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Hα photometry of low mass stars in 47 Tucanae: chromospheric activity and exotica

Published online by Cambridge University Press:  21 February 2013

Giacomo Beccari
Affiliation:
European Southern Observatory, Karl–Schwarzschild-Strasse 2, 85748 Garching bei München, Germany, email: gbeccari@eso.org
Guido De Marchi
Affiliation:
ESA, Space Science Department, Keplerlaan 1, 2200 AG Noordwijk, The Netherlands
Nino Panagia
Affiliation:
ESA, Space Science Department, Keplerlaan 1, 2200 AG Noordwijk, The Netherlands INAF-CT, Osservatorio Astrofisico di Catania, Via S. Sofia 78, 95123 Catania, Italy Supernova Ltd, OYV #131, Northsound Road, Virgin Gorda, British Virgin Islands
Luca Pasquini
Affiliation:
European Southern Observatory, Karl–Schwarzschild-Strasse 2, 85748 Garching bei München, Germany, email: gbeccari@eso.org
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Abstract

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We have used archival Hubble Space Telescope (HST) observations obtained with the Advanced Camera for Surveys (ACS) to study the Hα emission properties of main sequence (MS) stars in the globular cluster 47 Tucanae. An accurate photometric measurement of their Hα equivalent width, allows us to identify objects with large Hα emission. We demonstrate that this method allows us to identify and characterise candidate cataclysmic variables (CVs) with high efficiency, reconciling observations with theoretical predictions on the number of dynamically formed CVs expected in a 47 Tucanae-like globular cluster.

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2013

References

Bessell, M. S., Castelli, F., & Plez, B. 1998, A&A, 333, 231Google Scholar
De Marchi, G., Panagia, N., & Romaniello, M. 2010, ApJ, 715, 1Google Scholar