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Published April 1, 2011 | Published
Journal Article Open

Evidence for an FU Orionis-like Outburst from a Classical T Tauri Star


We present pre- and post-outburst observations of the new FU Orionis-like young stellar object PTF 10qpf (also known as LkHα 188-G4 and HBC 722). Prior to this outburst, LkHα 188-G4 was classified as a classical T Tauri star (CTTS) on the basis of its optical emission-line spectrum superposed on a K8-type photosphere and its photometric variability. The mid-infrared spectral index of LkHα 188-G4 indicates a Class II-type object. LkHα 188-G4 exhibited a steady rise by ~1 mag over ~11 months starting in August 2009, before a subsequent more abrupt rise of >3 mag on a timescale of ~2 months. Observations taken during the eruption exhibit the defining characteristics of FU Orionis variables: (1) an increase in brightness by ≳ 4 mag, (2) a bright optical/near-infrared reflection nebula appeared, (3) optical spectra are consistent with a G supergiant and dominated by absorption lines, the only exception being Hα which is characterized by a P Cygni profile, (4) near-infrared spectra resemble those of late K-M giants/supergiants with enhanced absorption seen in the molecular bands of CO and H_(2)O, and (5) outflow signatures in H and He are seen in the form of blueshifted absorption profiles. LkHα 188-G4 is the first member of the FU Orionis-like class with a well-sampled optical to mid-infrared spectral energy distribution in the pre-outburst phase. The association of the PTF 10qpf outburst with the previously identified CTTS LkHα 188-G4 (HBC 722) provides strong evidence that FU Orionis-like eruptions represent periods of enhanced disk accretion and outflow, likely triggered by instabilities in the disk. The early identification of PTF 10qpf as an FU Orionis-like variable will enable detailed photometric and spectroscopic observations during its post-outburst evolution for comparison with other known outbursting objects.

Additional Information

© 2011 American Astronomical Society. Received 2010 November 9; accepted 2011 January 24; published 2011 March 8. We thank Luisa Rebull for providing the Spitzer/MIPS data for LkHα 188-G4 in advance of her publication. We are in debt to John Johnson, John Sebastian Pineda, and Michael Bottom who obtained the HIRES spectrum for us. We thank Cullen Blake, Dan Starr, and Emilo Falco for their efforts to build and maintain PAIRITEL. We thank Meredith Hughes for a fruitful discussion concerning YSO accretion disks and Ryan Foley for information on the spectrophotometric uncertainty associated with Kast spectra. An anonymous referee provided comments that have improved this manuscript. A. A. M. is supported by the National Science Foundation (NSF) Graduate Research Fellowship Program. K.R.C. acknowledges support for this work from the Hubble Fellowship Program, provided by the National Aeronautics and Space Administration (NASA) through Hubble Fellowship grant HSTHF-51253.01-A awarded by the STScI, which is operated by the AURA, Inc., for NASA, under contract NAS 5-26555. J. S. B. acknowledges support of an NSF-CDI grant-0941742. A. A. M. and C. R. K. were partially supported by NSF-AAG grant-1009991. A.V.F.'s group is grateful for the support of NSF grant AST-0908886, the TABASGO Foundation, Gary and Cynthia Bengier, and the Richard and Rhoda Goldman Fund. The National Energy Research Scientific Computing Center, which is supported by the Office of Science of the US Department of Energy under contract No. DE-AC02-05CH11231, provided staff, computational resources, and data storage for this project. 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, andNASA. 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. PAIRITEL is operated by the Smithsonian Astrophysical Observatory (SAO) and was made possible by a grant from the Harvard University Milton Fund, a camera loan from the University of Virginia, and continued support of the SAO and UC Berkeley. The PAIRITEL project and those working on PAIRITEL data are further supported by NASA/Swift Guest Investigator Programs NNX09AQ66Q and NNX10A128G. We are grateful for the assistance of the staffs at all of the observatories used to obtain the data. This research has made use of NASA's Astrophysics Data System Bibliographic Services, the SIMBAD database operated at CDS, Strasbourg, France, the NASA/IPAC Extragalactic Database operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA, and the VizieR database of astronomical catalogs (Ochsenbein et al. 2000). 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 NASA and the NSF. Facilities: PO:1.2m (PTF), PO:1.5m, Hale (TripleSpec), Keck:I (HIRES), Shane (Kast), FLWO:2MASS (PAIRITEL)

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