IfA Colloquium Series


"Magnetized Exoplanets"

EVGENYA SHKOLNIK
Institute for Astronomy/NAI
                            		 	
Wednesday, September 7, 2005
IfA-Manoa Auditorium     3:30 pm


ABSTRACT

A new sub-field of extrasolar planet characterization is emerging, 
which deals with the magnetic and/or tidal interaction between 
close-in giant planets (hot jupiters) and their host stars.  We 
recently monitored the chromospheric activity in the Ca II H and K 
lines of 10 stars with hot jupiters - 5 for three years at the CFHT 
and 5 in a single run at the VLT.  There is an intriguing, yet 
tentative, correlation between short-term (night-to-night) stellar 
activity and the minimum mass of the hot jupiter.  This is akin to 
the linear mass-magnetic moment relationship for the magnetized 
planets in the Solar System. Both HD 179949 and upsilon And 
have shown chromospheric activity synchronized to the orbital 
period of their hot jupiters which implies magnetic, rather than 
tidal, interaction.  Because of their small separation (<=0.1 AU), 
many of the hot jupiters lie within the Alfven radius of their host 
stars, allowing direct magnetic interaction with the stellar surface. 
I shall discuss the conditions under which a planet's magnetic 
field might induce activity on the stellar surface and the probable 
reason no such effect was seen for the prime candidate, tau Boo.