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Decreasing Errors For Binary Star System Masses



 
 
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  #1  
Old October 24th 14, 07:34 AM posted to sci.astro.research
Robert L. Oldershaw
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Posts: 617
Default Decreasing Errors For Binary Star System Masses

In a recent thread some posters argued that estimated masses for
binary star systems do not get more accurate with time, so my choosing
of 2012 as the start for building a test sample was vigorously
criticized.

I would ask readers to take a few minutes to look at:

http://arxiv.org/abs/1410.6170

by Torres et al (Name ring a bell?)

While the Southwick catalog (now with about 14 new entries repeating
the same pattern]) of double-lined eclipsing binaries aims for =/ 2%
errors in mass estimates, the just posted paper by Torres et al
reports accurate stellar masses with errors of 0.7%. Now that, my
friends, appears to be a very nice improvement over typical older
errors.

And what are these new, highly accurate masses? I'll never tell. You
have to read the paper.

I would argue that stellar mass estimate research is undergoing fairly
rapid progress and the results are most interesting.

RLO
Fractal Cosmology

[Mod. note: reformatted -- mjh]
  #2  
Old October 25th 14, 07:26 AM posted to sci.astro.research
Phillip Helbig---undress to reply
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Posts: 629
Default Decreasing Errors For Binary Star System Masses

In article , "Robert L.
Oldershaw" writes:

In a recent thread some posters argued that estimated masses for
binary star systems do not get more accurate with time,


I just looked at all the posts still on my news server on this and
related topics, about 50 in all. I couldn't find a single one where
someone wrote that masses for binary star systems do not get more
accurate with time. The burden of proof is on you: quote the relevant
section from the post and provide the Message-ID.

so my choosing
of 2012 as the start for building a test sample was vigorously
criticized.


It was vigorously criticized, yes, but not for the reason you claim.
Rather, the reason was that the cut-off date was arbitrary, and you said
yourself that you chose it after it seemed that the data support your
hypothesis, and it was such cherry-picking which was criticized.

If you want anyone to take this date seriously, provide some evidence,
such as error bars as a function of publication date, showing a sharp
improvement in 2012.

I humbly suggest that further posts from you on this and related topics
be rejected by the moderator if you do not provide evidence for your
claim that someone wrote that the masses to not improve with time, and
if you do not provide any objective evidence if favour of the 2012
cutoff date. Since your further analysis is based on this, failure to
come up with the goods here makes further discussion pointless.
  #3  
Old October 25th 14, 07:27 AM posted to sci.astro.research
Craig Markwardt[_2_]
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Posts: 137
Default Decreasing Errors For Binary Star System Masses

On Friday, October 24, 2014 2:34:42 AM UTC-4, Robert L. Oldershaw wrote:
In a recent thread some posters argued that estimated masses for
binary star systems do not get more accurate with time, so my choosing
of 2012 as the start for building a test sample was vigorously
criticized.


Sorry, no, I won't be baited by your strawman argument. What you
actually claimed was that you should be able to *ignore* data from
papers published before 2012, just based on your intuition.
Responders properly discussed the problems with your assertion.
Responders *never* made the claim above.

If we were to follow your intuitive assertion for the Torres et al
paper you cite, and discount data from before the start of 2012, then
there basically wouldn't be any data left. Thus, by your own
arguments, shouldn't we ignore the Torres et al paper

Also, how does a single paper performing intensive observation and
analysis on a single eclipsing binary say anything about the accuracy
of orbit solutions published before 2012? The answer is, it doesn't.
As Figure 1 shows, equivalent precision for the source has been
accessible since 1996 using those observatories. Nothing special
happened in 2012.

CM
  #4  
Old October 25th 14, 07:30 AM posted to sci.astro.research
wlandsman
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Posts: 43
Default Decreasing Errors For Binary Star System Masses

On Friday, October 24, 2014 2:34:42 AM UTC-4, Robert L. Oldershaw wrote:


While the Southwick catalog (now with about 14 new entries repeating
the same pattern]) of double-lined eclipsing binaries aims for =/ 2%
errors in mass estimates, the just posted paper by Torres et al
reports accurate stellar masses with errors of 0.7%.


