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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. Discovering the most rapidly rotating magnetic star(s).

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

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  1. HR 7355 and HR 5907: The MOST rapidly-rotating magnetic stars • Gregg Wade (RMC) • on behalf of the MiMeS Collaboration

  2. The MiMeSProject Magnetism in Massive Stars

  3. 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!!

  4. HR 7355 - B2Ve P=0.5214404 d

  5. HR 5907 - B2Ve

  6. Rotationally-supported magnetospheres

  7. Doppler Imaging He I

  8. 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

  9. MOST observations ofHR 7355 and HR 5907 • 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

  10. Parameters 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

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