Spectral Classification Syntax for Binaries

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Discussion Overview

The discussion revolves around the spectral classification syntax for binary stars, specifically focusing on the classification of α Cnc (Alpha Cancri) and the interpretation of its spectral type notation "kA7VmF0/2III/IVSr". Participants explore the meaning of the "/" symbol in this context and seek clarification on the classification system used.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions the meaning of the "/" in the spectral classification, suggesting it may denote alternative subclasses or luminosities.
  • Another participant agrees that the "/" separates spectral classes but finds the notation strange, noting the lack of a separator between "A" and "F" classifications.
  • A later reply proposes that the notation could imply one of several combinations of spectral classes and luminosities, but expresses uncertainty about the meaning of combining "A" and "F" without a separator.
  • One participant suggests looking up the reference for clarification, while another provides a specific citation to a paper that may help elucidate the classification.
  • A participant who is not an astronomer seeks a clearer explanation of the classification, offering their interpretation of the components of the spectral type.
  • Responses indicate that some participants believe reading the referenced paper is necessary for a better understanding of the classification system.

Areas of Agreement / Disagreement

Participants generally agree that the "/" serves to separate components of the spectral classification, but there is no consensus on its precise meaning or implications. Multiple interpretations and uncertainties remain regarding the notation.

Contextual Notes

Limitations include the potential for missing assumptions about the classification system and the dependence on specific definitions that may not be universally understood. The discussion does not resolve the meaning of the spectral classification syntax.

Solkar
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for α Cnc one gets from

http://simbad.u-strasbg.fr/simbad/sim-id?Ident=alpha+cancri

a spectral type of
kA7VmF0/2III/IVSr

I don't get behind this special use of "/" - Syntax - what's that that meant to denote?

kA7Vm+F02III xor kA7Vm+F02IVSr?
Anything else?
 
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I think the / is intended to separate the spectral class of the components but this one looks strange. If you look up the star here http://vizier.u-strasbg.fr/viz-bin/VizieR?-source=B/mk you will see a range of classifications.
You can follow the links to the papers the last reference has it as Am (A5/A9/F0) in the body of the paper.
I tried to follow the link to your clasification but you had to pay for access.
Regards Andrew
 
andrew s 1905 said:
I think the / is intended to separate the spectral class of the components but this one looks strange.

Yes, of course. It's generally used both for separating alternative subclasses and luminosities - "alternative" here as opposed to "between" (that would be "-").

Here however it's unclear, especially because the "A" and" "F" classification are given en suite without such any seperator.

But talking about it - maybe the tail means

one of (F0III, F2III, F0IVSr, F2IVSr)

?

What however combining "A" and "F" without a separator shall denote ... well...

 
I think your only option is to look up the reference if you want to clarify the meaning.
Regards Andrew
 
andrew s 1905 said:
I think your only option is to look up the reference if you want to clarify the meaning.

Yep, So more precisely, I think the only option for me is to an accessible version of the doc ...

And indeed! There indeed is one:

[RA91] Rao, S. S. & Abhyankar, K. MK morphological study of Am stars at 66 Å/mm. Journal of Astrophysics and Astronomy, Springer, 1991, 12, 133-178. doi:10.1.1.489.5030 http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.489.5030&rep=rep1&type=pdf

So by [RA91] Table. 3, Simbad's encoding

"kA7VmF0/2III/IVSr" means:

K line: A7 V
m (i.e m 39) line: F0 III
m (i.e. m 43) line: F2 III/IV

and Sr line present.

So the "/" operator binds and only binds to the rightmost class ("F") or subclass ("0", "2") token to its left.

And it's nothing about "Binaries".
 
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kA7VmF0/2III/IV Sr

I am not an astronomer. Would like a better answer.

k Spectra with interstellar absorption features
A7 Main sequence star spectral class A7
V luminosity class five

m Enhanced metal feature
F0/2 spectral classes F0 and F2
III/IV luminosity class III/IV
Sr Strontium

This could mean the strontium emission line has a signal strength equivalent to a star with luminosity class III/IV. Emission line spectra contain more than one peak so you could measure more than one spectral class. Would look purple than an A7 should look.
 
stefan r said:
Would like a better answer.

Then I would propose you read the paper Solkar gave the link to.

Regards Andrew
 
andrew s 1905 said:
Then I would propose you read the paper Solkar gave the link to.

Regards Andrew
I did that before commenting.
 

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