Variable star spectral classification

[jdavies]

Hi all,
I have another beginner question. As I examine the data from Hipparcos, I notice that the start HIP 8 has a spectral classification of M6e-M8.5e Tc. I'm not sure how to interpret this data. Here are my questions:

1) Does the M6e-M8.5e mean that the apparent temperature of the star seems to vary between 6 and 8.5?
2) What does the "e" indicate on the M6e-M8e?
3) What does the "Tc" indicate at the end of the spectral class?

Many thanks in advance!

- Jeff

[MKruer]

Hi all,
I have another beginner question. As I examine the data from Hipparcos, I notice that the start HIP 8 has a spectral classification of M6e-M8.5e Tc. I'm not sure how to interpret this data. Here are my questions:

1) Does the M6e-M8.5e mean that the apparent temperature of the star seems to vary between 6 and 8.5?

Correct

2) What does the "e" indicate on the M6e-M8e?

Emission lines present

3) What does the "Tc" indicate at the end of the spectral class?

Tc just refers to a star whose spectrum reveals the presence of the element technetium

Many thanks in advance!

- Jeff

Read http://en.wikipedia.org/wiki/Stellar_classification it has most of the information. Sadly though it does not have any info on Tc.

Edit: Added the element to wikipedia

Edit2: BTW Tc stars by definition have to be fairly young stars because the technetium only has a half life of 211,100 years, so over the lifetime of the star it will loose its Tc status.

[ajtribick]

Edit2: BTW Tc stars by definition have to be fairly young stars because the technetium only has a half life of 211,100 years, so over the lifetime of the star it will loose its Tc status.

That would only be the case if the star isn't synthesising technetium, and given that stars have fusion reactions going on inside them, this is not a safe assumption! In fact, judging by a quick Google search, technetium stars are old, evolved stars.

[jdavies]

Many thanks for the info!

- Jeff

[jdavies]

I have a few followup questions, now that I am knee-deep in understanding these classifications. These questions may seem overly detailed, but I'm writing a program that parses this data and computers are always overly detailed.

Once again, examining the Hipparcos data, I see that HIP 60169 is classified as:
G2/G3Iab/Ib
Does the slashes mean the same thing as the dashes? Could this also have been written as G2-G3Iab-Ib? Or is there a different meaning for the slashes?

Also, I assume that the slash (or a dash) for the luminosity applies to both spectral types (i.e. it could also be written as G2Iab-G3Ib). Is that correct?

Examining HIP 18260 I see the classification
F5-G1ib + A:
Does the whitespace make any difference? For example, is F5-G1ib + A: equal to F5-G1ib+A:? And the "+" sign applies to the luminosity I assume. I cannot see what the letter A signifies though. It's not listed (that I can see) on the wiki page http://en.wikipedia.org/wiki/Stellar_classification

Another interesting one if HIP 69929 with the classification:
Ap Si(Cr)
This appears to be an A star with peculiarites. I know the Si indicates that Silicon is present, but what do the parenthesis around the Chromium mean? Strong or weak or somethign else?

Next is HIP 83320:
sdF:
The F: I can understand, but the sd prefix is new to me. What does that indicate?
I see now that the "sd" prefix indicates the star is a sub dwarf. My research shows that the "d" prefix is also used to indicate a dwarf version of the star, so I think I have an answer for this one.

And finally HIP 92316 and HIP 102190, respectively
sdB(Nova) and pec(Nova)
I suspect the sd prefix is related to my question above. Does it indicate a class B star that went nova? Is pec simply a lowercase version of PEC, to indicate an (unstated) peculiarity?

Thanks in advance for your help

- Jeff

[Hungry4info]

I have a few followup questions, now that I am knee-deep in understanding these classifications.

By the end of this thread, I hope you're drowning

G2/G3Iab/Ib
Does the slashes mean the same thing as the dashes? Could this also have been written as G2-G3Iab-Ib? Or is there a different meaning for the slashes?

The hyphens and slashes sort-of mean the same. G2/G3 means G2 or G3, which I suppose could also mean G2-G3.

Also, I assume that the slash (or a dash) for the luminosity applies to both spectral types (i.e. it could also be written as G2Iab-G3Ib). Is that correct?

