"Henri Wilson" HW@.... wrote in message
...
On Sun, 18 Feb 2007 10:59:26 -0000, "George Dishman"

wrote:


"Henri Wilson" HW@.... wrote in message
. ..
On Sat, 17 Feb 2007 14:22:20 -0000, "George Dishman"



Trial and error Henry, you feed what you think is the
true value of v*sin(i) and see whether the curves match
the observations. If not you alter the value until you
get a match and then you have found the value of v*sin(i).
At that point the predicted velocity curve should match
the published curve and you have found the true velocity
which takes into account the effect of ballistic theory
on the Doppler. Isn't that how you use it?

Not exactly.
Unless I have access to a reliable figure for the maximum radial
velocity
I
cannot really come to a firm conclusion about distance or unification
rate.

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.

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!

I feed in the max value and then try to match the brightness curve. In
doing so
I obtain velocity curves at both the source and the observer.

George, the latest upgrade of my program is now on my website if you would
like
to use it. www.users.bigpond.com/hewn/variables.exe
I have removed most of the bugs although it doesn't have comprehensive
instructions as yet. Extinction doesn't work for circular orbits.

That's OK, your existing distance factor can be
essentially used as the extinction factor as long
as we are observing from a much greater distance.

I really need three quantities, Vmax, distance and magnitude change. I
can
determine yaw angle and orbit eccentricity when matching the basic SHAPE
of a
brightness curve ....if I have such a curve.

All that can ever be observed are the spectral shift
and brightness for normal stars or the PRF for pulsars.
none of your results are valid unless you are working
back from those.

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.

For elliptical orbits, this has to be corrected for yaw angle, which I can
determine from curve shape.

Not a problem, this one is circular (you snipped the
figure of ~10^-7 for eccentricity earlier).


The pulses are assumed to move at (c+v)cos(a) towards a distant
observer,
where
a is the angle between the orbit tangent and the LOS.

Rats! I assumed you would ignore the cos(a) term because
the orbit radius is much smaller than the distance to
the system so cos(a) ~ 1.


Sorry that should have been c + v.cos(a) where v is the tangential speed
at any
point and a a function of time.
This merely describes the radial velocities towards the observer from all
points around the orbit.

The point stands, I assumed something incorrect so
my comment was wrong and I understand why you were
confused by it. Anyway it's easy to get round as
I say later, just use 1 light hour for the distance.

Setting the distance to zero is
then equivalent to finding the rate that the pulses hit
a flat plane perpendicular to the line of sight say just
beyond the orbital radius and before any bunching can take
place, or having the right orbital speed but zero radius.

The program then
calculates the arrival times of all the pulses emitted over a number of
orbits
at the observer distance.
At any instant the pulse positions form a regular spatial pattern. As
this
pattern moves past the observer, it gives the impression of brightness
variation. (dn/dt = dn/dx.dx/dt)

Thus, a bunching of pulses shows up as a brightness increase.

That's what I expected. At the distance where the
pulses first overlap (the fast ones catch the slow
ones) you get zero time between pulse arrivals hence
the inverse is an infinite number per second or
infinite brightness. It isn't really infinite as
there are only a finite number of pulses in the
stream but the calculation will go to very high
levels.

That's right. It does....but I have realised that this never happens,
probably
becasue of extinction.

That's why it sets an upper limit to the extinction
distance, the whole point of this excercise.

This is why DeSitter was wrong...and his argument has
always been the only 'evidence' against the BaTh.

No, the Sagnac experiment rules it out, this is only
every going to be a hypothetical curiousity.

Most variations are around 1.5 mag or less.
...and yes, I don't have much faith in the accuracies of many published
figures.

It's not a question of faith, numbers are accurate
but in this case there have only been two measurements
made AFAICS by different groups at different times.
It doesn't really matter, your brightness increase
would just be the number of pulses per second because
each pulse essentially carries the same energy other
than a random variation from pulse to pulse due to
the nature of the source.

