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Publication Details
AFRICAN RESEARCH NEXUS
SHINING A SPOTLIGHT ON AFRICAN RESEARCH
earth and planetary sciences
The ongoing pursuit of R Coronae Borealis stars: The ASAS-3 survey strikes again
Astronomy and Astrophysics, Volume 551, Article A77, Year 2013
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Description
Context. R Coronae Borealis stars (RCBs) are rare, hydrogen-deficient, carbon-rich supergiant variable stars that are likely the evolved merger products of pairs of CO and He white dwarfs. Only 55 RCB stars have been found in our galaxy and their distribution on the sky is weighted heavily by microlensing survey field positions. A less biased wide-area survey would enable us to test competing evolutionary scenarios, understand the population or populations that produce RCBs, and constrain their formation rate. Aims. The ASAS-3 survey monitored the sky south of declination +28 deg between 2000 and 2010 to a limiting magnitude of V = 14. We searched ASAS-3 for RCB variables using several different methods to ensure that the probability of RCB detection was as high as possible and to reduce selection biases based on luminosity, temperature, dust production activity and shell brightness. Methods. Candidates whose light curves were visually inspected were pre-selected based on their infrared (IR) excesses due to warm dust in their circumstellar shells using the WISE and/or 2MASS catalogues. Criteria on light curve variability were also applied when necessary to minimise the number of objects. Initially, we searched for RCB stars among the ASAS-3 ACVS1.1 variable star catalogue, then among the entire ASAS-3 south source catalogue, and finally directly interrogated the light curve database for objects that were not catalogued in either of those. We then acquired spectra of 104 stars to determine their real nature using the SSO/WiFeS spectrograph. Results. We report 21 newly discovered RCB stars and 2 new DY Per stars. Two previously suspected RCB candidates were also spectroscopically confirmed. Our methods allowed us to extend our detection efficiency to fainter magnitudes that would not have been easily accessible to discovery techniques based on light curve variability. The overall detection efficiency is about 90% for RCBs with maximum light brighter than V ∼ 13. Conclusions. With these new discoveries, 76 RCBs are now known in our Galaxy and 22 in the Magellanic Clouds. This growing sample is of great value to constrain the peculiar and disparate atmosphere composition of RCBs. Most importantly, we show that the spatial distribution and apparent magnitudes of Galactic RCB stars is consistent with RCBs being part of the Galactic bulge population. © 2013 ESO.
Authors & Co-Authors
Tisserand, Patrick
Australia, Canberra
The Australian National University
Australia, Sydney
Arc Centre of Excellence for All-sky Astrophysics
Clayton, Geoffrey C.
United States, Baton Rouge
Louisiana State University
Welch, Douglas L.
Canada, Hamilton
Mcmaster University
Pilecki, Bogumiåã'â'
Chile, Biobio
Universidad de Concepcion
Poland, Warsaw
University of Warsaw
Wyrzykowski, Łukasz
Poland, Warsaw
University of Warsaw
United Kingdom, Cambridge
Institute of Astronomy
Kilkenny, David
South Africa, Bellville
University of the Western Cape
Statistics
Citations: 28
Authors: 6
Affiliations: 8
Identifiers
Doi:
10.1051/0004-6361/201220713
ISSN:
00046361
e-ISSN:
14320746
Research Areas
Environmental
Study Design
Cross Sectional Study
Study Approach
Quantitative