Page 1 of 1

profile of 8-04

PostPosted: Sat Aug 05, 2017 1:44 am
by Firefly
Hi all,

The profile does not give any evidence of eclipse of VV Cep. Did we need to re-calculate the theoretical model & some certain parameters? :roll:

Cheers,

Dong

Re: profile of 8-04

PostPosted: Sat Aug 05, 2017 9:19 am
by Ernst Pollmann
Hi Dong,
Graczyk et al. wrote in IBVS No. 4679:

The most surprising feature of the eclipse 1997-98 is the disargreement between the observed time of mid-eclipse and the predicted time based on Gaposchkin´s (1937) ephemeris.
Image1.png
Image1.png (40.71 KiB) Viewed 2496 times

The O-C diagram for the orbital orbital period of the VV Cep system.

The O-C of 1997/98 eclipse obviously indicates a sudden large change in the orbital period between the last two minima. The ephemeris gives JD 2450790 for the mid-eclipse time, while the observations clearly show that it occurred at around JD 2450855. This means that the mid-eclipse occurred 65 d later than expected from the ephemeris.


There are two probable reasons for such event:
1. Period changes due to mass transfer between the components, or
2. mass ejection from the VV Cep sytem, if one accepts the medium mass model for VV Cep, with the mass of the M star about 2.5 solar masses and of the B star about 8 solar masses

My references to the beginning of the eclipse are based on the orbital elements of VV Cep by K. O. Wright (1977) at R.A.S.C. Jour., Vol. 71, No. 2.
I think we have to be patiently ... it comes, but question is when.

Ernst

Re: profile of 8-04

PostPosted: Sat Aug 05, 2017 10:29 am
by Olivier GARDE
Yes, I confirm... No more evolution since my last spectrum taken the 28th july.

Here's a comparison between 28th July and 4th August (corrected from heliocentrique velocity).

Image

And the full spectrum

Image

Re: profile of 8-04

PostPosted: Sat Aug 05, 2017 12:41 pm
by Firefly
8-) Well, let's be patient to catch the big fish... ;)

Thank you, Ernst for your explanation.

Dong

Re: profile of 8-04

PostPosted: Sat Aug 05, 2017 4:39 pm
by marcoastro+
Dear colleagues,

As I already proposed on July 7th on the BAA forum it is quite possible the eclipse could be later.
According to the work of Leedjärv et.al. (A&A 1999) it seems the orbital period has a tendency of increasing between the eclipses due to a possible mass transfer or mass ejection. (Estimation approximately 1% per two former eclipses).
Link to the eclipse Ernst referred to:
http://adsabs.harvard.edu/full/1999A%26A...349..511L

So we must be standby

Kind regards,
Marc.

Re: profile of 8-04

PostPosted: Sun Aug 06, 2017 7:22 am
by Ernst Pollmann
Dear Marco,
many thanks for this helpful supplement.

Ernst

Re: profile of 8-04

PostPosted: Sun Aug 06, 2017 9:48 pm
by jack martin
A clear night here in the UK and a quick spectrum shows no significant changes.

My fits file won't load !

Regards to all.

Jack

Essex UK