here is a message received today on Spectro-L Yahoo discussion group from Coralie Neiner & Dietrich Baade regarding a request to observe two Be stars: 28 Cygni and lam Pav:
Dear all,
In the frame of the BRITE observations (a constellation of
nano-satellites which monitors the variations of bright stars), Dietrich
Baade (from ESO) would like to obtain an Halpha monitoring of 2 bright
Be stars: 28 Cyg (in the Northern hemisphere, V=4.9) and lam Pav (in the
Southern hemisphere, V=4.2). See his email below.
We would be grateful if you could acquire data for these 2 stars. As you
will see in ArasBeam soon, for now we need 1 spectrum every 3 nights for
28 Cyg and 1 spectrum every 10 nights for lam Pav (all observers
together, not per observer, you can check ArasBeam to see if someone
else has already acquired a recent spectrum). However, as soon as an
outburst is detected (by one of you!) in any of these 2 stars, we will
require intensive monitoring (from as many observers as possible) during
the outburst(s). Hence, we ask you to submit your spectra to BeSS
promptly after acquisition, so that we can catch and monitor the
outburst(s) as early on as possible. You can also contact the BeSS
administrators directly if you notice any clear variation in the Halpha
emission.
We thank you in advance for your contribution!
Cheers,
Coralie
On 08/31/2016 07:26 PM, Dietrich Baade wrote:
> 1) 28 Cygni
>
> BRITE will observe this star through Oct. 20. The current light curve
> shows almost no gaps, and, on the small scale of the figure, I can't
> discern any obvious anomalies.
>
> In the last few days, the star may have increased its activity level.
> Because of the large amplitude of a few 0.01 mag, this should indicate
> varying amounts of matter in the inner disk. Therefore, Halpha spectra
> will help to check on this inference.
>
> It would be great if through the end of October observers could take a
> spectrum every 3 nights. If they do see variations, the observing
> frequency can be increased until the differences between consecutive
> spectra become insignificant.
>
> The observations can continue as long as the season lasts.
>
> Observers with equipment that can resolve the Halpha profile into two
> peaks, may wish to see whether the relative strength of the peaks
> changes (cyclically?). However, if the peaks reach well above the
> continuum, this can be a treacherous territory with some possibility
> of false alarms.
>
> 2) lambda Pavonis
>
> Test observations are already ongoing and have shown a temporary
> increase in amplitude to several 0.01 mag on a pulsational time scale
> of significantly less than a day. Currently, the star looks quiet.
> This may be a case of a small number of modes beating.
>
> The regular BRITE observations will only start about a year from now
> (the dates are not yet on the BRITE Wiki pages). lambda Pav has shown
> a fairly active Halpha life. Therefore, an initial observing
> frequency of one spectrum every 10 days may be OK.
>
> If variations are seen, the observing frequency can be increased until
> differences between consecutive spectra become insignificant.
>
> Observers with equipment that can resolve the Halpha profile into two
> peaks, may wish to see whether the relative strength of the peaks
> changes (cyclically?). However, if the peaks reach well above the
> continuum, this can be a treacherous territory with some possibility
> of false alarms.
>
> Although these observations would be a year ahead of the BRITE
> campaign, they would help a lot to derive the framework in which to
> interpret them. At DEC = -62 deg, the star is rarely observed. But
> it seems potentially quite rewarding.
Cordialement,
Olivier Thizy
