar es crucial. Los principios básicos de la asterosismología son, en esencia, similares a los que los geólogos usan en el estudio de terremotos terrestres. La asterosismología hace uso de descripciones matemáticas de las oscilaciones en cuerpos tridimensionales, creando para ello sofisticadas simulaciones numéricas. Es, por tanto, un claro ejemplo de ciencia multidisciplinar. El objetivo general de esta Tesis Doctoral es el estudio de las estrellas Be con las misión espacial CoRoT. Las estrellas Be son objetos de secuencia principal, con alta velocidad de rotación, que presentan un exceso infrarrojo y emisión en las líneas de Balmer, debido a la presencia de una envoltura circumestelar concentrada en el ecuador y generada por eyecciones discretas de materia originado por mecanismos que todavía no son bien conocidos. Los mecanismos propuestos para explicar la eyección de materia son hasta ahora, las pulsaciones no radiales combinadas con la alta velocidad de rotación característica de este tipo de estrellas. La observación de estrellas Be con el satélite de alta precisión CoRoT está aportando claves importantísimas para comprender la física de estos objetos y la naturaleza del fenómeno Be. Para la detección de señales periódicas en las estrellas seleccionadas utilizamos tanto observaciones fotométricas como espectroscópicas. A partir de las observaciones obtenemos las frecuencias, amplitudes y fases de las variaciones. Como se muestra en la tesis, las variaciones en las curvas de luz estudiadas podrían estar estrechamente relacionadas con los mecanismos de pulsación estelar. Para realizar el análisis de frecuencias hemos desarrollado un código basado en técnicas estándar de análisis de Fourier. Este código, llamado Pasper, nos permite analizar grandes conjuntos de datos de forma casi automática

Pensamiento computacional y resolución de problemas en educación infantil: una secuencia de enseñanza con el robot Bee-bot

El término “pensamiento computacional” (Wing, 2006) guarda una estrecha relación con muchos de los procesos asociados a la resolución de problemas. Además de ocupar una posición privilegiada en los textos curriculares de las primeras edades escolares, la resolución de problemas es un elemento central de la enseñanza de las matemáticas. Concretamente, el aula de infantil es un escenario propicio para la aparición de situaciones estimulantes de resolución de problemas que ayuden a estructurar el pensamiento lógicomatemático del estudiante a la vez que desarrollen facultades intelectuales y estrategias heurísticas. Desde esta perspectiva se presenta una secuencia de enseñanza basada en el robot Bee-bot i su app digital, ambos orientados a que estudiantes de primeras edades escolares den sus primeros pasos en programación como una forma de iniciar el aprendizaje de la resolución de problemas

Photometric and spectroscopic variability of the B5IIIe star HD 171219

We analyzed the star HD171219, one of the relatively bright Be stars observed in the seismo field of the CoRoT satellite, in order to determine its physical and pulsation characteristics. Classical Be stars are main-sequence objects of mainly B-type, whose spectra show,or have shown at some epoch, Balmer lines in emission and an infrared excess. Both characteristics are attributed to an equatorially concentrated circumstellar disk fed by non-periodic mass-loss episodes (outbursts). Be stars often show nonradial pulsation gravity modes and, as more recently discovered, stochastically excited oscillations. Applying the CLEANEST algorithm to the high-cadence and highly photometrically precise measurements of the HD171219 light curve led us to perform an unprecedented detailed analysis of its nonradial pulsations. Tens of frequencies have been detected in the object compatible with nonradial g-modes. Additional ighresolution ground-based spectroscopic observations were obtained at La Silla (HARPS) and Haute Provence (SOPHIE) observatories during the month preceding CoRoT observations. Additional information was obtained from low-resolution spectra from the BeSS database. From spectral line fitting we determined physical parameters of the star, which is seen equator-on (i = 90 ). We also found in the ground data the same frequencies as in CoRoT data. Additionally, we analyzed the circumstellar activity through the traditional method of violet to red emission H line variation. A quintuplet was identified at approximately 1:113 c d\u1000001 (12.88 Hz) with a separation of 0:017 c d\u1000001 that can be attributed to a pulsation degree ` 2. The light curve shows six small- to medium-scale outbursts during the CoRoT observations. The intensity of the main frequencies varies after each outburst, suggesting a possible correlation between the nonradial pulsations regime and the feeding of the envelope

Acceptance and intentions of using dynamic geometry software by pre-service primary school teachers

In this paper, we empirically verify the validity of the extended Technology Acceptance Model (TAM) for the use of Dynamic Geometry Software (DGS) in teaching geometry, as proposed by Pittalis. The model includes the notion of "perceived pedagogical-learning fit" in addition to the traditional belief and attitude variables of TAM. We employ a structural equation modeling approach to capture the relationships between the different latent constructs. With a sample of 135 pre-service primary school teachers as participants, our study provides valuable insights into the factors influencing the adoption of DGS in geometry teaching. The results reveal that the extended TAM serves as a suitable framework to evaluate the intentions of teachers to use DGS in teaching geometry. However, we also observe some discrepancies in the predictive power of various latent factors when compared to the original study. These findings not only contribute to our understanding of the factors affecting the adoption of DGS in geometry teaching but also provide valuable insights for future research and practice

Exploring the development of mental rotation and computational skills in elementary students through educational robotics

Interest in educational robotics has increased over the last decade. Through various approaches, robots are being used in the teaching and learning of different subjects at distinct education levels. The present study investigates the effects of an educational robotic intervention on the mental rotation and computational thinking assessment in a 3rd grade classroom. To this end, we carried out a quasi-experimental study involving 24 third-grade students. From an embodied approach, we have designed a two-hour intervention providing students with a physical environment to perform tangible programming on Bee-bot. The results revealed that this educational robotic proposal aimed at map-reading tasks leads to statistically significant gains in computational thinking. Moreover, students who followed the Bee-bot-based intervention achieved greater CT level compared to students following a traditional instruction approach, after controlling student's prior level. No conclusive results were found in relation to mental rotation