Planet around cataclysmic variable QS Virginis?

http://exoplanet.eu/star.php?st=QS+Vir

Planet-hosting CV FTW!

Discovery paper:

A giant planet in orbit around a magnetic-braking hibernating cataclysmic variable

Seriously, several substellar companion, even in planetary regime, have been discovered so far.

I wish to provide you parameters that EPE doesn't give in exoplanet page about the host star.

Qian et al. affirm parameters are almost the same found by O' Donoghue et al. (2003). Thus:

d= 48 pc
M₁= 0.78 M_Sun
R₁= 0.011 R_Sun= 1.1 R_Earth
T₁= 14,200 K
M₂= 0.43 M_Sun
R₂= 0.42 R_Sun
T₂= 3,100 K
i=75.7°
Age = 375 Myrs

So I get individual luminosities:

L₁= 0.0044 L_Sun

L₂= 0.0146 L_Sun

L_Tot= 0.019 L_Sun

And thus water zone should be located within 0.14 AUs from cataclysmic binary. So the planet should be as cold as Neptune.

But planet is eccentric (e=0.37)

Fascinating discovery! Thanks for the system parameters!
Were they able to determine the inclination of the planet's orbit?

Edit: Using SIMBAD's value for the visual magnitude of the system, I got a value of 0.00239 L_sol for the system luminosity I am assuming that the visual magnitude quoted at SIMBAD is the total of the system, so the luminosity is the total system luminosity. I'm not terribly confident in this measurement though. How did you get yours?

Edit2: Found the paper describing QS Vir here.

I have added a WikiPedia page about. I hope it is exhaustive enough:

http://en.wikipedia.org/wiki/QS_Virginis

Hang on a second, what does it mean by "hibernating"? Far as I can tell from the sources listed at SIMBAD, the system is detached rather than undergoing mass transfer and is still in the process of becoming a true CV.

(Unfortunately I do not have access to the paper to check this one out)

Edit: ah-ha... found a discussion of this system here... seems it was a true CV in the past, is probably going to become one again in the future, but at the moment while there is a small amount of mass transfer, it is not a true CV.

i found this on the wikipedia about QS Virginis: http://en.wikipedia.org/wiki/QS_Virginis

Hum, Daniel, I think you should see before posting a link. This link is the one created by Edasich...

Bye

Sedna

Hi Sedna and all the people, i commited a mistake here sorry... i´m new on this chat, thanks to correct me

Daniel wrote:

Hi Sedna and all the people, i commited a mistake here sorry... i´m new on this chat, thanks to correct me

Welcome to the forum!

I'm still not getting how white dwarfs emit radiation, and why this planet would be so cold given the white dwarf's high temperature.

Sirius_Alpha wrote:

I'm still not getting how white dwarfs emit radiation, and why this planet would be so cold given the white dwarf's high temperature.

Like stars they radiate because they are hot. All objects above absolute zero (i.e. everything that exists) give off thermal radiation. Doesn't matter if the star is producing energy in its interior by fusion reactions, or if it is a dead star that hasn't cooled down yet. As for the white dwarf's luminosity, bear in mind this also depends on the star's size. The white dwarf is small, this more than compensates for the high temperature.

For a spherical black body, L ∝ R²T⁴ (∝ means "is proportional to", I've dropped some constants to simplify things)

The R² factor comes from the surface area of the sphere, the T⁴ comes from the Stefan-Boltzmann law.

Stars are not black bodies, but are pretty good approximations to them, so this formula works quite well.

So luminosity relative to the Sun is given by L/L_sun = (R/R_sun)² × (T/T_sun)⁴

For the white dwarf, using the parameters given by Edasich, the luminosity is therefore (0.011)² × (14200 / 5780)⁴ = 0.0044 times solar. The small size of the white dwarf "wins" over the high temperature, despite the temperature factor having a larger exponent.

It doesn't matter, Daniel, everybody makes mistakes, but welcome to EV II.

