Double stars I discovered!

On May 27, 1:17 pm, wrote:
On May 26, 11:28 am, "Mike Dworetsky"



wrote:

This may be possible. Simplest naive calculation:

Separation is 35 arcsec x 130 pc distance, so about 4500 AU if both are in
the plane of the sky. Total mass roughly 10 Msun. Kepler's third law gives

M P^2 = a^3 or P = (roughly) 95,500 years. (Could be less if the masses are
a bit higher)

Assume for simplicity a circular orbit of B around A with rho 35 arcsec.
Circumference is 2pi times 35 so 220 arcsec. Proper motion difference is
around 6.5 mas/yr, or 1 arcsec evey 154 years. 154 x 220 = 34000 yr, very
roughly.

Now I haven't worked out any vectors, because the data are insufficient, but
by a factor of 3 the pm is a bit faster than one might expect for a bound
orbit, but any of the assumptions above (such as circular orbit in the plane
of the sky) could be wrong. So it is at least plausible (but not confirmed)
that they are gravitationally bound.

--
Mike Dworetsky

(Remove pants sp*mbl*ck to reply)

That's a really interesting way of analysing! I'll be sure to repeat
similar calculation for each of the pairs I've identified. Having
sifted through my list, I have narrowed to these 4 pairs that are
genuinely CPM and from what data I have, they seem worthy of further
investigations:

(1) In Lacerta

Primary: HD 213128 -- Star (A component)
========================================
ICRS coord. (ep=2000) : 22 28 13.7025 +51 54 19.833
Proper motions mas/yr [error ellipse]: -2.60 0.50
Error ellipse: [1.70 1.60 90]
Spectral type: A0 D
V 8.88

Secondary: BD+51 3386 -- Star (B component)
===========================================
ICRS coord. (ep=2000) : 22 28 15.8443 +51 54 39.408
Proper motions mas/yr [error ellipse]: -3.90 1.30
Error ellipse: [1.80 1.70 90]
Spectral type: A0 D ~
V 9.88

Rho is between 30 and 40 seconds of arc

(2) In Vulpecula

Primary: HD 344698 (A component)
========================================
ICRS coord. (ep=2000) : 19 39 57.6679 +23 17 25.165
Proper motions mas/yr: 5.20 -4.40
Error ellipse: [1.80 1.70 179]
Spectral type: A7 D
V Mag: 10.01

Secondary: HD 344697 (B component)
========================================
ICRS coord. (ep=2000) : 19 39 56.2687 +23 17 34.312
Proper motions mas/yr : 5.90 -3.70
Error ellipse : [1.80 1.70 90]
Spectral type : A7 D
V Mag : 10.18

Rho is ~ 22 seconds of arc

(3) In Cepheus

Primary: HD 344698 (A component)
========================================
ICRS coord. (ep=2000) : 19 39 57.6679 +23 17 25.165
Proper motions mas/yr: 5.20 -4.40
Error ellipse: [1.80 1.70 179]
Spectral type: A7 D
V Mag: 10.01

Secondary: HD 344697 (B component)
========================================
ICRS coord. (ep=2000) : 19 39 56.2687 +23 17 34.312
Proper motions mas/yr : 5.90 -3.70
Error ellipse : [1.80 1.70 90]
Spectral type : A7 D
V Mag : 10.18

Rho is around 53.5 seconds of arc

(4) In Hercules

Primary: BD+36 3014 (A component)
======================================
ICRS coord. (ep=2000) : 18 05 36.2030 +36 18 04.863
Proper motions mas/yr: -6.10 -11.40
Error ellipse: [6.50 2.10 90]
Spectral type: F2 D
V Mag: 9.44

Secondary: BD+36 3014p (B component)
========================================
ICRS coord. (ep=2000) : 18 05 32.9767 +36 18 10.551
Proper motions mas/yr : -12.10 -16.50
Error ellipse : [4.80 1.60 89]
Spectral type : K0 D
V Mag : 10.16

Rho is ~48 seconds of arc

Question:- Is there any old photografic survey going back to 1920s or
older that could be used to check if there is minute chang in sky
position of each star, I wonder? The POSS images I obtained from
aladdin previews must be quite recent, I posted some image files on
he

http://uk.geocities.com/aa_spaceagent/Double-Stars.html

cheers,
Abdul Ahad

Very small proper motions are about the same size as the real errors
on the proper motions. The real errors can be larger than the quoted
errors. They are usually catalogue dependent.

Try not to match any proper motions of less than +/- 10 mas/y.
Because of errors that is like saying 0 mas/y, and saying 0 is like
saying the star is too far away to see any proper motion, so its
proper motion could be anything.

Some catalogues you shouldn't use any proper motion data of less than
+/- 20 mas/y or even less. mas/y is milliarseconds per year, that is
0.001 arcseconds per year.

It is tricky, there are no concrete rules, and things depend which
data you are using, and many small reasons.

There is a yahoo group called binary stars uncensored. You could try
joining it and asking questions there. However, as with all groups,
this does not necessarily mean you will get any answers. You've had
some good advice here, it seems, amongst other stuff, that may be
enough for you.

But it has to be said that people who insist and insist their stars
are doubles no matter what is said about their candidates will likely
get increasingly less feedback. The same with variable stars, the
same with deepsky objects, the same with many things. There have been
a few around who have made many unfounded claims and they have lowered
the tolerance threshold of the communities towards persistent
viewpoints upon undecidable objects. This is a shame as all beginners
have to find their way and learn from experience what is practical and
what is not scientific due to there not being the information with
which to test the ideas expressed.

On 2 June, 15:56, wrote:

Just so you all know = John Greaves

Could this be the John Greaves who has called many of his own
published double star results "totally spurious"? Err, yes it could.
Did he then do anything about correcting them - err, no he didn't.

Could this also be the John Greaves who wrote as recently as 2008:
"I heartily recommend to all list owners, doing so both now and in the
past, that at best I be strongly moderated, and for full safety's sake
****listed (lifetime ban) as this is always the safest with respect to
myself. Filters are good too."

If you publish your results in a newsgroup, in a peer reviewed (or
indeed any) publication or on a web page Greaves will accuse you of
self aggrandisement. If you don't publish your results he will accuse
you of low productivity!

Sometimes, just for variety, he will also claim that :-

Your results are of no interest or value and/or
Your methodology is flawed and/or
You have copied results from somewhere else and/or
Nobody reads (fill in the source) anyway.

Martin Nicholson, Daventry, UK