CH Cyg session 2018.06.30

[Peter Somogyi]

Hello all,

As per aavso, CH Cyg is fading suddenly (see the light curve).
I have fully clear forecast for todays very short night, would like to get parallel coverage, chosing the optimal observing schedule plan.
My default plan:
- CH Cyg at R~13000, H-alpha (LHires 2400/mm, 35u slit, max 15 min if no relevant fluctuation, need to have the same time cover with H8)
- CH Cyg in the UV (Ca II region, 1 hour, maybe more if seeing rapid changes / too low snr)
- VV Cep in the UV
+ perhaps something else if fits

I'd appreciate if anyone could provide low resolution coverage (blue oriented, let the H-alpha burn in), e.g. LISA or Alpy in parallel.

If anyone have ability to observe CH Cyg H-alpha above R~10000 (or eventually an eShel), I'd likely skip this.

Cheers,
Peter

[Vincent Marik]

Hello,

Ok, I have a clear forecast to at Tours.
I'll try CH cygni tonight with Alpy

Clear sky
Vincent Marik

[Peter Somogyi]

Thank you Vincent! Alpy's blue end will be an important addition! - Peter

[Vincent Marik]

Hello,

This is the result
CH cygni. Expect this is usefull !

Vincent

[Peter Somogyi]

Hello Vincent!

Visually, your spectrum seem to match well with hd207076.
Here is my spec. compared to a miles M7III star (my resolution is R~5500 average - considerably higher than the miles), suspecting a similar event:

chcyg_uv_cmp_hd207076.png (22.04 KiB) Viewed 7329 times

Unfortunately, I will need to wait for a good sky again (= one of the next weekends unless anyone provide...) to catch an M7III star for substraction and calculate the precise M7III ratio, allowing to extract other features as well.
But, it looks roughly almost the whole Be comp. light has just been lost.

BTW I am speculating about this, though it's a tricky system and need to be very careful (at least wait 1-2 weeks to judge):

Title: Eclipses in the symbiotic system CH CYG
Authors: Skopal, A., Bode, M. F., Lloyd, H. M., & Tamura, S.
13 Feb 1996

http://adsabs.harvard.edu/full/1996A%26A...308L...9S

3.1 Eclipses in the inner binary
[...] 1967-1970, 1992-1995 (Fig1) [...]

Cheers,
Peter

[Peter Somogyi]

Forgot to add, processed all my UV spectra relative to Iot Cyg, and the drop is obvious (with M-ish features on top remained):

chcyg_uv_cmp3_ps_iotcyg.png (66.02 KiB) Viewed 7319 times

So it is showing better what I wanted to point out.

- Peter