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Nemec, J. M.,Smolec, R.,Benkő,, J. M.,Moskalik, P.,Kolenberg, K.,Szabó,, R.,Kurtz, D. W.,Bryson, S.,Guggenberger, E.,Chadid, M.,Jeon, Y.‐,B.,Kunder, A.,Layden, A. C.,Kinemuchi, K.,Kis Blackwell Publishing Ltd 2011 Monthly notices of the Royal Astronomical Society Vol.417 No.2
<P><B>ABSTRACT</B></P><P>Nineteen of the ∼40 RR Lyr stars in the <I>Kepler</I> field have been identified as candidate non‐Blazhko (or unmodulated) stars. In this paper we present the results of Fourier decomposition of the time‐series photometry of these stars acquired during the first 417 d of operation (Q0–Q5) of the <I>Kepler</I> telescope. Fourier parameters based on ∼18 400 long‐cadence observations per star (and ∼150 000 short‐cadence observations for FN Lyr and for AW Dra) are derived. None of the stars shows the recently discovered ‘period‐doubling’ effect seen in Blazhko variables; however, KIC 7021124 has been found to pulsate simultaneously in the fundamental and second overtone modes with a period ratio <I>P</I><SUB>2</SUB>/<I>P</I><SUB>0</SUB>∼ 0.593 05 and is similar to the double‐mode star V350 Lyr. Period change rates are derived from O − C diagrams spanning, in some cases, over 100 years; these are compared with high‐precision periods derived from the <I>Kepler</I> data alone. Extant Fourier correlations by Kovács, Jurcsik et al. (with minor transformations from the <I>V</I> to the <I>Kp</I> passband) have been used to derive underlying physical characteristics for all the stars. This procedure seems to be validated through comparisons of the <I>Kepler</I> variables with Galactic and Large Magellanic Cloud (LMC) RR Lyr stars. The most metal‐poor star in the sample is NR Lyr, with [Fe/H] =−2.3 dex; and the four most metal‐rich stars have [Fe/H] ranging from −0.6 to +0.1 dex. Pulsational luminosities and masses are found to be systematically smaller than <I>L</I> and <IMG src='/wiley-blackwell_img/equation/MNR_19317_mu1.gif' alt ='inline image'/> values derived from stellar evolution models, and are favoured over the evolutionary values when periods are computed with the Warsaw linear hydrodynamics code. Finally, the Fourier parameters are compared with theoretical values derived using the Warsaw non‐linear convective pulsation code.</P>
<i>Kepler</i> photometry of the prototypical Blazhko star RR Lyr: an old friend seen in a new light
Kolenberg, K.,Bryson, S.,Szabó,, R.,Kurtz, D. W.,Smolec, R.,Nemec, J. M.,Guggenberger, E.,Moskalik, P.,Benkő,, J. M.,Chadid, M.,Jeon, Y.‐,B.,Kiss, L. L.,Kopacki, G.,Nuspl, J.,Still, M Blackwell Publishing Ltd 2011 Monthly notices of the Royal Astronomical Society Vol.411 No.2
<P><B>ABSTRACT</B></P><P>We present our analysis of the long‐cadence <I>Kepler</I> data for the well‐studied Blazhko star RR Lyr, gathered during the first two quarters of the satellite’s observations and covering a total of 127 d. Besides being of great importance for our understanding of RR Lyrae stars in general, these RR Lyr data can be regarded as a case study for observations of bright stars with <I>Kepler</I>. <I>Kepler</I> can perform high‐precision photometry on targets like RR Lyr, as the saturated flux is conserved to a very high degree. The <I>Kepler</I> data on RR Lyr are revolutionary in several respects. Even with long‐cadence sampling (one measurement per 29.4 min), the unprecedented precision (< mmag) of the <I>Kepler</I> photometry allows the study of the star’s extreme light‐curve variations in detail. The multiplet structures at the main frequency and its harmonics, typical for Blazhko stars, are clearly detected up to the quintuplets. For the first time, photometric data of RR Lyr reveal the presence of half‐integer frequencies, linked to a period‐doubling effect. This phenomenon may be connected to the still unexplained Blazhko modulation. Moreover, with three observed Blazhko cycles at our disposal, we observe that there is no exact repetition in the light‐curve changes from one modulation cycle to the next for RR Lyr. This may be due to additional periodicities in the star, or to transient or quasi‐periodic changes.</P>
