Some Like it Hot: Evidence for the Shrinking Orbit of the 2.2-d Transiting Hot Jupiter Exoplanet HD b Tom Santapaga, Edw Guinan, R-L. Ballouz, S.G. Engle, L.E. DeWarf (Villanova Univ.) Stella Kafka (Carnegie Inst, Washington, D.C)

Scale Model for the HD Star- Planet System Showing the interaction of the planet and star’s Magnetic fields. As shown the planet’s orbital motion (~152 km/s) pushes against the magnetic field lines of the star causing the star to spin-up. Art credit Nick Tripicino

The 8 th mag K1.5 V star, HD A shown in the field of the nearby Dumbbell Nebula

A b B a = AU (8.75 R K ) [3% Distance Earth to Sun] ~220AU (12.2 arcsec)

HD A K1.5V Star M ~ 0.81 M ʘ R ~ 0.76 R ʘ P rot ~ d L ~ 0.26 L ʘ A b HD b M = 1.13 M J ; R = 1.14 R J P orb = 2.22 d; a = AU T = 844°C+; (~1550°F) Atm.: H 2 O, CH 4, (H 2 O vapor), methane, CO 2, sodium HD B (12” away from A: 220 AU; P ~3200 yr) M 5V Star/ age ~5-7 Billion yrs R ~ 0.2 R ʘ ; L ~ L ʘ (Bakos et al. 2006) Same V r μα μδ as star A B Model of the HD Star/ Planet System

HD – Selected Properties HD A (K star) HD b (Planet) HD B (M star) Mass0.81 M  ~1.15 M J ~0.2 M  Radius0.76 R  ~1.26 R J ~0.2 Ro Rotational Period ~11.95 d (tidally locked d) Est: >80 d Orbital Period d~3200 yr Orbital Radius AU~220 AU

Age Determinations for the HD System METHODValueAGEREFERENCE Rotation (dK star )~11.95 d~0.6 Gyr Henry et al. (2007); This study Ca II HK Emission (dK star) S(HK) = 0.52 <0.8 Gyr Ca II HK Emiss. (Moutou et al AA, 473. X-ray Activity (dK star ) ~10 Lx x  ~0.7 Gyr XMM/ Pilletteri et al. (2010); Age from this study Lithium Abundance ( dK star ) A (Li) < 0.01 >4 Gyr: Melo, C., (2006), A&A, 460, Age from Li-depletion X-ray Activity ( M star ) Log L x < 26.9 >4.5 Gyr XMM-Newton from Pillitteri I.,( 2010); Age – this study H-alpha emission ( M star ) EW ~0.0> 5-6 Gyr Spectra from S. Kafka (Carnegie Cray Telescope)

HD A K1.5V Star M ~ 0.81 M ʘ R ~ 0.76 R ʘ P rot ~ d L ~ 0.26 L ʘ A b HD b M = 1.13 M J ; R = 1.14 R J P orb = 2.22 d; a = AU T = 844°C+; (~1550°F) Atm.: H 2 O, CH 4, (H 2 O vapor), methane, CO 2, sodium HD B M 5V Star R ~ 0.2 R ʘ ; L ~ L ʘ (Bakos et al. 2006) Same V r μα μδ as star A B

A b B a = AU (8.75 R K ) [3% Distance Earth to Sun] ~220AU

Io – Jupiter - A possible Analog for understanding the HD Ab magnetically Interacting Planet-Star System

HD A & Ab HD A has signifcant chromospheric & coronal X-ray emissions. Also the star has starspots covering ~3% of star’s surface that produce brightness variations of up to 2%. The star’s rotation period (11.95 days) and its resulting magnetic dynamo-generated emissions are similar to dK0-5 stars in the Hyades cluster (age ~ 650 Myr). But the age indicators of the dM5 companion indicate a much older age (>5-6 Gyr). Artwork from Tinetti: ESA/NASA

The final fate of HD189733b as it reaches its Roche critical surface. This occurs at an orbital period of ~ 6 hr and at an orbital distance of ~2 stellar radii (i.e. at a = AU).