Found 105 talks archived in Stars

Video
Thursday November 24, 2011
Dr. Maritza A. Lara-Lopez
Australian Astronomical Observatory, Australia

Abstract

To understand the formation and evolution of galaxies, it is important to have a full comprehension of the role played by Metallicity, Star Formation Rate (SFR), and stellar mass of galaxies. The interplay of these parameters at different redshifts will substantially affect the evolution of galaxies and, as a consequence, the evolution of these parameters provides important constraints for the galaxy evolution models. We studied the relationships and dependencies between the SFR, stellar mass, and gas metallicity of star forming galaxies from the Sloan Digital Sky Survey-Data Release 7 (SDSS DR7) and Galaxy and Mass Assembly (GAMA) surveys. We have combined both surveys finding evidence of SFR and metallicity evolution for galaxies down to redshift ~0.2. Also, we have proved the existence of a Fundamental Plane in the 3D space formed by the SFR, mass and metallicity for the SDSS and GAMA samples.


Video
Monday September 12, 2011
Dr. Marc Balcells
Isaac Newton Group of Telescopes, Spain

Abstract

The vision for the use of the WHT in the coming decade is taking shape.   A key element is the construction and deployment of WEAVE, a wide-field massive-multiplex spectrograph.  With 1000 fibres and spectral resolutions of 5000 and 20000, the opportunities for discovery are tremendous.  Three key fields will be: Milky-Way and Local Group archaeology linked to the   Gaia mission; cosmology redshift surveys; and galaxy evolution studies linked to photometric surveys such as VISTA, UKIDSS, LOFAR, EUCLID, and  others. IAC has the opportunity to get involved in this important instrument for ORM from the beginning.


Video
Tuesday July 26, 2011
Dr. Katrien Uytterhoeven
Instituto de Astrofísica de Canarias, Spain

Abstract

The Kepler spacecraft is providing photometric time series with micromagnitude precision for thousands of variable stars. The continuous time-series of unprecedented timespan open up the opportunity to study the pulsational variability in much more detail than was previously possible from the ground. We present a first general characterization of the variability of A-F type stars as observed in the Kepler light curves of a sample of 750 candidate variable A-F type stars, and investigate the relation between gamma Doradus, delta Scuti, and hybrid stars. Our results suggest a revision of the current observational instability strips, and imply an investigation of pulsation mechanisms to drive hybrid pulsations.


Video
Thursday June 23, 2011
Dr. Patrick Gaulme
Institut d'Astrophysique Spatiale; Université Paris Sud, Paris, France

Abstract

At the end of 2008, on ideas of teams from the Observatoire de la Côte d’Azur (OCA) and IAC, the CoRoT satellite observed the star HD 46375, known to host a non-transiting Saturn-mass exoplanet with a 3.023 day period. HD 46375 is the brightest star with a known close-in planet in the CoRoT accessible field of view. As such, it was targeted by the CoRoT additional program and observed in a CCD normally dedicated to the asteroseismology program, to obtain an ultra-precise photometric lightcurve and detect or place upper limits on the brightness of the planet. In addition, a ground-based support was simultaneously performed with the high-resolution NARVAL spectro-polarimeter to constrain the stellar atmospheric and magnetic properties. In this seminar, I will present the main results, in particular the stellar constrain we obtained thanks to the detection of the oscillation mode signature and the plausible detection of the planetary signal, which, if confirmed with future observations, would be the first detection of phase changes in the visible for a non-transiting planet.


Video
Tuesday June 21, 2011
Miss Karla Yulién Peña Ramírez
Instituto de Astrofísica de Canarias

Abstract

The proper characterization of the least massive population of the young Sigma Orionis star cluster is required to understand the form of the cluster mass function and its impact on our comprehension of the substellar formation processes. SOri70 (T5.5±1) and SOri73, two T-type cluster member candidates, would have likely masses between 3 and 7 MJup if their age is 3 Myr. SOri73 awaits confirmation of its methane atmosphere. Here I present the results of a search of T-type objects in an area of ~120 arcmin^2 in the Sigma Orionis cluster, the confirmation of the presence of methane absorption in SOri73 and the study of SOri70 and 73 cluster membership via photometric colors and accurate proper motion analysis. This results would have a dramatic impact in the cluster mass function, in one of the scenarios explored, they suggest a decrease in cluster members with planetary masses in the interval 3.5-6 Mjup.


Video
Friday June 17, 2011
Dr. Mauro D'Onofrio
University of Padova, Italy

Abstract

We present the K band FP of the ETGs members of the clusters observed by the WINGS survey. The data confirm a different tilt of the FP with respect to the V solution and the presence of a substantial tilt in the K band. This led us to further investigate the hypothesis that ETG non-homology greatly contribute to the tilt of the FP.

The WINGS data show that there are now several evidence of both structural and dynamical non-homology for the class of ETGs. Among these we will discuss in detail the tight relation between the mass of the ETGs, their stellar mass-to-light ratio M/L, and the Sersic index n describing the shape of their light profiles. We guess through a series of mock simulations that this relation acts as a fine-tuning that keeps small the scatter around the FP. We therefore conclude that ETG non-homology is closely connected either with the problem of the tilt and with the small scatter around the FP.


Video
Monday June 13, 2011
Mr. Héctor Canovas
Astronomical Institute Utrecht, the Netherlands

Abstract

ExPo is an imaging polarimeter that has been built in Utrecht University. ExPo works in the visible, and it combines the dual-beam technique, together with very short exposure times and a high polarization sensitivity. After four successful campaigns at the William Herschel Telescope, we have obtained polarization images of circumstellar environments around T Tau's and Herbig Ae's stars, evolved (post-AGB) stars and planets like Venus and Saturn. Our results prove the utility of imaging polarimetry to characterize faint structures around very different objects. In this talk I will go through the instrument details, and I will show some of our science results.


Video
Friday May 20, 2011
Prof. Ramesh Narayan
Harvard-Smithsonian Center, USA.

Abstract

In his public talk, Prof. Narayan will summarize our knowledge of Black Holes in the universe. He will describe how Black Holes are discovered, how their properties are measured, and what the results mean. He will also discuss the many ways in which Black Holes influence their surroundings and the profound effect they have had on the evolution of the universe.


Video
Thursday May 19, 2011
Prof. Ramesh Narayan
Harvard-Smithsonian Center for Astrophysics, USA

Abstract

An astrophysical black hole is completely described with just two parameters: its mass and its dimensionless spin. A few dozen black holes have mass estimates, but until recently none had a reliable spin estimate. The first spins have now been measured for black holes in X-ray binaries. The talk will describe the method used to make these measurements and will discuss implications of the results obtained so far.


Video
Thursday April 7, 2011
Dr. María Jesús Martínez
Instituto de Astrofísica de Canarias, Spain

Abstract

This question is important because a large fraction of planetary nebulae (about 80%) are bipolar or elliptical rather than spherically symmetric. Modern theories invoke magnetic fields, among other causes, to explain the rich variety of aspherical components observed in PNe, as ejected matter is trapped along magnetic field lines. But, until recently, this idea was mostly a theoretical claim. Jordan et al. (2005) report the detection of kG magnetic fields in the central star of two non-spherical PNe, namely NGC1360 and LSS1362. We find that, contrary to that work, the magnetic field is null within errors for both stars. Then, a direct evidence of magnetic fields on the central stars of PNe is still missing — either the magnetic field is much weaker (< 600 G) than previously reported, or more complex (thus leading to cancellations), or both. The role of magnetic fields shaping PNe is still an open question.



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