# Circumbinary Planets at NSVS 14256825

## Circumbinary Planets at NSVS 14256825

The quest for companions to post-common envelope binaries. II. NSVS14256825 and HS0705+6700

We report new mid-eclipse times of the two close binaries NSVS14256825 and HS0705+6700, harboring an sdB primary and a low-mass main-sequence secondary. Both objects display clear variations in the measured orbital period, which can be explained by the action of a third object orbiting the binary. If this interpretation is correct, the third object in NSVS14256825 is a giant planet with a mass of roughly 12 M_Jup. For HS0705+6700, we provide evidence that strengthens the case for the suggested periodic nature of the eclipse time variation and reduces the uncertainties in the parameters of the brown dwarf implied by that model. The derived period is 8.4 yr and the mass is 31 M_Jup, if the orbit is coplanar with the binary. This research is part of the PlanetFinders project, an ongoing collaboration between professional astronomers and student groups at high schools.

Update:

http://exoplanet.eu/star.php?st=NSVS+1425

Within unconfirmed planets.

Edasich
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## Circumbinary Planets at NSVS 14256825

Two circumbinary planets in the eclipsing post-common envelope system NSVS 14256825
http://arxiv.org/abs/1210.3055

We present an eclipse timing variations analysis of the post-common envelope binary NSVS 14256825, which is composed by a sdOB star and a dM star in a close orbit (P_{orb} = 0.110374 days). High-speed photometry of this system was performed between July, 2010 and August, 2012. Ten new mid-eclipse times of NSVS 14256825 were analyzed together with all available eclipse times in the literature. We revisited the O--C diagram using a linear ephemeris and detected a clear orbital period variation. We investigated this variation on the assumption that it is a light travel time (LTT) effect. A full orbital motion analysis indicates that two LTT shifts with semi-amplitudes of ~20 s and ~5 s are superimposed on the O--C diagram and are consistent with two circumbinary bodies. The best solution provides the orbital periods, P_c = 3.49 +/- 0.21 years and P_d = 6.86 +/- 0.25 years, and the projected semi-major axes, a_c \sin I_c = 1.9 +/- 0.3 AU and a_d \sin I_d = 2.9 +/- 0.6 AU, for the circumbinary bodies. The masses of the external bodies are M_c ~2.8 M_{Jupiter} and M_d ~8.1 M_{Jupiter}, if we assume their orbits are coplanar with the close binary. Therefore NSVS 14256825 is composed by the close binary and two circumbinary planets in a 2:1 mean motion resonance. The closer planet in NSVS 14256825 has the minimum binary-planet separation among all known circumbinary planets in post-common envelope systems.

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Sirius_Alpha

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## Re: Circumbinary Planets at NSVS 14256825

It would have been nice if they'd done a stability analysis: this kind of thing seems to be a real problem with several of the claimed post-common envelope multiplanet systems.

In this case the eccentricity of the outer planet is quite high so the orbits should cross. Maybe the possible 2:1 resonance can help, but I am certainly suspicious about whether this is a plausible orbital configuration.

Lazarus
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## Re: Circumbinary Planets at NSVS 14256825

Lazarus wrote:In this case the eccentricity of the outer planet is quite high so the orbits should cross.

Crossing orbits is definitely within the error margins.

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## Re: Circumbinary Planets at NSVS 14256825

Are you sure that diagram is correct?

I get the periastron of the outer planet as 2.9 AU × (1−0.52) = 1.392 AU, versus the semimajor axis of the inner planet at 1.9 AU....

Lazarus
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## Re: Circumbinary Planets at NSVS 14256825

Perhaps different inclinations for both substellar companions could be envisaged.

Two bodies with high eccentricity around the cataclysmic variable QS Vir

Also, since (almost) officially published, why EPE doesn't list the planet QS Vir (AB)b one (the brown dwarf should be labelled as QS Vir C)? At least in unconfirmed planets.

Uhm, offtopic, perhaps....

