Rotation Periods of 34,030 Kepler Main-Sequence Stars: The Full Autocorrelation Sample

We analyzed 3 years of data from the Kepler space mission to derive rotation periods of main-sequence stars below 6500 K. Our automated autocorrelation-based method detected rotation periods between 0.2 and 70 days for 34,030 (25.6%) of the 133,030 main-sequence Kepler targets (excluding known eclipsing binaries and Kepler Objects of Interest), making this the largest sample of stellar rotation periods to date. In this paper we consider the detailed features of the now well-populated period-temperature distribution and demonstrate that the period bimodality, first seen by McQuillan, Aigrain & Mazeh (2013) in the M-dwarf sample, persists to higher masses, becoming less visible above 0.6 M_sun. We show that these results are globally consistent with the existing ground-based rotation-period data and find that the upper envelope of the period distribution is broadly consistent with a gyrochronological age of 4.5 Gyrs, based on the isochrones of Barnes (2007), Mamajek & Hillenbrand (2008) and Meibom et al. (2009). We also performed a detailed comparison of our results to those of Reinhold et al. (2013) and Nielsen et al. (2013), who have measured rotation periods of field stars observed by Kepler. We examined the amplitude of periodic variability for the stars with detected rotation periods, and found a typical range between ~950 ppm (5th percentile) and ~22,700 ppm (95th percentile), with a median of ~5,600 ppm. We found typically higher amplitudes for shorter periods and lower effective temperatures, with an excess of low-amplitude stars above ~5400 K.Comment: Accepted ApJS 20th Feb 2014, submitted 13th Jan 2014. 15 pages, 12 Figures, 6 Tables. Tables 1 & 2 are available in their entirety in a machine-readable form in the online supplementary material or from http://www.astro.tau.ac.il/~amy

Stellar Rotation Periods of the Kepler Objects of Interest: A Dearth of Close-in Planets around Fast Rotators

We present a large sample of stellar rotation periods for Kepler Objects of Interest (KOIs), based on three years of public Kepler data. These were measured by detecting periodic photometric modulation caused by star spots, using an algorithm based on the autocorrelation function (ACF) of the light curve, developed recently by McQuillan, Aigrain & Mazeh (2013). Of the 1919 main-sequence exoplanet hosts analyzed, robust rotation periods were detected for 737. Comparing the detected stellar periods to the orbital periods of the innermost planet in each system reveals a notable lack of close-in planets around rapid rotators. It appears that only slowly spinning stars, with rotation periods longer than 5-10 days, host planets on orbits shorter than 3 days, although the mechanism(s) that lead(s) to this is not clear.Comment: Accepted for publication in ApJL on 8th Aug 2013, 5 pages, 3 figures, 1 table. A full machine-readable version of Table 1 is available as an ancillary fil

Statistics of Stellar Variability from Kepler - I: Revisiting Quarter 1 with an Astrophysically Robust Systematics Correction

We investigate the variability properties of main sequence stars in the first month of Kepler data, using a new astrophysically robust systematics correction, and find that 60% of stars are more variable then the active Sun. We define low and high variability samples, with a cut corresponding to twice the variability level of the active Sun, and compare the properties of the stars belonging to each sample. We show tentative evidence that the more active stars have lower proper motions and may be located closer to the galactic plane. We also investigate the frequency content of the variability, finding clear evidence for periodic or quasi-periodic behaviour in 16% of stars, and showing that there exist significant differences in the nature of variability between spectral types. Of the periodic objects, most A and F stars have short periods (< 2 days) and highly sinusoidal variability, suggestive of pulsations, whilst G, K and M stars tend to have longer periods (> 5 days, with a trend towards longer periods at later spectral types) and show a mixture of periodic and stochastic variability, indicative of activity. Finally, we use auto-regressive models to characterise the stochastic component of the variability, and show that its typical amplitude and time-scale both increase towards later spectral types, which we interpret as a corresponding increase in the characteristic size and life-time of active regions.Comment: Accepted A&A, 13 pages, 13 figures, 4 table

Measuring the rotation period distribution of field M-dwarfs with Kepler

We have analysed 10 months of public data from the Kepler space mission to measure rotation periods of main-sequence stars with masses between 0.3 and 0.55 M_sun. To derive the rotational period we introduce the autocorrelation function and show that it is robust against phase and amplitude modulation and residual instrumental systematics. Of the 2483 stars examined, we detected rotation periods in 1570 (63.2%), representing an increase of a factor ~ 30 in the number of rotation period determination for field M-dwarfs. The periods range from 0.37-69.7 days, with amplitudes ranging from 1.0-140.8 mmags. The rotation period distribution is clearly bimodal, with peaks at ~ 19 and ~ 33 days, hinting at two distinct waves of star formation, a hypothesis that is supported by the fact that slower rotators tend to have larger proper motions. The two peaks of the rotation period distribution form two distinct sequences in period-temperature space, with the period decreasing with increasing temperature, reminiscent of the Vaughan-Preston gap. The period-mass distribution of our sample shows no evidence of a transition at the fully convective boundary. On the other hand, the slope of the upper envelope of the period-mass relation changes sign around 0.55 M_sun, below which period rises with decreasing mass.Comment: Accepted for publication in MNRAS. 15 pages, 14 figures, 5 tables. Full machine-readable versions of tables 2-5 are available as ancillary files, or with plots of the light curves, ACFs and periodograms at http://www.physics.ox.ac.uk/StellarRotatio

