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FUors : the smoking gun for episodic accretion, or misfit young stars?

Ábrahám et al., 2009, Nature, 459, 224. Courtesy: R. Hurt, SSC. FUors : the smoking gun for episodic accretion, or misfit young stars?. FUors : the smoking gun for episodic accretion, or misfit young stars?. The FU Orionis Eruption: 1936. Hartmann & Kenyon, 1996, ARAA, 34, 207.

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FUors : the smoking gun for episodic accretion, or misfit young stars?

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  1. Ábrahám et al., 2009, Nature, 459, 224 Courtesy: R. Hurt, SSC FUors: the smoking gun for episodic accretion, or misfit young stars?

  2. FUors: the smoking gun for episodic accretion, or misfit young stars?

  3. The FU Orionis Eruption: 1936 Hartmann & Kenyon, 1996, ARAA, 34, 207 Courtesy: C. Briceno Much wider than blackbody Zhu et al. 2008, ApJ 684, 1281 Kenyon et al. (2000, ApJ 531, 1028)

  4. Additional FUors 1950-1978 Hartmann & Kenyon, 1996, ARAA, 34, 207 V1057 Cyg V1515 Cyg A few other stars with similar properties to FU Orionis were discovered, forming the “classical” FUor group (Herbig, 1977, ApJ, 217, 693; Elias, 1978, ApJ, 223, 859)

  5. Dissecting the Electromagnetic Spectrum Far-IR Submm Millimeter X-ray UV Mid-IR Modified from Hartmann & Kenyon, 1996, ARAA, 34, 207 Optical Near-IR Radio

  6. FUors as of 2013 Audard+14

  7. FUor and EXor timescales are classically separable Herbig G. H., 1977, AJ., 217, 693

  8. Generic FUor

  9. Variability FU Ori -Typical periodic variability attributed to stellar rotation -Remaining few % color variations in UBVRI typical of FUors (Kenyon et al. 2000, Kenyon et al. 2009, Clarke et al. 2005, Green et al. 2013) – flickering/accretion event related (seen in T Tauri stars as well) Kenyon+09 HBC 722 Green+13

  10. Optical Spectroscopy • Broad blueshifted absorption in Na and Balmer lines (although sometimes P Cygni or weak emission in Hα) • Drive powerful winds • Magnetospheric accretion lines usually disappear during burst, or are not observed • Optical F-G supergiant in many cases; in others (HBC 722?) stellar continuum may still dominate, and contribute to lines

  11. Equivalent Width of Hβ absorption line jumped almost instantly -- uncorrelated with anything interesting happening in the overall lightcurve Park, Lee, Green, Cochran et al., in prep.

  12. Near-IR Spectroscopy • CO absorption (often double-peaked) at 2.2 μm (disk), H2O absorption; characteristic of M atmospheres (3000 K) • Some show CO in emission; whether this is the photosphere of the central star is unclear • *HBC 722 was actually not detected in CO in one try with NIRSPEC (C. Salyk, priv. comm.)

  13. Mid-IR (Spitzer)uncorrected for reddening: silicate dust is pristine Water vapor – disk photosphere? Amorphous silicates

  14. Hot water screening an even hotter disk? Sargent et al, subm.

  15. Mid-IR Ices H2O+CH3OH+CO2 mixtures from White et al. (2009) Quanz+07 Audard+10,12

  16. FUor Subgroups “Embedded” “Flared Disk” Inclination effect? Figure from Quanz et al., 2007, ApJ, 668, 359; see also Green et al., 2006, ApJ, 648, 1099

  17. The Mid-IR: Long-Term Outburst Effects Does dust processing from flash heating (or vertical transport and stirring of dust grains) occur on few month timescales? Unknown in FUors, which have yet to return to quiescence. Ábraham et al., 2009, Nature, 459, 224

  18. Herschel-eye View Green+13

  19. Far-IR Diagnostics Previously noted similarities at submillimeter wavelengths (e.g. Sandell & Weintraub, 2001, ApJS, 134, 155); --And from ISO: Lorenzetti et al., 2000, A&A, 357, 1035 Consistent with the Spitzer/Herschel perspective Class I Protostar Classical FUor Green et al., in prep. Green et al., 2013, ApJ, 772, 117

  20. CO Similarities Green+13c Green+14 in prep. Other molecular emission consistent with protostars

  21. [OI] vs. CO spatially discrepant in HBC 722 Line emission Local Continuum

  22. Millimeter – PdBI/SMA r (scattered light) vs. 13CO J=1-0 Pre-existing nebular material highlighted by burst; might even the “embedded” stage FUors be relatively evolved? V1515 Cyg Kóspál (2010)

  23. The Millimeter Environs of FUors 1.3 mm Dunham+12 Dunham+12, Green+11 CO J=2-1 Dunham+ in prep. Large spread in disk properties!

  24. FUorstage? HCO+ 3-2 (from CSO/ Green+13) Yes V1057 Cyg V1515 Cyg V1735 Cyg HBC 722 (confused) No FU Ori

  25. FUors are rarely seen…but they are common events! (Updated from Hartmann & Kenyon, 1996, ARAA, 34, 207) Within 1 kpc of the Sun: 104 – 105 T Tauri stars x avg. accretion rate 10-8 M⊙ yr−1 = 10-3 M⊙ yr−1 8 FUors, combined accretion rate ~ few x 10-4 M⊙ yr−1 -FUors are responsible for ~ 10-50% of the current nearby accretion in Class II objects (decreased if we include Class I) About 8 FUors since 1936; average star formation rate 1 / 50 yr (FUor list updated from Reipurth & Aspin 2010, Evolution of Cosmic Objects through their Physical Activity, 19; SFR from Miller & Scalo 1979, ApJS, 41, 513; see also Offner & McKee 2011, ApJ, 736, 53) -FUors occur at several times the rate of star formation; averaging multiple bursts per star

  26. So is FU Ori a typical FUor?

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