Celestia Forums

Hi all,

after plenty of work, I have decided to upload my
Perl-generated 'binaries.stc' file
with 203 accurate binary orbits that all have a well
determined primary/secondary mass ratio!

It's not yet final, but it's about time for testing it...

You may download the file for trying with one of the
recent 1.40pre Celestia versions from here:

http://www.shatters.net/~t00fri/binaries.stc.zip

Unzip the file and put it into the 'extras' directory. That's all.

We clearly need an extension of the celestial browser to
administrate double stars! Otherwise some of you will
have problems finding all these beautiful binary systems
in the sky . For testing, just note down some
respective HIP numbers from the binaries.stc file.

Here are some details about the "state of the art":


A) Features:
=======

1) The orbits are from a very sound and often cited
(82x) analysis by S. S?derhjelm (1999),

Astronomy and Astrophysics, v.341, p.121-140 (1999).
Or online:

http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1999A%26A...341..121S

2) All 203 orbits feature a well determined mass ratio
from combined fits to the Hipparcos and Tycho
astrometry data as well as (crucially) the Hipparcos
"Transit data"!

3) What I really appreciate in this analysis is a careful
determination of uncertainties. So all results
for m2/m1 and the orbit parameters have quoted
error bars!

4) The author claims that as a result of the global fits, he
came up with much improved values for the parallaxes
relative to the original Hipparcos data. So watch out that
there are changes relative to HIP.

5) I have cross correlated 3 catalogs via Perl to generate
the resulting Celestia stc file:


Nothing has been touched by hand in my binaries.stc file. It's all Perl....While there may be bugs,
typing errors are probably excluded

Here is a little preview for one of my 203 systems:




6) A few of the binaries are also in Grant's nearstar.stc
file. I left them in deliberately to allow a better
comparison of the differences!

7) If anyone wants to play with my Perl script, let me
know...


Of course the orbit parameters have to be rotated
from the plane-of-sky coordinates to the ecliptic in
Celestia,

which involves quite some trigonometry .


For testing purposes , here is what I worked out and use
in my Perl script

(Hehe Evil Dr. Ganymede, isn't that cool? ):




Of course, I checked for quite a few examples that it
agrees with what Grant is using...



B) Pending:
========

1) For the time being at least, I have used the quoted
Hipparcos Hp "visual" magnitudes for the primaries and
secondaries rather than the Johnson ones that are
normally used in Celestia. The differences are quite
moderate of the order of 0.1m or so.


2) I noticed that Grant has done this also tacitly in his
new nearstars.stc file, but there Johnson V and Hp are
even mixed together...

3) The major working compromise for now refers to the
spectral classes of the secondaries that are generally
lacking. I have done much work in that area, but while
that is unfinished, I have just arbitrarily substituted G2V
(our sun's ) spectral class for all secondaries. This will
certainly change in the near future!

Enjoy and let me know about bugs!

Bye Fridger

I am done Evil Dr. Ganymede!

Bye Fridger

t00fri wrote:I am done Evil Dr. Ganymede!

Bye Fridger

What are you telling me for? Or are you just trying to foist the blame on me for you stomping off in a huff?

Fridger,

It's your choice to cancel the project, but I really think that you should continue work on your catalog of star orbits. It's an important addition to Celestia. There's no point in taking these squabbles on the forum so seriously.

--Chris

OK, I have decided that life must go on. I have unlocked
the binaries.stc file for further download and testing.

I shall try to avoid any further (rhetorical) contact with
Evil Dr Ganymede....Let's see how it goes.

Bye Fridger

do you want a beer???

brunetto_64 wrote:do you want a beer???

In case this is not an "impolite" answer: yes, indeed!

But I must confess, there is one standing already next to my incredibly fast
new computer with the ADSL 3000, i.e 3 Mbit/sec line working since yesterday .

It' just amazing to download files with 380 KByte/sec =3 Mbit/sec...


Bye Fridger

Fridger wrote:200+ Binary Orbits for Download & Testing, RESUMED!

This is very good news indeed!

I am very glad to see that you have changed your mind about this, Fridger.

Fridger,

Very nice work. I did notice the minor position shifts in stellar distances, and I figured it was due to more precise calculation of parallax.

I agree that a way to locate these little beauties should be included in Celestia. I was thinking maybe a new button on the Star Browser to locate multiple star systems. It seems to fit in with the look and feel of the rest of the program.

One minor criticism would be the substitution of G2V type stars for those stars that have unknown classifications. I suppose where we know the abs magnitude of the companion a guess could be taken as to the stellar type. Where we don't, its likely that such stars are K or M class, simply by the law of averages.

Still, a great piece of work, especially given that we have had this functionality available for just over a week.

Regards,

Cormoran

Cormoran wrote:Fridger,

Very nice work. I did notice the minor position shifts in stellar distances, and I figured it was due to more precise calculation of parallax.

I agree that a way to locate these little beauties should be included in Celestia. I was thinking maybe a new button on the Star Browser to locate multiple star systems. It seems to fit in with the look and feel of the rest of the program.

One minor criticism would be the substitution of G2V type stars for those stars that have unknown classifications. I suppose where we know the abs magnitude of the companion a guess could be taken as to the stellar type. Where we don't, its likely that such stars are K or M class, simply by the law of averages.

Still, a great piece of work, especially given that we have had this functionality available for just over a week.

Regards,

Cormoran

Cormoran,

good you like the preliminary result. Of course, G2V was
just an initial "placeholder". I have lots more results
here, but want to go on testing a little before releasing
them in the next round.