Discovery Orientation, Cognitive Schemas, and Disparities in Science Identity in Early Adolescence

Why are some youth more likely to think of themselves as a science kind of person than others? In this paper, we use a cognitive social-theoretical framework to assess disparities in science identity among middle school–age youth in the United States. We investigate how discovery orientation is associated with science interest, perceived ability, importance, and reflected appraisal, and how they are related to whether youth see themselves, and perceive that others see them, as a science kind of person. We surveyed 441 students in an ethnically diverse, low-income middle school. Gender and race/ethnicity are associated with science identity but not with discovery orientation. Structural equation model results show that the positive association between discovery orientation and science identity is mediated by science interest, importance, and reflected appraisal. These findings advance understanding of how science attitudes and recognition may contribute to the underrepresentation of girls and/or minorities in science

Informal Science Experiences among Urban and Rural Youth: Exploring Differences at the Intersections of Socioeconomic Status, Gender and Ethnicity

The current study explores patterns of informal science experiences among youth in urban and rural middle schools by gender and socioeconomic status. Data come from surveys in two Midwestern middle schools, one in a mid-sized city, and the other in a rural-remote town. We asked about participation in informal science activities (e.g. visiting zoos or museums, or watching shows about science) and if youth had participated in science-focused clubs in the last 12 months (e.g. after-school science clubs, 4-H, scouts). Rural youth reported lower rates of participation in after-school science clubs and a greater desire to participate in after-school science programming than urban youth. Latino/a youth tend to have fewer informal science experiences than non- Latino/a youth, particularly in urban areas. There were few differences in informal science experiences between boys and girls, but in urban areas, girls report more science experiences than boys. Reported science experiences are overall higher in urban areas, yet youth with fewer resources (i.e. books in the home) have fewer informal science experiences overall. This study sheds new light on how socioeconomic status, gender, ethnicity, and geography interact with one another to shape youth science exposure and interest

Time variation of Kepler transits induced by stellar spots - a way to distinguish between prograde and retrograde motion. II. Application to KOIs

Mazeh, Holczer, and Shporer (2015) have presented an approach that can, in principle, use the derived transit timing variation (TTV) of some transiting planets observed by the $Kepler$ mission to distinguish between prograde and retrograde motion of their orbits with respect to their parent stars' rotation. The approach utilizes TTVs induced by spot-crossing events that occur when the planet moves across a spot on the stellar surface, looking for a correlation between the derived TTVs and the stellar brightness derivatives at the corresponding transits. This can work even in data that cannot temporally resolve the spot-crossing events themselves. Here we apply this approach to the $Kepler$ KOIs, identifying nine systems where the photometric spot modulation is large enough and the transit timing accurate enough to allow detection of a TTV-brightness-derivatives correlation. Of those systems five show highly significant prograde motion (Kepler-17b, Kepler-71b, KOI-883.01, KOI-895.01, and KOI-1074.01), while no system displays retrograde motion, consistent with the suggestion that planets orbiting cool stars have prograde motion. All five systems have impact parameter $0.2\lesssim b\lesssim0.5$, and all systems within that impact parameter range show significant correlation, except HAT-P-11b where the lack of a correlation follows its large stellar obliquity. Our search suffers from an observational bias against detection of high impact parameter cases, and the detected sample is extremely small. Nevertheless, our findings may suggest that stellar spots, or at least the larger ones, tend to be located at a low stellar latitude, but not along the stellar equator, similar to the Sun.Comment: V2: accepted to Ap

Accuracy of COVID-19 Relevant Knowledge among Youth: Number of Information Sources Matters

Can comics effectively convey scientific knowledge about COVID-19 to youth? What types and how many sources of information did youth have about COVID-19 during the pandemic? How are sources of information associated with accurate COVID-19 knowledge? To answer these questions, we surveyed youth in grades 5–9 in a Midwestern United States school district in the winter of 2020–2021. The online survey used measures of COVID-19 knowledge and sources, with an embedded experiment on COVID-19 relevant comics. Guided by an integrated science capital and just-in-time health and science information acquisition model, we also measured level of science capital, science identity, and utility of science for health and society. The school district protocol required parental consent for participation; 264 of ~15,000 youth participated. Youth were randomly assigned one of four comic conditions before receiving an online survey. Results indicate that, similar to knowledge gains in comic studies on other science topics, reading the comics was associated with 7 to 29% higher accuracy about COVID-19. We found that youth reported getting information about COVID-19 from between 0–6 sources including media, family, friends, school, and experts. The bivariate positive association of news versus other sources with accuracy of knowledge did not persist in the full model, yet the positive association of a higher number of sources and accuracy did persist in the multivariate models. The degree of valuing the utility of science for their health moderated the number of sources to accuracy association. Those with less value on science for health had a stronger positive association of number of sources and accuracy in COVID-19 knowledge. We conclude that during a pandemic, even with health and science information ubiquitous in the news media, increasing youth access to a variety of accurate sources of information about science and health can increase youth knowledge