(1) Seismology of stars: problems and prospects (2) Asteroseismic CoRoT targets and the ground-based follow-up observations (3) Classical novae and cataclysmic variables: a modern perspective

Fecha y hora
30 Abr 2008 - 00:00 Europe/London


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The asteroseismic window of the CoRoT satellite mission aims at the monitoring of several types of pulsators along the Main Sequence. To optimise the science results, i.e. to probe the internal structure of stars in order to understand star evolution, its targets are carefully chosen and selected. Preparatory observations from ground have been a key stone in the selection process. Also with the CoRoT satellite succesfully launched, simultaneous ground-based observations are very important and are complementary to the space data. Multi-colour photometry provides information on amplitude ratios and phase shifts while high-resolution spectroscopy allows the detection of high degree modes and the identification of both l and m values. I present a couple of (massive, M>1.5 solar-masses) protagonists in the CoRoT asteroseismic play, (preliminary) results of the analysis of their behaviour in the ground-based time-series, and a look-out for the refined results provided by the CoRoT data. Cataclysmic Variables (CVs) represent a large variety of astronomical objects. In general terms, a CV consists of a white dwarf accreting mass from a less evolved companion which is filling its Roche lobe. Classical Novae (CNe) are a subset of CVs, and there are reasons to believe that most, if not all CVs will repeatedly go through CN phases during their lifetime. The fundamental physical process underlying a CN is that only a limited amount of hydrogen can be accumulated on a white dwarf before it ignites thermonuclear fusion, and CNe are the observational consequence of this thermonuclear runaway. I have been member of a team which carried out a Target of Opportunity campaign, aimed at the spectroscopic study of CNe at maximum light. I will present some highlights from this project. Moreover, I will present a new program I am involved in, aimed at the study of CNe years (sometimes decades) after the outburst. Trying to link the outburst properties with the progenitor's properties. Data interpretation is a highly delicate matter and interpretation of oscillation frequencies of stars is no exception; the frequency of a pulsation mode is sensitive to every stellar parameter and the theoretical stellar models themselves have deficiencies. Here I review the basic principles of asteroseismology, some problems associated with interpreting the oscillation data, and touch briefly on how my research may address these obstacles.