HR 7355 and HR 5907: The MOST rapidly-rotating magnetic stars

HR 7355 and HR 5907: The MOST rapidly-rotating magnetic stars

Gregg Wade (RMC)on behalf of the MiMeS Collaboration

The

MiMeS Project

Magnetism in Massive Stars

The

MiMeS Project

Magnetism in Massive Stars

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Discovering the most rapidly rotating magnetic star(s)

• Before MiMeS the B2Ve He-strong star HD 37017 fastest rotating magnetic massive star• P~0.9 d

• MiMeS discovers most rapidly rotating magnetic star Sept/09 (HR 7355, Oksala et al. 2010)• P= 0.521 4404 d <- Based on HIPPARCOS/CTIO

• Feb/10 – MiMeS discovers a nearly-identical rapidly rotating magnetic star (HR 5907, B2V)• P=0.50830 d -> NEW RECORD HOLDER!!

P=0.5214404 d

HR 7355 - B2Ve

HR 5907 - B2Ve

Rotationally-supported magnetospheres

Doppler Imaging

He I

Significance of these results

– Extreme testbeds– Near twins

– Timescales and mechanisms for magnetic braking– Magnetospheric structure, density, emissivity– Role of rapid rotation and field geometry in channeling

and confining winds of massive stars– Link to Be stars: Keplerian vs. rigid discs– Role of slow rotation in generating photospheric

chemical peculiarities

– High precision lightcurves are a vital complement to spectroscopic and polarimetric monitoring:• Confirm and refine rotational periods• Test limits of RRM model in ultra-rapid rotation regime• Constrain magnetospheric geometry and density• Disentangle magnetospheric vs spot contributions• Provide baseline for direct spindown measurement

• Technical requirements:• 1 mmag errors, 1% (?) phase sampling (7 min integrations)• Acquired over multiple subsequent cycles or continuously

MOST observations ofHR 7355 and HR 5907

– HR 7355• RA 19h24• Dec -28 deg• V = 6.0• Prot = 0.5214404 d

• HR 5907• RA 15h53• Dec -24 deg• V = 5.4• Prot = 0.50283 d

Parameters ofHR 7355 and HR 5907

HR 7355 and HR 5907: The MOST rapidly-rotating magnetic stars

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