Abstract
We present the analysis of four first overtone RR Lyrae stars observed with the Kepler space telescope, based on data obtained over nearly 2.5 yr. All four stars are found to be multiperiodic. The strongest secondary mode with frequency f2 has an amplitude of a few mmag, 20-45 times lower than the main radial mode with frequency f1. The two oscillations have a period ratio of P2/P1 = 0.612-0.632 that cannot be reproduced by any two radial modes. Thus, the secondary mode is non-radial. Modes yielding similar period ratios have also recently been discovered in other variables of the RRc and RRd types. These objects form a homogenous group and constitute a new class of multimode RR Lyrae pulsators, analogous to a similar class of multimode classical Cepheids in the Magellanic Clouds. Because a secondary mode with P2/P1 ~ 0.61 is found in almost every RRc and RRd star observed from space, this form of multiperiodicity must be common. In all four Kepler RRc stars studied, we find subharmonics of f2 at ~1/2f2 and at ~3/2f2. This is a signature of period doubling of the secondary oscillation, and is the first detection of period doubling in RRc stars. The amplitudes and phases of f2 and its subharmonics are variable on a time-scale of 10-200 d. The dominant radial mode also shows variations on the same time-scale, but with much smaller amplitude. In three Kepler RRc stars we detect additional periodicities, with amplitudes below 1 mmag, that must correspond to non-radial g-modes. Such modes never before have been observed in RR Lyrae variables.
| Original language | English |
|---|---|
| Pages (from-to) | 2348-2366 |
| Number of pages | 19 |
| Journal | Monthly Notices of the Royal Astronomical Society |
| Volume | 447 |
| Issue number | 3 |
| DOIs | |
| Publication status | Published - 2015 |
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ASJC Scopus subject areas
- Space and Planetary Science
- Astronomy and Astrophysics
Cite this
Kepler photometry of RRc stars : Peculiar double-mode pulsations and period doubling. / Moskalik, P.; Smolec, R.; Kolenberg, K.; Molnár, L.; Kurtz, D. W.; Szabó, R.; Benkő, J.; Nemec, J. M.; Chadid, M.; Guggenberger, E.; Ngeow, C. C.; Jeon, Y. B.; Kopacki, G.; Kanbur, S. M.
In: Monthly Notices of the Royal Astronomical Society, Vol. 447, No. 3, 2015, p. 2348-2366.Research output: Article
}
TY - JOUR
T1 - Kepler photometry of RRc stars
T2 - Peculiar double-mode pulsations and period doubling
AU - Moskalik, P.
AU - Smolec, R.
AU - Kolenberg, K.
AU - Molnár, L.
AU - Kurtz, D. W.
AU - Szabó, R.
AU - Benkő, J.
AU - Nemec, J. M.
AU - Chadid, M.
AU - Guggenberger, E.
AU - Ngeow, C. C.
AU - Jeon, Y. B.
AU - Kopacki, G.
AU - Kanbur, S. M.
PY - 2015
Y1 - 2015
N2 - We present the analysis of four first overtone RR Lyrae stars observed with the Kepler space telescope, based on data obtained over nearly 2.5 yr. All four stars are found to be multiperiodic. The strongest secondary mode with frequency f2 has an amplitude of a few mmag, 20-45 times lower than the main radial mode with frequency f1. The two oscillations have a period ratio of P2/P1 = 0.612-0.632 that cannot be reproduced by any two radial modes. Thus, the secondary mode is non-radial. Modes yielding similar period ratios have also recently been discovered in other variables of the RRc and RRd types. These objects form a homogenous group and constitute a new class of multimode RR Lyrae pulsators, analogous to a similar class of multimode classical Cepheids in the Magellanic Clouds. Because a secondary mode with P2/P1 ~ 0.61 is found in almost every RRc and RRd star observed from space, this form of multiperiodicity must be common. In all four Kepler RRc stars studied, we find subharmonics of f2 at ~1/2f2 and at ~3/2f2. This is a signature of period doubling of the secondary oscillation, and is the first detection of period doubling in RRc stars. The amplitudes and phases of f2 and its subharmonics are variable on a time-scale of 10-200 d. The dominant radial mode also shows variations on the same time-scale, but with much smaller amplitude. In three Kepler RRc stars we detect additional periodicities, with amplitudes below 1 mmag, that must correspond to non-radial g-modes. Such modes never before have been observed in RR Lyrae variables.
AB - We present the analysis of four first overtone RR Lyrae stars observed with the Kepler space telescope, based on data obtained over nearly 2.5 yr. All four stars are found to be multiperiodic. The strongest secondary mode with frequency f2 has an amplitude of a few mmag, 20-45 times lower than the main radial mode with frequency f1. The two oscillations have a period ratio of P2/P1 = 0.612-0.632 that cannot be reproduced by any two radial modes. Thus, the secondary mode is non-radial. Modes yielding similar period ratios have also recently been discovered in other variables of the RRc and RRd types. These objects form a homogenous group and constitute a new class of multimode RR Lyrae pulsators, analogous to a similar class of multimode classical Cepheids in the Magellanic Clouds. Because a secondary mode with P2/P1 ~ 0.61 is found in almost every RRc and RRd star observed from space, this form of multiperiodicity must be common. In all four Kepler RRc stars studied, we find subharmonics of f2 at ~1/2f2 and at ~3/2f2. This is a signature of period doubling of the secondary oscillation, and is the first detection of period doubling in RRc stars. The amplitudes and phases of f2 and its subharmonics are variable on a time-scale of 10-200 d. The dominant radial mode also shows variations on the same time-scale, but with much smaller amplitude. In three Kepler RRc stars we detect additional periodicities, with amplitudes below 1 mmag, that must correspond to non-radial g-modes. Such modes never before have been observed in RR Lyrae variables.
KW - Stars: horizontal branch
KW - Stars: oscillations
KW - Stars: variables: RR Lyrae
KW - Techniques: photometric
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U2 - 10.1093/mnras/stu2561
DO - 10.1093/mnras/stu2561
M3 - Article
VL - 447
SP - 2348
EP - 2366
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
SN - 0035-8711
IS - 3
ER -