<p>The reason the KEBC doesn't have semi-major axes is because it's based entirely on photometric data with no EB modeling done.  Determining the SMA requires spectroscopic data and EB modeling.  Furthermore, <em>Kepler</em> mostly looked at solar-type stars, so there are few (if any) massive binaries in the KEBC.  Unfortunately, I'm not aware of any catalogs of the type you're looking for.  I'd recommend using Google Scholar (or better still, NASA ADS) instead of plain Google to search for such a catalog.</p>

CC BY-SA 4.0
2021-12-08T19:27:33.163Z
2021-12-08T19:27:33.163Z
mknote
<p>Kepler eclipsing binaries are unresolved - the telescope cannot provide images that separate the components. You only have the orbital period and some information about the eccentricity and the relative radii of the two stars.</p>
<p>To get the semi-major axis from the orbital period using Kepler's Third Law requires you to know the mass of the binary components. This is not available with any precision until you have spectroscopy that allows you to measure the velocities of the components.</p>
<p>Alternatively, you could estimate the masses of the stars from some estimate of their spectral type/colour and then use Kepler's Third Law, but this can be tricky when the spectral type is the combined spectrum or colour of two stars.</p>

CC BY-SA 4.0
2021-12-08T19:59:02.317Z
2021-12-08T19:59:02.317Z
ProfRob
<p>I have been searching for a massive binary (&gt;7 M<span class="math-container">$_{\odot}$</span>) catalog <strong>with semimajor axes given</strong>, but I wasn't able to find any, and I began to search for a binary star catalog and decided to filter it later.</p>
<p>A bit of a googling leads to the <a href="https://archive.stsci.edu/kepler/eclipsing_binaries.html" rel="nofollow noreferrer">Kepler Eclipsing Binary Catalog</a>, though useful, it doesn't have semimajor axes in it.</p>
<p>Please share links to how to calculate semimajor axes from the orbital period. Also, it would be much better if a catalog <strong>with</strong> binary separation data in it could be shared.</p>
<p>Thank you!</p>

<binary-star><star-catalogues><eclipsing-star-systems>
Semimajor axes data from Kepler Eclipsing Binary Catalog
AstroTeen
# Semimajor axes data from Kepler Eclipsing Binary Catalog

(Asked by: username_0 on 2021-08-12)

I have been searching for a massive binary (>7 M$\_{\odot}$) catalog **with semimajor axes given**, but I wasn't able to find any, and I began to search for a binary star catalog and decided to filter it later.

A bit of a googling leads to the [Kepler Eclipsing Binary Catalog](https://archive.stsci.edu/kepler/eclipsing_binaries.html), though useful, it doesn't have semimajor axes in it.

Please share links to how to calculate semimajor axes from the orbital period. Also, it would be much better if a catalog **with** binary separation data in it could be shared.

Thank you!

**Tags:** binary-star, star-catalogues, eclipsing-star-systems


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## 2 answers

### Answer by username_1 on 2021-12-08. Score: 1

The reason the KEBC doesn't have semi-major axes is because it's based entirely on photometric data with no EB modeling done. Determining the SMA requires spectroscopic data and EB modeling. Furthermore, *Kepler* mostly looked at solar-type stars, so there are few (if any) massive binaries in the KEBC. Unfortunately, I'm not aware of any catalogs of the type you're looking for. I'd recommend using Google Scholar (or better still, NASA ADS) instead of plain Google to search for such a catalog.


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### Answer by username_2 on 2021-12-08. Score: 0

Kepler eclipsing binaries are unresolved - the telescope cannot provide images that separate the components. You only have the orbital period and some information about the eccentricity and the relative radii of the two stars.

To get the semi-major axis from the orbital period using Kepler's Third Law requires you to know the mass of the binary components. This is not available with any precision until you have spectroscopy that allows you to measure the velocities of the components.

Alternatively, you could estimate the masses of the stars from some estimate of their spectral type/colour and then use Kepler's Third Law, but this can be tricky when the spectral type is the combined spectrum or colour of two stars.


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