Edasich
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## Re: Circumbinary Planets at NSVS 14256825

Edasich wrote:Also, since (almost) officially published, why EPE doesn't list the planet QS Vir (AB)b one (the brown dwarf should be labelled as QS Vir C)? At least in unconfirmed planets.
I thought QS Vir (AB)b was replaced with the brown dwarf? I don't recall there being two planets there. The paper you cite is from 2010? My memory is not the best on this system

Lazarus wrote:Are you sure that diagram is correct?
Not a hundred percent, but now that you point that out, it does seem sort-of off. It's from a programme I wrote a couple days ago where you feed it the semi-major axis, eccentricity and longitude of periapsis. Haven't really given it a rigorous test, other than a sort of by-eye comparison of several systems. It replicates the Solar system fairly well at least.

I basically calculate an array of positions in a coordinate plane. Relevant calculations:
This loops through for a specified value of points along the orbit, evenly spaced in time (I used your guidance on this thread to get the position of the planet around the orbit as a function of time, "next_degree").
Code:
double r = SMA / (1 + (ecc * Math.cos(next_degree)));double x_coord = r * Math.cos(next_degree);double y_coord = r * Math.sin(next_degree);tempArrayX[x] = x_coord;tempArrayY[x] = y_coord;
This loops through each point and rotates it by a value specified by LongPeri
Code:
double x_coord = (tempArrayX[x]*Math.cos(Math.toRadians(LongPeri))) - tempArrayY[x]*Math.sin(Math.toRadians(LongPeri)));double y_coord = (tempArrayX[x]*Math.sin(Math.toRadians(LongPeri))) + tempArrayY[x]*Math.cos(Math.toRadians(LongPeri)));tempArrayX[x] = x_coord;tempArrayY[x] = y_coord;

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## Re: Circumbinary Planets at NSVS 14256825

Example outputs.

Kepler-11

55 Cnc

61 Vir

Sol

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## Re: Circumbinary Planets at NSVS 14256825

Sirius_Alpha wrote:I thought QS Vir (AB)b was replaced with the brown dwarf? I don't recall there being two planets there. The paper you cite is from 2010? My memory is not the best on this system

The paper lists a third body with mass in brown dwarf regime (m3=0.056 mSol=ca. 56 mJupiter) in extremely eccentric orbit (e=0.92) and a fourth body with planetary mass (mm4=0.009mSol=9 mJupiter) in quite eccentric orbit too (e=0.62).

Under the assumption of coplanarity among the two external bodies and the inner binary, we obtain a giant planet with ~0.009 M⊙ and a brown dwarf with ~ 0.056 M⊙ around the eclipsing binary QS Vir.

More details in this poster

In this thread I had also posted a putative reconstruction with non coplanar orbits.

http://solar-flux.forumandco.com/t425p30-planet-around-cataclysmic-variable-qs-virginis#5471

Edasich
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## Re: Circumbinary Planets at NSVS 14256825

Hmmm your other diagrams look ok, maybe you mistyped the input parameters?

Lazarus
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## Re: Circumbinary Planets at NSVS 14256825

I really don't believe so.
Code:
DrawEllipse(1.9,0.0,11.4);DrawEllipse(2.9,0.52,97.5);
Arguments are a, e, ω, in that order.
I'm confident the problem isn't in the part of the programme that calculates the planet's position over equal time intervals, because if I turn it off and just draw the points at equal angular separations, the shape of the orbits remain the same.
Disabling the LongPeri rotations don't change the shape of the orbits either (though obviously their orientation changes).

Edit:
Found the problem. The eccentricity transformation isn't right.
Here are two orbits with a = 1. One has e = 0, the other has e = 0.5.
Increasing the eccentricity causes it to overestimate r. I've had this problem before...

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## Re: Circumbinary Planets at NSVS 14256825

Figured it out. Forgot to multiply r by (1 - e2) *doh*

NSVS 14256825

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## Re: Circumbinary Planets at NSVS 14256825

On the dynamical stability of the proposed planetary system orbiting NSVS 14256825
http://arxiv.org/abs/1302.4137

Apparently the system is unstable.

