Why are the 'Fixed Stars' so FIXED?

"Henri Wilson" HW@.... wrote in message
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On 20 Feb 2007 03:10:39 -0800, "George Dishman"
wrote:

On 19 Feb, 23:56, HW@....(Henri Wilson) wrote:
On 19 Feb 2007 00:41:06 -0800, "George Dishman" wrote:
On 19 Feb, 04:44, HW@....(Henri Wilson) wrote:
On Mon, 19 Feb 2007 00:36:42 -0000, "George Dishman"
wrote:
"Henri Wilson" HW@.... wrote in message
.. .
On Sun, 18 Feb 2007 10:59:26 -0000, "George Dishman"
But you cannot ever get that because the variable
speed messes up the Doppler equation. As with any
modelling technique, you put in your initial guess
of the actual parameters, the program caclulates
the observed signals and then you iterate until
the predicted observables match that actuals.

Ah, but I only need a value for the MAXIMUM orbital speed.

Ah, but you cannot know that, all you know is the
maximum Doppler shift.

That's all I need.

Yes but you have to process it appropriately. Your
program is not doing that at present.

It's near enough to do what I want at present..

No, it is wrong by a factor of 11000 at 8 light years.
Of course that's only a test but the number is going
to be badly wrong at any range of interest.

George, velocity and distance are conjugate.

If the velocity is 10% high then my distance will be10% low.
This is no big deal. I don't know where you are getting your figures.


.. although I will have to take
Yaw angle into acount eventually..

Does that matter at the moment for a circular
orbit?

No there is no error in a circular orbit.
However as I have shown, this is NOT a circular orbit according to BaTh. It has
an e ~ 0.06 with periastron furthest from observer.

The maximum OBSERVED radial velocity will differ only slighly from the maximum
PERIPHERAL velocity. However the phasing will be nearly 90 out!!!! So I'm going
to have to compensate for this when I compare phases.
I can do this fairly easily..and will do so soon.

I think this might explain why my curves for RT Aur were a fair way out in
phase.
Thakyou for your help George. You might have added another nail in Albert's
coffin.

All I am doing now is matching curves. The value of (distance x max velocity)
is rather arbitrary because I dont really know the unification distance and it
is not easy to obtain velocity diagrams.

The BaTh and SR
doppler equations are effectively the same.

No they aren't, that's the whole point. Look at the
bottom of your reply where you agree the _apparent_
speed should reach c at the critical distance!

Yes.... but during extinction, the wavelength contracts or expands, so as to
still maintain the correct details of source velocity.

No, the speed matching causes the 'wavelength',
which in this case is the distance between pulses,
to eventually settle down to a constant value but
it will not be the original.

Not according to me.

They do according to the theory, you don't have
a choice.

The final distance between adjacent pulses will vary according to their initial
velocity relative to the barycentre. Some will move closer together, others
further apart.

They will also move closer and farther due to their
initially different speeds but that part will become
constant as the speeds equalise.

Yes..but their spacing overall will retain a periodic bunching.
It is not CONSTANT all the way along.

The extreme test
example here is for viewing at 8 light years with
negligible extinction, or equivalently at infinity
with an exponential extinction distance of 8 light
years, and the wavelength is zero. Your software
still gives v/c=0.00009 when it should be v/c=1.

George, unless I have access to a curve showing variation in pulse arrival
times I cannot help you much.

I've given you that repeatedly. The frequency varies by
30.5 mHz either side of 339 Hz.

OK.


Reading the papers about this pulsar is quite confusing for me

Indeed, but the basic information you need is trivial
for me. Some of the more specialised terms are less
clear but the basic orbit is simple.

It turns out that this might not be true.

because the
authors make such a big issue of Shapiro delay. (They even admit light is
slowed by gravity).

The Shapiro delay is what makes the system special.
It allows the inclination to be determined which
leads to highly accurate determination of a lot
of other parameters.

Well the whole picture changes when you use c+v....as it does with most of
astrophysics. It becomes more simple and logical.

The BaTh interpretation would be quite different from
theirs.

It would, so stop looking for excuses and let's see what
your program says.

It is done.

It can. ..or you can set eccentricity at 0.01

No, set it to 2.3*10^-7 if anything, but you
don't need an explicit extinction term. Just
treat your program as an observer at infinity
and distance is the characteristic extinction
length.

