New Surprises from the

Microsatellite… aka the Humble space telescope

MOST Parameters• telescope diameter 15 cm• launched 2003 June• tracker lost 2006, but…• still working better than ever• 3” pixels, 1” pointing stability• follow object up to 8 weeks• time resolution ~sec-min• 3 modes: Fabry (V = 0…6), direct (V = 6…12), guide-star (<2006)• CCD + B/V filter

Tony Moffat & the MOST teamPrimary Science

• Asteroseismology structure, age• Exoplanets sizes, atmospheres

Luminous Hot-star Highlights• zeta Oph, O9.5Ve: Fig.1• HD127756, B1/2Vne; HD217543, B3Vpe: SPBe stars, 30-40 NRP g- (+ poss r-) modes, excited by Fe opacity bump, v(rot) close to break-up (Cameron et al. 2008).• delta Ceti, B2IV: Fig.2.• HD163899, B2Ib/II: Fig.3.• HD 313926, B5: : largest eccentricity (e = 0.2) among short-period (3.5d) early-type binaries v. young (Rucinski et al. 2007).• HD 163868, B5Ve: detection of ~60 modes, first r-modes (v. low freq.) & g-modes (Fe opacity bump) in a Be star NRP important in Be stars? (Walker et al. 2005).• HD 163830, B5II/III: Fig.4.• beta CMi, B8Ve: 1st detection of non-radial (high-order) g-modes in a Be-star > B6 pulsations excited in all classical Be stars? Fe-bump @ 200kK, v(rot) ~ break-up, 3.5 M (Saio et al. 2007).• sigma Ori E, B2Vpe: being analyzed (Townsend et al.).• Rosette Nebula, 5 OB: to be analyzed. • WR123, WN8: Fig.5. • WR103, WC9d: Fig.6.• WR111, WC5: Fig.7.• WR110, WN5-6: being analyzed; P = 2.1d & 4.0d + stochastic?• WR124, WN8h: being analyzed; P ~ 6d + stochastic? Fig.8.

Fig1: zeta Oph: v sin i ~ 400 km/s, runaway; clear beta Cep radial/NR pulsations driven by Fe opacity bump (Walker et al. 2005).

Fig.2: delta Cep: Left: folded lc f1 = 6.2 c/d = 1st radial overtone. Right: Fourier Sp after pre-whiten (f1, 2f1) multiperiodic (mono before). Models: 10.2 M, 18 Myr evolved beta Cep star (Aerts et al. 2006). N.B.: MOST’s first target!

Fig.3: HD163899, ~35 frequencies: p- & g-mode, latter 1st time in a BSG. Great potential for asteroseismology (Saio et al. 2006).

Fig.4: HD 163830, a new SPB (slowly-pulsating B-star) with largest no. of detected g-mode frequencies; model 4.5 M (Aerts et al. 2006).

Fig.5: WR123, runaway, no H. P = 10h: 1st ~clear pulsation period in a WR star SMP driven by normal Fe bump (Dorfi et al. 2006 – but took X(H) = 0.35) OR(?) g-modes driven by Fe bump at log T = 6.25 (Townsend & MacDonald 2006 – but took R = 2R cf. ~15 R observed). Spectral lines ~10% of total broadband flux & vary little observed variation (P = 10h & other) must be related to pulsations of the stellar core! (supported by sp analysis for WN8 stars by Haeffener & Hamann 2008). Delayed reaction of wind (sp lines) triggered by superposition of pulsation events. Lefevre et al. (2005).

Fig.6: WR103, similar to WR123, except sl. lower amplitude variations & no P. Both light-curves = superposition of short-lived (5-7d coherency), multiple-frequency pulsations of amplitude 5-20 mmag mostly at freq. <~1c/d. No periodic signal >0.2 mmag in traditional domain freq. >~10 c/d. Moffat et al. (2008).

Fig.7: WR111 (top) cf. WR123 (bottom) & WR103 (middle). No P of A > 0.05 mmag (~40 x less cf. SMP models: Glatzel et al. 1993) for f = 10 – 1000 c/d (P = 1.4m – 2.4 h), after removing f = 14.2 c/d MOST orbital + harmonics. Also: no damped oscillations or flares >~1 mmag. Moffat et al. (2007).

Fig.8: HST H-alpha image of M1-67 nebula around WR124 (Grosdidier et al. 1998).

ConclusionsDespite its modest size, MOST can provide powerful high-precision photometric constraints on the properties of hot luminous stars. The key is contiguous coverage over long time intervals from space.