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## Re: Circumbinary Planets at NSVS 14256825

Well that is quite unsurprising really.

Really I am quite surprised that there was no attempt to do this kind of thing in the original paper, the crossing orbits should have raised suspicion.

Lazarus
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## Re: Circumbinary Planets at NSVS 14256825

Revisiting the proposed circumbinary multi-planet system NSVS14256825
http://arxiv.org/abs/1311.3021

In this work we carry out an analysis of the observed times of primary and secondary eclipses of the post-common envelope binary NSVS14256825. Recently, \cite{Almeida2013} proposed that two circumbinary companions orbit this short-period eclipsing binary, in order to explain observed variations in the timing of mutual eclipses between the two binary components. Using a standard weighted least-squares minimisation technique, we have extensively explored the topology of χ2 parameter space of a single planet model. We find the data set to be insufficient to reliably constrain a one-companion model. Various models, each with similar statistical significance, result in substantially different orbital architectures for the additional companion. No evidence is seen for a second companion of planetary nature. We suspect insufficient coverage (baseline) of timing data causing the best-fit parameters to be unconstrained.

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## Nice Orbit Plotter! :)

When are you going to release this orbit-drawing program to the public? I want to use it to plot some Sci-Fi systems I made. Here's the tool that I used to generate them: http://www.oocities.org/aina.geo/stargen.html

stargate38
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## Re: Circumbinary Planets at NSVS 14256825

I hadn't intended to release it, and it doesn't have a GUI. I can send you the Java or C# code for it if you want it (send me a PM with your e-mail). You can throw it in an IDE and get it running pretty easily though.

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## Re: Circumbinary Planets at NSVS 14256825

I did run a simulation (Using a different program), and the inner planet gets ejected within 1000 years.

stargate38
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## Re: Circumbinary Planets at NSVS 14256825

Is there a circumbinary planet around NSVS 14256825?
https://arxiv.org/abs/1701.05211

The cyclic behaviour of (O-C) residuals of eclipse timings in the sdB+M eclipsing binary NSVS 14256825 was previously attributed to one or two Jovian-type circumbinary planets. We report 83 new eclipse timings that not only fill in the gaps in those already published but also extend the time span of the (O-C) diagram by three years. Based on the archival and our new data spanning over more than 17 years we re-examined the up to date system (O-C). The data revealed systematic, quasi-sinusoidal variation deviating from an older linear ephemeris by about 100 s. It also exhibits a maximum in the (O-C) near JD 2,456,400 that was previously unknown. We consider two most credible explanations of the (O-C) variability: the light propagation time due to the presence of an invisible companion in a distant circumbinary orbit, and magnetic cycles reshaping one of the binary components, known as the Applegate or Lanza-Rodono effect. We found that the latter mechanism is unlikely due to the insufficient energy budget of the M-dwarf secondary. In the framework of the third-body hypothesis, we obtained meaningful constraints on the Keplerian parameters of a putative companion and its mass. Our best-fitting model indicates that the observed quasi-periodic (O-C) variability can be explained by the presence of a brown dwarf with the minimal mass of 15 Jupiter masses rather than a planet, orbiting the binary in a moderately elliptical orbit (~ 0.175) with the period of ~ 10 years. Our analysis rules out two planets model proposed earlier.

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## Re: Circumbinary Planets at NSVS 14256825

I was sure that some kind of substellar companion was there.

The paper also mentions tertiary companions to *V471 Tau (seemingly disproved) and *V470 Cam (=HS 0705+6700). According to EPE's new criteria, shouldn't the latter too be listed in Planet List? Its minimum mass is estimated 33.7 ± 1.6 MJup and doesn't exceed 75 MJup at i > 27.2°.

Same for another WD+dM binary, SDSS J143547.87+373338.5, which hosts a potential third body with 19.78 ± 1.67 MJup. There could even be "circumtertiary" objects around *V404 Lyr and Y Sextantis, with m4 =49.2 MJup and m4 =44 MJup respectively.

Edasich
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