Two new pulsating hot subdwarf stars from the Edinburgh-Cape survey |
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| Authors: | D. Kilkenny D. O'Donoghue L. Crause C. Engelbrecht N. Hambly H. MacGillivray |
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| Affiliation: | Department of Physics, University of the Western Cape, Private Bag X17, Bellville 7535, South Africa;South African Astronomical Observatory, PO Box 9, Observatory 7935, South Africa;Department of Physics APK, University of Johannesburg, PO Box 524, Auckland Park 2006, South Africa;Wide Field Astronomy Unit, Institute for Astronomy, University of Edinburgh, Blackford Hill, Edinburgh EH9 3HJ |
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| Abstract: | We report the discovery of very rapid pulsations in two hot subdwarf stars from the Edinburgh-Cape blue object survey. The short periods, small amplitudes and multiperiodicity establish these stars as members of the class of rapidly-pulsating sdB stars. The spectrograms of both stars, however, show relatively strong He ii 4686 and they are therefore more properly classified as sdOB. The light curve of EC 01541−1409 is dominated by two strong (∼1 per cent) variations with frequencies near 7114 and 7870 μHz (periods near 140.6 and 127.1 s), though at least five frequencies are present with amplitudes above about 0.002 mag. The light curve of EC 22221−3152 appears to be generated by at least 10 frequencies in the range 5670–11850 μHz (about 175–85 s) with amplitudes between about 0.01 and 0.001 mag, including the first overtone of the strongest variation. Somewhat surprisingly, this number of frequencies is detectable in observing runs as short as 3 h, probably due to the fact that the detected frequencies are well-separated. |
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| Keywords: | stars: individual (EC 01541−1409, EC 22221−3152) stars: oscillations stars: variables |
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