Frequency and spectrum analysis of Doradus type Kepler target KIC6462033

Ulusoy, C.; Статева, И.; Iliev, I. Kh.; Ulaş, B.

doi:10.1016/j.newast.2014.01.002

Cited by 3 publications

(7 citation statements)

References 29 publications

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“…The largest discrepancy in Table 2 occurs for KIC 6462033 where we find T eff = 18400 K, but Ulusoy et al (2014) find T eff = 7150 K. Our spectrum shows strong He I 4437 and He I 4471 which can only occur in a B star, so the difference is very puzzling. The field is slightly crowded, but KIC 6462033 is by far the brightest star in the field.…”

Section: The Hot γ Dor Starscontrasting

confidence: 54%

The hot γ Doradus and Maia stars

Balona

Engelbrecht

Joshi

et al. 2016

Mon. Not. R. Astron. Soc.

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The hot γ Doradus stars have multiple low frequencies characteristic of γ Dor or SPB variables, but are located between the red edge of the SPB and the blue edge of the γ Dor instability strips where all low-frequency modes are stable in current models of these stars. Though δ Sct stars also have low frequencies, there is no sign of high frequencies in hot γ Dor stars. We obtained spectra to refine the locations of some of these stars in the H-R diagram and conclude that these are, indeed, anomalous pulsating stars. The Maia variables have multiple high frequencies characteristic of β Cep and δ Sct stars, but lie between the red edge of the β Cep and the blue edge of the δ Sct instability strips. We compile a list of all Maia candidates and obtain spectra of two of these stars. Again, it seems likely that these are anomalous pulsating stars which are currently not understood.

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Section: The Hot γ Dor Starscontrasting

confidence: 54%

The hot γ Doradus and Maia stars

Balona

Engelbrecht

Joshi

et al. 2016

Mon. Not. R. Astron. Soc.

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“…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.…”

Section: Kepler Datamentioning

confidence: 99%

Rotation, differential rotation, and gyrochronology of activeKeplerstars

Reinhold

Gizon

2015

A&A

182

170

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Context. In addition to the discovery of hundreds of exoplanets, the high-precision photometry from the CoRoT and Kepler satellites has led to measurements of surface rotation periods for tens of thousands of stars, which can potentially be used to infer stellar ages via gyrochronology. Aims. Our main goal is to derive ages of thousands of field stars using consistent rotation period measurements derived by different methods. Multiple rotation periods are interpreted as surface differential rotation (DR). We study the dependence of DR with rotation period and effective temperature. Methods. We reanalyze a previously studied sample of 24 124 Kepler stars using different approaches based on the Lomb-Scargle periodogram. Each quarter (Q1-Q14) is treated individually using a prewhitening approach. Additionally, the full time series and their different segments are analyzed. Results. For more than 18 500 stars our results are consistent with the rotation periods from McQuillan et al. (2014, ApJS, 211, 24). Of these, more than 12 300 stars show multiple significant peaks, which we interpret as DR. Dependencies of the DR with rotation period and effective temperature could be confirmed, e.g., the relative DR increases with rotation period. Gyrochronology ages between 100 Myr and 10 Gyr were derived for more than 17 000 stars using different gyrochronology relations, most of them with uncertainties dominated by period variations. We find a bimodal age distribution for T eff between 3200-4700 K. The derived ages reveal an empirical activity-age relation using photometric variability as stellar activity proxy. Additionally, we found 1079 stars with extremely stable (mostly short) periods. Half of these periods may be associated with rotation stabilized by non-eclipsing companions, the other half might be due to pulsations. Conclusions. The derived gyrochronology ages are well constrained since more than ∼93.0% of the stars seem to be younger than the Sun where calibration is most reliable. Explaining the bimodality in the age distribution is challenging, and limits accurate stellar age predictions. The relation between activity and age is interesting, and requires further investigation. The existence of cool stars with almost constant rotation period over more than three years of observation might be explained by synchronization with stellar companions, or a dynamo mechanism keeping the spot configurations extremely stable.

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“…Even when we consider the new theoretical instability strips of β Cep and SPB stars by Moravveji (2016), which were calculated based on the improved opacity tables, KIC 5309849 is still cooler then the red KIC 6462033 shows a rich spectrum of low frequencies. Uytterhoeven et al (2011) reported 46 independent frequencies, whereas Ulusoy et al (2014) identified five independent frequencies and hundreds of combinations and harmonics. Our selection criterion resulted in 509 frequencies.…”

Section: Kic 5309849mentioning

confidence: 99%

“…He I and Mg II lines, do not show clear broadening, which is not fully understood. Ulusoy et al (2014) carried out spectroscopic observations of KIC 6462033. By fitting Hα and Hβ line profiles, they found that the KIC T eff was too high.…”

Section: Identification Of Four B-type Variable Starsmentioning

confidence: 99%

“…As noted by Uytterhoeven et al (2011), the classifier used only three independent frequencies with the highest amplitudes, and no external information was taken into account. Based on KIC parameters and light curves with longer time coverage, KIC 6462033 (Uytterhoeven et al 2011;Balona 2014;Ulusoy et al 2014) and KIC 8324482 (Balona 2014) were identified as γ Dor pulsators, while KIC 8255796 was classified as a rotating A star (Balona 2013). As shown in Figure 5, these four stars all fall into the instability strip of SPB stars with updated stellar parameters.…”

Section: Oscillation Propertiesmentioning

confidence: 99%

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Misclassified B Stars in the Kepler Field

Zhang

Liu

et al. 2018

ApJ

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Stellar fundamental parameters are important in the asteroseismic study of Kepler light curves. However, the most used estimates in the Kepler Input Catalog (KIC) are not accurate enough for hot stars. Using a sample of B stars from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) spectral survey, we confirmed the systematic underestimation in KIC effective temperature and overestimation in KIC surface gravity. The good agreement between LAMOST and other follow-up observations proved the accuracy of effective temperature and surface gravity of B stars derived from LAMOST low-resolution spectra. By searching through LAMOST data, we found four misclassified main-sequence B stars in the Kepler field, which had been previously classified as A-type variables. We present spectroscopic and detailed frequency analysis of these four stars based on LAMOST spectra and Kepler photometry.

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Frequency and spectrum analysis of Doradus type Kepler target KIC6462033

Cited by 3 publications

References 29 publications

The hot γ Doradus and Maia stars

The hot γ Doradus and Maia stars

Rotation, differential rotation, and gyrochronology of activeKeplerstars

Misclassified B Stars in the Kepler Field

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