The PTF Orion Project: A Possible Planet Transiting a T-Tauri Star

Creators: van Eyken, Julian C.; Ciardi, David R.; von Braun, Kaspar; Kane, Stephen R.; Plavchan, Peter; Crepp, Justin R.; Howard, Andrew W.; Akeson, Rachel L.; Beichman, Charles A.; Boden, Andrew F.; Gelino, Dawn M.; Hoard, D. W.; Ramírez, Solange V.; Rebull, Luisa M.; Stauffer, John R.; Kasliwal, Mansi M.; Kulkarni, Shrinivas R.; Walters, Richard; Grillmair, Carl J.; Laher, Russ; Levitan, David B.; Sesar, Branimir; Surace, Jason A.; Fulton, Benjamin J.

Abstract

We report observations of a possible young transiting planet orbiting a previously known weak-lined T-Tauri star in the 7–10 Myr old Orion-OB1a/25-Ori region. The candidate was found as part of the Palomar Transient Factory (PTF) Orion project. It has a photometric transit period of 0.448413 ± 0.000040 days, and appears in both 2009 and 2010 PTF data. Follow-up low-precision radial velocity (RV) observations and adaptive optics imaging suggest that the star is not an eclipsing binary, and that it is unlikely that a background source is blended with the target and mimicking the observed transit. RV observations with the Hobby–Eberly and Keck telescopes yield an RV that has the same period as the photometric event, but is offset in phase from the transit center by ≈ − 0.22 periods. The amplitude (half range) of the RV variations is 2.4 km s^(−1) and is comparable with the expected RV amplitude that stellar spots could induce. The RV curve is likely dominated by stellar spot modulation and provides an upper limit to the projected companion mass of M_psin i_(orb) ≾4.8 ± 1.2 M_(Jup); when combined with the orbital inclination, i_(orb), of the candidate planet from modeling of the transit light curve, we find an upper limit on the mass of the planetary candidate of M_p ≾5.5 ± 1.4 M_(Jup). This limit implies that the planet is orbiting close to, if not inside, its Roche limiting orbital radius, so that it may be undergoing active mass loss and evaporation.

Additional Information

© 2012 The American Astronomical Society. Received 2011 October 24; accepted 2012 June 6; published 2012 July 25. The authors acknowledge Tim Morton and Dimitri Veras for their helpful input. S.B.C. wishes to acknowledge generous support from Gary and Cynthia Bengier, the Richard and Rhoda Goldman Fund, National Aeronautics and Space Administration (NASA)/Swift grant NNX10AI21G, NASA/Fermi grant NNX1OA057G, and National Science Foundation (NSF) grant AST–0908886. S.M. acknowledges support from NSF awards AST-1006676, AST-1126413, PSARC, and the NASA Astrobiology Institute. Observations obtained with the Samuel Oschin Telescope at the Palomar Observatory as part of the Palomar Transient Factory project, a scientific collaboration between the California Institute of Technology, Columbia University, Las Cumbres Observatory, the Lawrence Berkeley National Laboratory, the National Energy Research Scientific Computing Center, the University of Oxford, and the Weizmann Institute of Science. The Hobby–Eberly Telescope (HET) is a joint project of the University of Texas at Austin, the Pennsylvania State University, Stanford University, Ludwig-Maximilians-Universität München, and Georg-August-Universität Göttingen. The HET is named in honor of its principal benefactors, William P. Hobby and Robert E. Eberly. 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. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. The Byrne Observatory at Sedgwick (BOS) is operated by the Las Cumbres Observatory Global Telescope Network and is located at the Sedgwick Reserve, a part of the University of California Natural Reserve System. This research has made use of the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. This research has made use of the VizieR catalog access tool, CDS, Strasbourg, France, and of the software package Uncertainties: a Python package for calculations with uncertainties, Eric O. Lebigot.28 This work was partially supported by funding from the Center for Exoplanets and Habitable Worlds. The Center for Exoplanets and Habitable Worlds is supported by the Pennsylvania State University, the Eberly College of Science, and the Pennsylvania Space Grant Consortium. Support for this work was provided by an award issued by JPL/Caltech. Facilities: PO:1.2m (PTF), HET (HRS), Keck:I (HIRES), Keck:II (NIRC2), LCOGT (BOS), FTN, FTS, Mayall, Hale

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