Measured Velocities of HD 209458 (F8-G0V)

2000 Coordinates: RA= 22 03 10.7, Dec= +18 53 04; Vmag=7.65

HD209458 velocity curve with the Keplerian orbital fit for a period P=3.52 days. Error bars are shown. The derived companion mass is: M sin i = 0.63 Jupiter Masses. The transit ensures that the orbital inclination, i, is nearly 90 deg. So the companion mass is 0.63 Jupiter masses. The odd behavior in the velocities near phase=0.5 is due to the rotation of the star, as the planet blocks of the approaching and receding limbs of the star.

HD209458b orbital parameters

Parameter	Best-Fit
Period	3.528 days
Half amplitude (K)	81 +/- 3 m/s
Semimajor Axis	0.045 AU
Eccentricity	0.01 +/- 0.03
M sini (M jup)	0.63

HD209458 Compared to the Sun

Parameter	Sun	HD209458	Source
T (Kelvin)	5780	6000	.
Mv	4.79	4.29	Hipparcos.
Log grav (cgs)	4.45	4.31	Blackwell et al, 1994, A&A,;282, 899
Spec. Type	G2V	F8V	SIMBAD
R'hk	-4.937	-4.93	Keck/HIRES H&K Line
P rot (day)	25.4	~30 +- 10 d	from chromospheric K-line (Noyes et al.)
Vsini (Km/s)	1.8	3	Keck/HIRES Spectrum
[Fe/H]	0.00	Unknown?	-

Age = 3-7 Gyr, from H&K line, and Noyes et al. (1984)

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