GJ436c? (again...)

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GJ436c? (again...)

Post by Sirius_Alpha on 11th September 2008, 6:12 pm

New Observations and a Possible Detection of Parameter Variations in the Transits of Gliese 436b
http://fr.arxiv.org/abs/0809.1664

Abstract wrote:We present ground-based observations of the transiting Neptune-mass planet Gl 436b obtained with the 3.5-meter telescope at Apache Point Observatory and other supporting telescopes. Included in this is a detected transit in early 2005, over two years before the earliest reported transit detection. We have compiled all available transit data to date and perform a uniform modeling of all data using the JKTEBOP code. We do not detect any transit timing variations of amplitude greater than 1 minute over the 3.3 year baseline. We do however find possible evidence for a self-consistent trend of increasing orbital inclination, transit width, and transit depth, which supports the supposition that Gl 436b is being perturbed by another planet of < 12 Earth masses in a non-resonant orbit.

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Re: GJ436c? (again...)

Post by Lazarus on 11th September 2008, 7:12 pm

It does seem that there very likely is something else in this system.

The transit in 2005 is an interesting find, it extends the range of time over which transits are known to occur quite a way.

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Re: GJ436c? (again...)

Post by Lazarus on 3rd November 2008, 7:23 am

Lazarus wrote:It does seem that there very likely is something else in this system.
Or maybe not...

Transit infrared spectroscopy of the hot neptune around GJ 436 with the Hubble Space Telescope
We measure no departure from strict periodicity in the transits to the level of ~7 seconds. This strongly disfavours the proposed explanation of the orbital eccentricity of GJ 436b in terms of the perturbation by another close-by planet.

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Re: GJ436c? (again...)

Post by Sirius_Alpha on 3rd November 2008, 6:38 pm

As has been the case for a few days now, I'm forbidden to see the paper Sad

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Re: GJ436c? (again...)

Post by Lazarus on 3rd November 2008, 8:00 pm

Did you somehow manage to set off the bot detector or something? Is it the same on the uk, fr, etc. versions?

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Re: GJ436c? (again...)

Post by Sirius_Alpha on 3rd November 2008, 8:12 pm

I honestly don't know if I set the bot alarm off or not. I sent in an e-mail about it. I'm able to access the fr version (something I wasn't aware of until shortly after submitting my most recent post to this thread). I haven't tried other versions.

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Re: GJ436c? (again...)

Post by Sirius_Alpha on 17th December 2008, 9:33 pm

GJ436b not affected by a resonant planet?

Eccentricity modulation of a close-in planet by a companion - application to GJ 436 system
http://arxiv.org/abs/0812.3195

Abstract wrote:GJ 436b is a Neptune-size planet with 23.2 Earth masses in an elliptical orbit of period 2.64 days and eccentricity 0.16. With a typical tidal dissipation factor (Q' ~ 10^6) as that of a giant planet with convective envelope, its orbital circularization timescale under internal tidal dissipation is around 1 Gyr, at least two times less than the stellar age (>3 Gyr). A plausible mechanism is that the eccentricity of GJ 436b is modulated by a planetary companion due to their mutual perturbation. Here we investigate this possibility from the dynamical viewpoint. A general method is given to predict the possible locations of the dynamically coupled companions, including in nearby/distance non-resonant or mean motion resonance orbits with the first planet. Applying the method to GJ 436 system, we find it is very unlikely that the eccentricity of GJ 436b is maintained at the present location by a nearby/distance companion through secular perturbation or mean motion resonance. In fact, in all these simulated cases, GJ 436b will undergo eccentricity damp and orbital decay, leaving the present location within the stellar age. However, these results do not rule out the possible existence of planet companions in nearby/distance orbits, although they are not able to maintain the eccentricity of GJ 436b.

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Re: GJ436c? (again...)

Post by Lazarus on 18th December 2008, 7:45 pm

That analysis seems to be treating only the case of coplanar planets.

Has the Rossiter-McLaughlin effect been measured for GJ 436b? Might be time to invoke the Kozai mechanism?

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Re: GJ436c? (again...)

Post by Sirius_Alpha on 18th December 2008, 8:11 pm

Lazarus wrote:Has the Rossiter-McLaughlin effect been measured for GJ 436b?
No such measurement has been reported as of yet.

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Re: GJ436c? (again...)

Post by Sirius_Alpha on 5th January 2009, 9:16 pm

Transit Timing Observations of the Extrasolar Hot-Neptune Planet GL 436b

http://arxiv.org/abs/0901.0343
Abstract wrote:Gliese 436 is an M dwarf with a mass of 0.45 Msun and hosts the extrasolar planet GL 436b [3, 6, 7, 2], which is currently the least massive transiting planet with a mass of ~23.17 Mearth [10], and the only planet known to transit an M dwarf. GL 436b represents the first transiting detection of the class of extrasolar planets known as "Hot Neptunes" that have masses within a few times that of Neptune's mass (~17 Mearth) and orbital semimajor axis <0.1 AU about the host star. Unlike most other known transiting extrasolar planets, GL 436b has a high eccentricity (e~0.16). This brings to light a new parameter space for habitability zones of extrasolar planets with host star masses much smaller than typical stars of roughly a solar mass. This unique system is an ideal candidate for orbital perturbation and transit-time variation (TTV) studies to detect smaller, possibly Earth-mass planets in the system. In April 2008 we began a long-term intensive campaign to obtain complete high-precision light curves using the Apache Point Observatory's 3.5-meter telescope, NMSU's 1-meter telescope (located at APO), and Sommers Bausch Observatory's 24" telescope. These light curves are being analyzed together, along with amateur and other professional astronomer observations. Results of our analysis are discussed. Continued measurements over the next few years are needed to determine if additional planets reside in the system, and to study the impact of other manifestations on the light curves, such as star spots and active regions.

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Re: GJ436c? (again...)

Post by exofever on 3rd April 2010, 9:37 am

I recently noticed that Greg Laughlin's anagram includes the letters in “secular perturber”.
I don’t think its a coincidence. Perhaps the anagram solution is
about the Gliese 436 system: “A Gliese planet hath secular perturbers”.

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Re: GJ436c? (again...)

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