If I produce a 'brightness curve' for the pulsar, its height will reflect
the
number of pulses arriving per unit time...not its 'brightness'. Pulsars
are
constant.

Yes, that's why I said I wasn't really interested in
the brightness as such, but it has been helpful in
finding the critical distance.

I'm not sure what it is you are asking me to do.

OK, let's do it in small steps so that I can
give you clear questions.

Common to all: set the eccentricity to zero, yaw
becomes irrelevant. Set the orbital period to
1.5334494503 days.

Step 1. Set the distance to zero (your sim should
reproduce the conventional theory) and set the
actual velocity to 27983 m/s.

Check that the observed velocity curve you get
matches that and that the maximum velocity is
90 degrees after conjunction.

That wont work.
'Zero distance' means 'at the orbit centre'. Radial velocity is
zero...so
is
brightness variation.

....So I'm not with you at all, here.

Understandable, I made an assumption about your
software that wasn't correct. The orbital radius
is 1.9 light seconds so if you set the distance
to one light hour, there should be minimal
bunching as the critical distance (below) is
8 light years and cos(a) = 0.999999861. You
should get the conventional curves to 1 part
in 10^7.

What curve are you talking about George?

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.

Not the pulsar curve I hope. I don't claim that is a result of the BaTh at
all.
It's a spinning neutron star.

Step 2. Increase the distance until you just get
the velocity curves going to infinity and tell me
what distance you get.

I assume you mean the 'brightness curves'.

Effectively yes. I should have said the speed goes
to c, not to infinity.

Consider the pulsar at four points in the orbit
round the barycentre '+':

D

A + C Earth

B

The diagram assumes the motion is anti-clockwise.

The highest acceleration towards Earth occurs at
point A. Look closer at two consecutive pulses
assuming they occur equally either side of A:

v - * ~ -- slow, c-v
A-(
* - v ~ -- fast, c+v

At the critical distance, the fast pulse just
catches the slow pulse after 8 light years so
they arrive simultaneously for an observer at
that distance.

Compare that with the conventional view. It says
the maximum Doppler would be at point B. For the
pulses to arrive simultanseously, the pulsar would
have to be moving at c to keep up with the first
pulse and emit the second alongside.

I am guessing that the critical distance should be
around 4 light years but let's see what your program
says before we get on to the more interesting stuff.

Period = 0.0042 years
Velocity = 0.0000933c

Critical distance = ~ 8 LYs.

See: http://www.users.bigpond.com/hewn/J1909-3744.jpg

Note that the observed velocity curve (red) is very different from the
real
curve (blue) at that distance.

I asked and you answered:

2) Have you corrected your program to show the velocity curve
that would be derived from the ballistic Doppler shift?[*]

Yes.

At the point where the brightness goes to infinity,
the time between pulses goes to zero and the velocity
curve (red I think) should peak at c.

That is correct.

That should be
coincident with point A which should be where your
blue line crosses the white axis and is rising.

No it's more subtle than that. the point varies with distance.

I'm assuming you have related the phase back to the
source system. In other words you subtract the mean
time from the barycentre to the observer from the
actual time. Otherwise a few light hours change to
distance would create a major apparent phase shift.

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.

(I'm having some trouble producing the right colours with Vbasic on
windowsXP).

The colours are distinguishable on the jpeg so I that's
fine. The real concern is with the phase shift between
the blue and others. I'll have to give a little more
thought to the effect of propagation speed on arrival
time but have a think about what I'm saying and see if
you think your program is producing what I expect.

I have looked closely at this myself before.

The point of maximum brightness moves in phase wrt the source velocity
curve as
distance in varied.

You might like to run the 'lightfronts' section of my program. It shows
just
how the pulses move away from the source. Increase the time scale to about
20.

What I might do is try to produce my own version so
I can check what I expect. Your GUI is very unfriendly
or at least it was last time I tried to use it.

In the meantime, we will need to know the speed for
the peak of the red curve in comparison to the number
you enter so perhaps you could consider adding either
a speed scale or a box with the value at the peak like
the max/min brightness box.

George