My actual star class estimate will be based on combining
the HR relation (Temperature vs. Luminosity) with the
familiar Mass-Luminosity relation, both evaluated and
tested with the /primary/ stars of the 200+ binary
systems. Here I know from fits & data: mass, luminosity
and star classes <-> eff. temperature, so everything
may be tested and optimized...


This way a universal relation can be determined and
used for the secondaries subsequently. I just want to
improve a bit on the white dwarf secondaries which tend
to deviate (as usual) from the main sequence behavior...


Bye Fridger

Fridger,

I'm looking forward to it, as are many others I think.

While I am one of the many who use Celestia to create fictional systems, I'm a very big fan of basing them in fact, so I don't contradict known information.

I'd be very interested to see how you work out the stellar classifications for the unknown stars when we get to that stage.

Regards,

Cormoran

Hi all,

I thought perhaps some of you are interested in a
visualization of the various dependencies of my 200+
binary star sample on crucial parameters like (eff.)
temperature (<-> color class), (primary star) mass,
luminosity, etc..

There are two familiar correlations among those
parameters that I want to illustrate below:

1) Hertzsprung-Russell (HR) type, i.e.:
--------------------------------------------------------
Temperature versus Luminosity.

Here I use the luminosity calculated from the Hipparcos
visual magnitude (Hp) as an example. Of course I have
analogous plots for all other varieties that are slightly
different only. The pink dot corresponds to our
sun. All units are solar units, so the sun
correspoints always to the point (1,1) in each plot!

2) Luminosity versus Mass (here of the primary star)


since I have all catalog data and thus all dependencies
under control with my Perl scripts, I can easily plot
almost anything against almost anything as long as
'anything' has been determined by measurement..


Here are the two most well known cases for our 200+
binary systems:




You clearly see the strong correlations in both cases,
but you can also see a leftover substantial scatter among
the points. The main aim is to somehow reduce that
scatter to a minimum by combining those 2 plots in
a clever way! As long as there is a substantial scatter
remaining, we will necessarily misidentify the color
classes (temperatures) of a certain (small) fraction of the
secondary stars...which we want to avoid, of course.


Problematic cases are typically white dwarfs, for
example...

Bye Fridger

Hi all,

just to go on a bit...

What physical consideration could guide us to combine
the two plots above?

Well, we all know (I hope ) about Stefan Boltzmann's
law, according to which a so-called 'black-body' radiates.

In physics a 'black body' is an object that absorbs all
light that falls onto it: no light passes through it nor is
reflected. Despite the name, black bodies do radiate
light.

Per unit area, a black body radiates ~ T^4, the fourth
power of the temperature, which is the Stefan-Boltzmann
law.

Stars do so, too. In fact one finds that the luminosity L of
a star is



We want to know the temperature of our secondaries,
given their luminosities and masses!

So,


Now there are various known empirical and theoretical
dependencies, how the star radii should depend on their
masses (that we know!). OK feeding this in, leaves us
with an expression


That's what we were after....

Bye Fridger

This relation only applies to main sequence stars though, surely? (do subgiants and giants even have a consistent relationship connecting T, L and mass?)

Evil Dr Ganymede wrote:This relation only applies to main sequence stars though, surely? (do subgiants and giants even have a consistent relationship connecting T, L and mass?)

Which relation? Radius-Mass relations hold for all type of stars, yet the powers are different!

e.g.

for white dwarfs R ~ 1/M^3

for main sequence stars with M<M_sun,

R ~ M^0.8,

for main sequence stars with M>M_sun

R ~ M^1.2

etc.

Was it this what you were asking?

Bye Fridger

Hi all,

here is a nice Java applet where 'black-body' fans can
compose their favorite spectrum. Have a look. It's
instructive!

http://www.mi.infm.it/manini/dida/BlackBody.html?textBox=8000

Bye Fridger

Yes... there's a consistent relationship within the different star Size classifications (eg within D and V), but is that true for size II and III stars?

For example, the stellar evolution grids I have imply that two size II giants with different mass and the same luminosity will have a different radius and surface temperature. Is that to be expected?

Evil Dr Ganymede wrote:Yes... there's a consistent relationship within the different star Size classifications (eg within D and V), but is that true for size II and III stars?

For example, the stellar evolution grids I have imply that two size II giants with different mass and the same luminosity will have a different radius and surface temperature. Is that to be expected?

My binary sample does not involve size II stars , but quite a few size III ones. I am still searching for more information on these special cases. That's what consitutes the time consuming part of the project ...

At the end, a lot boils down just to try various combinations of powers of M and L empirically. Each try takes less than 10 seconds for 200+ binaries...

All that counts at the end is to get a smaller spread of the points than initially

Bye Fridger

Hi all,

below I report some further interesting studies about my
200+ binaries.

In the image on the r.h.s above, I had plotted the
Hp-Luminosity versus the Mass of the primary star. For
convenience this plot is shown again below on the l.h.s.

We clearly see a (~ linear) correlation between Mass and
Lumi but there is still a substantial spread of the points
leftover that we want to eliminate somehow.

++++++++++++++++++++++++++++++
So the next logical task would be to find out in this plot to
which color classes (<-> temperature ranges) the
various blue dots belong.
++++++++++++++++++++++++++++++

After a little further Perl exercise, I get the color-coded
plot on the r.h.s below that is quite interesting. The color
classes are associated with different colors, as labelled in
the plot.

You can see first of all what color classes the primaries
of my 200+ systems do involve altogether: B...M!

Unfortunately, it also means that I cannot reduce the
spread entirely by multiplying with appropriate powers
of the Temperature in the lumi versus mass plot. Still,
it's easy to find out. I'll keep you informed....

Bye Fridger