Szabó,, R.,Kollá,th, Z.,Molná,r, L.,Kolenberg, K.,Kurtz, D. W.,Bryson, S. T.,Benkő,, J. M.,Christensen‐,Dalsgaard, J.,Kjeldsen, H.,Borucki, W. J.,Koch, D.,Twicken, J. D.,C Blackwell Publishing Ltd 2010 MONTHLY NOTICES- ROYAL ASTRONOMICAL SOCIETY Vol.409 No.3
<P><B>ABSTRACT</B></P><P>The first detection of the period doubling phenomenon is reported in the <I>Kepler</I> RR Lyrae stars RR Lyr, V808 Cyg and V355 Lyr. Interestingly, all these pulsating stars show Blazhko modulation. The period doubling manifests itself as alternating maxima and minima of the pulsational cycles in the light curve, as well as through the appearance of half‐integer frequencies located halfway between the main pulsation period and its harmonics in the frequency spectrum. The effect was found to be stronger during certain phases of the modulation cycle. We were able to reproduce the period‐doubling bifurcation in our non‐linear RR Lyrae models computed by the Florida–Budapest hydrocode. This enabled us to trace the origin of this instability in RR Lyrae stars to a resonance, namely a 9:2 resonance between the fundamental mode and a high‐order (ninth) radial overtone showing strange‐mode characteristics. We discuss the connection of this new type of variation to the mysterious Blazhko effect and argue that it may give us fresh insights into solving this century‐old enigma.</P>
Reed, M. D.,Harms, S. L.,Poindexter, S.,Zhou, A.‐,Y.,Eggen, J. R.,Morris, M. A.,Quint, A. C.,McDaniel, S.,Baran, A.,Dolez, N.,Kawaler, S. D.,Kurtz, D. W.,Moskalik, P.,Riddle, R.,Zola, S.,Østense Blackwell Publishing Ltd 2011 Monthly notices of the Royal Astronomical Society Vol.412 No.1
<P><B>ABSTRACT</B></P><P>KPD 1930+2752 is a short‐period pulsating subdwarf B (sdB) star. It is also an ellipsoidal variable with a known binary period of 2.3 h. The companion is most likely a white dwarf and the total mass of the system is close to the Chandresekhar limit. In this paper, we report the results of Whole Earth Telescope (WET) photometric observations during 2003 and a smaller multisite campaign of 2002. From 355 h of WET data, we detect 68 pulsation frequencies and suggest an additional 13 frequencies within a crowded and complex temporal spectrum between 3065 and 6343 μHz (periods between 326 and 157 s). We examine pulsation properties including phase and amplitude stability in an attempt to understand the nature of the pulsation mechanism. We examine a stochastic mechanism by comparing amplitude variations with simulated stochastic data. We also use the binary nature of KPD 1930+2752 for identifying pulsation modes via multiplet structure and a tidally induced pulsation geometry. Our results indicate a complicated pulsation structure that includes short‐period (≈16 h) amplitude variability, rotationally split modes, tidally induced modes and some pulsations which are geometrically limited on the sdB star.</P>
Identifiability and Privacy in Pluripotent Stem Cell Research
Isasi, R.,Andrews, Peter W.,Baltz, Jay M.,Bredenoord, Annelien L.,Burton, P.,Chiu, I.M.,Hull, S.,Jung, J.W.,Kurtz, A.,Lomax, G.,Ludwig, T.,McDonald, M.,Morris, C.,Ng, H.,Rooke, H.,Sharma, A.,Stacey, G Cell Press 2014 Cell stem cell Vol.14 No.4
Data sharing is an essential element of research; however, recent scientific and social developments have challenged conventional methods for protecting privacy. Here we provide guidance for determining data sharing thresholds for human pluripotent stem cell research aimed at a wide range of stakeholders, including research consortia, biorepositories, policy-makers, and funders.