2+ planets around HU Aquarii

Page 1 of 2 1, 2  Next

View previous topic View next topic Go down

2+ planets around HU Aquarii

Post by Lazarus on 11th March 2011, 3:34 am

avatar
Lazarus
dG star
dG star

Number of posts : 2894
Registration date : 2008-06-12

View user profile

Back to top Go down

Re: 2+ planets around HU Aquarii

Post by Edasich on 11th March 2011, 5:07 am

Magnificent Very Happy
avatar
Edasich
dM star
dM star

Number of posts : 1530
Location : Tau Ceti g - Mid Latitudes
Registration date : 2008-06-02

View user profile

Back to top Go down

Re: 2+ planets around HU Aquarii

Post by Lazarus on 11th March 2011, 3:07 pm

Have to wonder if the third planet might be giving the second planet a spurious high eccentricity - in the given configuration, the periapse of the outer planet lies within the inner planet's orbit.
avatar
Lazarus
dG star
dG star

Number of posts : 2894
Registration date : 2008-06-12

View user profile

Back to top Go down

Re: 2+ planets around HU Aquarii

Post by Edasich on 11th March 2011, 6:02 pm

Indeed I don't get so feasible orbital configurations with zero eccentricity inner planet and 0.5 outer second one. I find more plausible a 0.2 eccentricity for the first and 0.36 for the outer.

Unless we are dealing with slighlty non-coplanar planets as for Upsilon Andromedae (i1=90 and i2=75), perhaps.

Surely way more strange would be QS Virginis system with two highly eccentric substellar objects (if confirmed)...
avatar
Edasich
dM star
dM star

Number of posts : 1530
Location : Tau Ceti g - Mid Latitudes
Registration date : 2008-06-02

View user profile

Back to top Go down

Re: 2+ planets around HU Aquarii

Post by atomic7732 on 18th March 2011, 3:47 am

Someone should run this in some orbit simulator. Try to find a stable configuration, cause I agree it sounds quite odd.

_________________
I'm not sure what to put here yet... but you'll find out soon enough. Then again, maybe no one will... Neutral
avatar
atomic7732
Meteor
Meteor

Number of posts : 16
Age : 20
Location : Gliese 581 g
Registration date : 2011-03-18

View user profile http://yoursolarsystem.wikia.com/

Back to top Go down

Re: 2+ planets around HU Aquarii

Post by Sirius_Alpha on 6th June 2011, 9:07 pm

A dynamical analysis of the proposed HU Aquarii planetary system
http://arxiv.org/abs/1106.0777

It has recently been suggested that the eclipsing polar HU Aquarii is host to at least two giant planets. We have performed highly detailed dynamical analysis of the orbits of those planets and show that the proposed system is highly unstable on timescales of < 5\times 10$^3$ years. For the coplanar orbits suggested in the discovery letter, we find stable orbital solutions for the planetary system only if the outer body moves on an orbit that brings it no closer to the host star than ~ 6 AU. The required periastron distance for the outer planet lies approximately 5 Hill radii beyond the orbit of the inner planet, and well beyond the 1-{\sigma} error bars placed on the orbit of the outer planet in the discovery letter. If the orbits of the proposed planets are significantly inclined with respect to one another, the median stability increases slightly, but such systems still become destabilised on astronomically minute timescales (typically within a few 10$^4$ years). Only in the highly improbable scenario where the outer planet follows a retrograde but coplanar orbit (i.e. inclined by 180 degrees to the orbit of the inner planet) is there any significant region of stability within the original 1-{\sigma} orbital uncertainties. Our results suggest that, if there is a second (and potentially, a third planet) in the HU Aquarii system, its orbit is dramatically different to that suggested in the discovery paper, and that more observations are critically required in order to constrain the nature of the suggested orbital bodies.

_________________
Caps Lock: Cruise control for 'Cool'!
avatar
Sirius_Alpha
Admin
Admin

Number of posts : 3528
Location : Earth
Registration date : 2008-04-06

View user profile http://solar-flux.forumandco.com/

Back to top Go down

Re: 2+ planets around HU Aquarii

Post by Lazarus on 7th June 2011, 12:50 pm

The HW Virginis system also looks like it will be unstable. NN Serpentis is probably in resonance which might help in that case.
avatar
Lazarus
dG star
dG star

Number of posts : 2894
Registration date : 2008-06-12

View user profile

Back to top Go down

Re: 2+ planets around HU Aquarii

Post by Sirius_Alpha on 12th October 2011, 8:27 pm

Revisiting the proposed planetary system orbiting the eclipsing polar HU Aquarii
http://arxiv.org/abs/1110.2542

