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.
Tonight I observed some classical targets in my program (P Cygni, VV CEp and this time mu Cep which is similar to the red giant of VV Cep binary system) and several Be stars including 28 Cyg:
Here is the comparison with Tim Lester spectrum take couple of weeks ago:
As reference, here is the MatLab function used to do this graph:
otz_plot -1000 1000 0.8 2 '_28cyg_20160831_838_34.fits' -f '_28cyg_20160808_268_tlester.fits' -w Ha -p png
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