1. NEAR-CONTACT BINARY V836 Cygni Çanakkale, 2004

2. Observations Ege University Obs. (30 cm.)
Turkish National Obs. (40 cm.)
Date range:
U B V filters

3. No brightness deficiency at 0.5(Zhukov & Markova1994)but at ~1.1

4. Before the analysis Mode definition for WD code
Evidence for (semi-detached?) configuration
Breinhorst et al.(1989): “detached, but...”
f2=0.98 ±0.02

8. f1=
Ωcr= >
f2=

9. *f(m) : Durbeck & Schumann (1982)

10. NCB test: the criteria P < 1 day 
Facing surfaces < 0.1 orb. radius apart X
Not in contact 
1 component at or near its Roche lobe 
Hotter: A v F ; cooler: 1 v 2 later 
Agreement in M-R-L relations of [Hilditch etal.(1988)] 
Two comp. lines parallel to the ZAMS [Oh et al. (2000)] ?
Harmony in M-R-L relations of collected data 
Shaw (1994)

11.
NCB  
A  
W X x

12. NCB 
A 
W X

13. Classification for 836
Shaw (1994)

14. about Evolution Disadvantage: Single-lined, only f(m) FO Vir type
A. if
come close enough to transfer required energy from hot to cool, photospere of the cool comp. is getting hot
then
A-type W UMa system. Shaw (1994)
!!(AML by magnetic breaking is needed)

15. B. Longer-period detached system
via Case-A mass transfer
semi-detached
(836 is here)
marginal contact (not in thermal eq.)
the deeper contact A-type W UMa system [Hilditch etal.(1988), Budding(1984)]

16.
NCB  
A  
W X x

17. Problems and Future Single-lined spectrae.
Prevent the morphology from varying study to study, by reducing the errors.
Eg. q range:
q= Ω cr= near R.L.
q=0.358 (10) Ω cr= at R.L.
q= Ω cr= at R.L.
AML: “ The secondaries of FO Vir types must be undermassive”.