Lazarus wrote:

For the white dwarf, using the parameters given by Edasich, the luminosity is therefore (0.011)² × (14200 / 5780)⁴ = 0.0044 times solar. The small size of the white dwarf "wins" over the high temperature, despite the temperature factor having a larger exponent.

Well, actually, it's more complicated than that. To do not make mistakes, WD must be taken case by case. WD have luminosities smaller than Sun's, but WD have luminosities greater than Sun's too.
If we take the case of QS Virginis, I agree with Lazarus, the radius wins over the temperature. But, if we take the case of NN Serpentis (see here), this is completely different. Taking the formula given above, we have (0.021)² x (57000 / 5780)⁴ = 4.17 L Sol. In this case, temperature wins over the radius, and we clearly see that the luminosity is greater than the Sun's one, despite it's a WD too. So, when you speak about WD, the first thing you must think about is "white dwarf = hard trick" or "white dwarfs' cases must be taken very carefully".

Sirius_Alpha wrote:

I'm still not getting how white dwarfs emit radiation, and why this planet would be so cold given the white dwarf's high temperature.

If you take a look at the planet's semi-major axis and make a comparison with our solar system, the planet is located between the outer edge of the asteroid belt and Jupiter. So the planet would be cold, but with the luminosity of the WD, the planet would be even colder. After doing some calculations, I have values between 6 and 35 K, so the planet would be as cold as a particular body in our solar system named Sedna.

Bye

Sedna

I remember reading somewhere (a paper enciclopedia iirc ) , that degenerated matter does not follow Boltzmann law anymore , but i suppose it was related to pressure , not luminosity.
Anyhow , i suppose something more than a little constant should be used to adjust stephan-boltzmann formula to bodies that are composed of degenerated matter instead of normal-star matter.

Anyway , its beside the point , it does not matter how warm the star is , the reduction of emision surface due to the reduction in size is so big that for a body beyond mars orbit , the parent star would be a little more than a faraway star , and , more important , the slice of radiation its orbit would cut at any given time would be n-power smaller with distance , so , very very cold place.

Sedna wrote:

Well, actually, it's more complicated than that. To do not make mistakes, WD must be taken case by case. WD have luminosities smaller than Sun's, but WD have luminosities greater than Sun's too.
If we take the case of QS Virginis, I agree with Lazarus, the radius wins over the temperature. But, if we take the case of NN Serpentis (see here), this is completely different. Taking the formula given above, we have (0.021)² x (57000 / 5780)4 = 4.17 L Sol. In this case, temperature wins over the radius, and we clearly see that the luminosity is greater than the Sun's one, despite it's a WD too. So, when you speak about WD, the first thing you must think about is "white dwarf = hard trick" or "white dwarfs' cases must be taken very carefully".

I think it should be fairly clear from the part you quoted that I was referring to the specific case of the QS Virginis white dwarf. Definitely didn't say anywhere that all white dwarfs are less luminous than the Sun.

As you point out there's no hard-and-fast rule as to whether white dwarfs will be more or less luminous than the Sun, but the equations are the same for white dwarfs and normal main sequence stars. They aren't really a special case at all.

ciceron wrote:

I remember reading somewhere (a paper enciclopedia iirc ) , that degenerated matter does not follow Boltzmann law anymore , but i suppose it was related to pressure , not luminosity.
Anyhow , i suppose something more than a little constant should be used to adjust stephan-boltzmann formula to bodies that are composed of degenerated matter instead of normal-star matter.

Well there are going to be various absorption features from the various constituents of the white dwarf's atmosphere, depending on the density at the photosphere. Same goes for main sequence stars though the densities will presumably be lower. But as far as I am aware, the blackbody approximation holds fairly well for white dwarfs.

Thanks for the math, I'm no longer confused

What kind of relativistic effects would the near-surface environment of the white dwarf have on the brightness of the white dwarf? Negligible?

