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 (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: v1, 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. Spring 2009 ASAS (V)

8 Z CMa Z Canis Majoris = HD = GSC (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. Spring 2009 ASAS (V)