K2 reveals pulsed accretion driven by the 2 Myr old hot Jupiter CI Tau b

CI Tau is a young (~2 Myr) classical T Tauri star located in the Taurus star forming region. Radial velocity observations indicate it hosts a Jupiter-sized planet with an orbital period of approximately 9 days. In this work, we analyze time series of CI Tau's photometric variability as seen by K2. The lightcurve reveals the stellar rotation period to be ~6.6 d. Although there is no evidence that CI Tau b transits the host star, a ~9 d signature is also present in the lightcurve. We believe this is most likely caused by planet-disk interactions which perturb the accretion flow onto the star, resulting in a periodic modulation of the brightness with the ~9 d period of the planet's orbit.Comment: Accepted for publication in ApJ Letter

Interventions designed to reduce sedentary behaviours in young people: A review of reviews

Background: Leisure time is increasingly spent in sedentary pursuits such as screen-viewing (eg, television/DVD viewing and computer use), motorised travel, school/work and sitting-based socialising (eg, social media and chatting). Sedentary screen time, particularly TV, appears to play an important role in the aetiology of obesity due to its co-occurrence with other unhealthy behaviours such as snacking on energy-dense foods, low levels of physical activity and inadequate sleep. More information is needed on how to reduce sedentary behaviours. Most interventions have focused on young people and a number of systematic reviews exist on this topic. Objective: To synthesise systematic reviews and metaanalyses of interventions aimed at decreasing sedentary behaviours among children and adolescents. Methods: Papers were located from computerised and manual searches. Included articles were English language systematic reviews or meta-analyses of interventions aiming at reducing sedentary behaviour in children (<11 years) and adolescents (12-18 years). Results: Ten papers met the inclusion criteria and were analysed. All reviews concluded some level of effectiveness in reducing time spent in sedentary behaviour. When an effect size was reported, there was a small but significant reduction in sedentary time (highest effect size=-0.29; CI -0.35 to -0.22). Moderator analyses showed a trend favouring interventions with children younger than 6 years. Effective strategies include the involvement of family, behavioural interventions and electronic TV monitoring devices. Conclusions: Results from systematic reviews and meta-analyses show that interventions to reduce children's sedentary behaviour have a small but significant effect. Future research should expand these findings examining interventions targeting different types of sedentary behaviours and the effectiveness of specific behaviour change techniques across different contexts and settings

Liability of Foreignness in Global Stock Markets: Liquidity Dynamics of Foreign IPOs in the US

Using a unique dataset of foreign and domestic IPOs listings in the US from 1990 to 2012, we study how foreignness affects IPO liquidity. We find that foreign IPOs enjoy higher liquidity than IPOs in their home countries, but do not fully gain the same liquidity benefits as for IPOs of domestic US issuers. In contrast to prior evidence for mature cross-listed firms, we show that liquidity differentials between foreign and domestic IPOs in the US are determined by information asymmetry related to foreignness rather than to home-country institutional environment characteristics. Thus, our results extend prior findings to reveal salient differences in liquidity and liquidity determinants between IPOs offerings by foreign and domestic firms in the US.postprin

Feasibility of Reducing and Breaking Up University Students' Sedentary Behaviour: Pilot Trial and Process Evaluation

BACKGROUND: Accumulating high levels of sedentary behaviour has been linked to poor health outcomes. This study examined the feasibility and preliminary, short-term effects of a theory-based intervention aimed at reducing total and prolonged sedentary behaviour in University students. DESIGN: A quasi-experimental (pre-post) pilot study. Methods: Nine ambulatory undergraduate students (Mean age = 22 ± 2.32) participated in a one-on-one session, including an educational component around the health effects of sedentary behaviour and three distinct activities (feedback, “pros and cons” exercise, and suggested behaviour change strategies). In addition, automated daily text messages targeting sedentary behaviour were sent for 6 days (four messages per day at fixed intervals). The Behaviour Change Wheel framework guided the intervention design process. Outcomes were assessed over 6 days in pre- and post-intervention periods and included accelerometer-based (activPAL) and self-reported (Nightly-Week-U) total sedentary time, as well as accelerometer-based number of steps and prolonged sedentary time. Students completed a process evaluation interview upon completing the trial. RESULTS: From pre- to post-intervention, there was a significant reduction in accelerometer-based total and prolonged sedentary time during weekend days. In addition, there was a significant increase in accelerometer-based standing time and stepping during weekend days. There were no statistically significant changes in accelerometer-based sedentary time, standing time or number of steps during weekdays. Process evaluation results indicated that the intervention and its assessment is feasible. Reductions in sedentary time were likely to be mediated by positive changes in the student's reflective and automatic motivation. CONCLUSIONS: Findings from this small, short-term intervention suggest that a single one-on-one session, together with automated text messages, may help University students reduce sedentary behaviour and enhance movement during weekend days. Additional strategies to maximise the intervention effects are discussed (e.g., establishing a collaboration with University staff, introducing sit-to-stand desks, and/or facilitating social support). A randomised control trial assessing sedentary behaviour over a longer period is needed to adequately study the intervention's effectiveness

Does relative rotation inclination affect disk lifetime in young binaries?