Hahaha!
See, your claim that the orbit is circular is based on a perfectly sinelike
'red curve'. The BaTh shows that the OBSERVED sinewave velocity curve requires
an orbit with e ~ 0.6 or more depending on observer distance.

Yes I can do that.
I only introduced the 'extinction' facility in order to try to obtain a value
for its rate.

Essentially your distance parameter is already that.

Yes. For a mag change of 0.2, I get a distance of about 0.7 LY


Like I said, all I need is period, distance and a value for the maximum
radial velocity.

Like I said, what you have is maximum Doppler shift.

No problem.

Indeed, but you need to fix the bug in the
software to convert from the shift to the
speed correctly.

George, this is a circular orbit and there is no difference between my and your
value of maximum velocity. I have tried to explain that extinction will not
affect measured doppler and its interpretation.

Extinction in itself wouldn't but the initial speed
difference does affect the Dopppler. Faster pulses
catch up to slower ones for a while before extinction
matches their speeds. That means the pulses are closer
together giving the _false_ impression of a higher
speed. Your blue curve is the true speed, the red
curve should be the _apparent_ speed deduced from
the closed-up pulses. It should be _higher_ than the
blue curve.

No. The program averages the ORIGINAL pulse speeds that arrive in set time
intervals. It should oscillate between 'higher' and 'lower'.

The red curve for the apparent speed. If you enter
27km/s the red curve should show that deviation
above and below the white axis. It would help if
you added a vertical scale or we cannot confirm
that. I'm presuming the value in the table on the
left called "Max. Vel." is your assumption for the
actual speed which you entered rather than the
highest point on the red curve.

The velocity curves are set to always have the same size on the screen. The
scale is linear and yes, the maximum is that shown in the velocity box. Ity
should be the same fro both red and blue curves.

No, it should be 0.00009c for the blue curve
at 8 light years and 1.0c for the red curve.
The 'wavelength' at that distance is zero.

George, I don't think we're taking about the same things here.

I might occassionally get the red and blue transposed
but I don't think I have so far.

The blue curve is the true radial velocity curve towards the observer.

Yes.

The red curve is generated in this way:

For the purpose of counting the arrival of pulses, the orbit period is divided
into 500 divisions, which form the elements of an array. The program adds all
the pulses that arrive in that division to make up the value of that array
element. It also follows each pulse individually so that it records the speed
at which the pulse left the source barycentre. It averages the velocities of
all the pulse that are placed into each array element.

That will give the wrong answer. The pubilished velocity
data uses the conventional Doppler formula so the speed is

v = c * (df / f)

where df is the frequency shift

To find that, you can use the time between arrivals which
is just the period, or the inverse of the frequency.

But you are using constant 'c'!!!. I'm using c+v...Naturally I will get a
different answer.

Introducing extinction doesn't really change anything.

It stops the period changing after some distance, the
way you have it at the moment is fine.

That's not good way to put it.
Nothing happens to the period no matter how extinction operates.

Just calculate
the Doppler shift from your pulse arrival times and you
will get the right answer.

Just stick c+v into your formula George and YOU will get right answer.
...Oh, and you might need a computer program to do it because v varies with
time.

I have realised though that when using ellitical orbits I have to compensate
for Yaw angle because the maximum observed velocity is not necessarily the
velocity at periastron.

That could be the cause of your extra phase
change.

It shouldn't make much difference at low eccentricities and doesn't affect
brightness curve shape anyway. ..just the distance.

It will have a small effect but for our circular
orbit, it is irrelevant. Can I ask that you lay
that aside on your to-do list until we finish
looking at J1909-3744.

It is done.
It supports the BaTh observation that extinction distance is inversely velocity
dependent...which is odd when you think about it.

There is second
order term involving the 'rate of change of acceleration'. You have
omitted it.

I don't believe there is such a term but that's why
I want to do the short distance test first.

No, I was wrong there, although not entirely. The main reason the point moves
is due solely to the difference in emission times. For short distances, a half
period is quite significant.

Getting the correct location for the maximum speed
will matter too, but for our circular orbit it
shouldn't matter.

