Some MILES stars missing in ISIS ?

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Re: Some MILES stars missing in ISIS ?

Postby Robin Leadbeater » Mon May 06, 2019 1:07 pm

Hi All,

I agree that it is important to use low IS extinction stars where we do not have an actual measured spectrum for the star but the MILES stars were actually measured and we know how they were corrected so we should be able to reproduce the original spectra even with high IS extinction. We know the E(B-V) used for each star from MILES library and we know from the original paper
https://ui.adsabs.harvard.edu/abs/2006M ... S/abstract
that the technique used to correct for IS extinction was that described here
https://ui.adsabs.harvard.edu/abs/1999P ... F/abstract

Christian, did you use the same technique? If so the spectra in ISIS should now be as observed even at high IS extinction

I have also contacted the MILES team to see if the original uncorrected spectra are available

Cheers
Robin
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Re: Some MILES stars missing in ISIS ?

Postby Robin Leadbeater » Mon May 06, 2019 1:59 pm

Hi Paolo,

Paolo Berardi wrote:Hi all,

Robin, perhaps another library spectrum should be checked: HD044691 (RR Lyn, V mag 5.54) is an eclipsing binary system (period ~10d). Primary and secondary components have different Teff (about 8000K and 7200K, reference doc) and continuum could vary over time.

The A3m profile in the Miles db (the star has type kA3hA7VmF2 in Simbad) resemble that of an F6 class star. Below the comparison with Miles HD058551 (F6V in both Miles and Simbad). The Pickles F6V continuum is very similar too.




Yes that does look like another which should be avoided. I found this reference via Skiff's database where a change from A4 to A7 from phase 0.23 to 0.82 was seen
https://ui.adsabs.harvard.edu/abs/1975M ... H/abstract
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Re: Some MILES stars missing in ISIS ?

Postby Robin Leadbeater » Mon May 06, 2019 4:52 pm

Hello Etienne,

etienne bertrand wrote:Pouvez vous m'expliquer, ces nouvelles étoiles servent à quoi exactement ? Est pour les spectros eshel et Lhires qu'on les utilise ? Les spectres sont en haute résolution il me semble. Pour l'Alpy j'utilise toujours la base : Pickles
Merci


You can use Pickles spectra with the ALPY but you need to be sure that the star has the expected spectrum for the published spectral class. This is sometimes not exactly right. (For example the published class can be wrong (check in the Skiff catalogue), the star might have high extinction (check E(B-V) ), The shape of the continuum depends a bit on the metallicity (see viewtopic.php?f=6&t=207&start=20#p1703 )

It is better if possible to use a reference star with a known measured spectrum. The MILES spectra are actual measured spectra of the particular star. Unfortunately the published version of the MILES spectra have been corrected for extinction which we need to remove before we use them.

Cheers
Robin
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Re: Some MILES stars missing in ISIS ?

Postby Robin Leadbeater » Mon May 06, 2019 5:03 pm

Hi All,

I think there is a danger that we have been here before and we are going round in circles.
viewtopic.php?f=6&t=207&start=10#p683
Reddening the MILES spectra using their published E(B-V) did not seem to work so we used the MILES as observed spectra that Francois found. We are now back to reddening the MILES spectra again

Robin
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Re: Some MILES stars missing in ISIS ?

Postby Robin Leadbeater » Mon May 06, 2019 9:51 pm

OK, I have contacted the MILES team and they will send me a copy of the as observed MILES spectra next week. Hopefully we can then use these and forget about IS extinction corrections

Cheers
Robin
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Re: Some MILES stars missing in ISIS ?

Postby Robin Leadbeater » Thu May 16, 2019 11:13 am

I have now received the original MILES spectra without IS extinction correction direct from Patricia Sanchez-Blazquez. She is the lead author on the original paper on the MILES library

http://adsabs.harvard.edu/abs/2006MNRAS.371..703S

They appear to be identical to those found by Francois Teyssier and used in Paolo Berardi's spreadsheet and the earlier ISIS database.

I will ask her about the dereddening anomaly we are seeing but for the moment I would recommend continuing to use these spectra and not the reddened MILES v9.1 spectra in the latest ISIS v8 database.

As an extra check I will also try measuring some of the high extinction MILES stars using low extinction stars as a reference. Would anyone else like to try this too?

Cheers
Robin
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Re: Some MILES stars missing in ISIS ?

Postby Christian Buil » Fri May 17, 2019 4:10 am

The ISIS database has been updated with the exact MILES algorithm to process the extinction. You can use it if you want

Christian
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Re: Some MILES stars missing in ISIS ?

Postby Robin Leadbeater » Fri May 17, 2019 1:09 pm

Hello Christian,

There is still a problem. The reddened MILES spectra in ISIS still do not agree with the uncorrected spectra from Patricia Sanchez-Blazquez. You can download them from my dropbox here
https://www.dropbox.com/s/9gqi2e16iphwu ... ar.gz?dl=0

HD223385 is an extreme example but there are differences with other stars too.

m_hd223385.png
m_hd223385.png (17.3 KiB) Viewed 565 times


Patricia Sanchez-Blazquez has agreed to help resolve this. Can you detail exactly how you made the reddening correction please ?

Also can anyone take a spectrum of HD223385 using a low IS extinction star as a reference please? (it is blocked by a tree for me now) It should be obvious from this which spectrum is correct.

Thanks
Robin
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Re: Some MILES stars missing in ISIS ?

Postby Robin Leadbeater » Sat May 18, 2019 1:20 pm

I have checked two of the stars (HD20041 and HD208501) which were identified by Paolo as showing a small difference between the MILES spectra as observed and the reddened spectra from the first version of the ISIS database V8.
viewtopic.php?f=8&t=2293&start=10#p12531
They are now in agreement in the current version of ISIS database V8 (It has the same version number on the website but I am calling it V8a for my records)

The star HD223385 is still significantly different though. I will raise the problem with this star with Patricia Sanchez-Blazquez

Cheers
Robin
LHIRES III #29 ATIK314 ALPY 600/200 ATIK428 Star Analyser 100/200 C11 EQ6
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