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Current targets

Slavek Rucinski & Michael Siwak

Halifax 2010

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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)

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TW Hya: MOST 2009

Siwak et al. 2010, to be published. Spectroscopy from LCO.

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Unstable accretionin young stars:

FU Ori & Z CMa

Slavek Rucinski & Michael Siwak

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FU OriFU 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.

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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”.

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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)

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Z CMaZ 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.

Spring 2009

ASAS (V)