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Published March 2013 | Submitted + Published
Journal Article Open

Highly Variable Extinction and Accretion in the Jet-driving Class I Type Young Star PTF 10nvg (V2492 Cyg, IRAS 20496+4354)


We report extensive new photometry and spectroscopy of the highly variable young stellar object PTF 10nvg (also known as IRAS 20496+4354 and V2492 Cyg), including optical and near-infrared time-series data as well as mid-infrared and millimeter data. Following the previously reported 2010 rise to R_(PTF)≾13^m.5 and subsequent fade, during 2011 and 2012 the source underwent additional episodes of brightening, followed by several magnitude dimming events including prolonged faint states at R_(PTF)≳20^m. The observed high-amplitude variations are largely consistent with extinction changes (ΔA_V up to 30 mag) having a ~220 day quasi-periodic signal. However, photometry measured when the source was near maximum brightness in mid-2010 as well as in late-2012 does not phase well to this period. Spectral evolution includes not only changes in the spectral slope but also correlated variation in the prominence of TiO/VO/CO bands and atomic line emission, as well as anti-correlated variation in forbidden line emission which, along with H_2, dominates optical and infrared spectra at faint epochs. Notably, night-to-night variations in several forbidden doublet strengths and ratios are observed. High-dispersion spectra were obtained in a variety of photometric states and reveal time-variable line profiles. Neutral and singly ionized atomic species are likely formed in an accretion flow and/or impact while the origin of zero-velocity atomic Li I λ6707 in emission is unknown. Forbidden lines, including several rare species, exhibit blueshifted emission profiles and likely arise from an outflow/jet. Several of these lines are also seen spatially offset from the continuum source position, presumably in a shocked region of an extended jet. Blueshifted absorption components of the Na I D doublet, K I λλ7665, 7669 doublet, and the O I 7774 triplet, as well as blueshifted absorption components seen against the broad Hα and Ca II triplet emission lines, similarly are formed in the outflow. CARMA maps resolve on larger scales a spatially extended outflow in millimeter-wavelength CO. We attribute the recently observed photometric and spectroscopic behavior to rotating circumstellar disk material located at separation ɑ ≈ 0.7(M_*/M_☉)^(1/3) AU from the continuum source, causing the semi-periodic dimming. Occultation of the central star as well as the bright inner disk and the accretion/outflow zones renders shocked gas in the inner part of the jet amenable to observation at the faint epochs. We discuss PTF 10nvg as a source exhibiting both accretion-driven (perhaps analogous to V1647 Ori) and extinction-driven (perhaps analogous to UX Ori or GM Cep) high-amplitude variability phenomena.

Additional Information

© 2013 American Astronomical Society. Received 2012 July 31; accepted 2012 December 7; published 2013 January 30. We commend PTF and PAIRITEL critical personnel Peter Nugent, Eran Ofek, and Dan Starr, and Cullen Blake for effective facility operation and data distribution. Mark Sullivan ran his PTF-specific PSF fitting code for us. In addition, we thank Joey Richards for helpful conversations and advice about the light curve analysis. We are also grateful to the many observers who kindly helped with the acquisition and/or reduction of spectra that are reported either in this paper or in Covey et al. (2011), including Katie Hamren, Everett Schlwain, Aaron Barth, Evan Kirby, Melissa Graham, Eric Hsiao, Peter Blanchard, Antonio Cucchiara, Adam Morgan, Daniel Perley, Christopher Griffith, Michael Kandrashoff, Luisa Rebull, Wilson Liu, John Angione, Shriharsh Tendulkar, Aaron Ofer, Kelsey Clubb, Greg Herczeg, Adam Kraus, Nick Law, Andrew Howard, Dan DeFelippis, Kunal Mooley, Trevor David, Geoff Marcy, and Howard Isaacson. CARMA Summer School students Isaac Shivvers, Che-Yu Chen, and Aaron Juarez participated in some of the CARMA observations and data reduction described herein. We are also very grateful for the assistance of staff members at the observatories where data were obtained. Funding acknowledgements are as follows. (1) K.R.C. acknowledges support for this work from the Hubble Fellowship Program, provided by NASA through Hubble Fellowship grant HST-HF-51253.01-A awarded by the STScI, which is operated by the AURA, Inc., for NASA, under contract NAS 5-26555, and support for publication charges generously provided by Dr. William Tifft. (2) A.V.F.'s group at UC Berkeley acknowledges generous financial assistance from Gary and Cynthia Bengier, the Christopher R. Redlich Fund, the Richard and Rhoda Goldman Fund, the TABASGO Foundation, and US National Science Foundation (NSF) grant AST-0908886. (3) PAIRITEL has been supported by a Swift Guest Investigator grant NASA/NNX12AE67G. (4) 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 NASA; the observatory was made possible by the generous financial support of the W. M. Keck Foundation. (5) The Infrared Telescope Facility is operated by the University of Hawaii under Cooperative Agreement No. NNX-08AE38A with the National Aeronautics and Space Administration, Science Mission Directorate, Planetary Astronomy Program. (6) Support for CARMA construction was derived from the Gordon and Betty Moore Foundation, the Kenneth T. and Eileen L. Norris Foundation, the James S. McDonnell Foundation, the Associates of the California Institute of Technology, the University of Chicago, the states of California, Illinois, and Maryland, and the National Science Foundation. Ongoing CARMA development and operations are supported by the National Science Foundation under a cooperative agreement (grant number AST-0838260) and by the CARMA partner universities. Facilities: PO:1.2m, FLWO:2MASS, Shane, Hale (two instruments), ARC,Keck:I,Keck:II, IRTF,CARMA,WIYN:0.9m, UKIRT, Spitzer, WISE.

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Submitted - 1208.2066v1.pdf


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