Sirius_Alpha wrote:

What kind of relativistic effects would the near-surface environment of the white dwarf have on the brightness of the white dwarf? Negligible?

Good question. IIRC the r coordinate of the Schwarzschild metric can be plugged into the usual Euclidean formula to get surface area, so there isn't too much weirdness there. However there is gravitational redshift to take into account - this means an observer located away from the object sees a lower effective temperature. IIRC the output luminosity scales as you'd expect with r (the coordinate of the Schwarzschild metric, which isn't the same thing as distance from the centre of mass!), but don't quote me on that... I haven't got my general relativity notes available!

Finally, a planet around a CV system. I remember there was a suspected one in the past. Don't remember the name.

marasama wrote:

Finally, a planet around a CV system. I remember there was a suspected one in the past. Don't remember the name.

OY Carinae?

Don't remember, thought it was a phone# name.

I know they have set even lower limits to a planetary companion around that system (roughly 7 Jupiter Masses and a=9.5 AUs).

Yet another planet around a CV (likely a SDSS J....) sounds new to me

More about the QS Virginis system: Activity on the M star of QS Vir - also mentions in the introduction that the hibernating cataclysmic model proposed suggests that the system became detached as a result of a nova eruption.

So it would seem that novae do not destroy gas giant planets, at least...

Orbital Period Variations in Eclipsing Post Common Envelope Binaries

Also not good for NN Serpentis either.

Though they state

Quote :

However, since the dynamics of the system throughout the common envelope phase are subject to large uncertainties, we cannot rule out the existence of this third body and it remains the only mechanism able to produce such a large period variation

I don't get why hurry to retract it.

It's a rather different candidate that is being proposed, which is highly inconsistent with the previous parameters. There might be a third object there but it is not the claimed planet.

(Also retraction would be the original authors stating their discovery claim was incorrect, this is another team)

http://iaus276.oato.inaf.it/IAUS_276/Abstract/Poster/Abstracts%20POSTER3.pdf

Quote :

Leonardo Andrade de Almeida – National Institute for Space Research, São José dos Campos, Brazil F. Jablonski
Two bodies with high-eccentricity orbits around the eclipsing cataclysmic variable QS Vir
QS Vir is an eclipsing cataclysmic variable with 3.618 hrs orbital period. This system has the interesting characteristics that it does not show mass transfer between the components through the L1 Lagrangian point and shows a complex orbital period variation history. Qian et al. (2010) associated the orbital period variations to the presence of a giant planet in the system plus angular momentum loss via magnetic braking.
Parsons et al. (2010) obtained new eclipse timings and observed that the orbital period variations associated to a hypothetical giant planet disagree with their measurements and concluded that the decrease in orbital period is part of a cyclic variation with period ~16 yrs. In this work, we present 24 new eclipse timings of QS Vir and suggest that the orbital period variations can be explained by a model with two circumbinary bodies.
The best fitting gives the lower masses M1×sin(I)~0.009M_odot and M2×sin(i)~0.049M_odot; orbital periods P1 ~7.6 yrs and P2 ~17.2 yrs, and eccentricities e1 ~0.62 and e2 ~0.9 for the two external bodies. Under the assumption of coplanarity among the two external bodies and the inner binary, we obtain M1 ~0.0093 M_odot and M2 ~0.05M_odot. We discuss these results in the context of the evolution of this system.

That doesn't sound like a particularly stable configuration. Then again, neither is the published orbital configuration for HW Vir.

This should not break any embargo, since poster from IAU meeting in Turin (Italy).
Re-exhumating QS Vir?

Two bodies with high-eccentricity orbits around the eclipsing cataclysmic variable QS Vir

It sounds a bit hard to manage a highly eccentric 9 Mj planet (e=0.62) brown dwarf with quite an interacting 50 Mj brown dwarf with extremely high (e=0.9) eccentricity. At least not coplanar.

Or else eccentricities with typos?