rho Cas

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etienne bertrand
Posts: 1040
Joined: Mon Aug 31, 2015 11:26 am

rho Cas

Post by etienne bertrand »

Bonjour,

Voici le spectre de l'étoile rho Cas avec le LhiresIII autour de la raie Ha.
Le fait qu'elle soit une hypergéante jaune de type spectral G2 fait qu'elle perd de la matière par éjection.
J'ai l'impression que la raie Ha est en émission du coté bleu, et cette raie me fait penser à une phase que l'on observe dans le spectre de RR Lyr (phase de pulsation). Qu'en pensez vous ? Je ne penses pas que ce soit les mêmes conditions physiques que pour l'étoile RR Lyr mais la forme de la raie y ressemble.
Cette étoile a-t-elle besoin d'un suivit spectro régulier ?
Image
Merci
Andrew Smith
Posts: 321
Joined: Fri Sep 30, 2011 12:23 pm

Re: rho Cas

Post by Andrew Smith »

Etienne, I have started to track Rho Cas and I get a similar result but with some differences. My spectra is at R ~ 10000 taken with 4 x 600s using an ODK 16 amd my MRes spectrograph.

I intend to track Rho Cas on a regular basis going forward.

Regards Andrew
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Rho Cas near Ha
Rho Cas near Ha
RhoCas_20171105_Ha.png (29.9 KiB) Viewed 7000 times
etienne bertrand
Posts: 1040
Joined: Mon Aug 31, 2015 11:26 am

Re: rho Cas

Post by etienne bertrand »

Hello Andrew,
Good results, it's interested to observe variations in he spectre. Enjoy.
Andrew Smith
Posts: 321
Joined: Fri Sep 30, 2011 12:23 pm

Re: rho Cas

Post by Andrew Smith »

Hi Etienne,

If you are still interested in Rho Cal googling " the spectrial variability of the cool hypergiant 1997" will bring up a link to adsabs.harvard.edu repositry for a paper by A. Lobel et al which covers H alpha in this fascinating star.

Regards Andrew
Rho Cas H alpha.png
Rho Cas H alpha.png (43.07 KiB) Viewed 6954 times
etienne bertrand
Posts: 1040
Joined: Mon Aug 31, 2015 11:26 am

Re: rho Cas

Post by etienne bertrand »

Hi Andrew,
Me too i'm interested to make survey on this star in Ha :) .
etienne bertrand
Posts: 1040
Joined: Mon Aug 31, 2015 11:26 am

Re: rho Cas

Post by etienne bertrand »

Le spectre d'hier soir, la raie en émission est plus prononcée que sur mon spectre du 22/06/2017
Image

La raie qui est en émission (entourée en rouge) est décalée vers le bleu, cela veut dire qu'il y a de la matière qui est éjectée vers nous ?
Que peut on savoir d'autre avec le spectre ? Peut on calculer les vitesses radiales, d'éjecta ?
Image

Image
Andrew Smith
Posts: 321
Joined: Fri Sep 30, 2011 12:23 pm

Re: rho Cas

Post by Andrew Smith »

Hi Etienne,

The theory proposed by Lobel et. al. is that the emission is from a shell disk of gas surrounding the star. Their theory is that this emission is practically static in wavelength (apart from the radial velocity if the star) but the absorption feature moves with the pulsation of the star as do the other absorption lines. This gives rise to the different measured shape of the line and the apparent movement of the emission peak. The peak as seen in the spectra is not the actual peak in emission as it is convoluted with the moving absorption from the star.

They give the same exploitation for the splitting of other metal lines like the Na doublet as shown in my spectra :
RhoCas_Na_D_line.png
RhoCas_Na_D_line.png (28.18 KiB) Viewed 6892 times
Regards Andrew
Last edited by Andrew Smith on Thu Nov 16, 2017 4:30 pm, edited 1 time in total.
Andrew Smith
Posts: 321
Joined: Fri Sep 30, 2011 12:23 pm

Re: rho Cas

Post by Andrew Smith »

Etienne, if you want to get copies of my two spectra of Rho Cas taken on the 5th and 12th Nov this year 2017 you can download them from the BAA database here https://www.britastro.org/specdb/index.php . Go to REview Spectra. I am user A Smith and they are filed under Rho Cas.

H alpha is in the RhoCas_2101711**.0030 file

Regards Andrew
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