Some MILES stars missing in ISIS ?

[Christian Buil]

Robin,

The interstellar extinction corrected spectra (the original MILES data) are downloaded here : http://www.iac.es/proyecto/miles/pages/ ... ibrary.php (FITS file).

The actual MILES version for ISIS is the apparent spectral profile (reddened). For the conversion, I use an automatic (internal) version of Misc -> Extinction tool of ISIS.

Christian

[Robin Leadbeater]

Thanks Christian,

@Woody, Ibrahima

I do not think just adding the MILES spectra directly as you suggest will work correctly as the spectra from the MILES website are not as observed, but Interstellar extinction corrected by default. You could perhaps take the non dereddened version from Paolo Berardi's Exel spreadsheet but now Christian has updated his database that would be the easiest way to go.

Robin

[Robin Leadbeater]

Hi Christian,

I am seeing large differences between the old and new ISIS databases. Here is MILES HD223385 for example. Is the reddening working correctly ?

Cheers
Robin

m_hd223385_isisdb2014.png (20.69 KiB) Viewed 7453 times

[Ibrahima]

Hi Robin.
Thanks for your comment. You are right, personnally I prefer using ISIS (and its included database) cause it is simpler for me.
Also thanks to Christian for the great job.

Best regards,
Ibrahima.

[Robin Leadbeater]

It looks like the spectra uncorrected for IS extinction used in PB's spreadsheet and the original ISIS database may be the problem. If we start with this spectrum for HD223385 and correct for IS extinction (using either PB's spreadsheet or ISIS) we get a much hotter star than type A3i. The IS extinction corrected spectrum in MILES is a good fit to the Pickles spectrum of the same type. I have not checked any other spectra to see if this is just a problem with this star or a more general problem

Robin

HD223385__MILES_IS_extn_corrected.png (15.5 KiB) Viewed 7443 times

[Paolo Berardi]

Hi all,

Christian, thanks a lot for the new database!

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.



Thanks to all for this useful topic.

Paolo

[Paolo Berardi]

Hi Robin, by a check on the highest E(B-V) values (> 0.5, 17 stars), only HD223385 shows such a great discrepancy:

http://quasar.teoth.it/html/spectra/hd223385.png

But there are anyway some differences between old and new ISIS db Miles profiles:

http://quasar.teoth.it/html/spectra/hd208501.png
http://quasar.teoth.it/html/spectra/hd198478.png
http://quasar.teoth.it/html/spectra/hd190603.png
http://quasar.teoth.it/html/spectra/hd185859.png
http://quasar.teoth.it/html/spectra/hd020041.png
http://quasar.teoth.it/html/spectra/hd017378.png

Paolo

[Christian Buil]

But ... it is not recommended at all to use hightly reddened stars to calculate spectral responses. Stars with large E (b-v) must absolutely be rejected for this task (the reddening model can change little from one author to another). Remember, calculating the instrumental response is the first function of the MILES database for me. Choses stars with E(b-v) value near zero.

Christian

[Forrest Sims]

Hi All,

What a great discussion. Thank you Robin, Ibrahima and Paolo for your ideas.

Hi Christian,

Many thanks for the new version of the database with many more Miles stars! This should make it easier in some locations in the sky to find a good reference star. And a good reminder to choose reference stars with E(b-v) near zero. François Teyssier stressed the importance of this to me at the beginning and now I have a better understanding of why this is so.

Is it correct to conclude that the Miles stars you have added in this latest version of the database are dimmer than Mag 7? if this is true can we just compensate with longer exposures to allow ISIS to calculate the instrumental response?

All the best,
Woody

[etienne bertrand]

Bonjour,

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