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

• Published in: The Astrophysical journal 2011-04, Vol.730 (2), p.80-jQuery1323909777083='48'
• Main Authors: Miller, Adam A, Hillenbrand, Lynne A, Covey, Kevin R, Poznanski, Dovi, Silverman, Jeffrey M, Kleiser, Io K. W, Rojas-Ayala, Bárbara, Muirhead, Philip S, Cenko, S. Bradley, Bloom, Joshua S, Kasliwal, Mansi M, Filippenko, Alexei V, Law, Nicholas M, Ofek, Eran O, Dekany, Richard G, Rahmer, Gustavo, Hale, David, Smith, Roger, Quimby, Robert M, Nugent, Peter, Jacobsen, Janet, Zolkower, Jeff, Velur, Viswa, Walters, Richard, Henning, John, Bui, Khanh, McKenna, Dan, Kulkarni, Shrinivas R, Klein, Christopher R, Kandrashoff, Michael, Morton, Alekzandir
• Format: Article
• Language: English
• Subjects: Astronomy; ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BINARY STARS; Earth, ocean, space; ELECTROMAGNETIC RADIATION; ERUPTIVE VARIABLE STARS; EVOLUTION; Exact sciences and technology; INFRARED RADIATION; INFRARED SPECTRA; NEAR INFRARED RADIATION; RADIATIONS; SPECTRA; STAR EVOLUTION; STARS; T TAURI STARS; VARIABLE STARS
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1088/0004-637X/730/2/80

We present pre- and post-outburst observations of the new FU Orionis-like young stellar object PTF 10qpf (also known as LkH Delta *a 188-G4 and HBC 722). Prior to this outburst, LkH Delta *a 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 LkH Delta *a 188-G4 indicates a Class II-type object. LkH Delta *a 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 H Delta *a 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 H2O, and (5) outflow signatures in H and He are seen in the form of blueshifted absorption profiles. LkH Delta *a 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 LkH Delta *a 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.