Anyway, bottom line at the moment is that you are
not calculating the apparent velocity correctly
from the pulse period so let's get that fixed
before worrying about the effects of eccentricity.

George you have it all back to front.

I don't want to calculate the velocity. I want to read about it in a table or
graph.

Little children learn they don't always get what they
want. The published tables give the period and time
difference and I have done the calculation to turn that
into frequencies for you. All you need to do is fix the
bug in your program and then find the orbital parameters
and extinction that matches the observation.

you are using constant c.
I'm using c+v.

Can you provide that info for me?

I have done many times Henry, stop trying to invent excuses.

George

On 20 Feb 2007 02:38:49 -0800, "George Dishman"
wrote:

On 20 Feb, 00:40, HW@....(Henri Wilson) wrote:
On 19 Feb 2007 05:32:38 -0800, "George Dishman" wrote:
On 19 Feb, 05:09, HW@....(Henri Wilson) wrote:
Too close, moving too slowly...

The distance is usually known from Hipparcos or
so far away that it is academic for this purpose.

The velocity can be determined from the spectrum
of course and your program is then supposed to
tell us the velocity, but in general nearby stars
that are too close to resolve must be moving quite
fast.

George, my program DOES NOT tell us anything about the maximum velocity.
Where did you get the idea that it does?


You fit the blue curve to the observed velocity curve
or the green curve to the observed brightness and the
red curve tells you the actual velocity curve.

No that's not what I do.
The blue curve is that which a very close observer (along the Earth's LOS)
would see.
Using that 'true' velocity relationship, I adjust the other parameters in order
to produce a brightness curve of the observed shape and magnitude change.
On that basis, the red curve is the velocity curve that should be seen on
Earth.
Contrary to what I said in the other message, I think the phasing is correct
between brightness and red velocity.



To do that you can change the orbital parameters within
Keplerian constraints, inclination and yaw for the
observer location and the extinction characteristic
distance but that's all.

Forget inclination. I only need edge on orbits.

If you can fit both the blue and green curves, including
their relative phase, with a single set of parameters
then you theory passes the test otherwise you look for
excuses (like it really is a Cepheid).

That 'excuse' was basd on the presence of overtones, not the velocity
brightness phasing.

I tried to expain this to Andersen in the case of HD10875

Which of the above did you suggest applied?

The addition of two sine curves 180 out...... plus extinction.

And did you provide him with spectroscopic evidence that
the intrinsic luminosities are that well matched?

he provided that himself. besides, brightness curves are generally not
filtered.


Yes I do, it would make a difference of about
45 parts per million to the critical distance
for the pulsar for example (mental arithmetic,
E&OE).

George, measurements made on Earth about the rate of change of velocity in the
Earth's gravity field don't really tell us much about the possible role that
the whole solar gravity field might play in regard to a local EM frame of
reference, if such exists.

You still haven't learnt what the phrase "frame of reference"
means Henry.

You are starting to ramble.George,..
The Earth's frame of reference includes it atmosphere.
Light entering the atmosphere at c+v will quickly adjust to c wrt that frame,
ie., the Earth..

I also suggest that any large centre of mass, such as a solar system or even a
whole galaxy will constitute a broad EM reference frame of not inconsiderable
'strength'.



Light entering that frame from outside and initially moving at c+v wrt Earth
might be affected much more than you think.

Nope, for weak fields Newton holds or you can use GR. Ignoring
the refractive index of the solar plasma, the speed becomes:

v_r^2 = v_i^2 + v_e^2

where v_r is at radius r from the Sun, v_i is the speed at
infinity or in deep space, the final value of c/n we talked
about before, and v_e is the escape velocity at that radius.

However I basically agree with what you say. Gravity is probably too weak to be
a major factor.

It's easy to quantify but even if you dispute the above
maths, since it is going to affect all the light equally
it cannot have any effect at the observer end. At the
emitted end it just slows all the light leaving the star
so the light spends longer in the region where extinction
happens so the speed difference between fast and slow will
be reduced, but only by a tiny amount.

George, I have written another very comprehensive program that does all the
maths for this.
http://www.users.bigpond.com/hewn/redshift.exe
It gives expected doppler shift when light leaves one mass and travels to
another mass. (there might be a small bug in this but persevere.)


George