28 Tau ARAS monitoring

Re: 28 Tau ARAS monitoring

Postby Ernst Pollmann » Fri Sep 27, 2019 6:59 pm

James,
all the evaluated parameter, RV, V/R, CA and EW in your spectrum fits perfectly into the corresponding monitorings.
Thanks!

Ernst
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Re: 28 Tau ARAS monitoring

Postby Ernst Pollmann » Thu Oct 31, 2019 3:10 pm

Dear colleagues,
I want to remind at the periastron passage of 28 Tau on November 13th this year. Halpha spectra are urgend required.

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Re: 28 Tau ARAS monitoring

Postby Ernst Pollmann » Wed Nov 27, 2019 1:49 pm

Dear colleagues,
the so far high cadence of spectra enables very well the determination of the exact time of the last periastron (important to determine the orbital period of the companion). Thanks a lot to all the colleagues who contributed so far!!
But in order to evaluate the total character of the periastron passage with parameter EW, V/R, RV and CA (= central absorption core) of the Halpha line profile, further spectra are urgently required.
Please try it, if it is possible ...

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Re: 28 Tau ARAS monitoring

Postby James Foster » Thu Dec 05, 2019 12:30 pm

Hope you got the 28 Tau data I submitted to BeSS!

James
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Re: 28 Tau ARAS monitoring

Postby Ernst Pollmann » Fri Dec 06, 2019 9:10 pm

Yes, James, I used all your BeSS spectra for the monitoring.

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Re: 28 Tau ARAS monitoring

Postby Ernst Pollmann » Fri Feb 14, 2020 5:22 pm

Dear colleagues,
I want to introduce results of the extraordinary successful ARAS periastron passage campaign of 28 Tau from November 2019 to February 2020.
Here the link the the report:

https://www.astrospectroscopy.de/.cm4al ... 8020&cdp=a

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Re: 28 Tau ARAS monitoring

Postby Ernst Pollmann » Fri Sep 25, 2020 4:45 pm

The observation period of 28 Tau has began.
A wonderful opportunity to complement our monitorings of the central depth (1), EW (2), radial velocity (3) and V/R (4) of Halpha.
conclusion_25.9.20.png
conclusion_25.9.20.png (179.72 KiB) Viewed 2718 times

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Re: 28 Tau ARAS monitoring

Postby Ernst Pollmann » Tue Oct 27, 2020 9:27 am

Dear colleagues,
don´t forget to observe the next periastron passage on February 1th 2021!!
This time there are very good opportunities to observe totally the rise and the descent of the parameters EW, V/R, RV and CA.

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Re: 28 Tau ARAS monitoring

Postby Ernst Pollmann » Sun Jan 10, 2021 9:21 am

Dear colleagues,
don´t forget to observe the next periastron passage on February 1th 2021!!
This time there are very good opportunities to observe totally the rise and the descent of the parameters EW, V/R, RV and CA.
Attached you can see the current state of observations.
28tau_CA.png

28tau_EW.png

28tau_RV.png

28tau_VtoR.png

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Re: 28 Tau ARAS monitoring

Postby J Labadie Bartz » Sun Jan 24, 2021 4:14 pm

Hi Ernst,

I'm looking ahead at interesting Be star targets that are being observed by TESS over the next ~1.5 years. 28 Tau ( = Pleione) is one of them- it is being observed by TESS for three months between 2021-Aug-20 - 2021-Nov-06. I believe this window also includes a periastron passage. Going by the ephemeris published in BLANK (...actually I can't find the paper now... will update when found), there is a periastron passage very late in August 2021

Ernst, do you expect periastron on/near this time?

Pleione (and the other bright members of the Pleiades) was observed by K2, as shown in the Fig. below (from White et al. 2017; 2017MNRAS.471.2882W). Pleione has photometric signals similar to other Be stars of relatively late spectral type (probably mostly SPB pulsation).

Screenshot from 2021-01-24 11-00-18.png



However, I think the TESS data will be even more interesting, especially if the September 2021 periastron is well observed with spectroscopy. For the K2 data, it was extracted and processed in a way that removed low frequency signals, so it got rid of any signals that may arise from tidal changes in the disk (like probably what causes the observed spectroscopic behavior). The TESS data can be processed more carefully to keep these longer-term signals intact. Especially since Pleione is in a shell phase, tidally-induced disk variability near periastron, should, I expect, cause photometric variability.

This next plot shows data from Halpha on BeSS over the past few years (similar to Ernst's plots), and the shaded rectangles show the TESS observing window (but propagated back in time according to orbital phase). The point is, the shaded rectangle shows the sort of spectroscopic activity that will probably happen during TESS observing. The horizontal black bar shows the orbital phase that K2 observed.

Pleione_Pleione_H-alpha_2.png
Pleione_Pleione_H-alpha_2.png (124.13 KiB) Viewed 1656 times


Also, I am very many years late to the party for 28 Tau, but is it perhaps interesting that in the plot of V/R, there seems to be 'extra' structure shortly after periastron? I mean that there seems to be a first quick spike (like near 8800 in my plot) on top of the bigger and slightly slower signal. I must caution that I haven't looked at the data very closely.

-Jon
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