METAL ABUNDANCES, RADIAL VELOCITIES, AND OTHER PHYSICAL CHARACTERISTICS FOR THE RR LYRAE STARS IN THEKEPLERFIELD

Abstract

Spectroscopic iron-to-hydrogen ratios, radial velocities, atmospheric parameters, and new photometric analyses are presented for 41 RR Lyrae stars (and one probable high-amplitude δ Sct star) located in the field-of-view of the Kepler space telescope. Thirty-seven of the RR Lyrae stars are fundamental-mode pulsators (i.e., RRab stars) of which 16 exhibit the Blazhko effect. Four of the stars are multiperiodic RRc pulsators oscillating primarily in the first-overtone mode. Spectroscopic [Fe/H] values for the 34 stars for which we were able to derive estimates range from −2.54 ± 0.13 (NR Lyr) to −0.05 ± 0.13 dex (V784 Cyg), and for the 19 Kepler-field non-Blazhko stars studied by Nemec et al. (2011) the abundances agree will with their photometric [Fe/H] values. Four non-Blazhko RR Lyrae stars that they identified as metal-rich (KIC 6100702, V2470 Cyg, V782 Cyg and V784 Cyg) are confirmed as such, and four additional stars (V839 Cyg, KIC 5520878, KIC 8832417, KIC 3868420) are also shown here to be metal-rich. Five of the non-Blazhko RRab stars are found to be more metalrich than [Fe/H]∼ −0.9 dex while all of the 16 Blazhko stars are more metal-poor than this value. New P -φ s 31 -[Fe/H] relationships are derived based on ∼970 days of quasi-continuous high-precison Q0-Q11 long-and short-cadence Kepler photometry. With the exception of some Blazhko stars, the spectroscopic and photometric [Fe/H] values are in good agreement. Several stars with unique photometric characteristics are identified, including a Blazhko variable with the smallest known amplitude and frequency modulations (V838 Cyg).

Rotation, differential rotation, and gyrochronology of activeKeplerstars

“…To reduce the number of false positives, i.e., periodic variability not related to stellar rotation, we discarded 17 eclipsing binaries 2 , 878 planetary candidates 3 , 2 RR Lyrae stars Szabó et al 2010;Benkő et al 2010;Guggenberger et al 2012;Nemec et al 2011Nemec et al , 2013Moskalik et al 2012;Molnár et al 2012), and 84 γ Doradus and δ Scuti stars Ulusoy et al 2014;Balona et al 2011;Uytterhoeven et al 2011;Lampens et al 2013;Balona 2014). In total, 981 stars were discarded, leaving 23 143 targets, which are analyzed as described in the following section.…”

Improving the cosmic distance ladder. Distance and structure of the Large Magellanic Cloud

“…We will use Nemec et al (2013) relations in 6 to derive photometric metallicities for the RR Lyrae stars.…”

“…Nemec et al (2013) Error of φ c 31 ; Column 5: Metallicity in the C09 metallicity scale derived with Eq. 1.13; Column 6: Error of metallicity in the C09 metallicity scale).…”

Dynamical Asteroseismology: towards improving the theories of stellar structure and (tidal) evolution

“…An observational probe of the near core regions, as well as the measurements of the internal rotation have recently become available for main-sequence (MS) stars of spectral types B to F [e.g., 22,26,33,35]. Space-based data provided us with e-mail: Andrew.Tkachenko@ster.kuleuven.be new insights into stellar objects at advanced evolutionary stages (e.g., RR Lyrae stars - [25]; subdwarf B-type stars - [8]), revolutionized our understanding of evolved red-giant stars exhibiting stochastically excited solar-like oscillations [e.g. , 7], and significantly improved our understanding of stars during early, pre-main-sequence (pre-MS) stages of their evolution [43].…”