It has recently been proposed, on the basis of eclipse-timing data, that the eclipsing polar cataclysmic variable HU Aquarii is host to at least two giant planets. However, that result has been called into question based upon the dynamical stability of the proposed planets. In this work, we present a detailed re-analysis of all eclipse timing data available for the HU Aquarii system, making use of standard techniques used to fit orbits to radial-velocity data. We find that the eclipse timings can be used to obtain a two-planet solution that does not require the presence of additional bodies within the system. We then perform a highly detailed dynamical analysis of the proposed planetary system. We show that the improved orbital parameters we have derived correspond to planets that are dynamically unstable on unfeasibly short timescales (of order 10^4 years or less). Given these results, we discuss briefly how the observed signal might in fact be the result of the intrinsic properties of the eclipsing polar, rather than being evidence of dynamically improbable planets. Taken in concert, our results highlight the need for caution in interpreting such timing variations as being planetary in nature.

_________________
Caps Lock: Cruise control for 'Cool'!
avatar
Sirius_Alpha
Admin
Admin

Number of posts : 3528
Location : Earth
Registration date : 2008-04-06

View user profile http://solar-flux.forumandco.com/

Back to top Go down

Re: 2+ planets around HU Aquarii

Post by Edasich on 13th October 2011, 9:14 am

No more in the list *sigh*
avatar
Edasich
dM star
dM star

Number of posts : 1530
Location : Tau Ceti g - Mid Latitudes
Registration date : 2008-06-02

View user profile

Back to top Go down

Re: 2+ planets around HU Aquarii

Post by Lazarus on 14th October 2011, 3:49 pm

:-(

Wonder how the other circumbinary planetary systems around cataclysmic variables (and pre-cataclysmic variables) will hold up.
avatar
Lazarus
dG star
dG star

Number of posts : 2894
Registration date : 2008-06-12

View user profile

Back to top Go down

Re: 2+ planets around HU Aquarii

Post by Edasich on 15th October 2011, 3:28 am

Wonder if it will come back with alternative solution as for NN Serpentis.
avatar
Edasich
dM star
dM star

Number of posts : 1530
Location : Tau Ceti g - Mid Latitudes
Registration date : 2008-06-02

View user profile

Back to top Go down

Re: 2+ planets around HU Aquarii

Post by Lazarus on 15th October 2011, 10:13 am

At least DP Leonis (AB)b has survived one round of reanalysis, hopefully some of the eclipse-timed systems are genuine planets.
avatar
Lazarus
dG star
dG star

Number of posts : 2894
Registration date : 2008-06-12

View user profile

Back to top Go down

Re: 2+ planets around HU Aquarii

Post by Sirius_Alpha on 1st December 2011, 9:37 pm

Maybe we shouldn't forget about the second planetary companion to HU Aqr just yet...

New Light-Travel Time Models and Orbital Stability Study of the Proposed Planetary System HU Aquarii
http://arxiv.org/abs/1112.0066

In this work we propose a new orbital architecture for the two proposed circumbinary planets around the polar eclipsing binary HU Aquarii. We base the new two-planet, light-travel time model on the result of a Monte Carlo simulation driving a least-squares Levenberg-Marquardt minimisation algorithm on the observed eclipse egress times. Our best-fitting model with $\chi_{r}^2=1.43$ resulted in high final eccentricities for the two companions leading to an unstable orbital configuration. From a large ensemble of initial guesses we examined the distribution of final eccentricities and semi-major axes for different $\chi_{r}^2$ parameter intervals and encountered qualitatively a second population of best-fitting parameters. The main characteristic of this population is described by low-eccentric orbits favouring long-term orbital stability of the system. We present our best-fitting model candidate for the proposed two-planet system and demonstrate orbital stability over one million years using numerical integrations.

