spectro-aras.com

Hi,
I have just in the past few days started using the Alpy 600 with the guiding and calibration module. One of the first spectra that I obtained was 'V545 Lyr'-a Rigidly Rotating Magnetosphere. As I understand it, it is a Be star where the circumstellar disk is magnetically locked into the star surface where the disk and star would have the same rotational velocity. At the time I got this spectrum there were no emission lines. At some time in the rotation cycle, I believe, there should be a H-alpha emission line. Is anyone familiar with this type of star and is my assumption correct? I used a 10" Meade f/10 SCT with a f/6.3 reducer and an Atik Infinity monochrome camera. I used Demetra to do the data reduction and captured 5 spectra with180 s exposure.
Thanks
Dick

Hi Dick,

Looking at this paper
https://iopscience.iop.org/article/10.1 ... /141/5/169
it seems the H alpha emission was weak and only appears in high resolution spectra as a modulation of the line profile shape of the net absorption line. Do you have a better reference for significant H alpha emission ?

Robin

Hi Dick,

The paper Robin points out, especially Fig. 4, shows well how subtle the Halpha features are in stars like this. In RRM stars, the amount of circumstellar material is roughly proportional to the wind mass loss rate (and also the magnetic field strength and possibly the rotational rate?), so for relatively late-type stars like this (B5), the wind mass-loss rate is low and you typically only see small signatures in emission/absorption. Also, unlike classical Be stars where the disks can be highly variable, I'm pretty sure that the circumstellar material of RRM stars is fairly constant over long time periods (but we still see rotational modulation). Some earlier-type RRM stars do have strong Halpha lines in emission, like sigma ori e and HD 345439, for example