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Need some help with reflected spectra

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Need some help with reflected spectra was created by Equinox

Ok I'm working on my lit survey for next year on exoplanets and there something thats doing my head in. I read in a paper that the only way to accuratly determine the velocity of a planet Vp is through reflected spectra of the planet.

Then reading a paper on reflected spectra I get this:

"With our knowledge of stellar mass and the planet's orbital period we can
estimate the orbital velocity of the planet Vp. The apparent RV amplitude
Kp of the reflected light is given by:
Kp = Vp sin i"

I can't find anything else calling Kp apparent RV amplitude. The same paper later calls it projected orbital velocity. Is it the same thing and if so
what it mean?

"In the event of a planet detection, analysis of the data should allow us
to determine fundamental properties:
(i)Kp, the planets projected orbital velocity, from which we obtain the systems inclination and planet mass, since Mp sin i, is knowcn from the stars Doppler wobble"

If the mass and inclination are already known from doppler, why and how are they getting it from Kp?

Any help greatly appreciated. :)
16 years 8 months ago #29128

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Replied by albertw on topic Re: Need some help with reflected spectra

Then reading a paper on reflected spectra I get this:


Got a reference for the paper?
[edit: Rather is it Leigh et. al. Monthly Notices of the Royal Astronomical Society, Volume 344, Issue 4, pp. 1271-1282. ]

I think I've some notes on this at home.

Cheers,
~Al
Albert White MSc FRAS
Chairperson, International Dark Sky Association - Irish Section
www.darksky.ie/
16 years 8 months ago #29131

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Replied by Equinox on topic Re: Need some help with reflected spectra

Sorry should have given the reference.

Collier Cameron et al, "A search for starlight reflected from upsilo And's innermost planet" Monthly Notices of the Royal Astronomical Society, Volume 330, Issue 1, pp. 187-204 (2002)
16 years 7 months ago #29226

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Replied by albertw on topic Re: Need some help with reflected spectra

Thanks, if anyone else wants to take a peek its at

adsabs.harvard.edu/abs/2001astro.ph.10577C
Albert White MSc FRAS
Chairperson, International Dark Sky Association - Irish Section
www.darksky.ie/
16 years 7 months ago #29227

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Replied by albertw on topic Re: Need some help with reflected spectra

I can't find anything else calling Kp apparent RV amplitude. The same paper later calls it projected orbital velocity. Is it the same thing and if so what it mean?


I've just glanced throught he paper.

RV means apparent radial velocity which is usually the velocity that the planet has to or from us, ie the velocity we measure. Which is Sin i times its actual velocity.

Since they describe Kp as 'projected orbital velocity' I guess they really do mean apparent radial velocity. ie its velocity projected as just 'to' and 'from' us. The actual velocity will be higher than what we see unless we are edge on to the planet, so the real orbital velocity (Vo) is related as Kp = Vo Sin i.

In the abstract and equation 3 he mention Kp as ~= 139 Sin i km/s

At least I think thats right :-)

Using the same phrase would help. I used to have a lecturer in UCD who would change his notation on a daily basis. One greek squiggle was as good as another!

Similarly for Mass estimates using doppler techniques, you can only give an upper limit without the knowing the inclination.
Albert White MSc FRAS
Chairperson, International Dark Sky Association - Irish Section
www.darksky.ie/
16 years 7 months ago #29231

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Replied by Equinox on topic Re: Need some help with reflected spectra

Thanks a million!

And don't talk to me about lecturers and their squiggles! One of them insists on using a capital x and a little x for two different things. And do many of them use the greek v for frequency where as I was always taught it was f.
16 years 7 months ago #29335

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