Can stellar activity make a planet seem misaligned?

Mahmoud OshaghInstitute for Astrophysics,

University of Göttingen, Germany

Collaborators: N. Santos, M. Gillon, S. Dreizler, A. Reiners, A. Triaud, A. Burdanov, P. FiguieraX. Bonfils, S. Udry

Outline

Stellar activity and photometric transit

Stellar activity and spectroscopic transit

Non-occulted stellar spots

Barros et al. 2014

CoRoT-7b

20% overestimation

Occulted stellar spotsHAT-P-11b observed by Kepler

Some people consider assigning a zero weight to the anomalous points of the light curve (e.g Sanchis-Ojeda & Winn 2011)

Transit timing measurementsJupiter size planet transiting a solar-like star overlaps a spot with a filling factor of 1 %, produces the maximum value of TTV around 200 seconds.

Oshagh et al ,2013b

SOAP-T

Best fit

Planet radius estimationsA radius of Neptune size planet transiting a solar-like star and overlapping a spot with filling factor of 1 %, can be underestimated by 4%.

Oshagh+2013b

SOAP-T

Best fit

Impact of stellar activity on spectroscopic transit

Rossiter–McLaughlin effect

RM and unocculted spots

Boldt & Oshagh et al, in prep

SOAP-T simulations

RM and occulted spots

RM and occulted spots

A Neptune-sized aligned planet transitsa solar like star with vsini=3 km/s

The inaccurate estimation on the spin-orbit angle due to stellar activity can be quite significant (up to 30 degrees).

We found that aligned transiting planets are the ones that can be easily misinterpreted as misaligned owing to the stellar activity.

Oshagh+2016

SOAP-T simulations

RM and occulted spots

WASP-16b, 2010 March, May 2011 (Brown et al 2012)

WASP-16b, 2010 Jul (Albrecht et al 2012)

20 degree -4 degree

Occulted spot could be a possible explanation for conflicting results on spin-orbit angle estimations, e.g, HAT-P-7:

E. Jehin/ESO Y. Beletsky (LCO)/ESO

Simultaneous HARPS and TRAPPISTWe obtained 6 nights on HARPS to perform consecutive RM observations of 6 planets (with simultaneous transit observation with TRAPPIST)

TRAPPIST HARPS

WASP-41b

Technical issue Too windy for TRAPPIST

WASP-19b

Improving our RM modeling

Cegla et al. 2016

1.Convective center-to-limb variations2.Inhibition of convective blueshift in active regions

Thanks for your attention!

Transit timing measurements200 seconds amplitude of TTV can be induced by an Earth-mass planet in a mean-

motion resonance with a transiting Jupiter-like planet on a 3 day orbit.

Mazeh+2013

SOAP-T SOAP-T produces the expected light curve and the radial velocity signal of a system

consisting of a rotating spotted star with a transiting planet. SOAP-T is able to reproduce the “positive bump” anomaly in the transit light curve and RV due to a planet-spot overlap (Oshagh et al, A&A, 2013a.).

Oshagh et al, A&A, 2013a.

Transit timing variation (TTV)

Boue+2012

Rossiter–McLaughlin effect

–McLaughlin effect