J/MNRAS/448/429 Starspots in short-period Kepler binaries (Balaji+, 2015)
Tracking the stellar longitudes of starspots in short-period Kepler binaries.
Balaji B., Croll B., Levine A.M., Rappaport S.
<Mon. Not. R. Astron. Soc., 448, 429-444 (2015)>
=2015MNRAS.448..429B 2015MNRAS.448..429B (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple
Keywords: binaries: close - binaries: general - stars: rotation - starspots
Abstract:
We report on a new method for tracking the phases of the orbital
modulations in very short-period, near-contact, and contact binary
systems in order to follow starspots. We apply this technique to
Kepler light curves for 414 binary systems that were identified as
having anticorrelated O-C curves for the mid-times of the primary and
secondary eclipses, or in the case of non-eclipsing systems, their
light-curve minima. This phase tracking approach extracts more
information about starspot and binary system behaviour than may be
easily obtained from the O-C curves. We confirm the hypothesis of Tran
et al. that we can successfully follow the rotational motions of spots
on the surfaces of the stars in these binaries. In ∼34% of the
systems, the spot rotation is retrograde as viewed in the frame
rotating with the orbital motion, while ∼13% show significant prograde
spot rotation. The remaining systems show either little spot rotation
or erratic behaviour, or sometimes include intervals of both types of
behaviour. We discuss the possibility that the relative motions of
spots are related to differential rotation of the stars. It is clear
from this study that the motions of the starspots in at least 50% of
these short-period binaries are not exactly synchronized with the
orbits.
Description:
The present study is based on Kepler long-cadence (LC) light curves,
sets of sequential measurements of the flux obtained from 29.4-min
integrations. We retrieved the LC light curve files for Quarters
1-17 for all of the ∼2600 candidates in the latest Kepler
eclipsing binary catalogue (Slawson et al. 2011, Cat. J/AJ/142/160;
Matijevic et al., 2012AJ....143..123M 2012AJ....143..123M) that were available at the
Multimission Archive at STScI. We used the light curves made with the
PDC-MAP algorithm (Smith et al., 2012PASP..124.1000S 2012PASP..124.1000S; Stumpe et al.
2012PASP..124..985S 2012PASP..124..985S), which is intended to remove instrumental
signatures from the flux time series while retaining the bulk of the
astrophysical variations of each target. For each quarter, the flux
series was normalized to its median value. Then, for each target, the
results from all available quarters were stitched together in a single
flux data file.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 20 414 Kepler binaries exhibiting anticorrelated O-C curves
figs/* . 4 Plot of the light curves
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See also:
V/133 : Kepler Input Catalog (Kepler Mission Team, 2009)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 8 I8 --- KIC KIC number
9 A1 --- n_KIC [*] Note on KIC (1)
11- 18 F8.6 d Per Period
20 A1 --- Fig [ABCD] Figure number in which the light curves
is plotted
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Note (1): The Kepler targets marked with a * are listed as 'false positives' in
the Kepler binary star catalogue. Their anticorrelated O-C curves, however,
may well indicate that they are, in fact, true short-period binaries.
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 04-Aug-2015