_________________
Caps Lock: Cruise control for 'Cool'!
avatar
Sirius_Alpha
Admin
Admin

Number of posts : 3528
Location : Earth
Registration date : 2008-04-06

View user profile http://solar-flux.forumandco.com/

Back to top Go down

Re: 2+ planets around HU Aquarii

Post by Edasich on 2nd December 2011, 4:51 am

I said it was not to disprove so quickly...
avatar
Edasich
dM star
dM star

Number of posts : 1530
Location : Tau Ceti g - Mid Latitudes
Registration date : 2008-06-02

View user profile

Back to top Go down

Re: 2+ planets around HU Aquarii

Post by Sirius_Alpha on 2nd December 2011, 10:48 am

HU Aqr c is back from the dead on the EPE.
http://exoplanet.eu/star.php?st=HU+Aqr(AB)

_________________
Caps Lock: Cruise control for 'Cool'!
avatar
Sirius_Alpha
Admin
Admin

Number of posts : 3528
Location : Earth
Registration date : 2008-04-06

View user profile http://solar-flux.forumandco.com/

Back to top Go down

Re: 2+ planets around HU Aquarii

Post by Edasich on 2nd December 2011, 11:33 am

Next to "re-animate" is QS Virginis. A new solution has been provided though a bit... "weird".

http://adsabs.harvard.edu/abs/2011IAUS..276..495A
avatar
Edasich
dM star
dM star

Number of posts : 1530
Location : Tau Ceti g - Mid Latitudes
Registration date : 2008-06-02

View user profile

Back to top Go down

Re: 2+ planets around HU Aquarii

Post by Sirius_Alpha on 29th January 2012, 9:20 pm

Might be time to return HU Aqr c to the grave.

The Curious Case of HU Aquarii - Dynamically Testing Proposed Planetary Systems
http://arxiv.org/abs/1201.5730

From the paper:
At the timescale considered here, with timing variations occurring over thousands of days, the most likely non-planetary explanation for the observed signal results from the behaviour of the secondary star in the system, the M dwarf. With a fast rotation period of order a few hours (a result of the star being tidally locked in its rotation about the primary, the white dwarf), the dynamo effect within the M dwarf would be expected to be large. If we assume that the stars in such stellar systems display a magnetic cycle similar to the Sunís double peaked 22-year cycle, the distribution of angular momentum between the two will change over time. This will, in turn, have the effect of modifying the shape of the secondary star, with the knock-on effect of affecting the gravitational interaction between the primary and secondary, and hence the orbital period of the pair

_________________
Caps Lock: Cruise control for 'Cool'!
avatar
Sirius_Alpha
Admin
Admin

Number of posts : 3528
Location : Earth
Registration date : 2008-04-06

View user profile http://solar-flux.forumandco.com/

Back to top Go down

Re: 2+ planets around HU Aquarii

Post by Edasich on 30th January 2012, 5:07 am

Sirius_Alpha wrote:Might be time to return HU Aqr c to the grave.

The Curious Case of HU Aquarii - Dynamically Testing Proposed Planetary Systems
http://arxiv.org/abs/1201.5730

From the paper:
At the timescale considered here, with timing variations occurring over thousands of days, the most likely non-planetary explanation for the observed signal results from the behaviour of the secondary star in the system, the M dwarf. With a fast rotation period of order a few hours (a result of the star being tidally locked in its rotation about the primary, the white dwarf), the dynamo effect within the M dwarf would be expected to be large. If we assume that the stars in such stellar systems display a magnetic cycle similar to the Sunís double peaked 22-year cycle, the distribution of angular momentum between the two will change over time. This will, in turn, have the effect of modifying the shape of the secondary star, with the knock-on effect of affecting the gravitational interaction between the primary and secondary, and hence the orbital period of the pair

Perhaps not. This abstract dates back September 2011. The new orbital solution is more recent (Dec 01/2011).
And it yet displays the old orbital solution.
avatar
Edasich
dM star
dM star

Number of posts : 1530
Location : Tau Ceti g - Mid Latitudes
Registration date : 2008-06-02

View user profile

Back to top Go down

Re: 2+ planets around HU Aquarii

Post by Lazarus on 21st May 2012, 11:14 am

On the HU Aquarii planetary system hypothesis

Further analysis of the data considering different time resolutions, the effect of observing in different spectral windows and consideration of dynamical stability. Seems the best model is a 1-planet system, a ~7 Jupiter mass planet in a low-eccentricity orbit at 4.3 AU.
avatar
Lazarus
dG star
dG star

Number of posts : 2894
Registration date : 2008-06-12

View user profile

Back to top Go down

Re: 2+ planets around HU Aquarii

Post by Lazarus on 23rd May 2012, 2:04 pm

http://exoplanet.eu/star.php?st=HU+Aqr%28AB%29

EPE update is weird, they've put the 4.3 AU single planet as "unconfirmed" but left the second planet of the two-planet solution as confirmed...
avatar
Lazarus
dG star
dG star