Surveys show strong evidence that disks typically dissipate in ~5 Myr, therefore planets must form on a similar timescale. However, the primary mechanisms driving disk-loss are still under investigation. Young binary stars are ideal targets for studying disk evolution because their stellar component provides a small control sample. This study probes the possibility that the relative rotation axes’ inclinations of young binaries may significantly affect disk lifetime, thus impacting their ability to form planets. A case study of the young binary DF Tau combines observational and computational analyses to investigate component rotation axes’ inclinations and compare them to the circumstellar disk properties of this system. Periodogram analyses of unresolved time-series photometry recover a rotation period of 10.5 d for the primary and an upper limit of 3.3 d for the secondary. Rotation periods combined with spectrally-derived projected rotation velocities yield an inclination of 90 degrees for both components. Additional investigation into a strong 9.3 d period present in periodogram indicates accretion hot spots are likely the source. DF Tau is one example target selected from a sample of ~100 different young binary observations and highlights the importance this data set has on informing our understanding of disk evolution and planet formation

Physical activity and sedentary behavior research in Indonesian youth : a scoping review

Background: This study aimed to map physical activity and sedentary behaviour research trends, designs, and topics for Indonesian youth. Methods: This review conforms to the "Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR)." A systematic search on eight platforms was performed in August 2018 and was updated in April 2020. Results: From 10,753 documents screened, 166 met the selection criteria. Over half of the studies were cross-sectional, and the majority utilized self-reported measurements (physical activity: 81.1%, sedentary behavior: 88.5%). More than two-thirds of the studies examined physical activity only (67.5%). The top three subtopics reported were prevalence/measurement, correlates, and outcomes of physical activity (28%, 24.6%, and 17%, respectively). The prevalence of "sufficient" physical activity ranges between 12.2% and 52.3%, while the prevalence of sedentary behavior >= 3 h per day ranges between 24.5% and 33.8%. Conclusions: Future studies need to focus more on intervention and validation, and research needs to be conducted more with nationally representative samples and on youth at the junior high school level. Future studies need to investigate more on psychological, cognitive, affective, social, cultural, and environmental correlates, and in-depth personal views of physical activity and sedentary behavior. More studies using device-based measurements, longitudinal designs, as well as qualitative and mixed-methods approaches are warranted

Amplitude modulation of short-timescale hot spot variability

Funding Information: L.I.B., L.A.P., and J.L. acknowledge support from NASA through an Astrophysics Data Analysis Program grant to Lowell Observatory (grant 80NSSC20K1001). A.C.C. and M.M.J. acknowledge support from the Science and Technology Facilities Council (STFC) consolidated grant No. ST/R00824/1, and the support of the visiting scientist program at Lowell Observatory in 2019 January and 2020 January. Data were obtained using the Mikulski Archive for Space Telescopes (MAST). STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.Variability of Classical T Tauri stars (CTTS) occurs over a vast range of timescales. CTTS in particular are subject to variability caused by accretion shocks, which can occur stochastically, periodically, or quasi-periodically on timescales over a few days. The detectability of young planets within these systems is likely hampered by activity; therefore, it is essential that we understand the origin of young star variability over a range of timescales to help disentangle stellar activity from signatures of planetary origin. We present an analysis of the stochastic small-amplitude photometric variability in the K2 lightcurve of CI Tau occurring on timescales of ≲1 day. We find the amplitude of this variability exhibits the same periodic signatures as detected in the large-amplitude variability, indicating that the physical mechanism modulating these brightness features is the same. The periods detected are also in agreement with the rotation period of the star (∼6.6 days) and the orbital period of the planet (∼9.0 days) known to drive pulsed accretion onto the star.PostprintPeer reviewe

High-speed Photometric Observations of ZZ Ceti White Dwarf Candidates

We present high-speed photometric observations of ZZ Ceti white dwarf candidates drawn from the spectroscopic survey of bright DA stars from the Villanova White Dwarf Catalog by Gianninas et al., and from the recent spectroscopic survey of white dwarfs within 40 parsecs of the Sun by Limoges et al. We report the discovery of six new ZZ Ceti pulsators from these surveys, and several photometrically constant DA white dwarfs, which we then use to refine the location of the ZZ Ceti instability strip.Comment: 4 pages, 1 table, 2 figures, to appear in "19th European White Dwarf Workshop" in the ASP Conference Serie