Subcategory: Astronomy and Astrophysics
Md Tanveer Karim - University of Rochester
Co-Author(s): Keivan Stassun, Vanderbilt University, Nashville, TN Cesar Briceno and Anna Katherina Vivas, Cerro Tololo InterAmerican Observatory, Chile Stefanie Raetz, European Space Research and Technology Centre, The Netherlands Nuria Calvet, University of Michigan, Ann Arbor, MI Cecilia Mateu, Juan Jose Downes, and Jesus Hernandez, Centro de Investigaciones de Astronomia, Venezuela Ralph Neuhauser and Markus Mugrauer, Astrophysikalisches Institut und Universitats-Sternwarte, Germany Hidenori Takahashi and Kengo Tachihara, Gunma Astronomical Observatory, Japan Rolf Chini, Astronomisches Institut, Ruhr-Universitat Bochum, Germany
Most existing studies of young stellar populations have focused on the youngest (< 2-3 million years old) T Tauri stars, which have not started fusing hydrogen to helium, and are usually associated with their natal gas. In contrast, older T-Tauri stars (~ 4-10 million years old), are located in regions where their parent gas and dust clouds have long since dissipated, and therefore are more difficult to find; as a result they have been less studied. However, because important physical processes are expected to take place during this later age range, these slightly more evolved young stars are key to our understanding of aspects like the angular momentum and protoplanetary disc evolution of lower-mass (0.1-2 Solar Mass) stars. We present a study of photometric variability of 1974 confirmed 4-10 million years old T-Tauri stars in the Orion OB1 association, using optical time-series from three different surveys: the Centro de Investigaciones de Astronomia-Quest Equatorial Survey Team (CIDA-QUEST), the Young Exoplanet Transit Initiative (YETI) and from a Kitt Peak National Observatory (KPNO) campaign. We used the Generalized Lomb-Scargle periodogram, the Multiband periodogram, and wavelet analysis to determine rotation periods of these stars. Multiple methods were used to ensure a reliable rotation period for each star. We further investigated rotation periods according to the type of star (Classical or Weaklined T Tauri stars) and their location, to look for populationwide trends with the help of the Anderson-Darling test. We identified 563 periodic variables and 1411 non-periodic variables; ~ 30% of Weak-line T-Tauri stars (WTTS) and ~ 20% of Classical T-Tauri stars (CTTS) are periodic. Though we did not find any noticeable difference in rotation period between CTTS and WTTS, our study shows a change in the overall rotation periods of stars 4-10 million years old, consistent with predictions of angular momentum evolution models, constraining theoretical models at an age range for which no similar data existed. References: Briceno, C., Vivas, A. K., Calvet, N., et al. 2001, Science, 291, 93; Lomb, N. R. 1976, Ap&SS, 39, 447; Scargle, J. D. 1982, ApJ, 263, 835; Neuhauser, R., Errmann, R., Berndt, A., et al. 2011, Astronomische Nachrichten, 332, 547; Press, W. H., Teukolsky, S. A., Vetterling, W. T., & Flannery, B. P. 1992, Numerical Recipes in C: The Art of Scientific Computing, Second Edition (New York: Cambridge University Press); VanderPlas, J. T., & Ivezic, Z. 2015, ArXiv e-prints, arXiv:1502.01344; Zechmeister, M., & Kurster, M. 2009, A&A, 496, 57.
Funder Acknowledgement(s): This project was conducted in the framework of the Vanderbilt University REU Program and the Cerro Tololo Inter-American Observatory REU Program, which are supported by the National Science Foundation.
Faculty Advisor: Cesar Briceno,