Number of posts : 2894
Registration date : 2008-06-12

View user profile

Back to top Go down

Re: 2+ planets around HU Aquarii

Post by tommi59 on 23rd May 2012, 3:57 pm

Not first time and not last but re-analysis concludes better fit for 1 planet
avatar
tommi59
Jovian
Jovian

Number of posts : 549
Age : 40
Location : Baile Atha Cliath
Registration date : 2010-07-31

View user profile

Back to top Go down

Re: 2+ planets around HU Aquarii

Post by Sirius_Alpha on 7th October 2012, 11:21 am

Investigating AM Her Cataclysmic Variables with OPTIMA
http://arxiv.org/abs/1210.0884

...The new observations of HU Aqr confirm that the O--C (Observed minus Calculated) diagrams exhibit variations known for this binary which can be explained by a single, massive Jupiter--like planet, possibly accompanied by a very distant companion.

_________________
Caps Lock: Cruise control for 'Cool'!
avatar
Sirius_Alpha
Admin
Admin

Number of posts : 3528
Location : Earth
Registration date : 2008-04-06

View user profile http://solar-flux.forumandco.com/

Back to top Go down

Re: 2+ planets around HU Aquarii

Post by Sirius_Alpha on 17th March 2014, 8:32 pm

More on the ambiguity of the HU Aqr system with more data.

On the ephemeris of the eclipsing polar HU Aquarii
http://arxiv.org/abs/1403.4160

The magnetic cataclysmic variable HU Aquarii displayed pronounced quasi-periodic modulations of its eclipse timing. These were interpreted in terms of the light-travel time (LTT) effect caused by a circumbinary planet or planetary system. We report new photometric observations that revealed another precise eclipse timing for the October 2013 epoch, the first obtained in a high accretion state after many years in low or intermediate states. The eclipse was observed to occur earlier by 95.3 +- 2.0 s or 62.8 +- 2.0 s than expected for an assumed linear or quadratic ephemeris, respectively. The implied apparent strong evolution of the orbital period calls for a revision of the current planetary model or the planetary parameters. The object deserves further monitoring to uncover the true nature of the observed variability and to constrain the properties of the proposed planet or planetary system. The new observations prove that advanced amateur equipment can successfully be used in the growing field of planet search in wide circumbinary orbits via the LTT effect.

_________________
Caps Lock: Cruise control for 'Cool'!
avatar
Sirius_Alpha
Admin
Admin

Number of posts : 3528
Location : Earth
Registration date : 2008-04-06

View user profile http://solar-flux.forumandco.com/

Back to top Go down

Re: 2+ planets around HU Aquarii

Post by Sirius_Alpha on 15th September 2014, 7:15 am

Weirdness abound.

Testing the planetary models of HU Aquarii
http://arxiv.org/abs/1409.3586

We present new eclipse observations of the polar (i.e. semi-detached magnetic white dwarf + M-dwarf binary) HU Aqr, and mid-egress times for each eclipse, which continue to be observed increasingly early. Recent eclipses occurred more than 70 seconds earlier than the prediction from the latest model that invoked a single circumbinary planet to explain the observed orbital period variations, thereby conclusively proving this model to be incorrect. Using ULTRACAM data, we show that mid-egress times determined for simultaneous data taken at different wavelengths agree with each other. The large variations in the observed eclipse times cannot be explained by planetary models containing up to three planets, because of poor fits to the data as well as orbital instability on short time scales. The peak-to-peak amplitude of the O-C diagram of almost 140 seconds is also too great to be caused by Applegate's mechanism, movement of the accretion spot on the surface of the white dwarf, or by asynchronous rotation of the white dwarf. What does cause the observed eclipse time variations remains a mystery.

_________________
Caps Lock: Cruise control for 'Cool'!
avatar
Sirius_Alpha
Admin
Admin

Number of posts : 3528
Location : Earth
Registration date : 2008-04-06

View user profile http://solar-flux.forumandco.com/

Back to top Go down

Re: 2+ planets around HU Aquarii

Post by Lazarus on 15th September 2014, 3:15 pm

Not looking good for the proposed planets around such systems, given that there does now seem to be some kind of intrinsic effect (or combination of effects) that can exceed the Applegate mechanism in causing period variations.
avatar
Lazarus
dG star
dG star

Number of posts : 2894
Registration date : 2008-06-12

View user profile

Back to top Go down

Re: 2+ planets around HU Aquarii

Post by Sponsored content


Sponsored content


Back to top Go down

Page 1 of 2 1, 2  Next

View previous topic View next topic Back to top


 
Permissions in this forum:
You cannot reply to topics in this forum