Sigh. The Southworth catalog includes mass estimates *better* than
2% and in many cases these are *much* better than 2%. For
example, the reported masses for CU Cnc in the Southworth catalog are
0.4333 +/- 0.0017 Msun (0.39%) 0.3980 +/- 0.0014 Msun (0.35%) which is
approximately twice the precision of the recent Torres et al result.

It is a reasonable heuristic to prefer a more recent mass
determination when you are comparing measurements *on the same star*.
It is not reasonable to say that a mass measurement of a 25th
magnitude star is more accurate than the measurement of a 5th
magnitude classical eclipsing binary because the faint star
measurement is "newer". And many of the post-2012 measurement in
the Southworth catalog are of faint globular cluster or Magellanic
Cloud stars.

But I don't understand why you are making any selections at all on the
Southworth catalog (and thus opening yourself to the accusation that
you simply make arbitrary selections on the catalog until you find the
subset that best agrees with your theory). The Southworth catalog is a
theorist's dream -- a large data set where every point has reliable
error bars with no systematics. Why not just use all the data?

Finally, it is hard to imagine how the simple application of Kepler's
law to eclipsing binaries could have systematics, but there is a
simple test for this. There are multiple mass determinations for
many of the classical eclipsing binaries in the literature, so you can
check whether these measurements agree within their error bars. I
have done this for a couple of the binaries and the distribution of
the measurements confirm that the error bars are reliable.
There is zero scientific justification for throwing out the pre-2012
data.


--Wayne

[Mod. note: reformatted, non-ASCII characters removed -- mjh]
  #5  
Old October 26th 14, 08:30 AM posted to sci.astro.research
Robert L. Oldershaw
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Default Decreasing Errors For Binary Star System Masses

On Saturday, October 25, 2014 2:30:40 AM UTC-4, wlandsman wrote:

There is zero scientific justification for throwing out the pre-2012
data.

---------------------------------------

In the 3 recent responses there seems to be an acknowledgement that
the accuracy of stellar mass estimates does tend to improve with time.

So I am at a loss to understand the very vigorous effort to discredit
my choice of a start date (data posted to arXiv.org or published
during or after 2012) for accepting estimated masses in this specific
test.

Given our assumption that the estimates tend to improve with time, it
is a no-brainer that one would want to choose some start date that
rules out the older, less accurate, estimates. Why would anyone who is
after a reliable test want to include the older lower-quality data?

As decades go by and the number of data points increases to much
larger numbers, will the critics still claim that the choice of a 2012
start date remains unacceptable? If so, such an attitude seems
unscientific and based on questionable motivations.

RLO
Fractal Cosmology
  #6  
Old October 26th 14, 12:14 PM posted to sci.astro.research
Phillip Helbig---undress to reply
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Posts: 629
Default Decreasing Errors For Binary Star System Masses

In article , "Robert L.
Oldershaw" writes:

There is zero scientific justification for throwing out the pre-2012
data.

---------------------------------------

In the 3 recent responses there seems to be an acknowledgement that
the accuracy of stellar mass estimates does tend to improve with time.


Again, no-one has ever doubted this.

So I am at a loss to understand the very vigorous effort to discredit
my choice of a start date (data posted to arXiv.org or published
during or after 2012) for accepting estimated masses in this specific
test.


There are two reasons. Because, without further justification, it is
arbitrary. If accuracy increases with time, unless there is a very
dramatic and sudden increase in accuracy in 2012, then there is no
objective reason to choose 2012. Also, you said yourself that you chose
this date because you noticed that it seemed to work better for you.
This cherry-picking is unscientific. Consider: If the date is a free
parameter, then just by chance some date will support some hypothesis
better. Choosing that date BECAUSE it supports your own hypothesis is
wrong. Similarly, choosing one statistical test BECAUSE it supports
your hypothesis is wrong.
  #7  
Old October 27th 14, 08:15 AM posted to sci.astro.research
wlandsman
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Default Decreasing Errors For Binary Star System Masses

On Sunday, October 26, 2014 3:31:07 AM UTC-4, Robert L. Oldershaw wrote:


In the 3 recent responses there seems to be an acknowledgement that
the accuracy of stellar mass estimates does tend to improve with time.


I certainly don't acknowledge this -- or at least I don't acknowledge
that the precision of stellar mass estimates tend to improve with
publication year. But you don't have to believe me -- just look at the
data.

