RR Lyrae mode switching in globular cluster M 68 (NGC 4590)
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We build on our detailed analysis of time-series observations of the globular cluster M 68 to investigate the irregular pulsational behaviour of four of the RR Lyrae stars in this cluster. M 68 is one of only two globular clusters in which mode switching of RR Lyrae stars has previously been reported. We discuss one additional case, as well as a case of irregular behaviour, and we briefly revisit the two previously reported cases with a homogeneous analysis. We find that in 2013, V45 was pulsating in the first-overtone mode alone, despite being previously reported as a double-mode (fundamental and first overtone) pulsator in 1994, and that the amplitude of the fundamental mode in V7 is increasing with time. We also suggest that V21 might not have switched pulsation modes as previously reported, although the first overtone seems to be becoming less dominant. Finally, our analysis of available archival data confirms that V33 lost a pulsation mode between 1950 and 1986.
Kains , N , Bramich , D M , Arellano Ferro , A & Figuera Jaimes , R J 2015 , ' RR Lyrae mode switching in globular cluster M 68 (NGC 4590) ' , Astronomy & Astrophysics , vol. 582 . https://doi.org/10.1051/0004-6361/201526819
Astronomy & Astrophysics
© ESO, 2015. Reproduced with permission from Astronomy & Astrophysics, © ESO. This work is made available online in accordance with the publisher’s policies. This is the final published version of the work, which was originally published at: http://dx.doi.org/10.1051/0004-6361/201526819
DescriptionD.M.B. acknowledges NPRP grant # X-019-1-006 from the Qatar National Research Fund (a member of Qatar Foundation). A.A.F. acknowledges the support of DGAPA-UNAM through project IN106615-17.
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