Alfirk - beta Cep

Ask your questions, show your results
Post Reply
Marco Leonardi
Posts: 30
Joined: Thu Sep 29, 2011 6:48 am
Location: Milan - Italy

Alfirk - beta Cep

Post by Marco Leonardi »

Hi All,

I am looking on some biblio information about beta Cep. In particulary I would like to understand better the peak at 6677,.. Angstroms. What is ? I have seen that this peak is in some spectra on Bess Data base. I have also made a spectra and found the same peak (see image below). Sorry for the silly question but I searched in internet and I did not find information about that peak but I learned that this star is a variable probably a system of three stars.

Thanks ,
marco
Attachments
betacep_20111126ci.jpg
betacep_20111126ci.jpg (69.67 KiB) Viewed 4755 times
Olivier Thizy
Posts: 370
Joined: Sat Sep 24, 2011 10:52 am
Location: in the french Alps...
Contact:

Re: Alfirk - beta Cep

Post by Olivier Thizy »

Marco,


This is probably He I at 6678.

What is the resolving power of your spectrograph? You should try to monitor beta Cep during a complete night and see if you can spot the Radial Velocity changes of Halpha and He I lines due to the pulsations of the star...


Cordialement,
Olivier Thizy
Vous ne verrez plus des étoiles comme avant !
http://www.shelyak.com/en/
Marco Leonardi
Posts: 30
Joined: Thu Sep 29, 2011 6:48 am
Location: Milan - Italy

Re: Alfirk - beta Cep

Post by Marco Leonardi »

Olivier,
thanks for your prompt answer ! The resolving power of my spectrograph is 3000 at neon abs. line 6532.88 Angstroms.

In BeSS data base I have seen some of your spectras made the same night at different hour and minute. Please could you suggest me an interval time between the different spectra: for example one each hour or one each 30' ...

Why this star is in BeSS database ? I think is not a Be star with emission at H alpha....does not it ? Or the definition of Be star is wider than what I think ?

Thanks,
Marco
Thierry Garrel
Posts: 193
Joined: Mon Sep 26, 2011 2:52 pm
Location: Montpellier
Contact:

Re: Alfirk - beta Cep

Post by Thierry Garrel »

Hello Marco,
never too late for answer.
H alpha was seen in emisison before 2004 http://arasbeam.free.fr/spip.php?page=b ... 0&from=100

To be a Be star, the star of O B A spectral type, needs to be a subgiant or dwarf star, meaning luminosity class V-III, that show emission line in the Balmer lines. Even if it was once. So it is ! :-)
That for classical Be. Among nonclassical Be stars there are supergiant Be stars, peculiar Be stars, and Herbig Be/Ae stars.
Note that Bess concern also Herbig Be/Ae that are proto early spectral type stars.
Be peculiar stars, B[e], are different from classical Be due to their IR excess and the appearance of forbidden lines. It is a heterogeneous group, concerning proto planetary nebula, symbiotic B[e] stars, supergiants stars, pre main sequence stars and a lot are still unclassified. Look at the attempt to form a new group calling FS cma in this forum in campaign section. A very exiting subject.
Supergiant Be are from three type: Luminous blue variable stars (eta car, P cyg...), supergiant B[e] (MWC 349, MWC 314...) and Hubble-Sandage stars (AF And...).

So considering your resolution, R3000 and so the the ability to go deep in magnitude, it is interesting to observe weak classical Be stars, Herbig Be/Ae stars and FS cma group instead of bright Be well covered by high resolution spectroscopy.
Post Reply