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<div class="moz-cite-prefix">Le 24/05/2022 à 21:23, Tom Donaldson a
écrit :<br>
</div>
<blockquote type="cite"
cite="mid:05157E84-04A9-4558-B2A8-530B3349D429@stsci.edu">
<pre class="moz-quote-pre" wrap=""> Hello VOUnits enthusiasts,
I was doing some validation on the units in our TESS Input Catalog (TIC) SCS and TAP results and came across one I didn’t see how to fix. We have apparently been using unit=”Sun” on two different types of columns, one meaning solar metallicity and one meaning solar density. Although "Sun" is mentioned in the VOUnits standard, I couldn't understand what was meant, and "Sun" is not on the list of known units (Table 2).
It's a little tempting to extrapolate from the known units "solLum", "solMass" and "solRad" and come up with something like "solDen" or even "solFEH", but those are obviously not on the known list either.
Does anyone have thoughts on whether there are official ways to represent these units, or if not, unofficial but preferable alternatives?
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</blockquote>
<p>Hi Tom,</p>
<p><font face="monospace"><b>Sun</b></font> is a valid vounit
symbol. It is described in the current Recommendation, and this<br>
should not change in version 1.1 currently in preparation. The
problem comes from the<br>
validator that ignored Sun, but this should get fixed, see :<br>
<a class="moz-txt-link-freetext" href="https://heptapod.host/nxg/unity/-/issues/11">https://heptapod.host/nxg/unity/-/issues/11</a></p>
<p>The description of "Sun" says : relative to the Sun, e.g.
abundances.<br>
In most cases, it is indeed used for abundances, often with
log(Sun) is the quantity is the<br>
metallicity relative to the Sun expressed in log scale.<br>
But your usage looks perfectly legit for density too, we have some
columns in VizieR<br>
where Sun is used as unit for "Stellar density in solar units".<br>
</p>
<p>One could argue that this is not a real unit, but a mere
description of how some dimensionless<br>
number was obtained. True, but it's a simple way to carry
information, and does no harm.<br>
</p>
<p>So in short : don't change your table metadata, the validators
should allow "Sun" (soon).<br>
And please don't invent "solDen" or "solFEH" :)</p>
<p>Sébastien<br>
</p>
<pre class="moz-signature" cols="72">--
((( Sebastien Derriere <a class="moz-txt-link-abbreviated" href="mailto:sebastien.derriere@astro.unistra.fr">sebastien.derriere@astro.unistra.fr</a>
(. .) Observatoire de Strasbourg Phone +33 (0) 368 852 444
(( v )) 11, rue de l'universite Telefax +33 (0) 368 852 432
---m-m--- F-67000 Strasbourg France
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