Star-crossed Lovers DI Tau A and B: Orbit Characterization and Physical Properties Determination

Creators: Tang, Shih-Yun; Stahl, Asa G.; Prato, L.; Schaefer, G. H.; Johns-Krull, Christopher M.; Skiff, Brian A.; Beichman, Charles A.; Uyama, Taichi

Abstract

The stellar companion to the weak-line T Tauri star DI Tau A was first discovered by the lunar occultation technique in 1989 and was subsequently confirmed by a speckle imaging observation in 1991. It has not been detected since, despite being targeted by five different studies that used a variety of methods and spanned more than 20 yr. Here, we report the serendipitous rediscovery of DI Tau B during our Young Exoplanets Spectroscopic Survey (YESS). Using radial velocity data from YESS spanning 17 yr, new adaptive optics observations from Keck II, and a variety of other data from the literature, we derive a preliminary orbital solution for the system that effectively explains the detection and (almost all of the) non-detection history of DI Tau B. We estimate the dynamical masses of both components, finding that the large mass difference (q ∼ 0.17) and long orbital period (≳35 yr) make the DI Tau system a noteworthy and valuable addition to studies of stellar evolution and pre-main-sequence models. With a long orbital period and a small flux ratio (f2/f1) between DI Tau A and B, additional measurements are needed for a better comparison between these observational results and pre-main-sequence models. Finally, we report an average surface magnetic field strength (B̅) for DI Tau A, of ∼0.55 kG, which is unusually low in the context of young active stars.

Additional Information

© 2023 The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. We are thankful for the comments and suggestions from an anonymous referee to help improve the quality of this paper. We thank the technical and logistical staff at McDonald and Lowell Observatories for their excellent support of the Immersion Grating Infrared Spectrograph (IGRINS) installations, software, and observation program described here. In particular, D. Doss, C. Gibson, J. Kuehne, K. Meyer, B. Hardesty, F. Cornelius, M. Sweaton, J. Gehring, S. Zoonematkermani, E. Dunham, S. Levine, H. Roe, W. DeGroff, G. Jacoby, T. Pugh, A. Hayslip, and H. Larson. We also thank G. Feiden for providing us with his magnetic evolutionary tracks and A. Kraus, M. Ireland, T. Dupuy, and E. Evans for helpful discussion on the NRM data of DI Tau. We thank Greg Doppmann for taking additional images of DI Tau; ultimately, these were not possible to calibrate and therefore are not included in this study. Partial support for this work was provided by NASA Exoplanet Research Program grant 80-NSSC19K-0289 (to LP). C.M.J. acknowledges partial support for this work through grants to Rice University provided by NASA (award 80-NSSC18K-0828) and the NSF (awards AST-2009197 and AST-1461918). G.H.S. acknowledges support from NSF AST-2034336. We are grateful for the generous donations of John and Ginger Giovale, the BF Foundation, and others which made the IGRINS-LDT program possible. Additional funding for IGRINS at the LDT was provided by the Mt. Cuba Astronomical Foundation and the Orr Family Foundation. IGRINS was developed under a collaboration between the University of Texas at Austin and the Korea Astronomy and Space Science Institute (KASI) with the financial support of the US National Science Foundation under grant AST-1229522 and AST-1702267, of the University of Texas at Austin, and of the Korean GMT Project of KASI. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. Some of the time at the Keck Observatory was granted by NOIRLab (NOIRLab PropID:2022B-970020; PI: G. Schaefer) through NSF's Mid-Scale Innovations Program. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. This work made use of the VALD database, operated at Uppsala University, the Institute of Astronomy RAS in Moscow, and the University of Vienna. This study also made use of the SIMBAD database and the VizieR catalog access tool, both operated at CDS, Strasbourg, France. Some observations were obtained at the Lowell Discovery Telescope (LDT) at Lowell Observatory. Lowell is a private, non-profit institution dedicated to astrophysical research and public appreciation of astronomy and operates the LDT in partnership with Boston University, the University of Maryland, the University of Toledo, Northern Arizona University and Yale University. We have used IGRINS archival data older than the 2 year proprietary period. This research has also made use of the Spanish Virtual Observatory (https://svo.cab.inta-csic.es) project funded by MCIN/AEI/10.13039/501100011033/ through grant PID2020-112949GB-I00. Facilities: LDT (IGRINS) - , Smith (IGRINS - , Tull Coudé Spectrograph) - , Keck:II (NIRC2) - , LO:0.8 m - , Hall. - Software: astropy (Astropy Collaboration et al. 2013, 2018), matplotlib (Hunter 2007), NumPy, (Harris et al. 2020) IGRINS RV (Stahl et al. 2021; Tang et al. 2021), PHOEBE (Conroy et al. 2020), pysynphot (STScI Development Team 2013).

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