Changes is Ups Sgr spectrum ?

[Robin Leadbeater]

"mwr" on the cloudynights forum reports changes in the spectrum of Ups Sgr compared with spectra taken last year which could be worth following up
https://www.cloudynights.com/topic/8343 ... -outburst/
(Although it is listed in BeSS as a classical Be star, the system appears to be more complex)

Cheers
Robin

[Guillaume Bertrand]

Hi Robin,
Thanks for your message.
Here a recent (from a few minutes ago) hight resolution spectrum of Ups Sgr.
There is indeed an absorption on the blue wing of the h-alpha line...
If you have any explanations regarding this particular profile, I'm interested!


https://guillaumebertrand.notion.site/u ... f00434c1cf

Cheers,
Guillaume

[Robin Leadbeater]

Hi Guillaume,

Great spectrum ! Sorry I do not know any more about this rather strange system. I cleaned up the telluric lines and produced a velocity plot from your spectrum.

upssgr_20220802_857_gbertrand_telrem_velocity.png (18.05 KiB) Viewed 19020 times

Assuming the emission is centred at the H alpha rest wavelength, the centre of the absorption line is at -300km/s. It is remarkable how much the emission and absorption are separated. Not like the usual P Cygni profile.

Cheers
Robin

[Robin Leadbeater]

Assuming the emission is centred at the H alpha rest wavelength, the centre of the absorption line is at -300km/s. It is remarkable how much the emission and absorption are separated. Not like the usual P Cygni profile.

According to this reference from 1967 (posted by MWR on cloudy nights) this is seen for 40 days during the 138 day orbit of the binary and they suggest a mechanism
https://adsabs.harvard.edu/pdf/1967PASJ...19..564N

Cheers
Robin

[HughAllen]

Thanks Robin for highlighting this interesting star. Even at the low resolution of my Alpy 600 the apparent P Cygni profile is quite distinct, although at this resolution not the plateau between the Hα emission and absorption visible in Guillaume's high resolution spectrum. For such a hot star the spectrum is unusually full of relatively strong absorption lines. It would be intersting to catch another spectrum in a month's time if that's possible at such a low altitude
Cheers
Hugh

Ups Sgr 2022.08.06.png (27.97 KiB) Viewed 18868 times

[Guillaume Bertrand]

Hi Robin & Hugh,
This "continuum" between the blue wing and the right wing of this pseudo P Cygni profile really caught my attention during the acquisition. It's indeed unusual ! Thanks for the link Robin, I'll go read that.

Cheers,
G

[Guillaume Bertrand]

Hi all,
The profile of ups Sgr has changed significantly in a few days
Here the comparison of two spectra (heliocentric correction applied). All lines are shifted! Probably the doppler effect of the binary system...

https://www.notion.so/guillaumebertrand ... 8746092272

[HughAllen]

That's a beautiful Doppler shift between your high resolution spectra Guillaume.
I captured another Alpy spectrum on 29th August that shows no sign yet of any weakening in the Hα absorption feature. Here's a comparison with my spectrum taken 23 days previously:

Full wavelength range normalised at 5550-5560 Å:

upsSgr_comparison_HughAllen.png (39.32 KiB) Viewed 18163 times

Zoom around Hα normalised at 6580-6590 Å:

upsSgr_comparison_Halphazoom_HughAllen.png (43.35 KiB) Viewed 18163 times

[HughAllen]

I captured another Alpy spectrum of ups Sgr on September 16th which shows that the blue shifted Hα absorption has now faded compared to the last spectrum I captured on August 29th:

upsSgr 2022.08.29-16.09.png (43.4 KiB) Viewed 17776 times

upsSgr 2022.08.29-16.09 Halpha zoom.png (44.89 KiB) Viewed 17776 times

All of the hydrogen Balmer lines appear to have weakend between these dates, and they all show a significant blue shift. The Hβ line provides a good example:

upsSgr 2022.08.29-16.09 Hbeta zoom.png (51.5 KiB) Viewed 17776 times

Cheers
Hugh