On https://www.dropbox.com/s/4qmg56et3q...worth.png?dl=0 I
have put a plot of the quoted precision of each mass measurement in
the Southworth catalog versus publication year. The data looks like a
scatter plot although for the entire data set there is a weak
correlation (Pearson correlation coefficient -0.28) between precision
and publication year. Most of this correlation comes from the earliest
years -- just looking at the last 17 years there is essentially no
correlation between precision and publication year (correlation
coefficient +0.05)

The reason of course is that new publications tend to report on newly
discovered and fainter eclipsing binaries. There is a very strong
correlation between publication year and faintness of the observed
eclipsing binary. Robert, do you believe that we get more accurate
mass measurements when we look at more distant and fainter binaries?

Of course I have no idea why you are using publication year as a proxy
for measurement precision -- and an extremely bad proxy at that --
when each mass measurement in the catalog is given with a quoted
precision.

--Wayne
  #8  
Old October 27th 14, 08:21 AM posted to sci.astro.research
Robert L. Oldershaw
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Posts: 617
Default Decreasing Errors For Binary Star System Masses

On Sunday, October 26, 2014 7:15:13 AM UTC-4, Phillip Helbig---undress to reply wrote:

Again, no-one has ever doubted this.

---------------------------------------------------

If there is to be a scientific discussion of the issues raised by this
thread, then I think it would be best to dispense with the straw man
arguments and the faulty theories of mind.

The Southworth catalog is an growing sample, and I made this clear in
the first post that ever mentioned the catalog (months ago).

I also said that at some point in the new millennium I noticed a
marked and general improvement in stellar mass estimates. This is
reflected in the decreased error values and the decrease in
conflicting mass estimates by different research groups.

The choice of a start date of 2012 can be characterized as arbitrary,
but most scientific tests based on observational data involves a
choice of the data to be used in the test.

The key question is whether or not the sample I chose is biased. If I
had specifically chosen only data from 2012 and 2013, then the case
for bias could be strong. However, since my explicitly chosen sample
is an open-ended and growing sample, the choice of a 2012 start date
is a trivial issue that becomes evermore trivial with time and sample
growth. [note: this argument has already been made several times, but
appears to be ignored for some reason].

I do not see the usefulness of harping on trivial issues, while
ignoring more substantial issues.

[Mod. note: reformatted. I would characterize this whole thread as
'harping on trivial issues' given that either the whole dataset or the
subset you arbitrarily chose rule out your preferred model at
extremely high confidence levels. I am tempted to close it here unless
there is anything more interesting to add. -- mjh]

RLO
It's A Fractal World
  #9  
Old October 28th 14, 09:51 AM posted to sci.astro.research
Phillip Helbig---undress to reply
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Posts: 629
Default Decreasing Errors For Binary Star System Masses

In article , "Robert L.
Oldershaw" writes:

On Sunday, October 26, 2014 7:15:13 AM UTC-4, Phillip Helbig---undress to reply wrote:

Again, no-one has ever doubted this.

---------------------------------------------------

If there is to be a scientific discussion of the issues raised by this
thread, then I think it would be best to dispense with the straw man
arguments and the faulty theories of mind.


You started the straw-man argument by claiming that others here had
claimed that accuracy (for a given magnitude) does not improve with time.

I also said that at some point in the new millennium I noticed a
marked and general improvement in stellar mass estimates.


"I noticed" is not good enough. You have to plot the error bars against
time. Someone else did this and falsified your claim.

The choice of a start date of 2012 can be characterized as arbitrary,
but most scientific tests based on observational data involves a
choice of the data to be used in the test.


Yes, but not an arbitrary choice.
  #10  
Old October 28th 14, 09:53 AM posted to sci.astro.research
Robert L. Oldershaw
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Posts: 617
Default Decreasing Errors For Binary Star System Masses

On Monday, October 27, 2014 3:15:40 AM UTC-4, wlandsman wrote:

I certainly don't acknowledge this -- or at least I don't acknowledge
that the precision of stellar mass estimates tend to improve with
publication year. But you don't have to believe me -- just look at the
data.


It is interesting and informative to apply your reasoning to the
entire history of the research effort to determine the value of the
Hubble constant.

Precision is all well and good, but it is profoundly trumped by
accuracy. Lately we have seen bold claims of 7-sigma detections go up
in flames, or get buried by dust. Clearly statistics are a
double-edged sword.

[Mod. note: reformatted -- mjh]
 




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