Correct. If the luminosity is different, then it will be specified as
something like G2IV/G2III , for example.

]Examining HIP 18260 I see the classification F5-G1ib + A:Does the whitespace make any difference? For example, is F5-G1ib + A: equal to F5-G1ib+A:? And the "+" sign applies to the luminosity I assume. I cannot see what the letter A signifies though. It's not listed (that I can see) on the wiki page http://en.wikipedia.org/wiki/Stellar_classification

I'm really not sure, I've never seen it before. It might imply a blend of two stars. SIMBAD just says that HIP 18260 is of type F8.

Another interesting one if HIP 69929 with the classification:
Ap Si(Cr)
This appears to be an A star with peculiarites. I know the Si indicates that Silicon is present, but what do the parenthesis around the Chromium mean? Strong or weak or somethign else?

I don't know that one either. I've never seen it before.

Next is HIP 83320:
sdF:
The F: I can understand, but the sd prefix is new to me. What does that indicate?
I see now that the "sd" prefix indicates the star is a sub dwarf. My research shows that the "d" prefix is also used to indicate a dwarf version of the star, so I think I have an answer for this one.

sd -> Subdwarf. Roman numeral VI. Just like V is dwarf, IV is subgiant, etc. Subdwarf stars seem to be in two categories. sdB and O stars, if I recall correctly, are on their way to the white dwarf phase, whereas cooler subdwarf stars are just dimmer. This has caused some to call upon B and O subdwarfs to have the spectral sdB or sdO, and M, K, G stars to just be, M5VI (for example).

And finally HIP 92316 and HIP 102190, respectively
sdB(Nova) and pec(Nova)
I suspect the sd prefix is related to my question above. Does it indicate a class B star that went nova? Is pec simply a lowercase version of PEC, to indicate an (unstated) peculiarity?

Yep, it's peculiarity.

[ajtribick]

Once again, examining the Hipparcos data, I see that HIP 60169 is classified as:
G2/G3Iab/Ib
Does the slashes mean the same thing as the dashes? Could this also have been written as G2-G3Iab-Ib? Or is there a different meaning for the slashes?

Also, I assume that the slash (or a dash) for the luminosity applies to both spectral types (i.e. it could also be written as G2Iab-G3Ib). Is that correct?

Slash means either/or, dash means between. E.g. G2/G3Iab/Ib is either G2 or G3, and either Iab or Ib.
G2-G3Iab-Ib would mean intermediate between G2 and G3, and intermediate between Iab and Ib.
Whereas G2Iab-G3Ib would presumably mean intermediate between G2Iab and G3Ib. I'm not sure this is necessarily the same thing.

Examining HIP 18260 I see the classification
F5-G1ib + A:
Does the whitespace make any difference? For example, is F5-G1ib + A: equal to F5-G1ib+A:? And the "+" sign applies to the luminosity I assume. I cannot see what the letter A signifies though. It's not listed (that I can see) on the wiki page http://en.wikipedia.org/wiki/Stellar_classification

Examining the literature on HIP 18260 (=RW Camelopardalis), it seems that this system consists of a Cepheid variable (F5-G1Ib) with a bluish companion star, so the F5-G1Ib + A: gives the spectrum of both stars. (The assignment of the A spectral type is uncertain)

[jdavies]

Thank you guys. With that information I believe I can construct the proper data-model to contain this information and make it searchable also.

- Jeff

[jdavies]

After writing code for more than 20 years, I really should know better than to say out loud that I think I have enough information

However, I am definitely getting closer to being done (there I go again). Have a parser that will parse and then reconstruct a wide varietly of spectral classifications precisely. However, there is a new notation that I don't understand:
S5,7:
Which is of course for an S type star and I understand the : peculiarity code. I'm puzzled by the 5,7 notation though. I'm used to seeing 5/7 or 5-7 but not 5,7. The research I've been able to do shows this S type star as pulsing (see http://webviz.u-strasbg.fr/viz-bin/VizieR-S?HIP%20110478 ). Does the comma merely indicate a pulsation (which I suppose is subtly different from the 5/7 notation)?

Thanks in advance (again) for your help!

- Jeff