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Current targets Slavek Rucinski & Michael Siwak Halifax 2010

Current targets Slavek Rucinski & Michael Siwak Halifax 2010. TW Hya: MOST 2008. Wavelet analysis: Evolving single periodicities. Tendency towards shorter periods: Keplerian orbital evolution within the disk. Time-scales 2 – 9 days; shot noise outside.

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Current targets Slavek Rucinski & Michael Siwak Halifax 2010

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  1. Current targets Slavek Rucinski & Michael Siwak Halifax 2010

  2. TW Hya: MOST 2008 • Wavelet analysis: Evolving single periodicities. • Tendency towards shorter periods: Keplerian orbital evolution within the disk. • Time-scales 2 – 9 days; shot noise outside. • Within an envelope of the “flicker noise”, a~1/√f spectrum; an extension to several years (ASAS). Published: MNRAS, 391, 1913 (2008)

  3. TW Hya: MOST 2009 Siwak et al. 2010, to be published. Spectroscopy from LCO.

  4. Unstable accretion in young stars: FU Ori & Z CMa Slavek Rucinski & Michael Siwak

  5. FU Ori • FU Orionis = GSC 00715 00159 • (2000): 05:45:22 +09:04:12, V ≈ 8.9 • Prototype of “FUors” (about a dozen). • FUors: Sudden brightening by 3 – 5 mag in 1 – 10 years. • Accretion events in the disk surrounding a pre-MS star. • Random fluctuations ~0.035 mag, “shorter than a day” (2000, ApJ, 531, 1028) • Extensive variability in various time scales. No continuous record so far.

  6. FU Ori Complex theoretical models, e.g. from arXiv:0906.1595v1, June 2009: “… outbursts can be explained by a slow accumulation of matter due to gravitational instability. Eventually this triggers the magneto-rotational instability, which leads to rapid accretion. The thermal instability is triggered in the inner disk but this instability is not necessary the reason for the outburst”.

  7. Currently FU Ori ASAS results for the 8 years (V-filter): A slow decline and day-to-day fluctuations by ±0.035 mag. Proposed MOST monitoring for ~30 days. Expect results similar to TW Hya & HD37806, but for a star with photometrically dominant accretion. ASAS (V) Spring 2009

  8. Z Canis Majoris = • HD 53179 = • GSC 05389 01211 • (2000): 07:03:43 -11:33:06 • V ≈ 9.85 (8.5?) • Similar to FU Ori, but earlier type: Bpe • Large fluctuations: ASAS data (V-filter) • More unstable accretion; probed at 1d time scale: ±0.2 mag(!). • Unknown for shorter time scales. Z CMa ASAS (V) Spring 2009

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