Issue |
A&A
Volume 677, September 2023
|
|
---|---|---|
Article Number | A177 | |
Number of page(s) | 20 | |
Section | Catalogs and data | |
DOI | https://doi.org/10.1051/0004-6361/202245634 | |
Published online | 26 September 2023 |
Frequency analysis of the first-overtone RR Lyrae stars based on Extended Aperture Photometry from K2 data★
1
Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Eötvös Loránd Research Network (ELKH); MTA Centre of Excellence,
1121
Konkoly Thege Miklós út 15–17,
Budapest, Hungary
e-mail: henia@netzel.pl
2
MTA CSFK Lendület Near-Field Cosmology Research Group,
1121
Konkoly Thege Miklós út 15–17,
Budapest, Hungary
3
ELTE Eötvös Loránd University, Institute of Physics,
1117,
Pázmány Péter sétány 1/A,
Budapest, Hungary
4
ELTE Eötvös Loránd University, Gothard Astrophysical Observatory,
Szent Imre h. u. 112,
9700
Szombathely, Hungary
Received:
7
December
2022
Accepted:
18
March
2023
Context. Additional low-amplitude signals have been observed in many RR Lyrae stars separate from pulsations in radial modes. The most common of these are short-period signals forming a period ratio of around 0.60–0.65 with the first overtone and long-period signals forming a period ratio of around 0.68. The RR Lyrae stars may also exhibit quasi-periodic modulation in their light curves, the so-called Blazhko effect.
Aims. We used the extensive sample of the first-overtone RR Lyrae stars observed by the Kepler telescope during the K2 mission to search for and characterize additional low-amplitude signals. The K2 data provides space-based photometry for a statistically significant sample. Hence, this data is excellent for studying the pulsation properties of RR Lyrae stars in detail.
Methods. We used K2 space-based photometry for RR Lyrae candidates from Campaigns 0–19. We selected RR Lyrae stars pulsating in the first overtone and performed a frequency analysis for each star to characterize their frequency contents.
Results. We classified 452 stars as first-overtone RR Lyrae. From that sample, we selected 281 RR0.61 stars, 67 RR0.68 stars, and 68 Blazhko stars. We found particularly interesting stars that show all of the above phenomena simultaneously. We detected signals in RR0.61 stars that form period ratios lower than those observed for the majority of stars of this type. These signals likely form a new sequence in the Petersen diagram, around a period ratio of 0.60. In 32 stars, we detected additional signals that form a period ratio close to that expected in RRd stars, but the classification of these stars as RRd is uncertain. We also report a discovery of additional signals in eight stars that form a new group in the Petersen diagram around the period ratio of 0.465–0.490. The nature of this periodicity remains unknown.
Key words: stars: variables: RR Lyrae / stars: oscillations / stars: horizontal-branch
Full Tables 1–4 are available at the CDS via anonymous ftp to cdsarc.cds.unistra.fr (130.79.128.5) or via https://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/677/A177
© The Authors 2023
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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